Abstract
BACKGROUND: Triple-negative breast cancer (TNBC) is an aggressive subtype characterized by early relapse and limited therapeutic options. Carboplatin added to anthracycline/taxane neoadjuvant chemotherapy (NACT) raises pathologic complete response (pCR) rates. The role of adjuvant capecitabine following NACT containing carboplatin remains unclear, particularly in real-world settings. METHODS: Data of patients who were diagnosed with TNBC and received NACT at CAISM/UNICAMP (2017-2023), followed up until June 2025 were analyzed retrospectively. The cohort study included 184 women with TNBC treated with anthracycline, taxane, and carboplatin-based NACT. Clinical, pathological, and treatment data were collected from institutional databases and the CAISM Biobank. Survival outcomes were analyzed according to pCR and use of adjuvant capecitabine among patients with non-pCR. Median follow-up was estimated using the reverse Kaplan-Meier method. Additional exploratory analyses included stratification by Residual Cancer Burden (RCB-I vs RCB-II/III), multivariable Cox models including capecitabine as the exposure variable, and administrative censoring sensitivity analyses at 36 and 48 months. Disease-free survival (DFS) and overall survival (OS) were estimated by Kaplan-Meier method and compared with log-rank tests; multivariable Cox models assessed prognostic factors. RESULTS: Among 184 women, pCR was achieved in 40% and was associated with younger age, earlier clinical stage and high histologic grade. Survival outcomes were significantly better for patients with pCR, with an approximately 85-87% reduction in the risk of recurrence and death compared with non-pCR. Among the 111 patients with residual disease, 44 received adjuvant capecitabine. Adjuvant capecitabine did not improve DFS (HR = 0.96; 95% CI 0.52-1.78) or OS (HR = 0.70; 95% CI 0.33-1.46) in univariable analyses. In multivariable models stratified by capecitabine use, Ki-67 remained the only independent prognostic factor slightly associated with worse DFS, while capecitabine showed no significant effect. CONCLUSIONS: In this real-world cohort, achieving pCR after carboplatin-containing NACT was the strongest determinant of favorable prognosis. Adjuvant capecitabine was not associated with statistically significant improvement in survival outcomes. The role of capecitabine following prior platinum exposure remains uncertain and warrants further investigation.