Cardiotoxic adverse effects of trastuzumab in breast cancer outpatients in Sunpasitthiprasong Hospital, Ubonratchathani: A retrospective cohort study

Trastuzumab, a monoclonal antibody, is recommened for agjuvant of non-metastatic and recurrent or stage IV HER2-positive breast cancer. Although the main adverse effect is that greatly reduces the cardiac function, the incidence of cardiac adverse effect has never been systematically evaluated in Sunpasitthiprasong Hospital. To determine the adverse effects and risk factors with trastuzumab-induced cardiotoxicity. A retrospective cohort study with the percentages changes of left ventricular ejection fraction (%LVEF) in the breast cancer patients. The inclusion criterias were the patient who had been followed-up at outpatient oncology clinic, patients who did not have the %LVEF were excluded from the study. The primary endpoint was the incidence of cardiotoxicity. The mean age of 66 patients treated with trastuzumab was 51.98±10.19 years. Of these, 26 patients (39.39%) had the cardiotoxicity. There were mean of %LVEF baseline was 69.64±7.14% and the mean of %LVEF after receiving trastuzumab was 63.09±9.20%. Mean reduction of %LVEF before and after receiving trastuzumab was 6.55  10.80, there was a statistically significant difference ( P <0.001). The mean of %LVEF after receiving trastuzumab was 56.96±7.75% and 38.50±0.50% in patients had a cardiotoxicity and the patients who had a discontinued treatment, respectively. However, the duration of trastuzumab exposure was directly correlated with statistically significant reduction of %LVEF in breast cancer patients ( P =0.021,  =0.215, R 2 =0.046). Among breast cancer patients treated with trastuzumab, 39.39% of the patients had cardiac adverse events, most of which were found to have %LVEF reduced greater than 10%. The duration of trastuzumab exposure resulted in an increased of %LVEF reduction.