Surgical prophylaxis against large bowel tumors in an animal model.

Subtotal removal of high-risk organs is of uncertain value as cancer prophylaxis. This study examined to what extent partial colectomy prevented carcinogen-induced large bowel tumors. Male Fischer 344 rats (N = 98) were given five weekly subcutaneous injections of azoxymethane 7 mg/kg, then treated as follows: group I (controls), the ileocecal junction was divided and reanastomosed without resection; group II, a proximal 1/3 colon resection was performed; and group III, a proximal 2/3 colon resection was performed. After 7 months the rats were sacrificed and colorectal tumors confirmed histologically. Sixty-nine animals survived for analysis. Tumor incidence and average number of tumors per rat were not significantly changed by resection. Surgical prophylaxis was compromised by a high frequency of multiple tumors and by a higher than expected frequency of tumors in the remaining bowel.