Cardiotoxicity of Adjuvant Trastuzumab

Trastuzumab (Herceptin®) increases the chances of cure in patients with Her-2 overexpressing early breast cancer. Unfortunately, both the chemotherapy drugs used in this setting (anthracyclines) and trastuzumab are known to cause cardiac dysfunction in a proportion of patients. Patients who develop heart problems when taking trastuzumab might have to stop this treatment, which could jeopardise their chances of cure. N-terminal pro-B-type natriuretic peptide (NT pro-BNP) is a cardiac biomarker that is measured in the blood, the levels of which have been shown to indicate the presence of heart failure. Some early research has suggested that there may be a correlation between elevated NT pro-BNP and heart damage due to cancer chemotherapy and also trastuzumab. Troponin is another substance measured in the blood that can indicate heart damage. Finally, certain variations in an individual's genetic makeup (called polymorphisms) could put them at increased risk of heart damage from trastuzumab. Here we are studying whether any of these factors (NT pro-BNP levels, troponin levels, or certain genetic polymorphisms) can accurately predict who is at highest risk of trastuzumab-related cardiotoxicity. The principal aim of this study is to evaluate the utility of NT pro-BNP as a predictive biomarker for the development of trastuzumab related cardiotoxicity (TRC). The investigators will also examine if single nucleotide polymorphisms in the HER2 gene or Fc-gamma-receptor genes predict for TRC.