Characterization of Durable Responder for Capecitabine Monotherapy in Patients with Anthracycline- and Taxane-Pretreated Metastatic Breast Cancer

Background The purpose of this study was to evaluate predictive factors and the clinical characteristics of durable responders to capecitabine monotherapy in heavily-treated patients with metastatic breast cancer (MBC). Patients and Methods Between December 2000 and May 2012, a total of 236 evaluable patients with MBC who had been treated with second- or greater-line palliative capecitabine monotherapy after a previous treatment regimen with anthracycline and taxane were included. Capecitabine (1250 mg/m² twice daily) was administered for 2 weeks followed by a 1-week rest period. Results The response rate was 23.3% and median progression-free survival (PFS) was 4.7 months (95% confidence interval, 4.0-5.5). Among 236 patients, 33 patients (14.0%) showed durable response (>12 months) to capecitabine monotherapy. Patients with durable response showed significantly greater incidence of estrogen receptor (ER) positivity (81.8% vs. 59.1%; P =.012), single-organ metastasis (51.5% vs. 32.0%; P =.047), and absence of lymph node metastasis (75.8% vs. 54.2%; P =.023), compared with patients without durable response. In multivariate analysis, ER positivity and single-organ metastasis retained a significant association with better PFS to capecitabine monotherapy (hazard ratio [HR], 0.51; P <.001 and HR, 0.62; P =.004). Conclusion Our data suggest that ER positivity and single-organ metastasis can be useful predictive markers for better PFS to second- or greater-line palliative capecitabine monotherapy in anthracycline- and taxane-pretreated MBC patients.