Document Type : Letter to the Editor
Department of Radiology, Faculty of Paramedical Sciences, Kurdistan University of medical sciences, Sanandaj, Iran
Hassan Ali Nedaie et al., recently have published “Assessment of Radiation-induced Secondary Cancer Risks in Breast Cancer Patients Treated with 3D Conformal Radiotherapy” paper in Iranian journal of Medical Physics. The aim of this study was to evaluate the secondary cancer risk in organs at risk for breast cancer radiotherapy by the 3D-CRT technique. The authors used BEIR VII model for measuring of excess absolute risk (EAR) and excess relative risk(ERR). This model was basically used for organs that received low dose (below 1-2 Gy).
Based on the same paper, it’s clear that organs like contralateral breast and ipsilateral lung, and heart received a high dose, about several Gy In Nedaie et al. paper, authors reported mean dose for thyroid, heart, contralateral breast and ipsilateral lung are ranged from 3.73 to 15.99, since BEIR VII model is not appropriate for high dose, hence, cancer risk estimation encounters an error. On the other hand, received dose for organs in field is inhomogeneously distributed, for changing inhomogeneously distributed dose to a homogeneous dose, the concept of organ equivalent dose (OED) has been applied. The OED was calculated using the Schneider paper, this model considered repair cells after radiotherapy, dose fractionation, dose–response curve, etc. Therefore, for estimating secondary cancer risk of organs in field that receive high dose, we should use OED model .