Dosimetric comparison of supine versus prone radiotherapy techniques in patients with breast cancer

Abstract

Early-stage breast cancer patients survive longer so a radiotherapy technique which can reduce late toxicity is important. In this study, we made a dosimetric comparison of supine and prone breast irradiation techniques in patients with left breast cancer. Ten patients scheduled for whole-breast radiotherapy after lumpectomy were included in this study. The patients underwent computed tomography scans in both supine and prone positions on a breast board. The breast was contoured as per standard guidelines. Treatment planning was done for both the positions. A dose of 40 Gy/15#/3 weeks was prescribed. Mean dose to the heart and left lung was calculated for each patient in the supine and prone positions. Dose-volume histograms were generated and compared between the two sets. Paired t test was applied to test the significance of difference between the mean doses received by the heart and left lung for the two techniques. The difference was considered statistically significant if p value was < 0.05. The heart and left lung were better spared in the prone position compared to supine. Mean heart dose in the supine and prone positions was 4.5558 Gy and 2.063 Gy (p = 0.02), respectively. Mean lung dose in the supine and prone positions was 6.5797 Gy and 0.8491 Gy (p = 0.001), respectively. Rotational setup error was noted in 3 and 1 patient in the prone position and supine position, respectively. The prone position for the radiotherapy treatment of left breast cancer was dosimetrically better than the supine position in terms of mean dose to the heart and left lung.