Efficacy of platinum-based chemotherapy in advanced triple-negative breast cancer in association with homologous recombination deficiency.

Abstract

e13051 Background: Previous studies have identified that at least 50% of triple negative breast cancer (TNBC) harbor mutation characteristics of homologous recombination deficiency (HRD). Thus, more sophisticated research into comprehensive genomic profiling of HRD is urgently needed. Whereas BRCA1/2-deficient advanced TNBC patients are sensitive to treatment with platinum, it is not yet clear whether HRD status could predict platinum response. Methods: 3DMed-HRD algorithm was developed based on loss of heterozygosity score (LOH), telomeric allelic imbalance score (TAI) and large-scale state transition score (LST) as previously described. HRD status was defined as HRD positive (deleterious mutation in BRCA1/2 or HRD score ≥30) or HRD negative (no deleterious mutation in BRCA1/2 and HRD score < 30). Tumor samples from 207 TNBC patients were analyzed by next-generation sequencing. Deleterious or suspected deleterious mutations were included for analysis. Among the overall cohort, 34 patients with advanced TNBC treated with chemotherapy were analyzed. Cox regression model was applied to evaluate the relationship between HRD status and clinical outcomes. Results: Deleterious BRCA1/2 mutations were detected in 22.2% (46/207) of TNBC patients as well as 54.6% (113/207) were defined as HRD positive. The most frequent mutations in HRD-positive patients were TP53 (93.5%), MYC (29.0%), PIK3R1 (22.6%), PTEN (22.6%) and MCL1 (19.4%), while TP53 (77.8%), MYC (29.6%), PIK3CA (18.5%), KMT2C (14.8%) and RIT1 (14.8%) enriched in HRD-negative patients. Mutations in DNA Damage Response (DDR), P53, Checkpoint and Receptor Tyrosine Kinase (RTK) pathways were most involved in HRD positive patients. In advanced TNBC cohort, 19 patients received platinum-based and 15 received platinum-free chemotherapy in the first-line treatment. The progression-free survival (PFS) of the platinum-based group was longer than that of the platinum-free group (media PFS 9.1 vs 2.2 months, HR 0.44, 95%CI, 0.20-0.94, P = 0.009). In HRD-positive patients, median PFS was significantly longer in platinum-based group (N = 6) than platinum-free group (N = 8) (media PFS 13.6 vs 1.9 months, HR 0.30, 95%CI, 0.09-0.95, P = 0.008). No significant difference in PFS between platinum-based and platinum-free group (p = 0.332) in patients with HRD-negative tumors. Patients with mutations in homologous recombination (HR) pathway had a worse PFS compared to wild-type in platinum-free group (1.4 vs 3.0 months, p = 0.050). Conclusions: Our findings illustrate the potential of HRD status as a marker to guide chemotherapy in advanced TNBC. In HRD positive patients, platinum-based chemotherapy might be a preferable regimen. Patients with mutations in HR pathway had a shorter PFS in platinum-free group. Prospective study with a larger sample-size is needed for further validation of our findings.