Predictive Factors of Lapatinib and Capecitabine Activity in Patients with HER2-Positive, Trastuzumab-Resistant Metastatic Breast Cancer: Results from the Italian Retrospective Multicenter HERLAPAC Study.

BACKGROUND: There are no validated predictive markers for lapatinib and capecitabine in patients with trastuzumab-resistant HER2 positive metastatic breast cancer. METHODS: Data of 148 consecutive patients treated with lapatinib and capecitabine from March 2007 to December 2013 were collected from 13 Italian institutions. Estimates of progression-free survival (PFS) and overall survival (OS) were obtained with the Kaplan-Meier method and compared with logrank test. The association of clinicopathological variables and the outcome was studied by binary logistic regression analysis and Cox proportional hazard analysis. RESULTS: At a median follow-up of 41 months, median PFS and OS were 7 and 21 months, respectively. Patents with a PFS longer than 7 months had a significantly longer OS, compared with patients with a PFS equal to or shorter than 7 months (36 vs 15 months; p<0.001). Multivariate analysis revealed the benefit of lapatinib-based therapy in terms of PFS and OS was significantly associated with time-to-progression (TTP) on prior first-line trastuzumab-based therapy. In particular, each additional month on first-line trastuzumab based therapy was associated with a reduction in hazard of progression and death after the initiation of lapatinib-based therapy of 2% and 4%, respectively. CONCLUSIONS: A longer TTP to first line trastuzumab seems to predict a prolonged PFS and OS with subsequent lapatinib and capecitabine.