Outcomes for patients treated in clinical trials may not reflect the experience in routine clinical care. We aim to describe the real-world treatment patterns and overall survival (OS) for women receiving trastuzumab for metastatic breast cancer (MBC).
Retrospective, whole-of-population cohort study using demographic, dispensing, and medical services data for women in the Herceptin Program for HER2+MBC. We estimated time on trastuzumab and OS from first dispensing of trastuzumab for MBC and rates of cardiac monitoring prior to and during treatment. We stratified outcomes by two groups based on year of initiation: 2001-2008 and 2009-2015. We benchmarked outcomes to two key trastuzumab clinical trials: H0648g (median OS 25 months) and CLEOPATRA (control group median OS 41 months).
Median age of the 5899 women at first trastuzumab dispensing was 57 years (interquartile range [IQR]: 48-66). Median time on trastuzumab increased from 15 months (7-33) in Group One to 18 months (8-42) in Group Two. Median OS increased from 27 months (12-57) in Group One to 38 months (16-83) in Group Two. Rates of cardiac monitoring increased at baseline (52%-76%), and on-treatment (47%-67%), in Group One and Two, respectively.
OS, duration of trastuzumab, and frequency of cardiac monitoring increased over the study period. Outcomes for trastuzumab in this heterogeneous real world population were reassuringly comparable to those from clinical trials, with the median OS > 3 years in Group Two and 25% of patients living 7 years or longer.