5-Year Outcomes of a Randomized Trial Comparing Prone and Supine Whole Breast Irradiation in Large-Breasted Women.

Purpose Prone position for whole breast irradiation (WBI) results in lower rates of toxicity and reduced ipsilateral mean lung and heart doses. No randomized trials comparing toxicity and cosmesis at 5 years with prone and supine positioning are available. Methods and Materials In this phase 2 open-label trial, 100 patients with large breast size requiring WBI were randomized between prone and supine positioning. Physician-assessed toxicity (retraction, fibrosis, edema, telangiectasia, pigmentation changes) was scored yearly for a total of 5 years, and photographs were taken at 5 years to assess cosmesis. The data were analyzed longitudinally and cross-sectionally. Results Longitudinal analysis shows lower grade 2 late toxicity with prone positioning. The results for at least grade 1 physician-assessed toxicity at 5 years are similar between supine and prone position, respectively, for retraction (56% vs 54%), fibrosis outside the tumor bed (33% vs 24%), tumor bed fibrosis (49% vs 46%), edema (11% vs 8%), telangiectasia (8% vs 3%), and breast pain (6% vs 8%) using cross-sectional analysis. However, the risk of pigmentation changes in prone position (0% vs 19%) 5 years after radiation therapy was significantly lower. Cosmesis was good or excellent in 92% and 75% of patients who used prone and supine positioning, respectively. The 5-year overall survival is 96% in both groups. Conclusion Prone positioning results in reduced rates of late toxicity.