Clinical outcomes of patients with breast cancer relapsing after (neo)adjuvant trastuzumab and receiving trastuzumab rechallenge or lapatinib-based therapy: a multicentre retrospective cohort study: ESMO open

BACKGROUND: In the prepertuzumab era, we evaluated the clinical outcomes of patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer who underwent first-line trastuzumab-based or lapatinib-based therapy according to prior exposure to (neo)adjuvant trastuzumab. MATERIALS AND METHODS: In this multicentre retrospective cohort study conducted in 14 Italian centres of the Gruppo Italiano Mammella, consecutive patients undergoing first-line trastuzumab or lapatinib-based therapy were included. Analyses were performed according to the type of first-line therapy for metastatic disease (trastuzumab or lapatinib). Dichotomous clinical outcomes were analysed using logistic regression and time-to-event outcomes using Cox proportional hazard models controlling for relevant demographic, clinicopathological and therapy characteristics. RESULTS: Out of 450 patients included in the study, 416 (92%) received trastuzumab and 34 (7.5%) lapatinib. As compared with the trastuzumab cohort, more patients in the lapatinib cohort had a trastuzumab-free interval