Myocardial damage in breast cancer patients treated with adjuvant radiotherapy: a prospective study.

PURPOSE: To look for early and late signs of cardiac side effects of postoperative radiotherapy in patients with left-sided breast cancer. METHODS AND MATERIALS: Seventeen left-sided primary (Stage I-III) breast cancer patients considered eligible were recruited. Their computer tomography-based dose planning showed a part of the heart's left ventricle irradiated with at least 85-95% of the total dose. Twelve patients were examined both before treatment and an average of 13 months later, at a first follow-up. In partially mastectomized patients tangential opposed photon fields were used to the breast tissue, while in patients with modified radical mastectomy electrons were given to the thorax. Echocardiography and a bicycle ergometry stress test with myocardial perfusion scintigraphy were carried out before and after radiotherapy to assess if any myocardial damage could be detected. RESULTS: Six of the 12 patients exhibited new fixed scintigraphic defects after radiotherapy indicating regional hypoperfusion. Four of them received treatment only to the breast after breast-conserving surgery. The localization of the defects corresponded well with the irradiated volume of the left ventricle. No deterioration in left ventricular systolic or diastolic function could be detected by echocardiography. CONCLUSIONS: In this study half of the patients exhibited new scintigraphic defects that indicate radiation-induced myocardial damage, probably affecting the microcirculation. There were no changes on electrocardiography or any deterioration of the left ventricular function at this stage. Long-term follow-up is necessary to assess whether this finding is a prognostic sign for developing radiation-induced coronary artery disease.