Long-term follow-up assessment of cardiac safety in SAFE-HEaRt, a clinical trial evaluating the use of HER2-targeted therapies in patients with breast cancer and compromised heart function.

Purpose: HER2-targeted therapies are associated with cardiotoxicity which is usually asymptomatic and reversible. We report the updated cardiac safety assessment of patients with compromised heart function receiving HER2-targeted therapy for breast cancer, enrolled in the SAFE-HEaRt trial, at a median follow-up of 3.5 years.

Methods: Thirty patients with stage I-IV HER2-positive breast cancer receiving trastuzumab with or without pertuzumab, or ado-trastuzumab emtansine (T-DM1), with asymptomatic LVEF (left ventricular ejection fraction) 40-49%, were started on cardioprotective medications, with the primary endpoint being completion of HER2-targeted therapy without cardiac events (CE) or protocol-defined asymptomatic worsening of LVEF. IRB-approved follow-up assessment included 23 patients.

Results: Median follow-up as of June 2020 is 42 months. The study met its primary endpoint with 27 patients (90%) completing their HER2-targeted therapies without cardiac issues. Of the 23 evaluable patients at long-term f/u, 14 had early stage breast cancer, and 9 had metastatic disease, 8 of whom remained on HER2-targeted therapies. One patient developed symptomatic heart failure with no change in LVEF. There were no cardiac deaths. The mean LVEF improved to 52.1% from 44.9% at study baseline, including patients who remained on HER2-targeted therapy, and those who received prior anthracyclines.

Conclusions: Long-term follow-up of the SAFE-HEaRt study continues to provide safety data of HER2-targeted therapy use in patients with compromised heart function. The late development of cardiac dysfunction is uncommon and continued multi-disciplinary oncologic and cardiac care of patients is vital for improved patient outcomes.