Influence of preoperative high-dose radiotherapy on postoperative outcome and colonic anastomotic healing - Experimental study in the rat

PURPOSE: Surgical treatment of rectal cancer is followed by local recurrenc e in up to 30 percent of cases. Recently, preoperative low-dose radiotherap y has been shown to improve both local recurrence rate and overall survival . Down-staging of locally advanced tumors, however, requires preoperative d oses of at least 50 to 60 Gy. Most experimental studies investigating the e ffect of preoperative radiotherapy have made use of a single dose or a limi ted number of fractionated doses. Moreover, in most studies, both Limbs of the anastomosis were irradiated, in contrast to clinical practice, in which one limb of the anastomosis consists of nonirradiated bowel. We studied th e effect of a fractionated, clinically relevant scheme of high-dose preoper ative radiotherapy on colonic anastomotic healing in the rat. METHODS: Male Wistar rats randomly received 0, 40, 60, or 80 Gy of preoperative radiothe rapy on one limb of the anastomosis only. Radiotherapy doses were validated with implanted dosimeters; before the start of radiotherapy, the cecum was fixed outside the radiation field. A clinically used fractionation scheme of 2 Gy per day, 5 days per week for 4 to 8 weeks was used. The day after r adiotherapy completion a side-to-side colorectal anastomosis was performed. Rats were killed 10 days after surgery. The following parameters were dete rmined: presence of abscess or peritonitis, anastomotic complications (sten osis, leak, or dehiscence), intestinal obstruction, anastomotic bursting pr essure, and anastomotic hydroxyproline content. RESULTS: No significant dif ferences were found in peritonitis rate, anastomotic complications, anastom otic bursting pressure, or hydroxyproline content. Irradiated animals gaine d weight more slowly than the control group. CONCLUSION: In this rat model, preoperative high-dose radiotherapy using a clinically relevant fractionat ion scheme does not affect outcome or anastomotic healing when only one lim b of the anastomosis is irradiated.