Efficacy of low-dose capecitabine in metastatic breast cancer.

Abstract

1065 Background: The FDA-approved dose of capecitabine (cape) of 1250mg/m2 twice daily (BID) is associated with treatment-limiting toxicities. Published reports suggest that lower starting doses of cape can be as effective as the approved dose in treating metastatic breast cancer (MBC). We compared the efficacy of lower than previously published doses of cape with results of registrational Phase III trials using the approved dose. Methods: We performed a retrospective analysis of patients treated at the University of Southern California hospitals who received cape as the first, second, or third line of chemotherapy for MBC to determine the progression-free survival (PFS) associated with low starting doses. The primary endpoint was PFS among patients with measurable disease, and secondary aims were to analyze the relationships between PFS and various clinical characteristics for all patients. Results: Patients (n=84) received a median cape dose of 565 mg/m2 BID, often administered as a flat dose (not adjusted for body surface area) of 1000 mg BID. Median PFS among patients with measurable disease (n=62) was 4.1 months (95% confidence interval or CI = 2.9-5.7), which was similar to the median PFS values of 4.4 months (95% CI = 4.14-5.42, n=480) (Sparano et al. JCO 2010;28:3256) and 4.2 months (95% CI = 3.81-4.50, n=377) (Thomas et al. JCO 2008;25:5210) for single-agent cape reported in the major trials with similar eligibility criteria. Among all patients, PFS was shorter in measurable disease, triple negative and HER2+ subtypes, and was similar in all lines of therapy. Only two patients (2.4%) discontinued cape due to toxicity. Conclusions: These data support the efficacy of very low doses of cape for MBC. Prospective randomized controlled trials testing lower starting doses of cape are needed to optimize the benefit/risk ratio. [Table: see text]