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Prevalence of HER2-low among Metastatic Breast Cancer Patients and Their Outcomes Compared to HER2 IHC 0 Background: Amplification and/or overexpression of the HER2 gene is detected in approximately 15% to 20% of breast cancer (BC) patients. HER2-targeted therapies improve survival in HER2+ BC. Current HER2 diagnostic tests and thresholds were designed and optimized to predict benefit from HER2-directed therapies. The DESTINY-Breast04 trial demonstrated notable efficacy of HER2 antibody-drug conjugate trastuzumab deruxtecan, in patients whose tumors are not conventionally HER2+, but defined as HER2-low (IHC 1 or 2+ without HER2 amplification). A better understanding of the HER2-low phenotype is therefore of critical importance. Methods: Eligible pts were adults with metastatic HER2 IHC (0,1+,2+/FISH negative) BC seen at MD Anderson between 2006 and 2019. Primary biopsy of the breast was used to test biomarkers. HER2 low was defined as IHC 1+ or 2+ and FISH-negative. HER2-negative was defined as HER2 IHC 0. Multi-covariate logistic regression models were used to evaluate effect of clinical factors on HER2 low status and pCR. Overall survival (OS) was defined as time from diagnosis date until death. Disease free survival (DFS) was defined as time from definitive surgery date until the first local/distant recurrence or death from any cause. Patients alive without events (death for OS, recurrence/death for DFS) were censored at last follow-up date. OS and DFS times were estimated by Kaplan-Meier method. Multivariate Cox proportional hazards regression models were applied to assess effect of covariates of interest on OS and DFS. Results: A total of 3053 early stage and 1203 de novo female BC patients were included in the analysis. The prevalence of HER2 low for early stage patients was 59.3% (1811/3053) and for de novo metastatic disease 59.3% (713/1203). In early stage patients, white race, higher nuclear grade and positive ER status were significantly associated with HER2 low status in multicovariate logistic regression. Univariately, pCR rate was significantly associated with negative ER (10.2% in negative vs 2.7% in positive), negative PR (8.6% vs 2%) and negative lymphatic vascular invasion (9.2% vs 2%). Multicovariate logistic regression showed ER (p=0.0124), PR (p=0.0439) status and lymphatic vascular invasion (p< 0.0001) were significantly associated with pCR status. With median follow-up of 8.5 years, median OS time was 5.3 years (95% CI: [4.9, 5.4]), 5.4 years and 4.8 years in HER2 low and HER2 0 groups, respectively. In multicovariate Cox regression, HER2 low was significantly associated with longer OS (HR=0.87, p=0.008), adjusted for age, race, stage, nuclear grade, lymphatic-vascular invasion and ER/PR status. In patients who received neoadjuvant chemotherapy, adjusted for stage, nuclear grade, ER and PR status and pCR, HER2 low was significantly associated with a longer OS time (HR=0.87, p=0.04). Median DFS time was 1.9 years (95% CI: (1.8, 2.0)). Age, stage, histology, nuclear grade, and ER and PR status were significantly associated with DFS by multicovariate Cox regression. Among de novo cases, higher nuclear grade (HR [II vs I]=1.838, p =0.008; HR [III vs I]=1.856, p=0.007) and positive ER status (OR=1.933, p Citation Format: Akshara Singareeka Raghavendra, Diane Liu, Jason Mouabbi, Debu Tripathy. HER2-04 Prevalence of HER2-low among Metastatic Breast Cancer Patients and Their Outcomes Compared to HER2 IHC 0 [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr HER2-04.

Background: Invasive lobular carcinoma (ILC) accounts for 10–15% of all breast cancers. Due to its distinctive growth pattern and biology, lobular carcinoma often fails to form distinct masses that can be easily detected by palpation or mammography. Because it is substantially less common than infiltrating ductal carcinoma (IDC), knowledge about clinical outcomes of ILC has been based on studies including relatively small patient (pt) numbers. Thus, we sought to assess the biologic and genomic features of ILC in the context of clinical outcomes. Methods: Eligible pts were adults with metastatic lobular or ductal BC seen at MD Anderson between 1997 and 2020. Overall survival (OS), progression-free survival (PFS), and disease-free interval (DFI) from the initial diagnosis were estimated using the Kaplan-Meier method. Survival distributions were compared using the log-rank test. Multivariate Cox proportional hazards regression models were applied to assess effect of covariates of interest on OS and DFS. No statistical adjustment was made for multiple testing. Results: A total of 7642 IDC and 1159 ILC female metastatic BC pts were included in the analysis. Clinical characteristics are presented in the table. Pts with ILC were on average older, had fewer metastases, and were more likely to have a family history of breast or ovarian cancer than pts with IDC. Lobular cases were less likely to be HER2+, had lower Ki-67, and lower nuclear grade than ductal cancer cases. The median follow-up was 4.37 years. The median OS for all pts from initial diagnosis was 5.38 years; 5.21 years and 6.57 years for IDC and ILC, respectively. ER positivity was associated with longer OS in both IDC [Hazard ratio (HR) 0.47, 95% confidence interval (CI): 0.45 - 0.49, P< 0.0001] and ILC (HR 0.63, 95% CI: 0.54 - 0.75, P< 0.0001). In de novo metastatic disease, the median OS was 3.74 years in IDC and 4.15 years in ILC. In recurrent IDC and ILC, the median OS was 5.84 and 7.89 years, respectively. De novo presentation had better OS from time of metastatic disease diagnosis for pts with both ILC and IDC than those presenting with recurrent cancer; however, de novo presentation was associated with worse PFS on 1st line therapy. In ILC, grade III had a poorer prognosis than grade I/II; (HR 1.47, 95% CI: 1.30 - 1.68, P< 0:0001). Among pts with IDC, grade I had the best outcomes, followed by grade II, then grade III. In IDC, significantly improved OS was observed in HER2+ BC (HR 0.85, 95% CI: 0.79 - 0.92), P< 0:0001). The median PFS for all pts was 0.53 years and the median DFI was 2.61 years. In both ILC and IDC, PFS and DFI were better in cancers that were ER+ or grade I/II. Conclusions: In metastatic BC pts, the biologic phenotypes and clinical behavior of ILC and IDC differ. More complete and reliable characterization of ILC may yield useful information regarding the biologic nature of ILC resulting in discovery of actionable findings leading to more personalized therapy. Further analyses of genomic features and patterns of metastatic sites between IDC and ILC will be presented. Patient characteristics of ILC and IDC Citation Format: Akshara Singareeka Raghavendra, Roland Bassett, Jason Mouabbi, Rachel M. Layman, Debu Tripathy. Biology and clinical course of lobular cancer in breast cancer (BC) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-05-38.

Background: Lobular carcinoma in situ (LCIS) is known to be a risk factor for the development of invasive lobular carcinoma (ILC). Recent genetic analysis indicates that LCIS is a facultative precursor of ILC. It was reported that ~50% of ILC co-occur with LCIS, however it is unclear whether patients with this co-occurrence behave similarly to patients with pure ILC. Methods: We retrospectively searched for patients treated at MD Anderson Cancer Center with a diagnosis of stage I-III ILC in our prospectively collected electronic database. Patients were divided into 2 groups: those with ILC with co-occurring ipsilateral LCIS (ILC/LCIS) and those with pure ILC without a histologically detected co-occurring ipsilateral in situ lesion (ILC alone). We obtained data on demographics, tumor size (T), lymph nodes (N) involvement, estrogen (ER), progesterone (PR) receptor status, HER2 expression, Ki67, treatment received, distant recurrence and survival status. The Kaplan-Meier product-limit method was used to compare distant recurrence-free survival (DRFS) and overall survival (OS) between the two groups. Multivariate analysis using Cox regression was used to assess association between co-variables and recurrence/survival. Results: We identified 4,217 patients with stage I-III ILC treated at MDACC between 1966 and 2021. 45% of cases (n = 1,881) had co-existing LCIS. 90% of ILCs were classical and 96% of LCIS were classical. Overall, the median age was 56 years, 95% of cases were ER+, 80% PR+, 5% HER2+. 40% of cases were T1, 60% N0 and 70% of tumors with available Ki67 data had low Ki67 (< 20%). Around 65% underwent mastectomy, 20% received neoadjuvant chemotherapy, and 35% received adjuvant chemotherapy. Statistically and numerically, ILC alone tended to have more T4 and N3 disease (P < 0.001), more ER/PR negative disease (P = 0.0002), more HER2+ disease (P = 0.010), higher Ki67 (P = 0.005), more non-classical ILC subtype (P = 0.04) and more exposure to neoadjuvant chemotherapy (P = 0.0002) than the ILC/LCIS group. The median follow-up time was 6.5 years. Patients with ILC co-existing with LCIS had better DRFS (28.0 vs 14.3 years, Hazard ratio (HR) 0.53, 95% confidence interval (CI) 0.47 – 0.59, P < 0.0001) and better OS (18.9 vs 13.7 years, HR 0.62, 95% CI 0.56 – 0.69; P < 0.0001). Multivariate (MV) analysis showed the absence of LCIS to be a poor prognostic factor along with a higher T and higher N for distant recurrence and overall survival (Table 1). Conclusion: The findings of this study suggests that the co-existence of LCIS with ILC is a good prognostic factor and that further studies are warranted to understand this phenomenon. Table 1. Multivariate Analysis between Clinico-Pathological Variables and Distant Recurrence-free Survival/Overall Survival Citation Format: Jason Mouabbi, Akshara Singareeka Raghavendra, Matthias Christgen, Amy Hassan, Gabriel N. Hortobagyi, Debu Tripathy, Rachel M. Layman. Absence of Lobular Carcinoma In Situ, a Poor Prognostic Marker in Invasive Lobular Carcinoma [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-05-04.

Supplementary Table from Targeting Metabolic Adaptations in the Breast Cancer–Liver Metastatic Niche Using Dietary Approaches to Improve Endocrine Therapy Efficacy

Estrogen receptor–positive (ER+) metastatic tumors contribute to nearly 70% of breast cancer–related deaths. Most patients with ER+ metastatic breast cancer (MBC) undergo treatment with the estrogen receptor antagonist fulvestrant as standard of care. Yet, among such patients, metastasis in liver is associated with reduced overall survival compared with other metastasis sites. The factors underlying the reduced responsiveness of liver metastases to ER-targeting agents remain unknown, impeding the development of more effective treatment approaches to improve outcomes for patients with ER+ liver metastases. We therefore evaluated site-specific changes in MBC cells and determined the mechanisms through which the liver metastatic niche specifically influences ER+ tumor metabolism and drug resistance. We characterized ER activity of MBC cells both in vitro, using a novel system of tissue-specific extracellular matrix hydrogels representing the stroma of ER+ tumor metastatic sites (liver, lung, and bone), and in vivo, in liver and lung metastasis mouse models. ER+ metastatic liver tumors and MBC cells grown in liver hydrogels displayed upregulated expression of glucose metabolism enzymes in response to fulvestrant. Furthermore, differential ERα activity, but not expression, was detected in liver hydrogels. In vivo, increased glucose metabolism led to increased glycogen deposition in liver metastatic tumors, while a fasting-mimicking diet increased efficacy of fulvestrant treatment to reduce the metastatic burden. Our findings identify a novel mechanism of endocrine resistance driven by the liver tumor microenvironment.Implications:These results may guide the development of dietary strategies to circumvent drug resistance in liver metastasis, with potential applicability in other metastatic diseases.

Cyclin-dependent-kinase-4/6 inhibitor (CDK4/6i) plus endocrine therapy (ET) is standard of care for patients with advanced hormone receptor (HR)-positive, HER2-negative breast cancer (BC). The Breast Medical Oncology database at MD Anderson Cancer Center (MDACC) was analyzed to assess effectiveness of the CDK4/6i palbociclib plus ET compared to ET alone. From a total of 5402 advanced HR+ HER2- BC patients referred to MDACC between 1997 and 2020, we identified eligible patients who received palbociclib in combination with first-line (n = 778) and second-line (n = 410) ET. We further identified "control" patients who received ET alone in the first-line (n = 2452) and second-line (n = 1183) settings. Propensity score matching analysis was conducted to balance baseline demographic and clinical characteristics between palbociclib and control cohorts to assess the effect of palbociclib treatment on progression-free survival (PFS) and overall survival (OS). For propensity-matched-cohort in the first-line setting (n = 708), palbociclib group had significantly longer median PFS (17.4 vs 11.1 months; P .0001) compared to controls. Median OS (44.3 vs 40.2 months) did not show a statistically significant benefit in the first line setting. However, in the second-line setting, with 380 propensity-matched-cohort, the palbociclib group had significantly longer PFS (10 vs 5 months, P .0001) as well as OS (33 vs 24 months; P .022), compared to controls. We conclude that in this single center analysis of a large cohort of metastatic HR+ HER2- BC patients, palbociclib in combination with ET was associated with improved PFS in both first-line and second-line settings and OS in the second-line setting compared to ET alone cohort.

Background: The checkpoint inhibitors atezolizumab (anti-PD-L1) and pembrolizumab (anti-PD-1) are FDA approved for the treatment of patients with PD-L1 positive, metastatic triple negative breast cancer in combination with chemotherapy. The response rates to checkpoint blockade in hormone receptor positive, HER2 negative metastatic breast cancer have been less encouraging (RR 12% for pembrolizumab in KEYNOTE-028 and RR 2.8% for avelumab in the phase 1b trial JAVELIN). We conducted a feasibility trial and enrolled patients with Stage II-III hormone receptor positive, HER2 negative breast cancer to treatment with 2 cycles of durvalumab (anti-PD-L1) plus tremelimumab (anti-CTLA-4) prior to standard neoadjuvant chemotherapy and breast surgery.Methods: Eligible patients were treated with durvalumab at a dose of 1500 mg and tremelimumab at a dose of 75 mg, both administered intravenously, on days 1 and 28. Pre- and post-treatment tumor biopsies and blood samples were available for 5 out of 8 patients and were analyzed by CyTOF, IHC, and NanoString. Patients then received standard neoadjuvant chemotherapy prior to breast surgery. The target enrollment was 20 patients. Results: After 8 patients were enrolled and treated on protocol, the trial was stopped early due to toxicity, slow accrual, and delays in patients receiving standard neoadjuvant chemotherapy. The median age of the patients was 55 (range 39-66) and all 8 patients were women. All patients had ER/PR positive, HER2 negative invasive ductal carcinoma (2 with lobular features, 1 with focal mucinous features) and all patients had clinical Stage II disease. Five patients received both cycles of durvalumab/tremelimumab and the remaining 3 patients only received the first cycle. One patient discontinued therapy out of concern for progression, though repeat breast and lymph node biopsies were benign and she went on to have a pathologic complete response after standard neoadjuvant chemotherapy. The remaining 2 patients discontinued treatment after the first cycle due to Grade 3 colitis (Patient #1) and Grade 3 thyroiditis/adrenal insufficiency (Patient #8). Both patients required treatment with steroids and experienced delays in receiving standard therapy due to these adverse events (AEs). The other AEs reported were all Grade 1 or 2. A post-durvalumab/tremelimumab breast ultrasound was performed in 7 of 8 patients and the percentage change in volume of each patient’s primary breast mass was: -55%, +104% (biopsy benign), +65%, -30%, +90%, -8%, and -53%. Patient #1 (colitis) had chemotherapy administered adjuvantly and Patient #8 (thyroiditis, adrenal insufficiency) declined chemotherapy. Only 1 of 8 patients had a pathologic complete response at the time of surgery. IHC, CYTOF, and gene expression analyses showed an increase in immune cell subsets in tumor stroma post neoadjuvant immunotherapy. Conclusions: We conducted a feasibility trial of neoadjuvant durvalumab plus tremelimumab administered prior to standard neoadjuvant chemotherapy in patients with hormone receptor positive/HER2 negative Stage II or III breast cancer. The trial was stopped early after 2 of 8 patients experienced Grade 3 immune-related adverse events (colitis in 1 patient and thyroiditis/adrenal insufficiency in another patient). Citation Format: Haven R. Garber, Sreyashi Basu, Sonali Jindal, Akshara Singareeka Raghavendra, Lumarie Santiago, Beatriz E. Adrada, Padmanee Sharma, James P. Allison, Jennifer Litton. Durvalumab and tremelimumab before surgery in patients with hormone receptor positive, HER2 negative stage II-III breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-14-14.

PURPOSE: Cyclin-dependent kinase 4/6 inhibitor (CDKi) therapy combined with endocrinetherapy is considered standard of care for patients with advanced hormone receptor (HR)-positive, HER2-negative breast cancer (BC). The Breast Medical Oncology Database at MDAnderson Cancer Center (MDACC) was analyzed to assess effectiveness of CDKi+palbociclib. PATIENTS AND METHODS: From a total of 5402 advanced HR+ HER2- BC patients referred toMDACC between 1997 and 2020, we identified eligible patients who received palbociclib incombination with first- (n=778) and second-line (n=410) endocrine therapy. We furtheridentified “control” patients who received endocrine therapy alone in the first- (n=2452) andsecond-line (n=1183) setting. We conducted a propensity score matching analysis to balancethe baseline demographic and clinical characteristics between the palbociclib treated andcontrol cohorts to assess the effect of palbociclib treatment on progression-free survival (PFS)and overall survival (OS). Stratified log-rank test was used to assess the effect of palbociclib inthe matched cohorts. RESULTS: For the propensity-matched cohort in the first-line setting (n=708), the palbociclibgroup had significantly longer median PFS (17.4 vs. 11.1 months; p Citation Format: Akshara Singareeka Raghavendra, Min Jin Ha, Nicole M. Kettner, Senthil Damodaran, Rachel Layman, Kelly K Hunt, Yu Shen, Debu Tripathy, Khandan Keyomarsi. Palbociclib plus endocrine therapy significantly enhances overall survival of HR+/HER2- metastatic breast cancer patients compared to endocrine therapy alone - A large institutional study [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-19-01.

PURPOSE Metastatic breast cancer (MBC) has a heterogeneous clinical course. We sought to develop a prognostic model for overall survival (OS) that incorporated contemporary tumor and clinical factors for estimating individual prognosis. METHODS We identified patients with MBC from our institution diagnosed between 1998 and 2017. We developed OS prognostic models by Cox regression using demographic, tumor, and treatment variables. We assessed model predictive accuracy and estimated annual OS probabilities. We evaluated model discrimination and prediction calibration using an external validation data set from the National Comprehensive Cancer Network. RESULTS We identified 10,655 patients. A model using age at diagnosis, race or ethnicity, hormone receptor and human epidermal growth factor receptor 2 subtype, de novo versus recurrent MBC categorized by metastasis-free interval, Karnofsky performance status, organ involvement, frontline biotherapy, frontline hormone therapy, and the interaction between variables significantly improved predictive accuracy (C-index, 0.731; 95% CI, 0.724 to 0.739) compared with a model with only hormone receptor and human epidermal growth factor receptor 2 status (C-index, 0.617; 95% CI, 0.609 to 0.626). The extended Cox regression model consisting of six independent models, for < 3, 3-14, 14-20, 20-33, 33-61, and ≥ 61 months, estimated up to 5 years of annual OS probabilities. The selected multifactor model had good discriminative ability but suboptimal calibration in the group of 2,334 National Comprehensive Cancer Network patients. A recalibration model that replaced the baseline survival function with the average of those from the training and validation data improved predictions across both data sets. CONCLUSION We have generated and validated a robust prognostic OS model for MBC. This model can be used in clinical decision making and stratification in clinical trials.

ImportanceApproximately 45% to 60% of hormone receptor (HR)–positive metastatic breast cancer (mBC) shows a low-level expression of ERBB2. Low ERBB2 expression is defined as ERBB2 immunohistochemical expression of 1+ or 2+ with a negative ERBB2 amplification by in situ hybridization. The efficacy of the antibody-drug conjugate trastuzumab deruxtecan in low-ERBB2, HR-positive mBC has been practice changing. However, there are conflicting data on the prognostic value of low ERBB2 expression in HR-positive mBC and whether low ERBB2 expression is a separate entity.ObjectiveTo examine whether outcomes differ by immunohistochemical analysis for patients with HR-positive mBC with low ERBB2 expression vs those without ERBB2 expression when treated with targeted therapy (TT) plus endocrine therapy (ET).Design, Setting, and ParticipantsThis single-institution cohort study used prospectively collected electronic data from the MD Anderson Cancer Center for patients with a diagnosis of HR-positive mBC treated with ET in combination with a TT (cyclin-dependent kinase 4/6 inhibitors [CDK4/6is], everolimus, or alpelisib) between January 1, 2010, and December 31, 2021.ExposureHR-positive mBC with either low or no ERBB2 expression.Main Outcome and MeasuresThe main outcomes were median progression-free survival and overall survival. Data on demographic characteristics, estrogen and progesterone receptor status, ERBB2 status, histologic subtype, menopausal status, treatment duration, and survival status were collected.ResultsA total of 1585 women (median [range] age, 51 [24-92] years) were included in the study. Of these women, 1013 (63.9%) had mBC with low ERBB2 expression and 572 (36.1%) had mBC with no ERBB2 expression. A total of 1084 (68.4%) were treated with a CDK4/6i (912 patients were treated in the first line and 172 were treated in the second line); 475 (30.0%) received everolimus and 26 (1.6%) received alpelisib. In the patients who received a first-line CDK4/6i, 618 (67.8%) received an aromatase inhibitor as their ET backbone and 265 (29.1%) received fulvestrant. With a median follow-up time of 17.9 months (range, 1-111 months), progression-free survival and overall survival were not statistically different between the patients with low and no ERBB2 expression treated with TT plus ET.Conclusions and RelevanceIn this cohort study of patients with HR-positive mBC treated with TT plus ET, low ERBB2 expression did not have a significant association with prognosis.

Background: Cyclin-dependent kinase 4/6 inhibitors (CDK4/6is) in combination with endocrine therapy (ET) have become the mainstay treatment for patients with hormone receptor (ER)-positive, HER2-negative metastatic breast cancer (BC). However, one-third of patients do not respond to the treatment (intrinsic resistance), leading to early tumor progression and treatment failure, and most patients eventually acquire resistance to therapy. The exact mechanisms of resistance to CDK4/6i are yet to be elucidated, and due to subsequent early (intrinsic) or late progression on CDK4/6i, long-term cures are not achieved. Methods: Transcriptomic profiles of BC cell lines that were sensitive or resistant to approved CDK4/6i, independent of subtype, were downloaded from the Cancer Cell Line Encyclopedia database. Bioinformatics analysis was performed by integrated Differential Expression and Pathway (iDEP) workflow. In parallel, transcriptomic profiles of metastatic biopsies from pre-CDK4/6i-treated BC patients (n = 54) were generated using RNA-Access technology. Key common biomarkers identified from the BC cell lines and patient tumor samples were validated by immunohistochemistry in formalin-fixed paraffin-embedded (FFPE) metastatic specimens from 73 patients prior to CDK4/6i therapy. Results: Transcriptomic profile comparisons of BC cell lines (n = 35) that were sensitive versus resistant to CDK4/6is identified Trefoil Factor 1 and 3 (TFF1 and TFF3) secretory proteins as top predictors of response. Correlation analysis showed a strong negative correlation between TFF1 and TFF3 levels to IC50 values of palbociclib and abemaciclib. Knockdown of TFF3 in CDK4/6i-sensitive BT20 cells with shRNA induced drug resistance in the cells. Transcriptomic data from 54 BC patients pre-treated with CDK4/6i showed the expression levels of TFF1 and TFF1/3 receptors (CCR4 and CCR7) were significantly increased in patients who developed late progression (> 6 months) compared to early progressors (< 3 months). In addition, IHC analysis of TFF1 and TFF3 expressions in 73 pre-treated BC patient samples showed significantly higher protein expression levels in late progressors than in early progressors. Conclusions: Our results identified and validated the common biomarkers, TFF1 and TFF3, as predictors of CDK4/6i response efficacy in ER-positive, HER2-negative BC patients. These findings provide a predictive tool capable of selecting de novo metastatic BC patients who will have the greatest benefit from the combination of CDK4/6i with endocrine treatment. Furthermore, our discovery of biomarkers in early versus late progression on CDK4/6i therapy will enable new therapeutic avenues and provide the rationale for future large-scale clinical trials. Citation Format: Linjie Luo, Yan Wang, Sophia Mastoraki, Akshara Singareeka Raghavendra, Juliana Navarro-Yepes, Nicole M. Kettner, Serena Kim, Debasish Tripathy, Kelly Hunt, Khandan Keyomarsi. TFF1 and TFF3 predict response to CDK4/6 inhibitors in breast cancer patients. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4346.

Background: Hormone receptor-positive (HR+) metastatic breast cancer (MBC) contributes to nearly 70% of breast cancer-related deaths. The liver is the third most common site for metastasis in breast cancer, and liver involvement has been found to have a poor prognosis. One contributing factor is resistance to hormonal treatments. Furthermore, estrogen receptor alpha gene (ESR1) activating mutations, which are enriched in metastatic tumors of the viscera such as the liver, have been linked specifically to resistance against hormone-blocking therapies. We seek to characterize the efficacy of specific treatment modalities, including hormone therapy, immunomodulators, radiotherapy, chemotherapy, and the role of ESR1 mutations in poor treatment response of MBC with liver metastasis. Methods: We conducted a retrospective matched cohort study of 3388 adults with HR+/HER2- MBC with liver and non-liver involvement, who were treated at MD Anderson Cancer Center from 1997-2021. Patients with liver and non-liver metastasis were matched by age at breast cancer diagnosis, race, BMI, and stage. All patients underwent fulvestrant monotherapy or fulvestrant-based combination therapy with CDK4/6 inhibitors, mTOR kinase inhibitors (everolimus), or PI3K inhibitors (alpelisib). We compared the overall and metastatic survival of patients with liver vs. non-liver metastasis on different treatment regimens. We also evaluated the impact of chemotherapy administered for metastasis. Results: Patients with liver metastasis experienced shorter overall and metastatic survival across all treatment regimens (HR, 1.44; 95% CI 1.34-1.57; P Citation Format: Christine Chien, Zeynep Madak-Erdogan, Mahima Goel, Suma Gangidi, Debu Tripathy, Akshara Singareeka Raghavendra. Efficacy of fulvestrant-based therapies in treating HR-positive, HER2-negative breast cancer with liver metastasis [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-02-39.

Background: The Advanced Breast Cancer (ABC) program at The University of Texas MD Anderson Cancer Center was created by metastatic breast cancer (MBC) patients for MBC patients. The ABC Program seeks to improve quantity and quality of life for patients living with MBC. MD Anderson actively treats 2,076 patients living with MBC. ABC program patient advocates voiced the need to increase MBC patients’ access to internal medicine services coordinated with oncology care. Significance: Previous literature suggests patients living with MBC have difficulty receiving oncology coordinated internal medicine services due to their terminal diagnosis and indefinite prescription of anti-cancer treatment. Comorbidities in this setting are known to be associated with inferior outcomes. ABC Program patient advocates reported various challenges seeking care from community based medical professionals including, timely awareness of their local provider on the status of their cancer. Other challenges included the lack of familiarity of some providers with novel MBC cancer treatment, side effects, and interactions of their cancer treatment with non-cancer conditions and treatment. Therefore, with the increasing life expectancy of MBC patients, there is a growing realization of the importance of managing the medical comorbidities in coordination with the MBC patient’s cancer treatment. Purpose: To increase access and coordinate internal medicine services for MBC patients with medical comorbidities. Interventions: In partnership with ABC Program patient advocates, the Linking Internal Medicine and Metastatic Breast cancer for Success (LIMBS) clinic was created in February 2021. The LIMBS clinic aimed to bridge the gap in lack of oncology coordinated internal medicine service for MBC patients. Evaluation: Breast Medical Oncology providers requested LIMBS clinic consults for 108 patients for comorbidity management since the clinic inception. This is a 44% increase in internal medicine consultations prior to LIMBS clinic creation (60 vs 108). The LIMBS clinic consults resulted in 474 follow up visits. Compared to MBC patients at MD Anderson, LIMBS patients were more likely to be African American (20% vs 13%) and were more likely to be older (59 years vs 57 years). Gender, marital status, and clinical trial enrollment did not differ between LIMBS patients and MBC patients. LIMBS patients had significantly higher rates of hypertension (46% vs 19%), Type II DM (19% vs 6%), hyperlipidemia (13% vs 10%), and hypothyroidism (13% vs 6%) compared to MBC patients in general. LIMBS patients had lower rates of anxiety (8% vs 11%) and depression (2% vs 7%) when compared to the MBC patients in general. The top 10 comorbidities for all MBC patients versus LIMBS patients are listed in Table 1. Discussion: It is feasible to build and integrate internal medicine with breast medical oncology services for patients with metastatic breast cancer. Future research should focus on exploring, describing, and meeting the internal medicine needs of MBC patients. Future initiatives are needed to bridge the gap in care for oncology coordinated internal medicine services between community and tertiary care centers. Table 1. Top 10 Comorbidities of all MBC patients versus LIMBS clinic patients Note. This table demonstrates the top 10 comorbidities for MBC population and the LIMBS population. Citation Format: Abbey Kaler, Akshara Singareeka Raghavendra, Ginny T. Kirklin, Dawn Cunningham, Ellen Manzullo, Debu Tripathy, Zayd Razouki. Linking Internal Medicine Care to Metastatic Breast Cancer Patients for Success: LIMBS [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-03-22.

Background: About 55% of hormone receptor (HR)-positive metastatic breast cancer (mBC) show a low-level expression of human epidermal growth factor receptor 2 (HER2-low). HER2-low is defined as HER2 immunohistochemistry (IHC) expression of 1+ or 2+ with a negative HER2 amplification by in situ hybridization. The efficacy of the antibody-drug conjugate trastuzumab deruxtecan in HER2-low HR+ mBC has been practice changing. However, there are conflicting data on the prognostic value of low HER2-expression in HR+ mBC with some reports showing no impact on prognosis and other showing inferior outcomes in HER2-low patients when treated with cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6is) in combination with endocrine therapy (ET). Methods: We retrospectively searched for patients treated at MD Anderson Cancer Center with a diagnosis of HR+ treated with ET in combination with a targeted therapy (CDK4/6is, everolimus or alpelisib). Patients were divided into 3 groups: All histologies, ductal histology (IDC) and lobular histology (ILC). We obtained data on demographics, estrogen (ER) and progesterone (PR) receptor status, HER2 expression, menopausal status, treatment duration and survival status. The Kaplan-Meier product-limit method was used to compare progression-free survival (PFS) and overall survival (OS) between the three different groups stratified by HER2 expression (HER2 low versus HER2 0). Results: We identified 1,649 patients (64% HER2-low, 36% HER2 0) with HR+/HER2- treated with targeted therapy (CDK4/6is, everolimus or alpelisib) in combination with ET. The median age was around 50 years in all groups, 75% were White, 55% premenopausal, 95% ER-positive and 83% PR-positive. 68% were treated with CDK4/6is (919 patients treated in first line (1L) and 202 treated in second line), 30% everolimus and 2% with alpelisib. In the patients who received first 1L CDK4/6is, 70% received an aromatase inhibitor as their ET backbone and 30% received fulvestrant. All the patients who received 1L fulvestrant recurred while on adjuvant AI. PFS and OS were not statistically different between the HER2-low and HER2 0 groups treated with targeted therapies (TT) plus ET or 1L CDK4/6is plus ET regardless of the histology (Table 1). Conclusion: In this single institution analysis, HER2-low status did not have a significant impact on prognosis in HR+/HER2- mBC treated with TT plus ET or 1L CDK4/6is plus ET. Table 1. Progression-free Survival and Overall Survival in HR+/HER2- mBC patients treated with targeted therapies (TT) plus endocrine therapy (ET) In patients treated with TT + ET in all histologies (A), in IDC (B) and in ILC (C). In patients treated in 1L with CDK4/6is + ET in all histologies (D), in IDC (E) and in ILC (F) Citation Format: Jason Mouabbi, Akshara Singareeka Raghavendra, Roland Bassett, Amy Hassan, Debu Tripathy, Rachel M. Layman. Histology-based survival outcomes in HR+/HER2- metastatic breast cancer treated with targeted therapies plus endocrine therapy based on HER2 expression [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-02-30.

Background Cancer-associated macrophage-like cells (CAMLs) are rare circulating gigantic atypical cells exclusively found in the peripheral blood of patients with solid cancers. CAMLs potentially originate from tumor-associated macrophages in the tumor microenvironment and may have a prognostic role in breast cancer. Obesity-induced local hypoxia attracts macrophages to the tumor microenvironment and activates macrophages to induce chronic inflammation, which can lead to breast cancer progression. However, little is known about the relationship between CAMLs, obesity, and body fat distribution. Also, the role of the CAMLs on breast cancer development needs to be investigated. We hypothesized that the number and size of CAMLs are correlated with body mass index (BMI), and we investigated the relationship between CAMLs and body composition. Materials and methods We prospectively collected 10 ml of peripheral blood from 30 patients initially diagnosed with advanced breast cancer who underwent computed tomography. Blood samples were drawn in CellSave tubes to preserve peripheral blood mononuclear cells. We used the CellSieve microfiltering system to isolate and identify CAMLs. After enumerating cells, we analyzed immunofluorescent staining for DAPI, CD14, CD45, CXCR4, and cytokeratin. CAMLs were identified by cell surface markers (CD14+, CD45+, and cytokeratin+) and morphology (multinuclear and giant cells >30 µm). BMI was measured at the time of diagnosis. The in-house 3D imaging analysis software Medical Executable for the Efficient and Robust Quantification of Adipose Tissue was used to calculate the total amount of abdominal visceral fat tissue (VAT) and subcutaneous fat tissue (SAT) between the upper diaphragm and pelvic end using multi-detector computed tomography data. The VAT:SAT ratio was also calculated. We quantified the expression of C-X-C chemokine receptor type 4 (CXCR4) in CAMLs to investigate the metastatic potential of the cells. Finally, we determined the relationship between the characteristics of CAMLs and BMI, body composition parameters, and CXCR4 using the Pearson correlation test. Results Of 30 collected samples, two had an inadequate amount of blood for evaluation. Among the remaining 28, we detected CAMLs in 24. The median BMI was 30.4 kg/m2, and half of the patients were categorized as obese by the World Health Organization BMI classification. BMI was correlated with the number (r=0.39, p=0.043), average size (r=0.42, p=0.039), and maximum size (r=0.50, p=0.013) of CAMLs. In body composition analysis, the maximum size of CAMLs was correlated with the total amount of VAT (r=0.51, p=0.012) and SAT (r=0.44, p=0.037) but not the VAT:SAT ratio. The number of CAMLs was correlated with maximum CXCR4 expression in CAMLs (r=0.58, p=0.004). CAMLs size and CXCR4 expression were inversely correlated. Conclusion The number and size of CAMLs are correlated with BMI, but CAMLs characteristics are not related to body composition. The number of CAMLs was associated with CXCR4, which indicated its metastatic potential. Further studies are needed to elucidate the biological role of CAMLs, especially whether the increased number and size of CAMLs in obesity reflect the tumor microenvironment. Citation Format: Toshiaki Iwase, Aaroh Parikh, Onur Sahin, Akshara S Raghavendra, Maryanne E Sapon, Anjali James, Tushaar V Shrimanker, Sudpreeda Chainitikun, Kumiko Kida, Daniel L Adams, Cha-Mei Tang, Andrea YD Medrano, Ann H Klopp, Naoto T Ueno. Prospective study of circulating cancer-associated macrophage-like cells (CAMLs) in obese patients with advanced breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS2-23.

Outcomes of treatments for patients with breast cancer brain metastasis (BCBM) remain suboptimal, especially for systemic therapy. To evaluate the effectiveness of systemic and local therapy (surgery [S], stereotactic radiosurgery [SRS] and whole brain radiotherapy [WBRT]) in BCBM patients, we analyzed the data of 873 BCBM patients from 1999 to 2012. The median overall survival (OS) and time to progression in the brain (TTP-b) after diagnosis of brain metastases (BM) were 9.1 and 7.1 months, respectively. WBRT prolonged OS in patients with multiple BM (hazard ratio [HR], 0.68; 95% CI, 0.52-0.88; P = .004). SRS alone, and surgery or SRS followed by WBRT (S/SRS + WBRT), were equivalent in OS and TTP-b (median OS, 14.9 vs 17.2 months; median TTP-b, 8.2 vs 8.6 months). Continued chemotherapy prolonged OS (HR, 0.35; 95% CI, 0.30-0.41; P

Background: Male breast cancer (MBC) is rare and accounts for 1% of all breast cancers. Much of the evidence to support the efficacy of CDKi come from clinical trials that have minimal male representation, either because they were excluded or because of very low accrual. Palbociclib in conjunction with aromatase inhibitors (AI) and fulvestrant has recently been approved in men for the treatment of advanced hormone receptor positive (HR+), HER2 negative breast cancer. A recent retrospective review of postmarketing reports and electronic health records showed the efficacy and safety profile of palbociclib in men may be similar to that of women. However, further studies are needed to support this conclusion. We set out to evaluate the response rate to palbociclib in a single institution known to see a high number of male breast cancer patients. Methods: We identified male patients with metastatic breast cancer treated with palbociclib through the MD Anderson Cancer Center Breast Medical Oncology database. The primary objective was to evaluate response rate to palbociclib in male patients with HR +, HER 2 negative breast cancer. Descriptive statistics were used. Response was assessed based on radiographic RECIST criteria version 1.1 Results: We identified 26 men treated with palbociclib from 1/2015 to 4/2018. The median age of breast cancer diagnosis was 54 years (range 25-70). Five patients (19%) presented with de novo metastatic disease. 14 (54%) patients were treated in the first-line, 3 (12%) second-line, and 9 (35%) third-line or greater. Palbociclib was combined with AI+GNRH in 13 pts (50%), fulvestrant+GNRH in 4 pts (15%), letrozole alone in 3 pts (13%), and fulvestrant alone in 6 pts (23%). Response rate was assessed in 25 of the 26 patients. The rate of response was 48% (12 of 25 patients), with 1 patient achieving a complete response (CR), 11 achieving a partial response (PR), 6 with stable disease (SD) and 7 with progressive disease (PD). Response rate was 59% (10/17) for those that received palbociclib in their first or second lines of therapy while response rate was 25% (2/8) if received as third or higher line of therapy. Response rate was higher in those that received palbociclib with letrozole 62.5% (10/16) versus those who received it with fulvestrant 22.2% (2/9). The median duration of response was 3.8 months. The median follow up from initiation of palbociclib was 15 months. The median PFS for all patients was 10.8 months (IQR 4.9-24.5). Those who received 1-2 lines of therapy had a median PFS of 12.4 months (IQR 4.9-24.5), while the median PFS was 9.2 months for those who received 3 or more lines of therapy (IQR 5.0-14.1). Conclusion: Palbociclib provides benefit for MBC patients with the majority of men in this study achieving clinical response to treatment. Citation Format: Oluchi Oke, Jiangong Niu, Akshara Raghavendra, Mariana Chavez-McGregor, Hui Zhao, Debu Tripathy, Sharon Giordano. Palbociclib in advanced male hormone positive breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-17-02.

Background: CDK 4/6 inhibitors have become frontline treatment for patients (pts) with advanced hormone receptor (HR) positive breast cancer. There is limited data regarding post-progression outcomes in pts receiving CDK 4/6 inhibitors as standard of care. In this study, we analyzed treatment patterns and clinical outcomes of post-progression treatment in pts with advanced HR positive breast cancer after receiving CDK 4/6 inhibitors. Methods: Pts with metastatic breast cancer receiving CDK 4/6 inhibitors who received treatment after progression were identified from a cohort of pts at MDACC. Pts receiving CDK 4/6 inhibitors in a clinical trial were excluded. Clinical and demographic data as well as progression-free survival (PFS) was collected. Data was analyzed using Fischer's exact test for categorized variables and T test/Wilcoxon rank-sum test for continuous variables. PFS was analyzed using the Kaplan Meier method. Results: 206 pts who met eligibility criteria were included. Median age at metastatic diagnosis was 56 years-old and the majority of pts were white (n=160, 77.7%) with a pre- treatment performance status of 0 (n=168, 81.6%). The largest fraction of pts (n=98, 47.6%) received a chemotherapy agent following progression on a CDK 4/6 inhibitor while 19.4% (n=40) received endocrine therapy, 21.8% (n=45) received a biologic, 6.3% (N=13) received a different CDK 4/6 inhibitor and 4.9% (n=10) received an investigational therapy. The majority of pts who progressed on a subsequent agent had visceral progression (n=193, 93.7%). The median time to progression on an agent after CDK 4/6 inhibitor was 122 days. There was no statically significant difference in time to progression after CDK 4/6 inhibitor between pts receiving different classes of therapies, including CDK 4/6 inhibitors and investigational therapies (p=0.3). Conclusion: Pts in our cohort were more likely to receive chemotherapy following progression on a CDK 4/6 inhibitor. Reassuringly, there was no significant difference between time to progression on different agents. As CDK 4/6 inhibitors become frontline therapy for HR positive metastatic breast cancer, it is important to evaluate the sequencing of therapies as well as outcomes on subsequent agents. Citation Format: Katherine Keaney Clifton, Akshara Singareeka Raghavendra, Min Yi, Jennifer Litton, Debu Tripathy, Meghan Karuturi. Practice patterns and outcomes of post progression treatment after CDK 4/6 inhibitors [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-11-03.

Patients with hereditary mutations in BRCA1 or BRCA2 (gBRCA1/2) and breast cancer have distinct tumor biology, and encompass a predilection for brain metastasis (BM). We looked into baseline risk of BMs among gBRCA1/2 patients. Patients with gBRCA1/2, stage I-III invasive breast cancer seen between 2000–2017 with parenchymal BMs. Among gBRCA1 with distant breast cancer recurrence, 34 of 76 (44.7%) were diagnosed with brain metastases compared to 7 of 42 (16.7%) patients with gBRCA2. In the comparator group, 65 of 182 (35.7%) noncarrier triple-negative breast cancer (TNBC) and a distant recurrence experienced BM’s. In a competitive risk analysis using death as a competing factor, the cumulative incidence of BMs was similar between gBRCA1 and noncarrier TNBC patients. The time from primary breast cancer diagnosis to detection of BMs was similar between gBRCA1 and noncarrier TNBC patients (2.4 vs 2.2 years). Survival was poor after BMs (7.8 months for gBRCA1 patients vs. 6.2 months for TNBC noncarriers). Brain was a more common site of initial distant recurrence in gBRCA1 patients versus TNBC noncarriers (26.3% vs. 12.1%). Importantly, the presence of BMs, adversely impacted overall survival across groups (HR 1.68 (95% CI 1.12–2.53), hazard ratio for death if a patient had BMs at the time of initial breast cancer recurrence vs. not). In conclusion, breast cancer BMs is common and is similarly frequent among gBRCA1 and noncarrier patients with recurrent TNBC. Our study highlights the importance of improving the prevention and treatment of BMs in patients with TNBC, gBRCA1 carriers, and noncarriers.

Approximately 70% of human breast cancers express estrogen receptor alpha (ERα), providing a potential for targeted endocrine therapy for patients. Unfortunately, 30-40% of ER+ patients still experience recurrence and metastasis, with a 5-year relative overall survival rate of just 24% for patients with metastatic disease. Previously, we described an increased reliance on NAD+ metabolism in metastatic breast cancer (MBC) cells, which are driven by clonal selection from monotherapy resistance and the metastatic organ microenvironment. In the current study, we investigated if inhibition of NAMPT to block NAD+ production would synergize with standard of care therapies for ER+ MBC. Combination therapy of the NAMPT Inhibitor, KPT9274 and the ERα agonist Fulvestrant (Fulv) synergistically reduced tumor burden in liver metastasis in vitro (combination index < 1 in cell viability assays) and in vivo in mouse xenograft models. A synergistic effect was not observed when KPT-9274 was combined with Palbociclib or Tamoxifen, nor Fulv with other metabolic inhibitors. RNA-Seq analysis showed that NAMPT inhibition restored antiestrogenic activity of Fulv. Metabolomics analysis showed that NAMPT inhibition reduced abundance of metabolites associated with glucose and lipid metabolism. Mechanistically, chromatin immunoprecipitation showed that NAMPT is recruited to ERα binding sites in MBC xenografts and PDX tumors. Targeting metabolic adaptations in endocrine-resistant metastatic breast tumors is a novel approach that could lead to new combined therapies that reduce mortality. Presentation: No date and time listed

PURPOSE: CDK4/6 inhibitors are currently used in combination with endocrine therapy to treat advanced hormone receptor-positive, HER2-negative breast cancer. While this treatment doubles time to progression compared to endocrine therapy alone, about 25–35% of patients do not respond, and almost all patients eventually acquire resistance. Discerning the mechanisms of resistance to CDK4/6 inhibition is crucial in devising alternative treatment strategies. EXPERIMENTAL DESIGN: Palbociclib resistant cells (MCF-7 and T47D) were generated in a step-wise dose-escalading fashion. Whole-exome sequencing, genome-wide expression analysis and proteomic analysis were performed in both resistant and parental (sensitive) cells. Pathway alteration was assessed mechanistically and pharmacologically. Biomarkers of altered pathways were examined in tumor samples from palbociclib treated breast cancer patients whose disease progressed while on treatment. RESULTS: Palbociclib resistant cells are cross resistant to other CDK4/6 inhibitors and are also resistant to endocrine therapy. IL-6/STAT3 pathway is induced while DNA-repair pathways are downregulated in the resistant cells. Combined inhibition of STAT3 and PARP significantly increased cell death in the resistant cells. Matched tumor samples from breast cancer patients who progressed on palbociclib were examined for deregulation of estrogen receptor, DNA repair, and IL-6/STAT3 signaling and results revealed that these pathways are all altered as compared to the pre-treatment tumor samples. CONCLUSION: Palbociclib resistance induces endocrine resistance and alteration of IL-6/STAT3 and DNA damage response pathways in cell lines and patient samples. Targeting IL-6/STAT3 activity and DNA repair deficiency using a specific STAT3 inhibitor combined with a PARP inhibitor could effectively treat acquired resistance to palbociclib. TRANSLATIONAL RELEVANCE: The majority of breast cancer deaths are due to progression of metastatic ER-positive disease. Identification of targetable biomarkers to predict treatment strategies to circumvent resistance to CDK4/6 class of inhibitors which are currently used in combination with endocrine therapy in ER-positive metastatic breast cancer patients will be instrumental in improving survival. We show that ER-positive breast cancer cells acquire resistance to palbociclib (CDK4/6 inhibitor) by downregulation of ER protein and DNA repair machinery and upregulation of IL-6/STAT3 pathway, which is overcome by treatment with STAT3 and PARP inhibitors. Matched biopsies from breast cancer patients who progressed on palbociclib showed deregulation in DNA repair, ER and IL-6/STAT3 as compared to their pre-treatment biopsy samples. By identifying and validating these mediators (or drivers) of palbociclib resistance, we propose that patients who progress on palbociclib can be targeted using clinically available inhibitors to STAT3 and DNA repair to circumvent resistance and improve clinical outcomes.

Background: Pertuzumab (P) in combination with trastuzumab (H) based chemotherapy is FDA-approved as a standard neoadjuvant treatment for patients with clinical stage II-III HER2-positive (HER2+) breast cancer (BC). The goal of this study was to evaluate the pathologic complete response (pCR) rate for neoadjuvant HP-containing regimens compared to H-containing regimens and report the 3-year relapse-free survival (RFS) for patients who had a pCR compared to those with residual disease (RD). Methods: All patients with stage II-III non-inflammatory HER2+ BC who received neoadjuvant H-containing or HP-containing therapy and underwent definitive breast and axillary surgery were identified from 2005 to 2016 through an institutional database. Medical records were examined for patient demographics, breast cancer stage, pathology results, surgical outcomes, and treatment details. pCR was defined as ypT0/is, ypN0. RFS was defined as the interval from surgery to date of last followup or death from any cause. Descriptive statistics, Cox proportional hazards, and Kaplan-Meier estimates were used for statistical analysis. Results: Patient characteristics and results by pCR or RD status are shown in the table below. The median age was 51 (22-84) years for the HP group and 50 (21-87) years for the H group. The median follow-up time was 1.9 (0-4.2) years for the HP group and 5.3 (0.1-12) years for the H group. For the HP group, the 3-year RFS was 98% (95% CI: 95, 100) for the pCR group and 90% (95% CI: 83, 97) for the RD group; HR 0.17 (0.04, 0.82), p=0.012. For the H group, the 3-year RFS was 91% (95% CI: 88,94) for the pCR group and 75% (95% CI: 71-79) for the RD group; HR 0.31 (0.22, 0.44), p Conclusion: Patients who achieve pCR have an improved 3-year RFS compared to patients who have RD. Treatment with HP-containing neoadjuvant regimens is associated with a high 3-year RFS. VariableHP (n=215)H (n=807) pCR n=121RD n=94pCR n=399RD n= 408Age at Diagnosis Citation Format: Murthy RK, Raghavendra AS, Hess KR, Barcenas CH, Lim B, Moulder SL, Giordano SH, Mittendorf EA, Thompson A, Ueno NT, Valero V, Litton JK, Tripathy D, Chavez-Macgregor M. 3-year relapse-free survival of stage II-III HER2-neu positive breast cancer treated with pertuzumab and trastuzumab-containing neoadjuvant therapy compared to trastuzumab-containing therapy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-04.

Background: Understanding to what extent a breast tumor's genetic composition may change over the course of a few months of neoadjuvant therapy has implications for optimal therapeutic approach. However, genomic changes observed across treatment may result from either treatment-induced clonal evolution or geographically disparate sampling of a heterogeneous tumor. We sought to characterize the geographic heterogeneity in primary breast tumors, and to incorporate this information into analysis of clonal evolution with neoadjuvant therapy. Methods: We assembled the largest cohort to date of multi-region (n=2-3) whole-exome sequenced (WES) or whole-genome sequenced untreated primary breast tumors with matched normal and adequate tumor purity for analysis: four tumors with data generated for this study and five tumors compiled from three previous studies. We also generated the first cohort of multi-region (n=2-6) WES breast tumors post-neoadjuvant HER2-targeted therapy and chemotherapy, sequencing one region from a pre-treatment diagnostic specimen, multiple regions from the post-treatment surgical specimen, and matched normal for five HER2+ breast tumors that did not achieve a pathologic complete response. We used an agent-based model of spatial tumor growth to investigate whether the mutational patterns we observed with treatment were consistent with pre-existing heterogeneity or treatment-induced selection. Results: In untreated primary breast tumors, on average 30% (range 1-70%) of apparently clonal mutations from a single region were absent or rare in a second, spatially disparate region (high-frequency regional, or HFR). Intra-tumor heterogeneity was similar post-treatment (HFR 28%, range 10-54%), and was higher in breast tumors than in previously analyzed colon, brain, lung, and esophageal tumors. Simulation studies confirmed that with high heterogeneity as observed in breast tumors, analysis of one pre-treatment and one post-treatment region could not distinguish treatment-induced clonal evolution from pre-existing heterogeneity; however, obtaining at least two post-treatment regions allowed for detection of clonal shifts with treatment. Analysis of multi-region data revealed that clonal replacement occurred with neoadjuvant therapy in two of the five tumors. Candidate causes of therapeutic resistance included amplifications in CCND1, ERBB4, and MYC in one subclone, and functional protein-altering mutations in ERCC2, SMO, and WT1 in another. Mathematical modeling suggested that these putative resistant subclones comprised 0.02-12.5% of the overall pre-treatment cell population, substantially larger than previous estimates of resistant tumor clone size. Conclusions: WES data from multiple regions of untreated and treated primary breast tumors revealed considerable heterogeneity that remained present throughout treatment with chemotherapy and HER2-targeted therapy, even while major clonal sweeps took place in a minority of tumors. Obtaining at least two samples for analysis from breast tumors post-neoadjuvant therapy may reveal the tumor's evolutionary path and, especially as increasing numbers of molecular and immune therapeutic targets are identified, inform new clinical strategies. Citation Format: Caswell-Jin JL, McNamara K, Reiter JG, Sun R, Hu Z, Ma Z, Suarez CJ, Tilk S, Raghavendra A, Forte V, Chin S-F, Bardwell H, Provenzano E, Caldas C, Lang J, West R, Tripathy D, Press MF, Curtis C. Clonal evolution and heterogeneity in breast tumors treated with neoadjuvant HER2-targeted therapy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-06-01.

Background: Serial biopsies (bx) of triple-negative breast cancer (TNBC) in the curative neoadjuvant setting provides critical information on dynamic changes in the tumor in response to neoadjuvant systemic therapy (NAST) and can help inform the development of novel therapeutic strategies. However, neoplastic seeding following image guided breast bx has previously been reported in TNBC, raising concerns that serial bx may worsen clinical outcomes. Thus, we sought to determine if serial bx were associated with poorer clinical outcomes (using rates of pathologic complete response [pCR]) in TNBC pts receiving NAST. Methods: We identified 370 TNBC pts who received NAST at MD Anderson Cancer Center from 2011-2017. 200 pts did not have any research bx done (controls) on the index breast carcinoma and 170 pts had at least one research bx done (cases) on the index breast carcinoma as part of the prospective molecular triaging ARTEMIS trial. Baseline characteristics were compared between cases and controls using the Student t-test, Wilcoxon Rank Sum test or Fisher's exact test as appropriate. Univariable and multivariable logistic regression was used to determine if rates of pCR following NAST were significantly different between cases and controls. Results: Demographic characteristics demonstrate no significant differences (Table). However, cases were more likely to have received an anthracycline (99% vs 96%, p=0.02) and a targeted agent (22% vs 0%, p Conclusion: This is the first study examining the impact of serial bx on clinical outcomes in TNBC pts in the curative neoadjuvant setting. Our data suggest that research bx in this setting do not compromise rates of pCR. Baseline and Treatment CharacteristicsCharacteristicControls (n=200)Cases (n=170)p valueMean age - years (standard deviation [SD])52 (12)53 (12)0.54Ethnicity White – n (%)113 (57)115 (68)0.09Black – n (%)48 (24)29 (17) Other – n (%)39 (20)26 (15) Mean tumor size – cm (SD)3.2 (1.4)3.3 (1.7)0.62T stage – n (%) T134 (17)35 (21)0.96T2145 (73)111 (65) T314 (7)17 (10) T47 (4)7 (4) N stage – n (%) N0101 (51)89 (52)0.83N170 (35)55 (32) N27 (4)6 (4) N322 (11)20 (12) Stage – n (%) I19 (10)21 (12)0.74II140 (70)113 (66) III41 (21)36 (21) Grade – n (%) 19 (5)00.14227 (14)22 (13) 3164 (82)148 (87) Neoadjuvant therapy – n (%) Anthracycline191 (96)169 (99)0.02Taxane199 (100)166 (98)0.18Platinum23 (12)23 (14)0.63Targeted agent037 (22) Citation Format: Yam C, Raghavendra A, Hess KR, Adrada BE, Candelaria RP, Damodaran S, Gilcrease MZ, Helgason T, Hortobagyi GN, Huo L, Layman RM, Lim B, Litton JK, Mittendorf EA, Murthy RK, Piwnica-Worms H, Rauch GM, Santiago L, Symmans F, Thompson AM, Tripathy D, Ueno NT, Valero V, Barcenas CH, Moulder SL, Yang W. Impact of serial biopsies in triple-negative breast cancer patients receiving neoadjuvant systemic therapy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-15-06.

Genomic changes observed across treatment may result from either clonal evolution or geographically disparate sampling of heterogeneous tumors. Here we use computational modeling based on analysis of fifteen primary breast tumors and find that apparent clonal change between two tumor samples can frequently be explained by pre-treatment heterogeneity, such that at least two regions are necessary to detect treatment-induced clonal shifts. To assess for clonal replacement, we devise a summary statistic based on whole-exome sequencing of a pre-treatment biopsy and multi-region sampling of the post-treatment surgical specimen and apply this measure to five breast tumors treated with neoadjuvant HER2-targeted therapy. Two tumors underwent clonal replacement with treatment, and mathematical modeling indicates these two tumors had resistant subclones prior to treatment and rates of resistance-related genomic changes that were substantially larger than previous estimates. Our results provide a needed framework to incorporate primary tumor heterogeneity in investigating the evolution of resistance., When examining the evolution of treatment resistance in breast cancer, perceived genomic changes may be due to clonal evolution or heterogeneous tumors. Here, the authors show that apparent clonal change can in fact be due to pre-treatment heterogeneity, and samples from at least two regions are necessary to detect treatment-induced clonal shifts

e13076 Background: Administration of bone targeted therapy such as zoledronic acid (ZA) or of denosumab (D) decrease the risk of skeletal related events (SRE) such as radiation to the bone, pathological bone fractures, and spinal cord compression in patients with a diagnosis of metastatic breast cancer (MBC) and bone metastasis. As these patients continue to live longer it is unknown what are the impacts from long-term administration of ZA or D among those who live longer than 2 years. Methods: This was a retrospective analysis of patients with MBC and bone metastasis who lived for more than 2 years since diagnosis and received treatment at MD Anderson Cancer Center for MBC in addition to ZA and/or D between 2015 and 2021. Patient demographics, date of diagnosis, tumor characteristics, bone targeted agent treatment plans and SRE were extracted from the institutional database and electronic health records. We defined 3 patterns of receipt of bone targeted therapy: Pattern A: ZA every 3-4 weeks; Pattern B: D every 4-6 weeks; Pattern C; D every 4-6 weeks for a period followed by every 3 months. The association between these patterns and SRE was assessed using Fisher’s exact test. Results: We included 178 patients: Pattern A with 49 patients, Pattern B with 85 patients, and Pattern C with 44 patients. The proportion of patients who suffered a SRE in Patterns A, B, and C were 22.4% (11/49), 20% (17/85), and 21.4% (10/44). There was no statistical difference in the proportion of SRE between these three groups (p = 0.92). Conclusions: We did not observe a difference in the rate of SRE between the three different patterns of bone targeted therapy administration in patients with MBC and bone metastasis. Other treatment patterns will be considered in future analysis.[Table: see text]

1067 Background: The majority of invasive lobular breast cancers (ILC) are hormone receptor (HR)-positive, HER2-negative and are clinically treated similarly to HR+ HER2-negative invasive ductal cancers (IDC). However, ILC differs distinctly from IDC in its clinicopathologic characteristics and molecular alterations. ILC also differs in response to systemic therapy, with studies showing ILC as less sensitive to chemotherapy. It is currently unknown if patients with ILC or mixed ductal/lobular (MDL) histologies derive similar benefits as IDC from endocrine therapy (ET) in combination with cyclin-dependent kinase 4/6 inhibitors (CDK4/6is), mTOR inhibitor everolimus or PI3K inhibitor alpelisib. Methods: We retrospectively searched for patients treated at MD Anderson Cancer Center with a diagnosis of HR+, HER2-negative metastatic breast cancer (MBC) with ET in combination with CDK4/6is, everolimus or alpelisib. Patients were divided into 3 groups based on their histology: ILC, IDC and mixed. We obtained data on demographics, estrogen (ER) and progesterone (PR) receptor status, menopausal status, treatment duration and survival status. The Kaplan-Meier product-limit method was used to compare progression-free survival (PFS) and overall survival (OS) between the three different groups stratified by the treatment received. Results: We identified 2,971 patients (2,432 IDC [82%], 427 ILC [14%], 112 Mixed [4%]) with HR+ HER2-negative MBC treated with ET in combination with CDK4/6is, everolimus and/or alpelisib between 2010 and 2021. Median age was around 50 years in all groups. Around 80% of patients were white, 10% Hispanic and 5% black. Around 55% of patients were post-menopausal, 99% had ER+ and 88% PR+ tumors; 1,895 patients (81% IDC, 15% ILC, 4% mixed) received CDK4/6is, 1,027 (82% IDC, 14% ILC, 4% mixed) received everolimus and 49 (81% IDC, 19% ILC) received alpelisib. PFS and OS were not statistically different between the 3 groups (Table). Conclusions: HR+ HER2-negative MBC patients with IDC, ILC and MDL benefited from ET in combination with CDK4/6is, everolimus or alpelisib similarly with no significant differences in PFS and OS. [Table: see text]

Purpose A subset of patients with intermediate 21-gene signature assay recurrence score may benefit from adjuvant chemoendocrine therapy, but a predictive strategy is needed to identify such patients. The 95-gene signature assay was tested to stratify patients with intermediate RS into high (95GC-H) and low (95GC-L) groups that were associated with invasive recurrence risk.Methods Patients with ER-positive, HER2-negative, node-negative breast cancer and RS 11-25 who underwent definitive surgery and adjuvant endocrine therapy without any cytotoxic agents were included. RNA was extracted from archived formalin-fixed, paraffin-embedded samples, and 95-gene signature was calculated. Results Two hundred six patients had RS of 11-25 (95GC-L, N = 163; 95GC-H, N = 43). In Cox proportional hazards model, 95GC-H was significantly associated with shorter time to recurrence than was 95GC-L (HR 5.94; 95%CI 1.81-19.53; P = 0.005). The correlation between 95-gene signature and 21-gene signature assay scores was not strong (correlation coefficient r = 0.27), which might suggest that 95-gene signature reflects biological characteristics differing from what 21-gene signature shows.Conclusions The 95-gene signature stratifies patients with ER-positive, HER2-negative, node-negative invasive breast cancer and intermediate RS of 11-25 into high and low groups that are associated with recurrence risk of invasive disease. Further retrospective analysis in the prospectively-accrued TAILORx population is warranted to confirm that 95-gene signature can identify patients who would benefit from adjuvant chemoendocrine therapy.

Simple Summary In this survey study, we examined survey responses from 397 women with stage 0 to III unilateral breast cancer and found that partners, physicians, and the media were significant relative to the patient’s own influence in their decision to undergo a CPM. The findings of this study may inform policy by highlighting the need for educational aids, programs, or tools that help women with unilateral breast cancer make informed, evidence-based decisions regarding CPM efficacy. Abstract (1) Background: The relatively high rate of contralateral prophylactic mastectomy (CPM) among women with early stage unilateral breast cancer (BC) has raised concerns. We sought to assess the influence of partners, physicians, and the media on the decision of women with unilateral BC to undergo CPM and identify clinicopathological variables associated with the decision to undergo CPM. (2) Patients and Methods: Women with stage 0 to III unilateral BC who underwent CPM between January 2010 and December 2017. Patients were surveyed regarding factors influencing their self-determined decision to undergo CPM. Partner, physician, and media influence factors were modeled by logistic regressions with adjustments for a family history of breast cancer and pathological stage. (3) Results: 397 (29.6%) patients completed the survey and were included in the study. Partners, physicians, and the media significantly influenced patients’ decision to undergo CPM. The logistic regression models showed that, compared to self-determination alone, overall influence on the CPM decision was significantly higher for physicians (p = 0.0006) and significantly lower for partners and the media (p < 0.0001 for both). Fifty-nine percent of patients’ decisions were influenced by physicians, 28% were influenced by partners, and only 17% were influenced by the media. The model also showed that patients with a family history of BC had significantly higher odds of being influenced by a partner than did those without a family history of BC (p = 0.015). (4) Conclusions: Compared to self-determination, physicians had a greater influence and partners and the media had a lower influence on the decision of women with unilateral BC to undergo CPM. Strong family history was significantly associated with a patient’s decision to undergo CPM.

Background: Smoking negatively affects overall survival after successful breast cancer (BC) treatment. We hypothesized that smoking cessation would improve survival outcomes of BC patients who were smokers at the time of diagnosis. Methods: This was a retrospective analysis of self-identified smokers with BC treated at The University of Texas MD Anderson Cancer Center. Patient demographics, date of diagnosis, tumor stage, tobacco treatment program (TP) participation, and time to death were extracted from our departmental databases and institutional electronic health records. We examined associations between tobacco abstinence status and survival using survival models, with and without interactions, adjusted for personal characteristics and biomarkers of disease. Results: Among all 31,069 BC patients treated at MD Anderson between 2006 and 2017, we identified 2126 smokers (6.8%). From those 2126 self-identified smokers, 665 participated in the TP, reporting a conservative estimate of 31% abstinence (intent-to-treat) 9 months into the program. Patients without reported follow-up abstinence status (including TP and non-TP participants) were handled in the analyses as smokers. Survival analysis controlled for multiple factors, including disease characteristics and participation in the TP, indicated that abstainers were more likely to be alive with no evidence of disease compared to non-abstainers (HR, 0.593; 95% CI, 0.386–0.911; p = 0.017). Conclusion: Our results suggest that quitting smoking is associated with improved survival among BC patients who were smokers at time of diagnosis across all tumor stages. Comprehensive approaches for smoking cessation in patients diagnosed with BC may prolong survival when started as early as the time of diagnosis.

Background As systemic therapy for metastatic breast cancer (BC) improves, the survival benefit from hormonal and targeted therapy urges treatment of brain metastases (BMs) with minimal toxicity and less systemic therapy interruption. Here we assessed clinical outcomes in BC patients who received upfront stereotactic radiosurgery (SRS). Methods We identified 236 patients who received upfront SRS with/without surgery for BMs from metastatic BC from 06/2007 to 05/2018. Twenty-four patients who received SRS for surgical cavity were excluded for analysis. Overall survival (OS) and salvage radiation-free survival (SRFS) were estimated using Kaplan-Meier analysis. Cox proportional hazard regression was used to identify prognostic factors. Results At a median follow-up time of 15.4 months (range, 0.8–119.6), the estimated median OS was 18.5 mo (95% CI, 14.9–21). Factors associated with OS on multivariate analysis (MVA) were molecular subtypes (12.2 months for triple-negative [n=68], 13.3 months for HR+/HER2- [n=66], 36.4 months for HR+/HER2+ [n=46], and 28.1 months for HER2+ [n=32], p=0.002), KPS >80 (p/= 4 [n=50], p=0.36). The 12-month salvage RT rate was 25% for WBRT and 26.4% for SRS. The median SRFS was 7.4 months (95% CI, 6.5‒8.3). Factors associated with SRFS on MVA were subtypes (p=0.002), KPS (p=0.011), and receipt of hormone therapy after diagnosis of BM (p=0.031). Conclusions The median OS for BC patients who developed BM is over 15 months. Molecular subtypes (HER2+ and HR+/HER2+), good KPS, and anti-HER2 or hormone therapy predicted better OS and SRFS. Prospective studies are needed to verify these results and refine the best treatment strategies for these patients.

Background: Treatment options for patients (pts) with leptomeningeal metastasis (LM) are limited, and the prognosis is poor (median overall survival (OS) ~ 4-5 months). Tucatinib is a potent and highly selective HER2-targeted tyrosine kinase inhibitor approved for use in combination with trastuzumab and capecitabine in pts with metastatic HER2+ breast cancer who have received ≥1 prior HER2-based regimen in the metastatic setting, including pts with brain metastases. TBCRC049 (NCT03501979) is an investigator-initiated, phase 2, single-arm study evaluating the safety and efficacy of tucatinib, trastuzumab and capecitabine in HER2+ breast cancer with newly diagnosed LM. We have previously demonstrated therapeutic levels of tucatinib in CSF in pts with HER2+ LM (Stringer-Reasor et al, ASCO 2021). We now report efficacy outcomes of the study. Methods: Eligible pts were adults with HER2+ metastatic breast cancer, Karnofsky performance status (KPS) > 50, and newly diagnosed, untreated LM (defined as positive CSF cytology and/or radiographic evidence of LM, plus clinical signs/symptoms). Pts with treated or concurrent/new brain metastases were allowed. Pts received tucatinib 300 mg orally twice daily starting with cycle 1, day 1 (C1D1); capecitabine 1000 mg/m2 orally twice daily on days 1-14 of a 21-day cycle, starting on C1D1; and trastuzumab loading dose of 8 mg/kg IV on C1D1, and then 6 mg/kg IV once every 21 days, starting with C2D1. The primary endpoint was OS. Planned enrollment was 30 pts; however, due to lack of accrual since the FDA approval of tucatinib (4/2020), the study was closed after 17 patients were enrolled. Results: Baseline disease characteristics at LM diagnosis are shown in Table 1. Eight pts (47%) had abnormal CSF cytology (positive or equivocal). All pts had MRI evidence of LM in the brain, and 14/17 (82%) had brain metastases, of which 11 (65%) had received prior treatment for brain metastases. Median age at study treatment initiation was 53 years. Median number of treatment cycles received was 5 (range: 2-27). Median OS time was 11.9 months (95% CI: 4.1, NR). At data cutoff (6/22/21), 7/17 pts (41%) remained alive and median followup was 17 months(8-26). Median time to CNS progression was 6.9 months (95% CI: 2.8, 13.8). Conclusions: In pts with LMD from HER2+ metastatic breast cancer who were treated with tucatinib, trastuzumab, and capecitabine, the median OS time was nearly 1 year. This is the first prospective evidence of clinical benefit with a systemic regimen for HER2+ LM. Further studies evaluating brain-penetrant oral drugs in this rare pt population are needed. Baseline Disease Characteristics (N=17)Number%Baseline CSF cytologyPositive529%Negative847%Equivocal318%None obtained1*6%Symptoms attributable to LMDYes1588%No212%MRI evidence of LMDBrain only1165%Brain and Spine635%History of brain metastasisYes1482%Prior treatment1165%New/concurrent diagnosis – no prior treatment318%No318%Extra-CNS DiseaseYes1165%No635%*One patient had VP shunt and difficulty sampling fluid; all CSF sent for research PK and non-PK studies Citation Format: Rashmi K Murthy, Barbara O'Brien, Donald A Berry, Akshara Singareeka-Raghavendra, Maria Gule Monroe, Jason Johnson, Jason White, Jennifer Childress, Justin Sanford, Jill Schwartz-Gomez, Michelle Melisko, Aki Morikawa, Sherise Ferguson, John F de Groot, Ian Krop, Vicente Valero, Mothaffar Rimawi, Antonio Wolff, Debu Tripathy, Nancy U Lin, Erica Stringer-Reasor. Safety and efficacy of a tucatinib-trastuzumab-capecitabine regimen for treatment of leptomeningeal metastasis (LM) in HER2-positive breast cancer: Results from TBCRC049, a phase 2 non-randomized study [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD4-02.

BACKGROUND. The use of preoperative magnetic resonance imaging (MRI) for newly diagnosed breast cancer remains controversial. We examined factors associated with detection of occult multicentric, multifocal, and contralateral malignant lesions only seen by MRI. METHODS. We performed a retrospective analysis of consecutive patients undergoing preoperative MRI for breast cancer. Clinicopathologic data were assessed regarding the findings of multifocality, multicentricity, and the presence of contralateral lesions. We analyzed the association of factors with these findings on MRI. RESULTS. Of 857 patients undergoing MRI, 770 patients met inclusion criteria. Mean age was 54.7 years. Biopsy-proven detection rates by MRI for multifocal, multicentric, and contralateral cancers were 6.2% (48 out of 770), 1.9% (15 out of 770) and 3.1% (24 out of 770), respectively. African-American race and heterogeneously or extremely dense mammographic density were associated with multifocal cancers on MRI. Larger lesion size and mammographic density were associated with multicentric cancers. Invasive lobular carcinoma (ILC) and progesterone receptor (PR)-positivity were associated with contralateral cancers. CONCLUSIONS. African-American race, heterogeneously or extremely dense mammographic density, invasive lobular carcinoma, and PR-positivity were associated with additional biopsy-proven cancers based on MRI. These factors should be considered when assessing the clinical utility of preoperative breast MRI.

Background An increasing proportion of human epidermal growth receptor 2 (HER2) positive (HER2+) metastatic breast cancer (MBC) is diagnosed as de novo stage IV disease. We hypothesize that a subset of these patients who achieve no evidence of disease (NED) status after multimodality HER2-targeted treatments may have prolonged progression-free survival (PFS) and overall survival (OS). Materials and Methods Patients with de novo stage IV, HER2+ MBC (n = 483) diagnosed between 1998 and 2015 were identified at two institutions (Yale and MD Anderson Cancer Centers). Clinical variables, treatment details, and survival outcomes were compared between those who achieved NED and those who did not. Results All patients received trastuzumab, and 20% also received pertuzumab as first-line therapy. The median OS was 5.5 years (95% confidence interval [Cl]: 4.8–6.2). Sixty-three patients (13.0%) achieved NED; their PFS and OS rates were 100% and 98% (95% CI: 94.6%–100%), respectively, at 5 years and remained the same at 10 years. For patients with no NED (n = 420), the PFS and OS rates were 12% (95% CI: 4.5%–30.4%) and 45% (95% CI: 38.4%–52.0%) at 5 years and 0% and 4% (95% CI, 1.3%–13.2%) at 10 years, respectively. NED patients more frequently had solitary metastasis (79% vs. 51%, p = .005) and surgery to resect cancer (59% vs. 22%, p ≤ .001). In multivariate analysis, NED status (hazard ratio [HR]: 0.014, p = .0002) and estrogen receptor positive status (HR: 0.72; p = .04) were associated with prolonged OS. Conclusion Among patients with de novo stage IV, HER2+ MBC, those who achieve NED status have a very high PFS and OS. Further randomized studies are required to fully understand the impact of systemic or locoregional therapy on achieving these excellent long-term outcomes. Implications for Practice In this retrospective review at two institutions, it was demonstrated that 13% of patients with de novo stage IV, human epidermal growth receptor 2 positive metastatic breast cancer achieved no evidence of disease (NED) status with trastuzumab-based therapy plus/minus local therapies, and these patients had a very high progression-free survival (100%) and overall survival (98%) at both the 5- and 10-year time points. Achieving NED status may be an important therapeutic goal. However, further randomized studies are required to fully understand the impact of systemic or locoregional therapy on achieving these excellent long-term outcomes.

BACKGROUND: Inherited BRCA gene mutations (pathogenic variants) cause 10% of breast cancers. BRCA pathogenic variants predispose carriers to triple-negative breast cancer (TNBC); around 30% of patients with TNBC carry BRCA pathogenic variants. The 2018 NCCN Guidelines for Genetic/Familial High-Risk Assessment: Breast and Ovarian recommend genetic counseling referrals for patients with TNBC diagnosed at age ≤60 years. This study sought to describe genetic counseling referral patterns among long-term TNBC survivors at The University of Texas MD Anderson Cancer Center. METHODS: This single-institution retrospective analysis of female long-term (disease-free for ≥5 years) TNBC survivors sought to determine the rate of genetic counseling referral among patients diagnosed at age ≤60 years between 1992 and 2008. Patients who underwent treatment and surveillance visits at our institution and were followed until 2017 were included. We collected BRCA pathogenic variant status among tested patients. Descriptive statistical methods and a univariate analysis were used to identify patient characteristics associated with genetic counseling referral. RESULTS: We identified 646 female long-term TNBC survivors with a median age at diagnosis of 47 years. Of these, 245 (38%) received a recommendation for a genetic counseling referral. Among those referred, 156 (64%) underwent genetic testing, and 35% of those tested had BRCA pathogenic variants. Interestingly, among those referred, 20% declined genetic testing. The rate of genetic referrals improved over time, from 25% among TNBC survivors whose last surveillance visit was between 2011 and 2013 to 100% among those whose last surveillance visit was between 2014 or later. Younger age and premenopausal status at diagnosis and a family history of breast or ovarian cancer were associated with an increased rate of referral for genetic counseling. CONCLUSIONS: Among long-term TNBC survivors, the rate of referral to genetic counseling increased over time, and among those tested, 35% carried a BRCA pathogenic variant. Survivorship care provides an excellent opportunity to refer eligible patients for genetic counseling.

Although traditional assessment with clinical examination, mammogram, and ultrasound is generally accepted for detection and staging of breast cancer, MR imaging is commonly used to detect occult cancers in the breast and regional nodes in the early stage and to determine the extent of disease in patients with metastatic disease. Several studies have shown a variety of uses for MR imaging in the staging of breast cancer and assessment of treatment response in the neoadjuvant (preoperative) setting. This article reviews the impact of MR imaging in different settings on medical oncology decision-making in patients with breast cancer.

Introduction: The 21-gene recurrence score (RS) assay categorizes hormone receptor positive, node negative breast cancers (BC) into 3 risk groups for recurrence. We previously showed that the AAMC Model, using only standard pathology data, accurately does the same. This study compares the recurrence rate of the AAMC Model's risk groups to RS-based risk groups. A 2-step approach then is used, in which the AAMC model is applied first, and the RS assay is used only for AAMC intermediate risk cases. AAMC intermediate cases were reclassified by RS into low or high risk groups. Methods: From a prospective registry of newly diagnosed BC, we selected invasive, hormone receptor positive, HER2 negative, lymph node negative cases from 2005 to 2015 tested with RS assay. Five-year Kaplan-Meier distant recurrence rates were calculated for each risk category. Results: 1268 cases were included. Five-year recurrence rates were similar between the AAMC Model's low risk group and RS30 high risk group. Applying the RS assay to the 715 cases in the AAMC Model's intermediate group resulted in re-classifying 417 (58%) as low risk and 41 (6%) as high risk. Using RS alone, 33% of cases were intermediate risk (n=424), whereas in the 2-step approach 20% were intermediate risk (n=257). For the 2-step approach, the 5-year distant recurrence rate was 3.3% for the low risk group (n=740) and 24.4% for the high risk group (n=271). Conclusions: Five-year recurrence rates in the AAMC Model's low and high risk groups were similar to those in RS-based risk groups. The 2-step approach, with RS used only for AAMC intermediate cases, resulted in larger low and high risk groups with equivalent prognostic accuracy, compared to use of the RS assay alone. The 2-step approach reliably identifies a large number of patients unlikely to benefit from 21 gene assay and provides substantial cost savings. Kaplan-Meier Calculated 5-year Distant Recurrences Rates for 4 Models: 1268 Patients Oncotype DXTAILORxAAMC Model2 Step Model with OncotypeDX for AAMC IntermediatesLow RiskRS < 18 (n=703)RS < 11 (n=250)Grade 1 and PR ≥ 1% (n=323)AAMC Low or AAMC intermediate/RS 30 (n=141)RS > 25 (n=231)Grade 3 or ER < 20% (n=230)AAMC High or AAMC intermediate/RS > 30 (n=271) 23.0% (95% CI 14.7 – 31.3%, nf=27)22.9% (95% CI 15.9 – 29.9%, nf=39)22.8% (95% CI 16.1 – 29.5%, nf=41)24.4% (95% CI 18.0 – 30.7%, nf=51)RS= Recurrence Score, nf=number of recurrences, CI = confidence interval. Citation Format: Mylander C, Rosman M, Gage M, Fujii T, Le Du F, Raghavendra A, Sinha A, Espinosa Fernandez JR, James A, Ueno N, Tafra L, Jackson R. Getting the most out of the 21-gene recurrence score assay: Increasing actionable results with a combined pathologic-genomic model [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-09-05.

Background Triple-negative breast cancer (TNBC) is an aggressive subtype with high propensity of developing brain metastases (BM). Clinical outcomes and prognostic factors after stereotactic radiosurgery (SRS) for BM were not well defined. Methods We identified 57 consecutive TNBC patients (pts) treated with single fraction SRS for BM during 05/2008–04/2018. Overall survival (OS) from BM diagnosis and freedom from BM progression (FFBMP) after initial SRS were evaluated. BM progression was defined as local and/or distant brain failure (LBF, DBF) after SRS. Kaplan-Meier analyses and Cox proportional hazard regression were used to estimate survival outcomes and identify prognostic factors. Results The median time to BM development from TNBC diagnosis was 23.7 months (mo) (range 0.7‒271.1). Median OS was 13.1 mo (95%CI 8.0‒19.5). On univariate analysis, Karnofsky performance score (KPS) >70 (p=0.03), number of BMs Conclusions TNBC pts with BM treated with SRS had an OS of 13.1 mo and FFBMP of 7.4 mo. Good KPS was an independent prognostic factor for OS. Further studies with more pts or conducted prospectively are needed to better understand and to improve treatment outcomes in this pt population.

Deregulation of the cell cycle machinery is a hallmark of cancer. While CDK4/6 inhibitors are FDA approved (palbociclib) for treating advanced estrogen receptor-positive breast cancer, two major clinical challenges remain: (i) adverse events leading to therapy discontinuation and (ii) lack of reliable biomarkers. Here we report that breast cancer cells activate autophagy in response to palbociclib, and that the combination of autophagy and CDK4/6 inhibitors induces irreversible growth inhibition and senescence in vitro, and diminishes growth of cell line and patient-derived xenograft tumours in vivo. Furthermore, intact G1/S transition (Rb-positive and low-molecular-weight isoform of cyclin E (cytoplasmic)-negative) is a reliable prognostic biomarker in ER positive breast cancer patients, and predictive of preclinical sensitivity to this drug combination. Inhibition of CDK4/6 and autophagy is also synergistic in other solid cancers with an intact G1/S checkpoint, providing a novel and promising biomarker-driven combination therapeutic strategy to treat breast and other solid tumours., CDK4/6-Cyclin D pathway is often deregulated in cancer; therefore specific inhibitors have been developed. Here the authors show that treatment with CDK4/6 inhibitors activate autophagy in breast cancer cells; thus, combination of such inhibitors with autophagy inhibitors results in a synergistic effect on tumour growth.

BACKGROUND Invasive disease-free survival (IDFS) rates are excellent in patients with breast cancer (BC) with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-), axillary lymph node-negative (LN-) tumors with a 21-gene expression assay recurrence score (RS) of 0 to 10. However, to the authors' knowledge, the outcomes among patients with an RS of 11 to 25 who are treated with endocrine therapy alone are unknown. METHODS In this retrospective single-institution study, the authors described the characteristics of patients with HR+, HER2-, LN- BC who underwent a 21-gene expression assay. In addition, among those individuals diagnosed between 2005 and 2011, we measured IDFS, recurrence-free survival, distant recurrence-free survival, and overall survival rates, focusing on patients with an RS of 11 to 25 by receipt of chemotherapy. The Kaplan-Meier method was used to estimate survival rates and multivariable Cox proportional hazards models were used to calculate hazard ratios and 95% confidence intervals (95% CIs). RESULTS Among 1424 patients, the RS distribution was 0 to 10 in 297 patients (21%), 11 to 25 in 894 patients (63%), and >25 in 233 patients (16%); of these, 1.7%, 15%, and 73.4% of patients, respectively, received chemotherapy. With a median follow-up of 58 months, those patients with an RS of 11 to 25 had an IDFS rate at 5 years of 92.6% (95% CI, 89.6%-94.7%), which was comparable between those who received chemotherapy and those who did not. The hazard ratios of the effect of chemotherapy were 1.64 for IDFS (95% CI, 0.73-3.71), 1.46 for recurrence-free survival (95% CI, 0.41-5.23), 1.25 for distant recurrence-free survival (95% CI, 0.32-4.92), and 2.19 for overall survival (95% CI, 0.44-11.0). CONCLUSIONS The results of the current study demonstrate similar outcomes with or without chemotherapy in patients with HR+, HER2-, LN- BC who have an RS of 11 to 25, but a benefit from chemotherapy in this group cannot be ruled out. Cancer 2017;123:2422–31. © 2017 American Cancer Society.

Background: The current breast cancer staging system, based on anatomy, does not always reflect the variable clinical course outcomes seen in the clinic. Other important and known determinants of prognosis and survival in breast cancer are age, grade, and receptor subtypes. In this analysis, we sought to demonstrate that these additional factors were important determinants of breast cancer specific and overall survival with an intention to propose a new staging classification. Methods: Through a prospectively maintained electronic database at the University of Texas MD Anderson Cancer Center, we identified patients with newly diagnosed invasive breast cancer, stage I-IV, who received surgery as an initial treatment from 1997 to 2014. Data points for the earliest invasive breast cancer event were recorded: age, pathologic stage (7th edition AJCC), grade, ER status, PR status, HER2-neu status, adjuvant treatment history, and outcomes (breast cancer-specific survival [BCSS] and overall survival [OS]). Cox proportional hazards model was used for the statistical analysis. Results: Of 22,131 patients, 99% were women in the following age groups (median age at surgery, 53 years [range, 16-98 years]): age < 40 (13%), 40-69 (76%), >70 (11%). Pathologic stages were: I: 50%, II: 39%, III: 9% and IV: 2%; 768 (3.5%) patients had bilateral breast cancer. Biological subtypes were as follows: Triple-negative (TN): 6%, Hormone receptor-positive/HER2-negative (HR+/HER2-): 70%, HER2-positive (HER2+): 24% (HR+, 9%; HR- 15%). Median follow-up was 7.9 years (95% CI, 7.8-8.0). In multivariate Cox regression modeling, age, grade, and clinical biomarker-based subtypes were significantly associated with breast cancer specific survival (BCSS). Table 1. Breast cancer specific-survival: Multivariate modelCovariateLevelHR95% CI (p value)Overall p valueAge at DiagnosisLess than 401.521.37-1.68 ( Conclusion: More individualized prediction of outcomes for breast cancer is possible by considering clinical and biologic characteristics in addition to anatomic stage. We intend to integrate pathologic stage, age, and biologic factors into a novel prognostic model to propose a new staging classification for breast cancer. Citation Format: Murthy RK, Song J, Raghavendra AS, Li Y, Hsu L, Barcenas CH, Tripathy D, Berry D, Hortobagyi GN. Proposal for a new breast cancer staging classification: Incorporating clinical and biologic factors [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-09-35.

BACKGROUND Women with dense mammographic breast density (BD) have a 2-fold increased risk of developing primary breast cancer (BC). The authors hypothesized that dense mammographic BD also is associated with an increased risk of developing contralateral breast cancer (CBC). METHODS Among female patients treated at The University of Texas MD Anderson Cancer Center for sporadic, AJCC stage I to stage III BC between January 1997 and December 2012, the authors identified patients who had developed metachronous CBC (cases) and selected 1:2 matched controls who did not develop CBC using incidence density sampling, matched on attainted age, year of diagnosis, and hormone receptor status of the first BC. Mammographic BD, assessed at the time of first BC diagnosis, was categorized as “nondense” (American College of Radiology breast categories of fatty or scattered density) or “dense” (American College of Radiology categories of heterogeneously dense or extremely dense). Multivariable conditional logistic regression models were used for statistical analysis. RESULTS A total of 229 cases and 451 controls were evaluated. Among the cases, approximately 39.3% had nondense breast tissue and 60.7% had dense breast tissue. Among controls, approximately 48.3% had nondense breast tissue and 51.7% had dense breast tissue. After adjustment for potential prognostic risk factors for BC, the odds of developing CBC were found to be significantly higher for patients with dense breasts (odds ratio, 1.80; 95% confidence interval, 1.22-2.64 [P

Background: Pathologic complete response (pCR) is associated with improved survival outcomes in patients with HER2-positive primary breast cancer. We developed a nomogram to predict the probability of pCR rates by using oestrogen receptor (ER) expression, progesterone receptor (PR) expression and HER2/CEP17 ratio as continuous variables. Methods: We retrospectively reviewed patients with stages I–III HER2-positive invasive breast cancer who had definitive surgery in 1999–2015 and received neoadjuvant systemic therapy (NST). Multivariate logistic regression models were applied to assess the effect of variables on pCR. A nomogram was built to estimate the probability of pCR. The discriminative ability was estimated by the concordance index (C-index). The accuracy was assessed graphically with a calibration curve. Results: A total of 793 patients were included in the analysis. Low ER expression (P

The original version of this Article omitted from the Author Contributions statement that ‘R.S. and J.G.R contributed equally to this work.’ This has been corrected in both the PDF and HTML versions of the Article.

We developed prognostic models for breast cancer-specific survival (BCSS) that consider anatomic stage and other important determinants of prognosis and survival in breast cancer, such as age, grade, and receptor-based subtypes with the intention to demonstrate that these factors, conditional on stage, improve prediction of BCSS. A total of 20,928 patients with stage I–III invasive primary breast cancer treated at The University of Texas MD Anderson Cancer Center between 1990 and 2016, who received surgery as an initial treatment were identified to generate prognostic models by Fine-Gray competing risk regression model. Model predictive accuracy was assessed using Harrell’s C-index. The Aalen–Johansen estimator and a selected Fine–Gray model were used to estimate the 5-year and 10-year BCSS probabilities. The performance of the selected model was evaluated by assessing discrimination and prediction calibration in an external validation dataset of 29,727 patients from the National Comprehensive Cancer Network (NCCN). The inclusion of age, grade, and receptor-based subtype in addition to stage significantly improved the model predictive accuracy (C-index: 0.774 (95% CI 0.755–0.794) vs. 0.692 for stage alone, p

1067 Background: Endocrine therapy with a CDK4/6 inhibitor is standard of care for patients (pts) with estrogen-receptor-positive (ER+), HER2-negative MBC, yet resistance ultimately develops. We have shown that low doses of palbociclib activates autophagy, which reverses initial G1 cell cycle arrest. High concentrations of palbociclib induce senescence, but these are off target effects of the drug. The autophagy inhibitor hydroxychloroquine (HCQ) induces senescence at a lower (i.e. on-target) continuous dosing of palbociclib, in in vitro and in vivo models. This strategy is being tested in a phase I/II trial (NCT03774472). Results from the phase I portion are reported here. Methods: The phase I part of this study uses a dose escalation 3+3 design testing HCQ, 400, 600 and 800 mg daily (6 pts at 800 mg) with continuously dosed palbociclib at 75 mg and letrozole 2.5 mg daily. Dose limiting toxicity (DLT) includes any study drug-related grade ≥ 3 nonhematological (lab) toxicity. Responding pts may continue on therapy beyond 8 weeks for up to 52 weeks. Primary objective is to determine safety, tolerability and the recommended phase 2 dose (RP2D) of HCQ. Secondary objectives are overall tumor response and time to progression. Eligible pts are ≥18 years of age, postmenopausal (ovarian suppression allowed) with ER+/HER2-negative MBC, ECOG performance status score of ≤1 and with adequate renal, hepatic, and hematologic function. Response is assessed per RECIST v1.1. Results: Between 9/24/18 and 12/15/20, 14 pts were evaluable for safety. Median age was 41 with Asian (1, 7.1%), Black (2, 14.3%) White (11, 78.6%) patients enrolled. No DLTs were observed. One pt progressed during the DLT period and 2 withdrew consent (one during the DLT period); two pts were replaced for DLT assessment. Reasons for coming off study were grade 3 skin toxicity (1), per protocol at 8 weeks (non-measurable or pt/physician preference, 9), and (2) full duration treatment at 50 and 52 weeks. Adverse events (AEs) of grade ≥3 were hematologic (29), metabolism/nutrition (2), musculoskeletal/ connective tissue (1), and skin/subcutaneous tissue (3), with no serious AEs reported. The percent of palbociclib doses held per pt due to neutrophil level ranged from 0-37.5% with no apparent relation to HCQ dose. Best response was partial (2) stable (11); and progression (1). For measurable disease, tumor decreases of 11%, 12%, 21%, 26%, 30%, 55% and increase in 1 pt by 55% were seen. Conclusions: This phase I study showed acceptable safety and no HCQ dose-toxicity relationship. The RP2D of HCQ is 800 mg/day with continuous dosing palbociclib at 75 mg/day and letrozole at 2.5 mg/day. The phase 2 trial will proceed in the neoadjuvant setting, with Ki67 proliferative index response as the primary endpoint. Clinical trial information: NCT03774472 .