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PURPOSE Cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) with endocrine therapy (ET) improves progression-free survival (PFS) and overall survival (OS) in hormone receptor–positive (HR+), human epidermal growth factor receptor 2–negative (HER2–) metastatic breast cancer (MBC). Although preclinical and clinical data demonstrate a benefit in changing ET and continuing a CDK4/6i at progression, no randomized prospective trials have evaluated this approach. METHODS In this investigator-initiated, phase II, double-blind placebo-controlled trial in patients with HR+/HER2– MBC whose cancer progressed during ET and CDK4/6i, participants switched ET (fulvestrant or exemestane) from ET used pre-random assignment and randomly assigned 1:1 to the CDK4/6i ribociclib versus placebo. PFS was the primary end point, defined as time from random assignment to disease progression or death. Assuming a median PFS of 3.8 months with placebo, we had 80% power to detect a hazard ratio (HR) of 0.58 (corresponding to a median PFS of at least 6.5 months with ribociclib) with 120 patients randomly assigned using a one-sided log-rank test and significance level set at 2.5%. RESULTS Of the 119 randomly assigned participants, 103 (86.5%) previously received palbociclib and 14 participants received ribociclib (11.7%). There was a statistically significant PFS improvement for patients randomly assigned to switched ET plus ribociclib (median, 5.29 months; 95% CI, 3.02 to 8.12 months) versus switched ET plus placebo (median, 2.76 months; 95% CI, 2.66 to 3.25 months) HR, 0.57 (95% CI, 0.39 to 0.85); P = .006. At 6 and 12 months, the PFS rate was 41.2% and 24.6% with ribociclib, respectively, compared with 23.9% and 7.4% with placebo. CONCLUSION In this randomized trial, there was a significant PFS benefit for patients with HR+/HER2– MBC who switched ET and received ribociclib compared with placebo after previous CDK4/6i and different ET.

1030 Background: Combining a CDK4/6 inhibitor (CDK4/6i) with endocrine therapy (ET) in advanced, hormone receptor (HR)-positive, HER2-negative breast cancer (BC) doubles median progression-free survival, but eventually drug resistance and disease progression occur. For most patients, the mechanism of resistance is unknown. Exosomes are membrane-bound extracellular vesicles that contain lipids, proteins, and nucleic acids, and are released from tumors as a form of intercellular communication. Exosomes can be recovered from plasma, and analysis of their cargo provides a dynamic read-out of biological pathways that are activated in cancer cells. Proteomic analysis of plasma exosomes may provide insight into mechanisms of resistance that emerge during treatment with CDK4/6i-ET. Methods: The Big Ten Cancer Research Consortium conducted a single arm, phase II trial of palbociclib plus tamoxifen as first line therapy for advanced, HR+/HER2- BC (NCT02668666). Whole blood was collected in Streck tubes from study participants (n = 49) at baseline, at disease progression, and at time points during study treatment. Plasma was separated and stored at -80C within 48 hours of collection. Exosomes were isolated from thawed plasma using commercially available kits and ultracentrifugation. Exosome extraction and purification was optimized for protein recovery. Purified exosomes were processed for proteomic analysis and labeled with TMT10 (tandem mass tag 10plex) and quantified with the QExactive HF mass spectrometer. Ultrasensitive mass spectrometry provided deep proteomic coverage of exosomal proteins and detected various post-translational modifications (PTM). Data were analyzed with a pipeline developed in our lab using an improved SEQUEST/ProLuCID database search engine and Percolator data filtering toolchain. Exosome protein expression was determined at baseline, at best response and at the time of progression. Results: With our ultrasensitive proteomic method, we detected more than 500 exosome proteins from as little as 100 ng of purified exosomes. A significant enrichment of exosome specific markers was observed when comparing patient samples with healthy donor samples. Enrichment of surface glycoproteins (e.g. CD44) was seen in BC patient samples, as in previous reports. Ultrasensitive proteomics also detected PTM including phosphorylation, methylation, oxidation, deamidation, and glycosylation. Differential proteomic and PTM profiles comparing samples collected from responding patients at baseline vs. at progression will be presented. Conclusions: Our innovative method provided an unparalleled portrait of the proteomic landscape of plasma exosomes during treatment with CDK4/6i-ET. This powerful approach may provide novel insights into mechanisms of resistance that emerge during treatment. This study was funded by Pfizer. Clinical trial information: NCT02668666 .

1056 Background: Palbociclib is a CDK4/6 inhibitor used to treat metastatic hormone receptor-positive (HR+) breast cancer (MBC) in combination with endocrine therapy. Tamoxifen is an effective treatment for HR+ MBC, with different toxicity profile compared with aromatase inhibitors (AI) and fulvestrant. Preclinical data demonstrated synergy for the combination of tamoxifen and palbociclib, being effective in a model of acquired tamoxifen resistance. Methods: We conducted an open-label, single-arm, multicenter phase II trial of palbociclib in combination with tamoxifen in patients with HR+/HER2 - advanced BC, with no prior therapy for MBC. Ovarian suppression was recommended for pre-menopausal women, but not required. Primary objective was progression free survival. Secondary objectives: objective response rate (CR or PR) based on RECIST 1.1 or MDA Criteria (for patients with bone only disease); safety and tolerability (using CTCAE v4); clinical benefit rate (CR, PR or SD lasting min 24 weeks); 2-year overall survival. Correlative objectives: proteomic analysis of plasma exosomes to identify mechanisms of primary and secondary resistance to tamoxifen/palbociclib. Results: Between 6/30/2016 and 7/02/2019, we enrolled 49 patients (47 evaluable): 23 pts with de-novo metastatic disease and 24 pts with recurrent BC (12 pts were on adjuvant treatment with AI at time of recurrence and 12 pts on surveillance). As of 1/5/21 data cut-off, 7 pts were still on treatment. Median follow-up time was 24 months (range 8-42). Median age was 60 (range 39-82). The median PFS was 14.6 months with 95% CI (7-41) for pts with de-novo MBC and 6 months (2-12) for pts with recurrent BC. The ORR was 30% overall, 39% for pts with de novo MBC, 21% for pts with recurrent BC. CBR was 64% overall, 78% for pts with de novo MBC and 50% for pts with recurrent BC. CBR was 65% for white pts and 55% for African American pts. Best response per RECIST1.1: 14 pts (34%) had PR, 18 pts (44%) had SD, 9 pts (22%) had PD. All 6 pts with bone only disease had SD. The most common drug related grade ≥ 3 AE was neutropenia (51%), transient and manageable by dose modifications, no cases of febrile neutropenia. Four patients developed thromboembolic events (1 grade 2, 2 grade 3, 1 grade 4). One patient died while on treatment from PD. Conclusions: The combination of palbociclib and tamoxifen showed tolerable, expected safety profile. This may be an alternative approach for selected patients in first line treatment of HR+ MBC, especially those who are intolerant to AI, although this small study indicates a lower PFS. Clinical trial information: 02668666 .[Table: see text]

e12621 Background: HR and HER2 status is critical for determining initial management of BC. Current guidelines define estrogen receptor (ER) and progesterone receptor (PR)+ as ≥1%. Previous reports of small cohorts with low HR+/HER2- disease showed similar rates of pathologic complete response (pCR) following neoadjuvant chemotherapy (NAC) as triple negative BC (TNBC). This study aims to further characterize this group of patients (pts), focusing on modern management and breast/axillary pCR rates following NAC. Methods: Pts with newly diagnosed stage I-III, HR+/HER2- BC from 1/1/2009–4/1/2019 were found using the University of Wisconsin Hospital and Clinics Cancer Registry. Medical records were reviewed for demographics, tumor characteristics with quantification level of ER and PR ( < 33%), treatments including NAC and adjuvant chemotherapy (chemo), endocrine therapy, surgery and radiation, and follow-up clinical data. Results: Data reviewed from 2,905 pts: 2,604 (89.6%) were HR+/HER2-, 282 (9.7%) were ER+/PR-, and 19 (0.7%) were ER-/ PR+. A total of 64 pts [median age 54 (22-87), 100% female] met inclusion criteria. At diagnosis, 23 (36%) were anatomic stage 1, 30 (47%) stage II, and 11 (17%) stage III; 18 (28%) had biopsy (bx) proven nodal disease. 57 (89%) had invasive ductal carcinoma; 9 (14%) were ER+/PR+, 43 (67%) ER+/PR-, and 12 (19%) ER-/ PR+. The majority [51 (80%)] received chemo, ~ half with NAC 30 (48%), 1 pt chemo plan was unknown. NAC regimens included an anthracycline (A) and taxane (T) [26 (41%)], a sole A regimen [1 (1%)], and an A+T and platinum regimen [3 (5%)]. 4 pts received capecitabine after NAC. 50 (78%) pts had a sentinel lymph node bx, but 13 (20%) had an axillary node dissection (ALND). 10 (16%) pts did not receive any endocrine therapy, 28 (44%) got tamoxifen, 22 (34%) an aromatase inhibitor, and 4 (6%) unknown. Of 28 pts who had NAC followed by breast and axillary surgery, 12 (43%) had pCR (ypT0/Tis/ypN0). Of the 12 pts who had bx proven nodal disease at diagnosis and NAC, 7 (64%) pts had pCR at the axilla. One pt had progressive disease on NAC, 1 had local recurrence and 8 (13%) pts had distant recurrence. Median time to recurrence was 13.6 (5.6 – 48.7) months. Only 2 pts with pCR had distant recurrence. Conclusions: BC that are HER2- and weakly HR+ treated with NAC demonstrated an axillary and overall pCR rate more similar to TNBC than breast cancers with strong HR+. Neoadjuvant approaches may reduce need for ALND and pCR may provide important prognostic information. Clinical trials should be developed to focus on this unique patient cohort.

3127 Background: Immune checkpoint inhibitors (ICIs) represent a major advance for treating solid tumors. However, only a minority of patients (pts) benefit from these therapies and markers that predict response have been elusive. Versican (VCAN) is an immunosuppressive proteoglycan in the tumor microenvironment (TME), which releases an immunostimulatory N-terminal fragment versikine (Vkine) when cleaved by ADAMTS proteases. We have demonstrated in colorectal cancers (CRC) that a low VCAN/high Vkine (VCAN proteolytic predominant [VPP]) phenotype correlates with increased tumor-infiltrating CD8+ T lymphocytes (TILs). Here we examine the accumulation of VCAN as a marker of immune exclusion and its proteolysis as a marker of an immune-permissive TME. Methods: Immunohistochemistry for VCAN, Vkine and CD8+ was performed on samples from 1662 pts across breast (BC), CRC, endometrial cancer, pancreatic adenocarcinoma (PDAC), esophageal cancers and neuroendocrine tumors (NETs), across stages of disease (I-IV) and with diverse prior treatments. Stromal intensities of VCAN and Vkine staining quantified in collaboration with blinded surgical pathologists using a 0-3+ scale. 0/1+ were considered “low” for both VCAN and Vkine, whereas 2/3+ were considered “high”. The number of CD8+ TILs were counted using 400x magnification, the equivalent of a high power field (hpf). Results: Across the entire cohort VCAN phenotypes were diverse (VCAN high/Vkine low, 21%; VCAN high/Vkine high, 23%; VCAN low/Vkine low, 29%; VCAN low/Vkine high (VPP), 27%). Consistent with VCAN accumulation as a marker of T cell exclusion, VCAN low cancers had increased TILs compared to VCAN high (4.8 vs 18.3 TILs/hpf, p < 0.001). Low VCAN was identified in 85% esophageal, 79% NET (including small cell lung cancer [SCLC]) 72% endometrial, 47% MSI-H CRCs, 28% triple-negative BC and only 22% MSS CRC, 18% PDAC, 17% ER+ BCs. The VPP subgroup had the highest TILs per hpf across tumors. VPP was identified in 47% of esophageal, 45% endometrial, 41% NETs (including SCLC), 24% MSI-H CRCs, and only 9% MSS CRC, 7% ER+ BCs, 3% triple-negative BCs, and 0% of PDAC (n = 131 PDAC pts). Conclusions: VCAN accumulation correlates with T lymphocyte exclusion, while VCAN proteolysis predicts an immune permissive phenotype. VCAN accumulation and proteolysis are now incorporated into ICI clinical trials as a potential marker of response. Future studies will clarify the role of these biomarkers in predicting benefits of immuno-oncology treatment strategies.

505 Background: Ribociclib (R) + letrozole (L) is superior to L in metastatic breast cancer (BC). Preoperative endocrine prognostic index (PEPI) score 0 after neoadjuvant endocrine therapy (NET) is associated with low risk of relapse without chemotherapy in ER+ BC. On-therapy change in Ki-67 predicts adjuvant recurrence. FELINE is a biomarker-based multicenter randomized trial comparing changes in Ki-67 and PEPI between L+ Placebo (P) & L+R. Methods: Postmenopausal women with >2 cm or node+ ER+ HER2- BC were randomized 1:1:1 between L+P, L+R 400 mg continuous dose (Rc) and L+R 600 mg, 3 weeks on/1 week off - intermittent dose (Ri). Treatment was continued for six 28-day cycles. Core biopsies, blood samples were obtained at baseline, Day 14 cycle 1 (D14C1), and surgery. Clinical measurement, mammogram and US were obtained at baseline, surgery; MRI at baseline, week 8. Primary endpoint was rate of PEPI score 0 between L+P and L+R (i+c combined). Other endpoints were change in centrally performed Ki-67, complete cell cycle arrest (CCCA): Ki-67 3 AEs were observed in 4 (10%) patients in L+P, 23 (56%) in L+Ri, 19 (46%) in L+Rc arms. Conclusions: Addition of R to L as NET did not result in more women with a PEPI score of 0. At D14C1 twice as many women on L+R had CCCA compared to L+P (92% vs 52%). However, significantly more women on L+R had increased proliferation between D14C1 and surgery , resulting in similar CCCA at surgery. Correlative studies are being performed to determine mechanisms of on-therapy acquired resistance to ribociclib. Continuous and intermittent doses of R have similar efficacy, toxicity. Clinical trial information: NCT02712723 . [Table: see text]

e14640 Background: Poly(ADP-ribose) polymerase (PARP) enzymes are involved in DNA repair and activated by DNA strand breaks. DNA damage from carboplatin is associated with activation of PARP. Preclinical data indicate that PARP inhibition and trapping potentiates the anti-tumor effect of platinum chemotherapy. Talazoparib (T) is an oral, selective PARP inhibitor. This phase I study combines T with carboplatin (C) and paclitaxel (P). Methods: Two dosing schedules are being investigated. C is administered on day 1 and P on days 1, 8, and 15 of a 21-day cycle. T (100-1000mcg) is dosed once daily for days 1-7 (schedule A) or days 1-3 (schedule B). Dose escalation is by 3+3 design. Patients (pts) must have tumor type that is expected to respond to C + P or have BRCA germline or somatic mutation and adequate organ function. After 4-6 cycles of combination therapy, pts may continue the combination, change to C and intermittent T without P or change to T alone. Each schedule will have a 6 pt dose expansion at the MTD. The dose level (DL) 1 for schedule B is the previously reported MTD from schedule A (T 250mcg with C AUC 6 + P 80mg/m2). Results: Schedule B results are reported: 15 pts (median age 56 yrs [range 43-76]) have been enrolled. Primary malignancies include colorectal (4), pancreas (4), prostate (2), urothelial (2), and other (3). Dose was initiated at Schedule A MTD. DL2 (T 350mcg with C AUC 6 + P 80mg/m2) exceeded the MTD with 2 of 6 pts experiencing hematologic dose limiting toxicities (DLTs). DL1 is the confirmed schedule B MTD. Dose expansion to 6 pts is ongoing. Of the 11 pts with measurable disease, 3 (27%) had PR and 5 (45%) had SD. Pts were on study a median of 10 weeks (range 5-36+). Most common grade 3/4 AEs include leukopenia (53%), neutropenia (47%), and anemia (47%). One grade 5 AE of intracranial hemorrhage occurred, possibly related to therapy in the setting of grade 3 thrombocytopenia and concern for CNS disease. Conclusions: The schedule B MTD and RP2D is T 250 mcg with C AUC 6 and P 80mg/m2. Data from the full dose expansion will be presented. This combination was tolerated with prolonged responses seen at lower dose T in combination with C+P. Clinical trial information: NCT02317874.

314 Background: Poly(ADP-ribose) polymerases (PARP) are activated by DNA strand breaks and important for DNA repair in response to platinum-based chemotherapy. PARP inhibition with Vel might enhance anti-tumor effects of Cap with Ox. This phase I study (NCI 8604) examines the tolerability, safety and preliminary efficacy of the combination of Vel with Cap and Ox. Methods: This is a phase I dose escalation protocol testing escalating doses of Vel with Cap and Ox every 28 days (Table 1). Pts were treated in cohorts of 3-6 pts until cycle 1 DLTs were defined. Key eligibility criteria included age ≥ 18 with histologically confirmed malignancy meeting at least one of the following: documented BRCA1/2 mutation and a BRCA related malignancy; a 20% probability of harboring a BRCA mutation; metastatic colorectal cancer; mucinous ovarian cancer; other GI malignancy in which Ox has demonstrated activity. Results: 17 pts (median age 52 [range 19-71]; 14 female, 3 male) were treated at 4 dose levels (DL) (Table 1). Pts had cholangiocarcinoma (6), breast (4), ovarian (4), neuroendocrine (1), pancreas (1), and colon (1) cancers. 7 pts (4 breast, 3 ovarian) are BRCA1+. Dose escalation was initiated at DL1. One DLT (mucositis) occurred at this dose level. At DL2, two DLTs (mucositis with neutropenic fever and thrombocytopenia) were noted. The protocol was amended for escalation to begin at DL1A. At DL2A, a grade 2 DLT of fatigue requiring dose delay occurred in one pt. Pts were on study for median 10 weeks (range 1 – 88). 24% of pts remained on study ≥ 6 months. Of the 14 pts with measurable disease, 5 had PR (2 ovarian, 2 breast, 1 colon) and 4 had SD (3 cholangiocarcinoma, 1 pancreas). Common AEs include nausea/vomiting (94%), diarrhea (47%), mucositis (41%), anemia (35%), neutropenia (24%), and thrombocytopenia (18%). Conclusions: Vel in combination with Cap and Ox is safe and well tolerated in pts with advanced solid malignancies. The recommended phase II dose is DL2A Vel 40mg BID (D 1-7, 15-21), Cap 1000mg/m2 BID (D 1-7, 15-21), and Ox 85mg/m2 (D 1 and 15). Clinical trial information: NCT01233505. [Table: see text]

2570 Background: Loss of PTEN function leads to increased PI3Kβ signalling. AZD8186 (AZD) exhibits significant anti-tumour activity in PTEN-deficient preclinical models, particularly when combined with anti-androgens or the dual mTORC1/2 inhibitor vistusertib (AZD2014). Here we report on the dose-finding part of this Phase 1 study. Methods: AZD single agent was administered twice daily (BD) in 3 different schedules (5 days on/ 2 days off, 2 days on/ 5 days off and continuous). Escalating doses of AZD were evaluated in cohorts of 3-6 patients treated until progression, unacceptable toxicity, or consent withdrawal. Accrual is ongoing in the combination arms with vistusertib or abiraterone acetate. Results: As of 16 Jan 2017, 87 patients have received AZD at doses of 30–360 mg BD, with 28 confirmed as PTEN deficient (IHC). The selected RP2D for the 5 days on/2 days off monotherapy schedule is 60 mg BD. PK parameters show that systemic exposures to AZD and its major active metabolite increase in a dose proportional manner. 69 serious adverse events (SAEs) were reported in 31 patients on AZD monotherapy with 23 SAEs considered possibly related to AZD. In the 5/2 schedule: 5 dose limiting toxicities (G3 rash with ≥G2 fever and/or chills) were observed in 5 patients at doses of 120-360mg. Adverse events ≥G1 in > 20% included diarrhoea, nausea, fatigue, LFT elevations and decreased appetite. 20 patients remained on study for > 100 days. Dose-dependent target inhibition has been demonstrated in surrogate tissue (platelets). Evaluation of direct tumour target engagement in paired biopsies is currently ongoing. Preliminary efficacy: Confirmed PRs seen in a CRPC patient (BRCA2 and androgen receptor mutant) treated in combination with vistusertib (on study for 411 days) and in one ongoing monotherapy PTEN-deficient colorectal cancer patient (on study > 329 days). Updated data will be presented. Conclusions: AZD has potential for treatment of PTEN-deficient tumours. Investigation of the safety/tolerability and preliminary efficacy in combination with vistusertib or abiraterone acetate is continuing. Clinical trial information: NCT01884285.

18 Background: Impaired work performance that when significant leads to decreased productivity (work limitations) contribute to the “financial toxicity” of cancer treatment. Factors influencing work limitations and employment outcomes are poorly understood for cancer pts. We prospectively examined the proportion of cancer pts with significant increases in work limitations during curative treatment (co-primary endpoint). Methods: Eligible pts were ≥ 18 years, employed, intended to work during or after end of treatment (EOT), and had received ≤ 1 CT cycle. The Work Limitations Questionnaire (WLQ) survey was administered (baseline [BL], EOT, 3 and 6-months post EOT) to determine change in work limitations (WLQ index scale: 0 = no limitations to 28.6 = limited all of the time). “Significantly affected” pts had > 5-point increase in WLQ - an increase associated with decreased work productivity. Descriptive statistics (estimates with 95% confidence intervals [CI]; means with standard deviations [SD]) were calculated. A two-factor ANOVA (pt, timepoint) was used for analysis of WLQ changes over time. Results: 120 pts enrolled 5/2013 - 10/2015 at 8 sites (85 breast, 16 colon, 19 other). 110 took 1+ surveys: median age 50 (range 24-69), 92 (84%) female, 105 (96%) White; 93 (85%) had surgery, 110 (100%) CT, 57 (52%) RT. The mean increase in WLQ index from BL to EOT was +4.4 (95% CI [+2.1,+6.8], p < 0.001). A total of 44% were “significantly affected” by treatment (37/85, 95% CI [33%,55%]). WLQ index decreased at 3 and 6-mos (as compared to BL or EOT, see table). Conclusions: Among largely White pts getting CT, 44% experienced a significant increase in work limitations from BL to EOT. An improvement in group WLQ scores was noted after EOT. Analysis of factors (e.g., job type, education, symptoms) most associated with work limitations is underway to assist in prospectively identifying at-risk pts. [Table: see text]

e15037Background: Median PFS for second line treatment of mCRC with anti-EGFR ranges from 4.5-5.5 months. Preclinical data support the hypothesis that dual blockade of the EGFR with a monoclonal an...

2554 Background: A wide variety of human cancers exhibit dysregulated c-Met activity that has implications in oncogenesis. Phosphorylation of c-Met results in activation of the PI3K/AKT/mTOR pathwa...

538 Background: Endocrine therapies are the treatment of choice for HR+ metastatic breast cancer; novel drugs are needed due to resistance. Reducing both androgens and estrogens may circumvent resi...

2591 Background: Cancer patients often take multiple medications increasing the potential for drug-drug interactions. There is limited data regarding the frequency of cytochrome P450 (CYP) medicati...

2555 Background: Disregulated c-Met activity is implicated in tumor progression and metastasis. Phosporylation of c-Met leads to activation of the PI3K/AKT/mTOR pathway. Preclinical studies demonst...

2607 Background: The AKT protein kinase is a key mediator of signaling in the human epidermal growth factor receptor-2 (HER2) pathway. HER2 inhibition can result in feedback regulation of signaling, leading to high AKT activity. Preclinical studies demonstrate activity of combined HER2 and AKT inhibition. Lapatinib is an oral tyrosine kinase inhibitor of HER2. MK-2206 is an oral selective inhibitor of AKT with a maximum tolerated dose (MTD) of 60mg qod. Both agents cause rash and diarrhea. This study was designed to determine the MTD, dose limiting toxicities (DLTs), adverse events (AEs), clinical activity and pharmacokinetic (PK) parameters of the combination. Methods: This phase I study evaluated the safety of MK-2206 (30-60 mg qod) and lapatinib (1000-1500 mg qd) continuously. Cycles were 28 days, except cycle 1 (35 days), due to a 1 week MK-2206 lead-in to evaluate for PK interactions. Because of the continuous nature of therapy, protocol-specified intolerable grade 2 AEs were considered DLTs during cycle 1. Results: 23 pts (median age 59 [range 22-72];15 female:8 male) were enrolled. The most common malignancies were colorectal (8 pts), lung (4 pts), and breast (3 pts). 4 pts were unevaluable per protocol; 19 evaluable pts were on study a median of 8 weeks (range 3-35). 3 pts experienced DLTs. At dose level one, 1 pt had grade (gr) 3 hyponatremia and fatigue. At dose level four, 1 pt had gr 4 hyponatremia, gr 3 rash and hypocalcemia and 1 pt had intolerable gr 2 mucositis with delivery of

e17025 Background: Histone deacetylase (HDAC) inhibitors suppress tumor cell proliferation in medullary thyroid cancer (MTC) and differentiated thyroid cancer (DTC) in vivo. We conducted a multicenter single arm phase II trial of panobinostat, a potent inhibitor of Class I, II, and IV HDAC enzymes, in MTC and radioactive iodine (RAI)-refractory DTC. Methods: We enrolled 13 patients (pts) with progressive metastatic MTC or RAI-refractory DTC. Panobinostat was given at 20 mg orally TIW until disease progression or intolerable toxicities. The primary objective was anti-tumor response rate; secondary objectives included overall survival (OS), progression-free survival (PFS), tolerability, and changes in serum thyroglobulin (Tg) concentration. Results: Mean age was 61±13 yrs; 7 pts were female. 11 pts had DTC; 2 had MTC. Median study follow-up was 11.8 months (mos). 9 pts required dose holds/reductions due to thrombocytopenia (n=7), hypocalcemia (n=3), neutropenia (n=2), diarrhea (n=1), bone pain (n=1), or asthenia (n=1). Due to protocol specified rules, 2 pts were withdrawn from therapy with thrombocytopenia or neutropenia, both asymptomatic. Of the 3 pts with ≥ grade 3 thrombocytopenia, 2 had no bleeding. The third pt continued to bleed from her chronically erosive tumor without exacerbation. Median duration of treatment was 2.1 mos (range, 0.8-11.8). Stable disease (SD) was seen in 7 pts, with a median duration of 5.8 mos (range,1.8-13.8). All 7 SD pts are currently alive, including 2 with SD 4.9 mo and 11.8 mo on treatment. Progressive disease (PD) occurred, and was the cause of death, in 6 pts.No anti-tumor responses were observed. Median PFS for the 13 pts was 3.6 mos (95% CI, 1.8-5.8), with 2 pts having a PFS longer than 6 mos.Median OS for the 13 pts was 18.4 mos (95% CI, 5.8-not estimable). 5 of 11 pts had reductions of their serum Tg on study; however, changes in serial Tg values did not distinguish PD from SD pts. Conclusions: 20 mg TIW was not tolerated by most pts. However, dose modified treatment yielded SD in half of our previously progressing pts. This promising disease stabilization warrants further evaluation, possibly in combination with a VEGFR TKI. Clinical trial information: NCT01013597.

6063 Background: Differences in BC outcomes have been noted between rural and urban women. The influence of tumor biology vs treatment factors as the driver of these differences remains unclear. The Oncotype Dx 21-gene assay RS predicts distant recurrence risk for HR+BC; a RS>18 indicates possible chemotherapy benefit. We assessed rural vs urban differences in RS and therapies received (endocrine therapy; chemotherapy for RS>18). Methods: Retrospective chart review was conducted on BC pts diagnosed 2005–2010 with a 21-gene assay RS. Stage, grade, medications and receptor status were abstracted; RS information was obtained from Genomic Health. Rural-Urban Commuting Area (RUCA) codes defined rural vs urban status. Comparisons between rural vs urban pts were made using two-sample tests, chi-square or Fisher’s exact test for discrete data such as RS (≤ 18 vs > 18), stage and ER status. T- or Wilcoxon rank sum test were used for continuous data (RS 0-100 and age.) All tests were at a two-sided significance level of 0.05. Results: Of 495pts with RS, 488 had RUCA codes (91% white, 61% postmenopausal). For rural vs urban pts, mean RS was 18 vs 19, p=0.15. The table shows univariate analysis for other predictors. For treatment, 321/354 (97%) rural vs 118/134 (94%) urban pts started endocrine therapy (p=0.2). For RS>18, 17/55 (31%) rural vs 83/165 (50%) urban pts received chemotherapy (p=0.02, Chi-square test). Conclusions: Rural pts did not have significantly different RS compared with urban pts, but received significantly less chemotherapy for RS>18. This suggests that for HR+ BC, rural vs urban discrepancies may be explained in part by treatment factors. We suggest prospective comparison or confirmation in another cohort. [Table: see text]

555 Background: Obesity at diagnosis has been associated with poorer overall survival in BC patients. The Oncotype Dx 21-gene assay RS has been shown to predict the risk of distant recurrence in estrogen receptor (ER) positive BC. This study aimed to evaluate if an association exists between body mass index (BMI) and RS. Methods: Retrospective chart review of patients (pts) with BC diagnosed 2005-2010 and a 21-gene assay was performed. Risk factors including BMI, hormone use, and menopausal status were collected as well as tumor characteristics such as ER/PR/HER2 status, stage, and grade. Univariate analysis of the association between BMI level (18), stage (I vs II), and grade (1 vs 2 vs 3) was conducted using Chi square test. Correlation of BMI with RS (0-100) was also assessed via Spearman’s correlation. All tests were at a two sided significance level of 0.05. Results: Of 495 pts with a RS value, 482 had a BMI within 6 months of diagnosis. Median BMI was 27.7 kg/m2 (range 17-63). BMI for pts presenting with stage 2 disease is significantly higher (30±6.9) than those with stage 1 (29±7.8), p=0.04 (Wilcoxon rank sum test). No association was found between BMI level and stage, grade or RS. See Table. Mean RS was 18.8 vs 18.2 (BMI

563 Background: Observational studies suggest that EHU, such as oral contraceptive (OCPs) or postmenopausal hormone replacement therapy (HRT), increases the risk of developing BC. However, the prognosis of women taking EHU compared to nonusers remains controversial. The Oncotype Dx 21-gene assay RS predicts the distant recurrence risk for early stage, HR+ BC. We assessed RS in patients (pts) on EHU at diagnosis (users) vs nonusers. Methods: Retrospective chart review was conducted on BC pts with a RS, diagnosed 2005–2010. Stage, grade, estrogen (ER), progesterone (PR) and HER2 receptor status were abstracted. Manual review of medications, as well as electronic data pull within ≤5yrs of diagnosis, defined users as pts on EHU within 1 yr of diagnosis for ≥1 yr. Nonusers had been on EHU > 5 yrs before diagnosis or never. Comparisons between EHU users and nonusers were made using two-sample tests; chi-square or Fisher’s exact test for discrete data such as stage and ER status and t-test or Wilcoxon rank sum test for continuous data such as RS. All tests were at a two-sided significance level of 0.05. Results: 495 pts had RS. EHU was documentable for 475, 77 were using exogenous hormone at diagnosis. Type of hormone use included systemic HRT (48%), OCPs (36%), other (4%), and unknown (12%). For users vs nonusers, mean RS was 17 vs 19, (p=0.007, t-test). See table for other predictors. Conclusions: Prior study shows21-gene assay predict distant recurrence risk for HR+BC. In our study, an association existed between EHU and lower RS, suggesting that BC developing on EHU may have less risk of recurrence. Prospective evaluation is warranted. [Table: see text]

13554 Background: S, an oral platinum (P) compound, has single agent anti-tumor activity. C, an oral pro-drug of 5-FU, has efficacy against many solid tumors. Furthermore, P agents and 5-FU have sy...