Survival Impact of Adjuvant Capecitabine In Triple-Negative Breast Cancer Patients with Residual Disease: A Real-World Study

Abstract Purpose Patients with triple-negative breast cancer (TNBC) who do not achieve pathological complete response (non-pCR) after neoadjuvant chemotherapy (NACT) have a high risk of relapse. While adjuvant capecitabine (AdjCape) has demonstrated improved overall survival (OS) and disease-free survival (DFS) in Asian populations, its effectiveness in non-Asian settings remains uncertain. We aimed to evaluate the effect of AdjCape on survival outcomes using real-world data from a Latin American population. Methods We conducted a retrospective cohort study (2008–2024) including 360 women with non-metastatic TNBC and non-pCR treated at a single institution. Propensity score matching (PSM) was applied to adjust for baseline differences. Cox regression models assessed the association of AdjCape with OS and DFS, and stratified analyses identified subgroups with differential treatment effects. Results Among 360 patients, 106 (29.4%) received AdjCape. After PSM, 187 patients (72 AdjCape, 115 controls) were analyzed. AdjCape was not associated with improved OS (HR 0.79, 95% CI 0.51–1.23, p = 0.302) or DFS (HR 0.81, 95% CI 0.53–1.23, p = 0.321). However, significant benefit was observed in patients with high residual tumor burden (pT3–pT4: OS HR 0.29, p = 0.020; DFS HR 0.37, p = 0.044) and in those not receiving radiotherapy (DFS HR 0.47, p = 0.038). Conclusions AdjCape did not improve OS or DFS in the overall TNBC non-pCR cohort but may offer benefit in patients with extensive residual disease or those not treated with radiotherapy. These findings highlight the need for individualized treatment strategies and further evaluation of capecitabine in the context of modern therapies.