Abstract

Sandi Bosnic, William Tran, Melanie Davidson, Paulette McKeon, Danny Vesprini, Jean-Philippe Pignol
University of Toronto, Toronto, ON

Purpose: When patients are positioned prone for whole breast irradiation (WBI), treatment widths (separation) become narrower. Smaller separation facilitates the use of lower energy beams and thus may reduce the risk of moist desquamation in skin folds and other regions of the breast where supine patients typically develop toxicity. The aim of this study was to identify patterns in acute skin toxicity in patients receiving WBI in the prone position utilizing intensity-modulated radiotherapy (IMRT).

Materials and Methods: A retrospective review of 62 patients who received IMRT WBI only in the prone position was undertaken. Skin toxicity was assessed at weekly time intervals during treatment and at follow-up using the CTCAE scale (v 4.03).

Results: Grade 0-1 skin toxicities developed in 43/62 patients (69.5%), Grade 2 in 15/62 (24%) and Grade 3 in four of 62 (6.5%). Grade 2 and 3 toxicities peaked at weeks 4 and 5, where six of 62 patients (9.7%) reported moist desquamation that mainly developed in regions of the inframammary fold. There were 56/62 patients (90%) who required 6MV radiation only, three of 62 (5%) mixed 6/18 MV and three of 62 (5%) 18MV only.

Conclusions: Lower energy beams were utilized in the majority of prone patients receiving WBI IMRT. Prone patients experienced lower than expected rates of moist desquamation in comparison to previous reports where standard WBI was given in the supine position. A large randomized trial is neeeded to further exploit the dosimetric and skin toxicity disparities between supine and prone positions.