Predictors of trastuzumab-induced cardiotoxicity among racially and ethnically diverse patients with HER2-positive breast cancer.

Background: While trastuzumab has been shown to improve disease-free and overall survival in patients with HER2-positive breast cancer, it may also cause trastuzumab-induced cardiotoxicity (TIC). Although racial and ethnic minorities are at higher risk for cardiovascular disease (CVD) compared to non-Hispanic Whites (NHW), limited data exists on TIC incidence in diverse multi-ethnic populations. Our objective was to assess racial and ethnic differences in TIC and left ventricular ejection fraction (LVEF) recovery among patients with HER2-positive breast cancer.

Methods: We conducted a retrospective cohort study including patients diagnosed with stage I-III HER2-positive breast cancer between 2007 and 2022 who had received adjuvant trastuzumab. We analyzed associations between sociodemographic factors, tumor characteristics, treatment regimens, and CVD risk factors with the primary outcomes of TIC and LVEF recovery, using multivariable logistic regression models. TIC was defined as > 10% decrease in LVEF to an overall LVEF < 50%; LVEF recovery as a return to a LVEF > 50%.

Results: Among 496 evaluable patients, median age was 53 years (IQR: 45.0-62.0) with 36.6% NHW, 15.8% non-Hispanic Black (NHB), 27.8% Hispanic, and 19.8% Other. Fifty-three (10.6%) patients developed TIC, half of whom experienced LVEF recovery. Compared to NHW, NHB had a higher rate of TIC (9.3% vs. 17.7%, respectively) and lower rate of LVEF recovery (70.6% vs. 21.4%, respectively), however, race/ethnicity was not a significant predictor of TIC after adjusting for confounders. Increasing age, lower baseline LVEF, anthracycline use, and presence of hypertension or coronary artery disease were significantly associated with TIC in multivariable analysis.

Conclusions: TIC was more common among NHB compared to NHW, however, Black race was not consistently associated with TIC after adjustment for CVD risk factors. This suggests that CVD comorbidities (e.g., hypertension) that more frequently affect racial and ethnic minorities and are modifiable may explain differences in TIC incidence and recovery.