Growth rate of experimental colon cancer in the absence of fecal stream and antitumor effect of UFT in rats.

Growth rate of a chemically-induced colon tumor in the absence of fecal stream was investigated and the tumors to a chemotherapeutic agent tested. Eighty Sprague-Dawley rats received dimethylhydrazine (40 mg/kg) s.c. once weekly for 10 wk to induce colon cancer. Then a colostomy was performed to produce a defunctioning colon without fecal stream. 22 wk after beginning the carcinogen treatment, a barium enema was performed to visualize tumors in the defunctionalized colon. 29 rats died postoperatively and 16 had no tumor radiographically. The remaining 35 rats were divided into a control group and UFT treatment group. After 5 wk of treatment, the barium enema was repeated. The mean doubling time of 19 tumors in the control group was 9.8 days +/- 4.0 (SD). Response to UFT was judged as effective when the doubling time exceeded 17.8 days, calculated from the mean +/- 2SDs in the control group. The response rate of UFT was 48%. The growth rate of colon tumors without fecal stream was faster and more stable than those with fecal stream; as a result, the sensitivity to UFT became higher than that in tumors with fecal stream (36%), which was reported in our previous study. The present experimental system may be more accurate for assessing the response to chemotherapeutic agents.