LATE EFFECTS OF INTRAOPERATIVE RADIATION-THERAPY IN ANASTOMOTIC RAT COLON

Purpose: to determine whether intraoperative radiotherapy causes long- term negative effects on the healing of colonic anastomoses in the rat . Methods and Materials: 175 rats were divided into seven equal groups . One group served as sham-irradiated control group. In the others, fo llowing a colonic resection, 1 or 2 cm of the distal bowel limb was ir radiated with a single dose of 10, 15, or 20 Gy (groups 10/1, 15/1, 20 /1, 10/2, 15/2, and 20/2, respectively). Subsequently, an anastomosis was constructed. The animals were killed after 6 (n = 10 in each group ) or 12 (n = 15) months. The abdomen was inspected for abnormalities a nd the colonic diameter was measured. The anastomotic segment was anal yzed biochemically (hydroxyproline) and histologically. Results: Durin g the experimental period, 1 rat (group 15/1) died because of anastomo tic leakage and 3 others died from unknown causes. There was no differ ence in colonic diameter between groups. Altogether 17 rats developed an adenocarcinoma in the irradiated area: 11 of these had received a d ose of 20 Gy. Histological observation indicated that fibrosis was pre sent only in a limited number of animals, mostly after irradiation wit h a dose of 15 or 20 Gy. All anastomoses were functional and showed no rmal histology. The hydroxyproline content of the anastomotic segment was increased-with respect to the control group-only in the 20/2 group after 6 months. After 12 months, the hydroxyproline concentration in the (irradiated) segment distal to the anastomosis proper was higher i n the 10/1 and 15/1 groups than in the control group. Otherwise, there were no differences between groups. Conclusion: Intraoperative irradi ation with a single dose of 10-20 Gy, delivered to the distal limb use d for anastomotic construction, does not appear to constitute a threat to anastomotic integrity. Dose-related changes included formation of adenocarcinomas and fibrosis, but function and histology of the anasto mosis proper remained unaffected. (C) 1998 Elsevier Science Inc.