Background:

Adjuvant treatment of HER2+ breast cancer includes adriamycin and trastuzumab, a monoclonal antibody that produces cardiotoxicity. The actual epidemiologic impact of trastuzumab-related cardiotoxicity in unselected populations in Argentina remains unknown.

Objectives:

The aim of this study was to evaluate the impact of trastuzumab-related cardiotoxicity during adjuvant treatment for breast cancer in an unselected population after >12 months of completing therapy.

Methods:

Among 888 patients prospectively evaluated for breast cancer, 231 (38%) were HER2+ and received adjuvant therapy with adriamycin and trastuzumab. Left ventricular ejection fraction was evaluated before treatment, after completing adriamycin and then every 3 months during follow-up. Cardiotoxicity was defined as a decline in left ventricular ejection fraction >10%, according to the definition of the American College of Cardiology and was compared with the definitions of the B-31 trial and the MD Anderson Cancer Center.

Results:

A decline in left ventricular ejection fraction >10% from baseline values occurred in 65% (n=150) of the patients during a mean follow-up of 48±12 months. In the per group analysis, patients included in the B-31and MD Anderson Cancer Center vs. the American College of Cardiology definitions presented greater percent fall in left ventricular ejection fraction during treatment: 20% vs. 20% vs. 16%, respectively (p<0.04) and ended treatment with left ventricular ejection fraction <50% in 42% vs. 41% vs. 33% of cases, respectively (p=0.01).

Conclusions:

In the population treated with trastuzumab under cardio-oncology surveillance during 48±12 months:

1 - Left ventricular ejection fraction was significantly decreased in more than 60% of patients.

2 - Different guidelines show different cardiotoxicity risks which demands continuous cardio-oncological monitoring.