Radiobiological estimation of radiation-induced heart complication of postmastectomy radiation therapy patients using the relative seriality model

Background and Aim: In Nigeria today, most radiotherapy (RT) centers do manual planning using anatomical landmarks rather than precise planning using imaging modalities such as Computerized Tomography and Magnetic Resonance Imaging. This puts the collateral organs at a greater risk of damage. The objective of this study is to carry out a comparison of the risk of cardiac complication in the right and left breasts of postmastectomy radiation therapy patients using radiobiological evaluation tools. Methods: Ninety-six patients treated in the University of Benin Teaching Hospital, RT Center, Nigeria, between January 2012 and March 2014 were recruited for this study. The relative seriality model was used to compute the risk of cardiac mortality to the breast of these patients. Results: The results showed that the equivalent uniform dose (EUD) to the heart for patients with left breast cancer is significantly (P < 0.05) higher than the EUD to the heart of patients with right breast and also the risk of cardiac mortality is significantly (P < 0.05) higher in the left breast than the right breast; due to proximity to the heart to the left side. Conclusion: This implies that the long-term risk of having cardiac disease should be of particular concern for women treated for left-sided breast cancer. As a result of this, care should be taken in planning patients using computerized treatment planning system that embraces imaging simulation rather than the conventional anatomical landmark; this will go a long way to prevent cardiac-induced mortality especially in cancer of the left breast.