Evaluation of Toxicity of Three Dimensional Conformal Whole Breast Radiotherapy in The Prone Position

ABSTRACT
Objective:To investigate the toxicity of prone position in whole breast radiotherapy after breast conserving surgery (BCS) in breast cancer patients with large pendulous breasts.
Patient and methods : Thirty patients (stage I-II) with large pendulous breast were simulated in both supine and prone positions. Target volumes and organs at risk were contoured on CT images. For each patient, the two planes were calculated and dose volume histograms were compared. The prescribed dose was 40 Gy in 15 fractions over 3 weeks to whole breast with 6-10 MV photon followed by 10 Gy in 5 fractions over one week boost to the tumor bed. The selection of treatment position was based on best target coverage and optimal sparing of organs at risk.
Results: Among 30 patients, 13 patients (43.3%) were treated in the prone position, while the remaining 17 patients (56.7%) were treated in supine position. Higher grades of acute dermatitis were significantly reported in supine position (p=0.01).Grades 1 and 2 chronic radiation dermatitis were more in supine position, but no statistically significant difference (p=0.41). Grade I radiation pneumonitis was developed in 2 patients (14.3%) in supine group which was not significantly different (p=0.49). No cardiac symptoms were noted among both groups. Grade I lymphedema was noted in (11.8%) in supine group versus (23.1%) in prone group (p=0.6).
Conclusion: Prone position is a suitable alternative to supine position in large pendulous breast with accepted toxicity profile.