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.