Efficacy and toxicity of lapatinib plus capecitabine therapy in HER2-positive metastatic breast cancer

We retrospectively investigated the efficacy and toxicity of lapatinib plus capecitabine in 45 HER2-positive breast cancer patients. The median number of treatment courses was 6(1-22). Brain metastasis developed in 18 cases(40%), and 19 cases(42.2%)had received previous capecitabine treatment for metastatic breast cancer. The objective response rate(ORR=CR+PR)was 22.2%(10/45), and clinical benefit rate(CR+PR+long SD=24w)was 46.7%(21/45).The median time to progression(TTP)was 24.9 weeks(95% CI: 15.2 -34.6 ), and the median overall survival(OS)was 78.1 weeks(95% CI: 55.7 -100.5)in all 45 cases. The median TTP was significantly longer in patients who had not received capecitabine previously(30 vs 16 weeks, 95% CI: 16.3 -43.7, p=0.0051 ). There was no statistical difference in median OS associated with previous capecitabine exposure(42.7 weeks, 95% CI: 21.4 -64, p=0.057 ). The median TTP was significantly longer in patients who received less than 2 treatment regimens with trastuzumab for MBC rather than 3 regimens more(27.3 vs 16 weeks, p=0.0257 ), but there was no statistical difference in median OS(81 vs 40.9 weeks, p=0.26 ). Lapatinib in combination with capecitabine is likely more useful in patients who are naive to capecitabine, who received less than two regimens for metastatic breast cancer.