Cardiac Toxicity of Trastuzumab: Experience at the Ghent Unversity Hospital, Belgium

Introduction: Trastuzumab (TRAS) is a humanised monoclonal antibody that is targeted against the HER2 growth factor receptor. Over-expression of the receptor occurs in around 15-25% of women with early breast cancer (CA). Four major adjuvant trials compared trastuzumab treatment with observation after neoadjuvant or adjuvant chemotherapy in women with high risk HER2-positive breast cancer. Results of these trials showed that trastuzumab treatment given every 3 weeks for 1 year achieved a significant improvement of disease free survival and overall survival. However, cardiac toxicity occurred more in the trastuzumab arm than in the observation arm resulting in symptomatic congestive heart failure and a significant drop in left ventricular ejection function (LVEF).

Aim Of The Study: The purpose of this analysis is to evaluate cardiac toxicity of adjuvant trastuzumab treatment in 30 breast cancer patients. Study parameters were cardiac toxicity assessed by LV function, disease free survival and overall survival.

Materials And Methods: Based on the adjuvant trials and in expectation of the reimbursement of trastuzumab in the adjuvant setting, a convention was set up between the Belgian National Institute for Health and Disability Insurance and hospital centres specialized in the treatment of breast cancer. In this convention, trastuzumab was offered to patients diagnosed with invasive, non-metastatic breast cancer with an over-expression of HER2 proven by a positive FISH test. Metastatic lymph nodes or a tumour measuring more than 10 mm had to be present. At least 4 cycles of adjuvant or neoadjuvant chemotherapy had to be given to the patient. Radiotherapy could be administered. The time interval between chemotherapy or radiotherapy and treatment with trastuzumab could not be more than 6 months. LVEF determined by MUGA scan or by ultrasonography at the start of trastuzumab treatment had to be more than 55%.

Results: 30 breast cancer patients were treated with adjuvant trastuzumab in our hospital between June 2006 and July 2007. All patients met the inclusion criteria. Six patients stopped trastuzumab treatment because of cardiac toxicity. All these patients had received prior anthracycline neoadjuvant or adjuvant chemotherapy. Five of these patients were found to have a LVEF < 55%, one showing symptoms of congestive cardiomyopathy.The sixth patient was diagnosed with a newly developed tricuspid valve insufficiency grade 3. Follow-up data of 20 months since the start of trastuzumab treatment showed that 27 patients were disease-free. Two patients died because of progressive breast cancer disease. One patient was lost of follow-up.

Conclusion: In this small group of breast cancer patients, treated with adjuvant trastuzumab, cardiac toxicity expressed as a decreased left ventricular function seems to have a higher incidence compared to the other adjuvant trials. Therefore, a close cardiac monitoring for several years should be recommended in patients treated with trastuzumab.