When treating bladder cancer with 55 Gy in 20 fractions, what small bowel dose constraints do people use?   

The protocol for the James trial (NEJM 2012) states: "non-target tissue may be excluded at the discretion of treating physician." For gyn applications, rad oncs are using D2cc bowel to 60 Gy (and possibly 65 Gy) and D5cc of 55 Gy. As one approach, these could be converted to 20-fx limits. Another approach is to use a D0.035cc of 53.5 Gy. Is there experience in treating to 55 Gy in 20 fx to a PTV that includes small bowel (without underdosing the overlap with the bowel)?