Individualized positioning for maximum heart protection during breast irradiation

Abstract

Background. Prone positioning has been found feasible and appropriate for the reduction of radiation exposure of the lungs, but its effects on the heart dose remain controversial. Individual anatomical features were sought for the selection of optimal treatment positioning. Material and methods. In 138 left-sided breast cancer cases awaiting postoperative whole-breast radiotherapy, conformal radiotherapy plans were generated in both prone and supine positions. Results. The radiation doses to the left anterior descending coronary artery (LAD) and heart in the two positions differed individually, and were strongly related to the body mass index (BMI). Image fusion of the CT scans revealed that prone positioning was detrimental if the heart was situated distant from the chest wall in the supine position, but moved to the chest wall in the prone position. For characterization of the geography of the heart and the breast, the median distance between the LAD and the chest wall (d_median), and the heart area included in the radiation field on a single CT scan at the middle of the heart in the supine position (A_heart) proved most appropriate. Conclusion. A validated statistical model, utilizing the BMI, d_median and A_heart, permits individualized positioning for maximum heart protection.