Survival outcomes for Australian women receiving trastuzumab for HER2-positive metastatic breast cancer following (neo)adjuvant trastuzumab: A national population-based observational study (2006-2014)

Abstract

Background:Patients treated with (neo)adjuvant trastuzumab who relapse and receive trastuzumab for metastatic breast cancer (MBC) are a growing population with little outcome data given their exclusion from most clinical trials. We aim to estimate survival outcomes for this trastuzumab 'pre-treated' population.Methods:Population-based study of Australian women receiving trastuzumab for HER2-positive MBC between 2006 and 2014, who also received (neo)adjuvant trastuzumab. We used Kaplan-Meier methods to estimate the following: overall survival (OS) from initiation of trastuzumab for MBC; duration of trastuzumab for MBC; and time from last (neo)adjuvant trastuzumab to first trastuzumab for MBC.Results:Of 3199 patients dispensed trastuzumab for MBC, 634 (20%) had received (neo)adjuvant traztuzumab. Pre-treated patients had a median (interquartile range) OS of 21.8 months (10.9-51.6), trastuzumab duration of 12.8 months (4.7-17.5), and time from last (neo)adjuvant trastuzumab to first trastuzumab for MBC of 15.6 months (6.5-28.6). Median OS for patients initiating trastuzumab <12 months and? 3/412 months from their last (neo)adjuvant trastuzumab were 17.1 months and 24.8 months, respectively.Conclusions:Patients starting trastuzumab for MBC following (neo)adjuvant trastuzumab had a median treatment duration of 1 year and OS of almost 2 years. These data help inform clinical practice and service planning for this under-researched population.