Cardiac safety of trastuzumab as adjuvant treatment for Japanese patients with early breast cancer

Recently, randomized trials revealed that trastuzumab as adjuvant treatment was effective in human epidermal growth factor receptor 2 (HER2)-positive breast cancer patients. Safety information on adjuvant trastuzumab use in Japanese patients, especially cardiac toxicity data, is needed. We retrospectively reviewed 48 patients with early-stage HER2-positive breast cancer who were treated with curative surgery and adjuvant trastuzumab at the National Cancer Center Hospital East (Kashiwa, Japan). The cardiac safety as well as the short-term efficacy of trastuzumab were evaluated. The median age of the patients was 54 years. All patients received adjuvant or neoadjuvant cytotoxic chemotherapy. Twenty-seven patients (56%) received adjuvant radiation therapy. Forty-four patients (92%) received trastuzumab without concurrent cytotoxic chemotherapy and 4 patients (8%) on taxanes received trastuzumab concurrently. Twenty-five patients completed 1 year of trastuzumab treatment and 5 patients completed 2 years of trastuzumab treatment. Nine patients discontinued trastuzumab treatment, because of progressive disease (1 patient), decrease in left ventricular ejection fraction (LVEF; 2 patients), patient's refusal (4 patients), and other reasons (2 patients). There were five cardiac events. A decrease in LVEF to less than 50% was seen in 2 patients. The relationship between trastuzumab treatment and the cardiac events was unclear in 3 patients. The median follow-up time was 21.2 months. The disease-free survival (DFS) was 97.5% at 1 year and 92.9% at 2 years. The incidence of cardiac events caused by trastuzumab treatment was low in our analysis. Adjuvant trastuzumab treatment for up to at least 1 year should be safe for Japanese breast cancer patients.