High-sensitivity troponin T as a marker to predict cardiotoxicity in breast cancer patients with adjuvant trastuzumab therapy.

The humanized monoclonal antibody trastuzumab has been in routine use for chemotherapy for human epidermal growth factor receptor II (HER2)-positive breast cancer. A major adverse effect of trastuzumab is cardiotoxicity. Well-established biomarkers or echocardiographic parameters to predict trastuzumab-induced cardiotoxicity have not yet been determined. We attempted to identify useful biomarkers and/or echocardiographic parameters to predict trastuzumab-induced cardiotoxicity. We prospectively investigated the cases of 19 women who received chemotherapy including anthracyclines and trastuzumab for HER2-positive breast cancer. We measured cardiac biomarkers and echocardiographic parameters before their chemotherapy and every 3 months up to 15 months until the end of the adjuvant trastuzumab therapy. We divided the patients into two groups: group R was the nine patients who showed a reduction of left ventricular ejection fraction (LVEF) ≥5%, and group N was the 10 patients who showed a reduction of LVEF <5%. The high-sensitivity troponin T (hs-TnT) level at 6 months was significantly higher in group R than in group N (11.0 ± 7.8 pg/mL vs. 4.0 ± 1.4 pg/mL, p < 0.01). The hs-TnT level with a cutoff value of 5.5 pg/mL at 6 months had 78% sensitivity and 80% specificity for predicting a reduction of LVEF at 15 months. In our evaluation of echocardiographic parameters at baseline, the diastolic function was more impaired in group R than in group N. The hs-TnT and echocardiographic parameters of diastolic function could be useful to predict trastuzumab-induced cardiotoxicity.