General population with metabolic syndrome are known to have an increased risk of cardiovascular disease and a greater risk of cardiotoxicity has recently been established in overweight and obese breast cancer patients treated with anthracyclines and/or trastuzumab, according to a meta-analysis reported in the Journal of Clinical Oncology by Guenancia et al.

To assess the association between obesity and overweight and Trastuzumab induced cardiotoxicity (TIC) in Moroccan patients with breast cancer.

A total of 971 patients treated with sequential anthracyclines and trastuzumab were followed in the Casablanca cardio-oncology unit from January 2017 to November 2018. Cardiac monitoring included physical examination and an assessment of LV function by echocardiography: it was evaluated before Trastuzumab initiation and every 12 weeks after. We then evaluated the risk for cardiotoxicity associated with being overweight defined by a body mass index BMI between 25kg/m² and 29.9kg/m² and obesity BMI≥30kg/m².

Among 971 patients, 186 (19.2%) were obese and 305 (31.4%) were considered overweight. Overall, the mean rate of cardiotoxicity was 9,3%. Multivariate analysis showed that obesity was significantly associated with a higher risk of cardiotoxicity (P=0, 042, 95% CI: 0.77–1.68) whereas overweight wasn’t (P=0.931, 95% CI: 0.53–0.89).

Unlike Guenancia's meta-analysis, where a significantly increased risk was observed if obesity and overweight were combined (BMI>25kg/m²) but not for obesity alone and overweight alone, our study shows a significant association between obesity alone and cartiotoxicity, but not with overweight. However, the specific TIC could not be assessed clearly, since all our patients also received anthracyclines. Moreover, we were unable to adjust for other classic risk factors of cardiotoxicity. Further studies are needed to determine the independent predictive value of obesity on cardiotoxicity.