Factors for time to trastuzumab-induced cardiotoxicity in breast cancer patients.

Trastuzumab is a drug used for the treatment of metastatic breast cancer patients. Due to blockage of the human epidermal growth factor receptor 2 signaling in cardiac myocytes, cardiotoxicity has been observed. There are many studies that investigated risk factors for trastuzumab-induced cardiotoxicity, but no study has been published for factors on the time to cardiotoxicity. This study aimed to investigate the factors for the time to occur trastuzumab-induced cardiotoxicity. From January 2014 to December 2015, a retrospective study was performed with breast cancer patients who were treated with trastuzumab. Associations between presence of and time to cardiotoxicity and various factors were analyzed. Based on multivariate models, it was found that baseline left ventricular ejection fraction (LVEF) < 62.5% (AHR 5.96, 95% CI 2543-13.95) and anthracycline-based chemotherapy (AHR 7.90, 95% CI 1.05-59.71) were significant factors for time to cardiotoxicity after adjusting other confounding factors. Multivariate analysis also showed that BMI ≥ 23 kg/m2 and baseline LVEF value < 62.5% increased cardiotoxicity 3.0 and 6.6 times, respectively. Our study showed that BMI ≥ 23 kg/m2, LVEF < 62.5%, and anthracycline-based chemotherapy were associated with time to trastuzumab-induced cardiotoxicity. Thus, close monitoring of cardiac function is recommended especially for patients using the above risk factors.