Acceptable but Limited Efficacy of Capecitabine-Based Doublets in the First-Line Treatment of Metastatic Triple-Negative Breast Cancer: A Pilot Study

BACKGROUND: This open-label, nonrandomized phase II clinical trial investigated the efficacy of capecitabine-based doublets in the first-line treatment of metastatic triple-negative breast cancer (mTNBC). METHODS: Eligible mTNBC women with measurable diseases were recruited to receive either TX regimen (docetaxel 75 mg/m(2) i.v. on day 1 plus capecitabine 1,000 mg/m(2) b.i.d. on days 1-14 every 3 weeks) or NX regimen (vinorelbine 25 mg/m(2) i.v. on days 1 and 8 plus capecitabine 1,000 mg/m(2) b.i.d. on days 1-14 every 3 weeks) for up to 6 cycles until disease progression or unacceptable toxicity. The primary end point was objective response rate (ORR) and secondary end points included progression-free survival (PFS), overall survival (OS) and clinical benefit rate (CBR). RESULTS: Forty-five mTNBC patients, 27 in TX and 18 in NX were recruited. The total ORR was 20.0% and CBR was 40%. After a median follow-up of 28 months, PFS was 5.2 months (95% CI, 4.1-6.3 months) and OS was 18.2 months (95% CI, 8.7-27.7 months). The response rate was numerically but not statistically lower in the TX group than in the NX group (27.8 vs. 14.8%, p = 0.449). No difference was found in either PFS (4.9 vs. 5.2 months, p = 0.483) or OS (21.5 vs. 18.3 months, p = 0.964) between the two regimens. CONCLUSIONS: Although the OS seems to be reasonable, the efficacy of capecitabine-containing TX or NX regimen was limited in terms of response and PFS in mTNBC patients, suggesting capecitabine-based doublet may be acceptable but has limited potency in this subtype.