Aim. The aim of the study was to examine the dosimetric effect of rectal retraction, using a rectal retractor, by performing a comparative treatment planning study. Material and Methods. Treatment plans using volumetric arc therapy (VMAT) were produced for ten patients both with and without rectal retraction. A hypofractionation scheme of 42.7 Gy in seven fractions was used. The dose to the rectal wall was evaluated for both methods (with and without retraction) using four dose-volume criteria: V40.1 Gy, V38.3 Gy, V36.5 Gy, and V32.6 Gy. Results. The retraction of the rectal wall increased the distance between the rectal wall and the prostate. The rectal wall volume was reduced to zero for all dose-volume values except for V32.6 Gy, which was 0.2 cm3 in average when the rectal retractor was used. Conclusion. There was a significant decrease of V40.1 Gy, V38.3 Gy, V36.5 Gy, and V32.6 Gy when the rectal retractor was used without compromising the dose coverage of planning target volume (PTV).
EP-1884: Automated treatment planning of volumetric arc therapy for patient with prostate cancer
