Fig. 1

Contours and IMRT treatment plan with a simultaneous integrated boost for a patient with RPS treated with post-operative radiation therapy. a Contours on a representative simulation computed tomography scan. Red contour represents the high risk posterior margin that will receive a high dose (CTV1), while the green contour represents CTV2, which provides a lower, bowel tolerant dose to a larger area at risk. b IMRT treatment plan with isodose lines. Contours the same as above (red contour = CTV1, green contour = CTV2). The volume receiving 6300 cGy is green, while the lower dose volumes, 5250 cGy and 4200 cGy are yellow and blue respectively