Impact of Homologous Recombination Deficiency on Outcomes in Patients With Triple-Negative Breast Cancer Treated With Carboplatin-Based Neoadjuvant Chemotherapy: Secondary Analysis of the NeoCART Randomized Clinical Trial

Pathologic complete response (pCR) rates of patients with triple-negative breast cancer who were administered docetaxel plus carboplatin were significantly higher than those of patients administered epirubicin/cyclophosphamide followed by docetaxel in the neoadjuvant NeoCART trial. Here, we performed a preplanned secondary analysis of the homologous recombination deficiency (HRD) score as a predictor of the pCR in patients with triple-negative breast cancer from the NeoCART cohort.Pretherapeutic tumor tissues were assessed retrospectively by DNA extraction and sequencing. BRCA1/2 mutations were evaluated in both somatic and germline forms. HRD scores were calculated from genome-wide allele-specific copy number results and comprised telomeric allelic imbalance, loss of heterozygosity, and large-scale state transitions. High HRD scores were defined as ≥ 38, and HRD was defined as either a high HRD score or a deleterious BRCA1/2 mutation.HRD testing was completed for 43 (79.6%) of 54 NeoCART cohort patients. Thirty of 43 (69.8%) tumors had high HRD scores, and eight patients had BRCA-mutated tumors. No significant association between BRCA1/2 mutation status and pCR was observed either in the general population or in the two treatment arms. Docetaxel plus carboplatin group patients who achieved pCR had higher HRD scores than non-pCR patients, and this difference approached significance (61.69 ± 24.26 v 39.44 ± 22.83, P = .061). No significant correlations between HRD scores and pCR (61.29 ± 24.02 v 53.21 ± 24.31, P = .480) or residual cancer burden 0/1 (62.50 ± 22.50 v 51.85 ± 24.74, P = .324) were observed in the epirubicin/cyclophosphamide followed by docetaxel group.HRD is a potential predictive biomarker for clinical benefit from neoadjuvant carboplatin-based chemotherapy and provides a possibility for screening the optimum chemotherapy backbone to combine with immunotherapy.