Presenting Author:

Sonal Oza, M.D.

Principal Investigator:

Jonathan Strauss, M.D.

Department:

Radiation Oncology

Keywords:

Breast Cancer, Musculoskeletal Health, Survivorship

Location:

Ryan Family Atrium, Robert H. Lurie Medical Research Center

C125 - Clinical Women's Health Research

Dose to Upper Quadrant Musculature from Whole Breast Radiotherapy in the Supine and Prone Positions

Purpose/Objectives: Radiotherapy (RT) for breast cancer is associated with an increased risk of upper quadrant dysfunction (upper back, shoulder, and arm), although the pathophysiology is poorly characterized. A few studies have quantified the dose and volume delivered to the glenohumeral joint and shoulder region, but limited data are available on RT dose to individual muscle groups and no studies have evaluated women treated in the prone position. Methods Breast cancer patients who had undergone CT simulation in both the prone and supine positions were identified retrospectively. Whole breast RT plans were made on ten patients using 3D planning by contouring the whole breast and treating with tangential beams for both prone and supine positions. The pectoralis major, pectoralis minor, teres major, teres minor, latissimus dorsi, and subscapularis muscles were contoured on each scan. Muscle mean dose and V45 Gy were calculated and compared using Wilcoxon signed rank test. Results The mean doses (Gy) and V45 Gy for each muscle group in each position are shown in Table 1. The mean dose to each muscle group was significantly less in the prone position with the exception of pectoralis major. Prone positioning resulted in a lower V45 Gy to teres major, latissimus dorsi, and pectoralis minor and major. Conclusion Breast RT incidentally delivers significant dose to the adjacent musculature. The dose to most muscle groups is lower for women treated in the prone position as compared to the supine position. The impact of dose to these muscles is not yet known, but may be related to functional changes seen after RT. Further work is needed to elucidate the effect of RT dose on muscle function and whether the prone position is associated with superior functional outcomes as a result of muscle sparing.