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Objective Patients with HER2-positive metastatic breast cancer (MBC) benefit from trastuzumab-based therapy but eventually develop intrinsic or acquired resistance. Whether plasma HER2 gene copy number (GCN) could predict survival after trastuzumab treatment remained controversial. We evaluated the prognostic value of plasma HER2 GCN using low-coverage whole-genome sequencing (LC-WGS). Methods The plasma was collected from HER2-positive MBC patients whose pre-therapeutic samples were available before first-line trastuzumab-based treatment. Plasma DNA was extracted and assessed by LC-WGS for HER2 GCN. The optimal cut-off point for HER2 GCN to shorter survival was determined by receiver operating characteristic (ROC) curve analysis. Results A total of 49 patients were retrieved from 2013 to 2017, among whom 21 had multiple organ involvement (≥3 sites). Variations of HER2 GCN in pre-therapeutic plasma ranged from 1.89 to 23.86 (median = 2.59). ROC analysis identified the optimal cut-off point for HER2 GCN as 2.82 (P = 0.005), with 23 patients had high-level HER2 GCN and 26 in the low-level group. Both progression-free survival (PFS, P = 0.032) and overall survival (OS, P = 0.006) were adversely associated with high-level HER2 GCN. In multivariate analyses, high HER2 GCN was independently associated with shorter PFS [hazard ratio (HR) = 2.042, P = 0.037], while both high HER2 GCN (HR = 4.909, P = 0.004) and more metastatic organs (HR = 4.019, P = 0.011) were negative prognostic factors for OS. Conclusion In this population of patients with HER2-positive MBC, individuals with high HER2 GCNs in plasma had worse prognosis after trastuzumab-based therapy. Plasma HER2 GCN may be a prognostic marker in these patients.

Objective To compare the efficacy of platinum- and non-platinum-based regimens as first-line treatment for advanced triple-negative breast cancer (TNBC) and analyze the relationship between their efficacy and BRCA gene status. Methods Retrospectively analyze clinical data of 220 patients diagnosed pathologically with advanced TNBC and treated at the Department of Breast Oncology, Peking University Cancer Hospital from 2013 to 2018 and evaluate the efficacy of chemotherapy. A total of 114 patients had BRCA1/2 gene tested by next generation sequencing (NGS) using peripheral blood, and we analyzed the correlation between their efficacy and BRCA1/2 gene status. Results Non-platinum-based chemotherapy (NPCT) was administered to 129 and platinum-based chemotherapy (PBCT) to 91 study patients. The clinical benefit rate (CBR) and median progression-free survival (PFS) were not statistically different between NPCT and PBCT groups. The median overall survival (OS) was 30.0 and 22.5 months for PBCT and NPCT group, respectively [P=0.090, hazard ratios (HR)=0.703]. BRCA status was assessed in 114 patients, 14 of whom had deleterious germline BRCA1/2 (gBRCA) mutations (seven in each group). In PBCT group, the CBR was 85.7% and 35.1% for patients with and without deleterious gBRCA mutations, respectively (P=0.039). The median PFS were 14.9 and 5.3 months and median OS were 26.5 and 15.5 months for patients with and without deleterious gBRCA mutations, respectively (P=0.001, P=0.161, respectively). Patients in PBCT group had significantly greater rates of grade 3-4 anemia (5.5%vs. 0%) and thrombocytopenia (8.8% vs. 0%), whereas palmar-plantar erythrodysesthesia (12.4% vs. 0%) and peripheral neuropathy (8.6% vs. 1.1%) occurred more frequently in NPCT group. Conclusions Platinum-based regimens are more effective in patients with deleterious gBRCA mutations, but no difference in patients without BRCA gene mutations, so non-platinum is an option in patients without BRCA gene mutations considering the toxicity and side effect. And we recommend that patients with advanced TNBC should have BRCA gene test.

Background: More than 30% of estrogen receptor-positive breast cancers are resistant to primary hormone therapy, and about 40% that initially respond to hormone therapy eventually acquire resistance. Although the mechanisms of hormone therapy resistance remain unclear, aberrant DNA methylation has been implicated in oncogenesis and drug resistance. Purpose: We investigated the relationship between methylome variations in circulating tumor DNA and exemestane resistance, to track hormone therapy efficacy. Methods: We prospectively recruited 16 patients who were receiving first-line therapy in our center. All patients received exemestane-based hormone therapy after enrollment. We collected blood samples at baseline, first follow-up (after 2 therapeutic cycles) and at detection of disease progression. Disease that progressed within 6 months under exemestane treatment was considered exemestane resistance but was considered relatively exemestane-sensitive otherwise. We obtained circulating tumor DNA-derived methylomes using the whole-genome bisulfide sequencing method. Methylation calling was done by BISMARK software; differentially methylated regions for exemestane resistance were calculated afterward. Results: Median follow-up for the 16 patients was 19.0 months. We found 7 exemestane resistance-related differentially methylated regions, located in different chromosomes, with both significantly different methylation density and methylation ratio. Baseline methylation density and methylation ratio of chromosome 6 [32400000-32599999] were both high in exemestane resistance. High baseline methylation ratios of chromosome 3 [67800000-67999999] ( P = .013), chromosome 3 [140200000-140399999] ( P = .037), and chromosome 12 [101200000-101399999] ( P = .026) could also predict exemestane resistance. During exemestane treatment, synchronized changes in methylation density and methylation ratio in chromosome 6 [32400000-32599999] could accurately stratify patients in terms of progression-free survival ( P = .000033). Cutoff values of methylation density and methylation ratio for chromosome 6 [149600000-149799999] were 0.066 and 0.076, respectively. Conclusion: Methylation change in chromosome 6 [149600000-149799999] is an ideal predictor of exemestane resistance with great clinical potential.

Objective Triple-negative breast cancer (TNBC) is a heterogeneous disease with poor prognosis. Circulating tumor cells (CTCs) are a promising predictor for breast cancer prognoses but their reliability regarding progression-free survival (PFS) is controversial. We aim to verify their predictive value in TNBC. Methods In present prospective cohort study, we used the Pep@MNPs method to enumerate CTCs in baseline blood samples from 75 patients with TNBC (taken at inclusion in this study) and analyzed correlations between CTC numbers and outcomes and other clinical parameters. Results Median PFS was 6.0 (range: 1.0-25.0) months for the entire cohort, in whom we found no correlations between baseline CTC status and initial tumor stage (P=0.167), tumor grade (P=0.783) or histological type (P=0.084). However, among those getting first-line treatment, baseline CTC status was positively correlated with ratio of peripheral natural killer (NK) cells (P=0.032), presence of lung metastasis (P=0.034) and number of visceral metastatic site (P=0.037). Baseline CTC status was predictive for PFS in first-line TNBC (P=0.033), but not for the cohort as a whole (P=0.118). This prognostic limitation of CTC could be ameliorated by combining CTC and NK cell enumeration (P=0.049). Conclusions Baseline CTC status was predictive of lung metastasis, peripheral NK cell ratio and PFS in TNBC patients undergoing first-line treatment. We have developed a combined CTC-NK enumeration strategy that allows us to predict PFS in TNBC without any preconditions.

Enumeration of circulating tumor cells (CTCs) is a promising tool in the management of metastatic breast cancer (MBC). This study investigated the capturing efficiency and prognostic value of our previously reported peptide-based nanomagnetic CTC isolation system (Pep@MNPs). We counted CTCs in blood samples taken at baseline (n = 102) and later at patients' first clinical evaluation after starting firstline chemotherapy (n = 72) in a cohort of women treated for MBC. Their median follow-up was 16.3 months (range: 9.0-31.0 months). The CTC detection rate was 69.6 % for the baseline samples. Patients with ≤2 CTC/2 ml at baseline had longer median progression-free survival (PFS) than did those with2 CTC/2 ml (17.0 months vs. 8.0 months; P = 0.002). Patients with ≤2 CTC/2 ml both at baseline and first clinical evaluation had longest PFS (18.2 months) among all patient groups (P = 0.004). Particularly, among patients with stable disease (SD; per imaging evaluation) our assay could identify those with longer PFS (P 0.001). Patients with2 CTC/2 ml at baseline were also significantly more likely to suffer liver metastasis (P = 0.010). This study confirmed the prognostic value of Pep@MNPs assays for MBC patients who undergo firstline chemotherapy, and offered extra stratification regarding PFS for patients with SD, and a possible indicator for patients at risk for liver metastasis.

e12565 Background: Platinum-based therapy remains an effective treatment for triple-negative breast cancer (TNBC), however, the usage is largely limited due to its side effect and rapidly developed drug resistance. High prevalence of BRCA1/2 mutations are reported in TNBC. Here we explored efficacy of platinum-based regimens as the first-line treatment for Chinese patients (pts) with advanced TNBC, and analyzed its association with mutations of germline BRCA1/2 (gBRCA). Methods: We retrospectively analyze 220 patients diagnosed as advanced TNBC who were treated at the Dept. of Breast Oncology, Peking University Cancer Hospital in 2013-2018, and routinely evaluated by RECIST 1.1. Statistical analysis is performed in R 3.5.1. Cox proportional-hazard models are used for survival analysis. Results: 129 pts received non-platinum chemotherapy (NPCT) as the first-line therapy, and 91 pts received platinum-based chemotherapy (PBCT). The clinical benefit rate (CBR) and median PFS were not statistically different between NPCT and PBCT groups The median OS was 30.0 and 22.5 months for PBCT and NPCT group respectively (P = 0.09, HR = 0.70). Among them, 114 pts had BRCA gene tested, of which 14 had deleterious gBRCA mutations, 7 in each group. In PBCT group, the CBR was 85.7% and 35.1% for pts with and without deleterious gBRCA mutations respectively (P = 0.04). The median PFS, OS were 14.9 months and 5.3months (P = 0.001), 26.5 and 15.5 months (P = 0.16) for pts with and without the gBRCA mutations. No significant difference was observed between NPCT pts with and without gBRCA mutations as regards the CBR, PFS and OS. PBCT Pts had significantly more grade 3-4 anaemia (5.5% vs 0%) and thrombocytopenia (8.8% vs 0%) while higher percentage of palmar-plantar erythrodysesthesia (PPE) (12.4% vs 0%) and peripheral neuropathy (8.6% vs 1.1%) were observed in NPCT pts. Conclusions: The efficacy of platinum-based regimens as the first-line treatment of advanced TNBC insignificantly differs from that of non-platinum therapy. However, they are more effective for patients with deleterious gBRCA mutations, suggesting a BRCA1/2 genetic testing may be warranted for such patients.

Triple‐negative breast cancer (TNBC) accounts for 15–20% of all newly diagnosed breast cancers, and is enriched for germline mutation of BRCA. In Asian patients diagnosed with breast cancer, 268 deleterious mutations of BRCA1 and 242 of BRCA2 have been identified so far, including a reported BRCA1 frameshift mutation (rs80350973), apparently found only in Asian people, with a low prevalence of 0.3–1.7% in different breast cancer cohorts. Here, we reported the high prevalence (7.2%) of rs80350973 among 125 Chinese patients with TNBC, which implies its mutational predilection for certain breast cancer subtypes. Although its low prevalence had not indicated any particular clinical significance in previous studies, our results associated rs80350973 mutation with cell checkpoint malfunction, and was found to be more common in TNBC patients with high Ki‐67 indices (P = 0.004). As Ki‐67 overexpression is a predictor of poor prognosis in TNBC, inclusion of this mutation into genetic assessments may improve the clinical management of Chinese patients with TNBC.

e13018Background: Only a subset of patients with HER2 positive (HER2+) metastatic breast cancer (MBC) responds to anti-HER2 therapy. This study aimed at detecting plasma HER2 gene copy number (GCN)...

e24029Background: In estrogen receptor-positive breast cancer patients (pts), more than 30% have primary hormone therapy (HT) resistance while the precise mechanism underlies remain unclear. Our st...

1080Background: Circulating DNA fragments (ctDNA) are using to longitudinal non-invasive molecular monitoring and resistance mechanism interrogation of the disease by detecting genomic alteration c...

1105 Background: CTCs have emerged as an independent prognostic factor for metastatic breast cancer. However, the prognostic value of baseline CTCs regarding PFS in TNBC is still controversial, especially beyond first-line. We evaluated a novel combined NK cell/CTC detection system for enumeration to better understand the impact of cell count on prognosis in TNBC. Methods: 83 consecutive patients with metastatic TNBC were enrolled and received a new line of therapy (median=2, range: 1~5). Baseline circulating CTCs and NK cells were isolated and enumerated simultaneously prior to starting a new line of therapy using our previously published method targeting EpCAM (Bai et al. J Mater Chem B, 2014) and flow cytometry (antibodies against CD3-, CD45+, CD56+) respectively. The NK cell level was expressed as the proportion of total lymphocytes (%). Patients with normal to high NK cell proportion (≥ 9.15%) and > 2 CTC/2 ml were defined as NK resistant CTC, the rest were defined as non-NK resistant CTC. Results: 33 out of 83 TNBCs had first-line of therapy. Pts with ≤ 2 CTC/2 ml had a significantly longer median PFS than those with > 2 CTC/2 ml ( P = 0.028). The differences in median PFS were not significant ( P=0.110) for the entire group of pts with TNBC receiving different lines of therapy. Pts with non-NK resistant CTCs had a significantly longer median PFS than those with NK resistant CTCs ( P= 0.025), regardless of line of therapy. Conclusions: Including peripheral NK cell level into consideration can improve CTC prognostic efficiency in predicting PFS for TNBCs receiving different line of therapy. Further analysis of the unique biological features of NK-resistant CTCs and associated clinical consequence holds promise in guiding clinical practice. [Table: see text]