Investigating the Radiation Dose Received by the Heart and Its Electrocardiographic Changes after Three-dimensional Conformal Radiation Therapy in Patients with Left Breast Cancer

Background and Objective: Breast cancer is one of the most common cancers and the fifth leading cause of cancer deaths in Iran. The present study aimed to investigate the absorbed dose received by the heart and its relationship with cardiac complications in radiotherapy of patients with left breast cancer using a three-dimensional conformal radiotherapy technique. Materials and Methods: A total of 181 women with left breast cancer who received radiotherapy after surgery were included in the study. Dosimetric parameters were obtained using dose-volume histograms for the heart, whole lung, left lung, and clinical target volume. Electrocardiography tests were performed for all patients before and one year after the radiotherapy. Results: The mean doses of heart, left lung, whole lung, and clinical target volume were 6.3±3.1, 13.3±4.5, 6.9±3.7, and 47.3±6.4 Gray (Gy), respectively. A significant reduction in T-wave amplitude was observed in 57% of patients three months after radiotherapy. T-wave amplitude decreased from 3.03±0.92 mm to 1.56±0.83 mm. The reduction in the T-wave amplitude displayed a significant relationship with the mean dose of the heart (β = 2.653; P= 0.019). Conclusion: In women with left-sided breast cancer, cardiac complications are frequent, for which electrocardiographic tests can be used for cardiac evaluation after radiotherapy. Based on the obtained results, the most frequent side effect caused by radiotherapy in these patients was an abnormality in T-wave