Exploratory analysis of cardiac biomarkers in women with normal cardiac function receiving trastuzumab for breast cancer

Aim: As there is no method to detect trastuzumab-related cardiotoxicity (TRC) preclinically, patients are monitored with serial assessments of left ventricular ejection fraction (LVEF) with instigation of cardiac therapy and possible interruption of trastuzumab therapy if TRC develops. Serum cardiac biomarkers, including troponins and natriuretic peptides, represent possible tools to detect cardiotoxicity at a preclinical level. Methods: We sought biochemical evidence of cardiac damage or strain in a cohort of women already receiving trastuzumab by performing a cross-sectional study of serum cardiac biomarkers. All patients had a normal LVEF and no clinical evidence of cardiac failure. Serum troponin I and N-terminal pro-B type natriuretic peptide (NT pro-BNP) were assayed immediately prior to trastuzumab infusion (t0; n = 36) and 24 hours later (t24; n = 31). Results: Troponin I was not elevated in any patient at t0 or t24. Overall 14/36 (39%) patients had at least one NT pro-BNP level above the upper limit of normal (ULN) and both levels were above the ULN in 8/31 (26%) patients. There was no significant change in NT pro-BNP from t0 to t24. Conclusion: NT pro-BNP levels are elevated in a significant proportion of patients with normal LVEF receiving trastuzumab. Troponin I levels are not raised in this group, perhaps reflecting the mechanism of cardiotoxicity. The data provide biochemical evidence of subclinical cardiac strain in women receiving trastuzumab. Results are exploratory and have informed the design of a larger study examining the predictive utility of serial serum NT pro-BNP levels for TRC in the adjuvant setting.