A pooled analysis of the cardiac events in the trastuzumab adjuvant trials

Background: Trastuzumab-associated cardiotoxicity remains an issue for patients with HER2-positive breast cancer. This pooled analysis of 3 adjuvant trials investigated the incidence, timing, impact on treatment completion, and risk factors for trastuzumab-associated cardiotoxicity. Methods: This is an individual patient data level pooled analysis of HERA, NSBAP B-31, and NCCTG 9831 (Alliance Trials). Definitions of cardiac events were as per each individual study. Results: A total of 7445 patients enrolled in the 3 trials were included in the analysis, of which 4017 were in the trastuzumab and 3428 in the control (observation) arms, respectively. Median follow-up exceeded 10 years (119.2–137.2 months). Nearly all patients (97.4%) in the trastuzumab arms received anthracycline-based chemotherapy. In total, 452 patients in the trastuzumab arms experienced a cardiac event (11.3%), with most being mildly symptomatic or asymptomatic left ventricular ejection fraction (LVEF) decrease (351 patients, 8.7%). Severe congestive heart failure was more common in the trastuzumab arm (2.3%) than in the control arm (0.8%). Most cardiac events occurred during trastuzumab treatment (78.1%) and cardiac events were the main cause of discontinuation across the sample (10.0%); nevertheless, a large majority of patients completed trastuzumab treatment (76.2%). Baseline risk factors that were significantly associated with the development of cardiac events were baseline LVEF < 60%, hypertension, body mass index > 25, age ≥ 60 and, non-Caucasian ethnicity. Conclusion: One year of trastuzumab increases the risk of cardiac events, though most consist of asymptomatic or mildly symptomatic LVEF drops. Adjuvant trastuzumab should be considered a safe treatment from a cardiac standpoint for most patients. Trastuzumab-associated cardiotoxicity is the main cause of discontinuation and further research is needed to individualize prevention and management.