Genetic Alterations, Therapy Response, and Survival Among Patients With Triple-Negative Breast Cancer: A Secondary Analysis of a Randomized Clinical Trial

Importance: Subgroup definitions for possible deescalation of neoadjuvant cancer treatment are urgently needed in clinical practice. Objective: To investigate the effect of BRCA1 and/or BRCA2 tumor pathogenic variants (tPVs) by comparing 2 deescalated neoadjuvant regimens (nab-paclitaxel plus either carboplatin or gemcitabine) on pathologic complete response (pCR), invasive disease-free survival (IDFS), and overall survival (OS) of patients with early-stage triple-negative breast cancer (TNBC). Design, Setting, and Participants: This was a preplanned secondary analysis of a phase 2 prospective randomized clinical trial (ADAPT-TN) conducted by the West German Study Group (WSG) at 45 sites in Germany between June 2013 and February 2015. The trial enrolled patients with noninflammatory early-stage TNBC (clinical tumor size ≥1 cm; estrogen receptor and progesterone receptor expression <1%; and ERBB2 negative). DNA samples from pretreatment biopsies were obtained. Genetic analysis was performed between January 2018 and March 2020. Final data analyses took place in September 2023. Exposure: Patients were randomized to 12 weeks of treatment with nab-paclitaxel plus either carboplatin or gemcitabine; omission of otherwise mandatory anthracycline-containing chemotherapy was allowed in the case of pCR. tPVs in 20 cancer-associated genes, including BRCA1 and BRCA2, were analyzed using a customized gene panel. Main Outcomes and Measures: The prevalence of BRCA1 and/or BRCA2 tPVs and their effect on pCR rate, IDFS, and OS were evaluated using logistic and Cox proportional hazards regression. Results: Of the 307 patients with DNA samples from pretreatment biopsies available, tumor next-generation sequencing analyses were successful for 266 patients. The 266 patients included in this analysis were female, with a median age of 51 years (range, 26-76 years). A total of 162 patients (60.9%) had a clinical tumor size of 2 cm or greater, and 70 (26.3%) had clinical node-positive disease. BRCA1 and/or BRCA2 tPVs were detected in 42 patients (15.8%). The highest pCR rate among patients with BRCA1 and/or BRCA2 tPVs was seen in the nab-paclitaxel plus carboplatin group (9 of 14 patients [64.3%]) compared with the nab-paclitaxel plus gemcitabine group (10 of 28 [35.7%]) (odds ratio, 3.24 [95% CI, 0.85-12.36]; P = .08); the highest numeric 5-year IDFS and OS rates (84.4% and 92.9%, respectively) were seen in the nab-paclitaxel plus carboplatin group. Conclusions and Relevance: In this secondary analysis of the WSG-ADAPT-TN randomized clinical trial on tPVs, deescalated nab-paclitaxel plus carboplatin was superior to nab-paclitaxel plus gemcitabine, particularly in patients with BRCA1 and/or BRCA2 tPVs. These findings suggest that BRCA1 and/or BRCA2 tPV status could be a candidate marker for a deescalation strategy in early-stage TNBC; however, prospective validation of survival outcomes in larger cohorts with differentiation between germline and somatic pathogenic variants is necessary. Trial Registration: ClinicalTrials.gov Identifier: NCT01815242.