Risks of trastuzumab-related cardiotoxicity in breast cancer patients in Taiwan

Aims: In contrast to Western patients with breast cancer, Asian patients are relatively younger at diagnosis, and most are free from traditional cardiovascular risk factors. Despite trastuzumab-related major adverse cardiac and cerebrovascular event (MACCE) being reported, its incidence and predictors remain unknown in Taiwan. Methods and results: Through a three-hospital retrospective cohort study, we analysed the incidence of MACCE in 386 breast cancer patients' exposure to trastuzumab from 2010 to 2018. To further reconfirm our findings, in a nationwide study using the Taiwanese National Health Insurance Research Database and National Cancer Registry, we identified 13 502 women diagnosed with breast cancer who received chemotherapy from 2010 to 2015 and found 6751 women who received initial treatment with trastuzumab. After 1:1 propensity score matching with trastuzumab non-users, the incidence of MACCE was measured with a median follow-up of 36 months. In the hospital-based study, among 386 patients receiving trastuzumab, the 5-year incidences of MACCE and heart failure (HF) were 5.4 and 2.8%, respectively. In the national cohort, the crude incidences of MACCEs and HF were 4.67 and 3.21%, respectively. After adjustment for age and comorbidities, the hazard ratio of MACCE was 1.485 (95% CI 1.246–1.769). Notably, among the endpoints, only the hazard ratio of HF was significantly higher in patients receiving trastuzumab than in nonusers. In the subgroup analysis, except for patients also using taxanes, those receiving trastuzumab had a higher risk of MACCE than non-users. Conclusions: From clinical observations in a nationwide cohort, we found an increased risk of MACCE, especially HF, in patients receiving trastuzumab. Given that its cardiotoxicity is independent of traditional cardiovascular risks, our findings highlight critical concerns regarding the cardiac safety of trastuzumab use.