Adjuvant capecitabine in residual triple-negative breast cancer after carboplatin-based neoadjuvant chemotherapy: a real-world cohort
Abstract
Introduction: Patients with triple-negative breast cancer (TNBC) who do not achieve pathologic complete response (pCR) after neoadjuvant chemotherapy have a worse prognosis. Adjuvant capecitabine has demonstrated benefit in selected populations, but its role after prior carboplatin exposure remains uncertain, particularly in real-world public healthcare settings. Methods: This retrospective cohort included 111 patients with residual TNBC after carboplatin-containing neoadjuvant chemotherapy between 2017 and 2023, with follow-up until June 2025. Patients were stratified according to adjuvant capecitabine use and residual cancer burden (RCB). Disease-free survival (DFS) and overall survival (OS) were estimated using Kaplan–Meier methods and Cox regression models. Results: Among patients with residual disease, 44 received adjuvant capecitabine. Capecitabine-treated patients were younger and more likely to have higher residual tumor burden (RCB II–III), suggesting potential confounding by indication. No significant improvement in DFS (hazard ratio [HR] 0.96; 95% confidence interval [CI] 0.52–1.78) or OS (HR 0.70; 95%CI 0.33–1.46) was observed. Stratified analyses by RCB showed no significant benefit in either subgroup. Multivariable models confirmed that capecitabine was not independently associated with survival outcomes, while the Ki-67 proliferation index remained a prognostic factor. Conclusion: In this real-world cohort of patients with residual TNBC after carboplatin-based neoadjuvant chemotherapy, adjuvant capecitabine was not associated with improved survival outcomes, regardless of residual disease burden. These findings differ from prior trials conducted in platinum-naïve populations and highlight the uncertainty regarding the benefit of capecitabine, particularly in the context of prior platinum exposure, reinforcing the need for optimized treatment strategies in this high-risk population.