Trastuzumab-related cardiotoxicity: calling into question the concept of reversibility.

PURPOSE To assess the spectrum and reversibility of the cardiotoxicity observed in the adjuvant trastuzumab trials. DESIGN The design and efficacy of the major adjuvant trastuzumab trials was assessed, including the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-31, North Central Cancer Treatment Group N9831, Herceptin Adjuvant, Breast Cancer International Research Group 006, and Finland Herceptin trials. The cardiotoxicity data were evaluated with a focus on the follow-up cardiac evaluations of women who were diagnosed with cardiotoxicity. Proposed mechanisms of trastuzumab-related cardiotoxicity were considered. The natural history of congestive heart failure (CHF) was reviewed with the goal of placing the trastuzumab experience in context. RESULTS Up to 4% of patients enrolled onto the adjuvant trastuzumab trials experienced severe CHF during treatment. In these trials, early stopping rules that identified an unacceptable level of cardiotoxicity were never reached. Despite this, a large number of patients on these trials experienced some form of cardiotoxicity that ultimately required discontinuation of trastuzumab. Approximately 14% of patients in the NSABP B-31 trial discontinued trastuzumab because of asymptomatic decreases in left ventricular ejection fraction (LVEF). Results of follow-up cardiac evaluations of patients diagnosed with any degree of cardiotoxicity in the NSABP B-31 trial document that a clinically significant proportion of patients have sustained decrements in their LVEF to less than 50%. CONCLUSION Adjuvant trastuzumab provides substantial benefits to patients with human epidermal growth factor receptor 2-positive breast cancer, however, competing immediate and long-term cardiovascular risks are a great concern. Continued cardiac follow-up of these women is of critical importance.