OBJECTIVES: This study sought to evaluate the long-term risk of developing heart failure (HF) in patients receiving trastuzumab therapy.

BACKGROUND: Trastuzumab has improved the prognosis in patients with HER2-positive breast cancer, but it can induce left ventricular dysfunction with reduced ejection fraction or HF during treatment. The long-term risk of HF is less well described.

METHODS: In a nationwide Danish retrospective cohort study, 9,901 patients scheduled for adjuvant treatment for early-stage breast cancer were identified in the Danish Breast Cancer Cooperative Group database. Of these, 8,812 patients (25% HER2-positive; 51.7 ± 8.5 years of age) received chemotherapy including anthracycline; and if they were HER2 positive, trastuzumab was added. The primary endpoint was a diagnosis of HF assessed before and after 18 months in a landmark analysis to distinguish short- and long-term risks.

RESULTS: Median follow-up was 5.4 years (interquartile range [IQR]: 4.1 to 6.8 years). In the trastuzumab group, 60 patients had HF by 9 years versus 51 in the group who were treated with chemotherapy alone, corresponding to incidence rates per 1,000 patient years of 5.3 (95% confidence interval [CI]: 4.1 to 6.8) versus 1.4 (95% CI: 1.1 to 1.8), respectively. The cumulative incidence of HF was higher in the trastuzumab group at both the short- and long-term (p < 0.01), yielding adjusted hazard ratios of 8.7 (95% CI: 4.6 to 16.5; p < 0.01) for early HF and 1.9 (95% CI: 1.2 to 3.3; p = 0.01) for late HF associated with trastuzumab treatment.

CONCLUSIONS: Trastuzumab treatment is associated with a 2-fold increased risk of late HF compared with chemotherapy treatment alone.