Results of a phase II study of capecitabine-based doublets in the treatment of metastatic triple-negative breast cancer (mTNBC)

e11538 Background: It is extremely important to identify proper cytotoxic agents for TNBC which had limited choices except chemotherapy. Capecitabine are well established as a major chemotherapeutic agent in metastatic setting. The efficacy of capecitabine-based chemotherapy has not been prospectively studied in TNBC and data remains scant. This study was designed to investigate the efficacy of capecitabine-based doublets in the treatment of metastatic TNBC. Methods: Eligible metastatic TNBC women with measurable diseases were recruited to receive either TX regimen (docetaxel 75mg/m2 iv d1 plus capecitabine 1000mg/m2 bid, d1-14,q3w) or NX regimen (vinorelbine 25mg/m2 iv d1, 8 plus capecitabine 1000mg/m2 bid, d1-14, q3w) at the discretion of physicians for up to 6 cycles, until disease progression or unacceptable toxicity. The primary endpoint was objective response rate and secondary endpoints included progression free survival (PFS), overall survival (OS). Results: 45 mTNBC patients, 27 in TX and 18 in NX were recruited, mostly (73.3%) as 1st line and the remaining as the 2nd line. The total objective response rate was 20.0% and clinical benefit rate was 62.2%. After a median follow-up of 28 months, PFS was 5.2 months (95%CI, 4.1-6.3mons) and OS was 18.2months (95%CI, 8.7-27.7mons). Almost half of the patients (22/45) progressed during treatment or within one month of the treatment discontinuation. PFS was significantly longer if patients got CR/PR (9.6 vs 4.3mons, P=0.015). When comparing two doublets, the response rate was numerically but not statistically lower in TX group than in NX group (14.8% vs 27.8%, P=0.449). Similarly, no difference was found in either PFS (4.9 vs 5.2 mons, P=0.483) or OS (21.5 vs 18.3 mons, P=0.964) between two regimens. Conclusions: Although the overall survival seems to be reasonable, efficacy of capecitabine-contained TX or NX regimen was relatively poor in terms of tumor remission and progression free survival in mTNBC patients, suggesting capecitabine may have limited potency in this subtype. These two combinations may be considered to be acceptable but may not be recommended as prior choice for mTNBC patients.