Features of durable response and treatment efficacy for capecitabine monotherapy in advanced breast cancer: real-world evidence from a large single-centre cohort

Purpose In metastatic breast cancer (MBC) population treated with capecitabine monotherapy, we investigated clinical-pathological features as possible biomarkers for the oncological outcome. Methods Retrospective study of consecutive MBC patients treated at University Hospitals Leuven starting capecitabine between 1999 and 2017. The primary endpoint was the durable response (DR), defined as non-progressive disease for > 52 weeks. Other main endpoints were objective response rate (ORR), time to progression (TTP) and overall survival (OS). Results We included 506 patients; mean age at primary breast cancer diagnosis was 51.2 years; 18.2% had de novo MBC; 98.8% were pre-treated with taxanes and/or anthracycline. DR was reached in 11.6%. Patients with DR, as compared to those without DR, were more likely oestrogen receptor (ER) positive (91.5% vs. 76.8%, p = 0.010) at first diagnosis, had a lower incidence of lymph node (LN) involvement (35.6% vs. 49.9%, p = 0.039) before starting capecitabine, were more likely to present with metastases limited to ≤ 2 involved sites (54.2% vs. 38.5%, p = 0.020) and time from metastasis to start of capecitabine was longer (mean 3.5 vs. 2.7 years, p = 0.020). ORR was 22%. Median TTP and OS were 28 and 58 weeks, respectively. In multivariate analysis (only performed for TTP), ER positivity (hazard ratio (HR) = 0.529, p