What bowel dose constraints do you use when treating bladder cancer with moderate hypofractionation?

Two additional steps I take when using hypofractionation doses as noted above is to 1) ensure that the V55 Gy to small bowel is limited to less than 5 cc (based on some data in gynecological cancers) and 2) make sure the full thickness bowel loop is not in the PTV2 volume.

Good question. In the BC2001 trial reduced high-dose volume (RHDV) arm, PTV1 was outer bladder wall + 1.5 cm and PTV2 was the bladder tumor + 1.5 cm. Oncologic results were similar with RHDV treatment compared to whole bladder irradiation. The hypofractionation option prescription for PTV2 was 55 Gy...