When treating recurrent rectal cancer with re-irradiation using accelerated hyperfractionation (39-45 Gy at 1.2 or 1.5 Gy BID), what normal tissue constraints would you recommend for the bladder and bowel?   

We have always been very careful about excluding the small bowel if it has been treated before. The initial experience from Mohuidin et al indicated that chronic diarrhea could happen if small bowel was treated. For this reason we have used smaller 3D treatment volumes but included the sciatic notch...

Try this reference if you really feel the need for OAR constraints (reasonable reference if writing a protocol). Cai et al., PMID 25497847. 22 patients (took over 5 and 1/2 years for this enrollment) they detail in the article the prior surgeries, prior chemo, prior radiation and its timin...