The prevention of colon carcinogenesis in rats by dietary cellulose is greater than the promotive effect of dietary lard as assessed by repeated endoscopic observation.

We developed a method which we used in the current study to observe the rat colon endoscopically. Our goal was to evaluate the entire course in the development of experimental large bowel tumors through serial observations in the same rat. We compared the effects of dietary lard and cellulose on rat colon tumorigenesis in a 2 x 3 factorial design. Sprague-Dawley rats (n = 90) were divided into 6 diet groups: rats were fed a diet without cellulose that contained 5, 10, and 15 g/100 g lard, or diets containing 15% cellulose diet (15 g cellulose/100 g diet) and the same concentrations of lard. The development of large bowel tumors induced by the administration of 1,2-dimethylhydrazine (25 mg/kg body weight) for 19 wk was examined endoscopically. Tumor induction rates in the 15% cellulose groups were lower than in the 0% cellulose groups (P = 0.008), independent of the lard concentration. These results suggest that the preventive effect of cellulose against large bowel tumorigenesis is greater than the promotive effect of fat under the current experimental conditions.

Natural History of Colorectal Adenoma and the Effect of Endoscopic Polypectomy on Occurrence of Subsequent Cancer.

Colorectal cancer is thought to originate in colorectal adenoma and endoscopic polypectomy may prove prophylactic. To clarify the natural history of colorectal adenoma and the potential effects of endoscopic polypectomy, we retrospectively studied cohort patients undergoing full colonoscopies at 14 hospitals in Aomori Prefecture between January 1972 and December 1985. Subjects were divided into 3,574 non-adenoma controls and 1,020 adenoma patients, including 530 treated by polypectomy at initial examination. Subjects were followed up until the end of 1987 through record linkage with Aomori Colorectal Cancer Registry files to observe colorectal cancer occurrence. The ratio of observed number/expected number in the general population (O/E ratio) was 0.70 for the adenoma group and 0.36 for controls. The adenoma group was subdivided into polypectomy and non-polypectomy subgroups, with the O/E ratios of 0.39 for polypectomy patients and 0.75 for non-polypectomy patients. The O/E ratio in the adenoma group was about twice in controls, and this ratio in the nonpolypectomy subgroup was also about twice in thepolypectomy subgroup. The results suggest that colorectal adenoma provides a precancerous lesion that can be treated prophylactically by endoscopic polypectomy.