Relationship of Polyps to Cancer of the Large Intestine

Abstract

Pathologic and epidemio-logic evidence indicates that patients with sporadic (nonfamilial) adenoma-tous polyps of the large intestine are at high risk of developing colorectal cancer. Our primary goal in this study was to evaluate the colorectal cancer mortality rate among persons who have had a histologically confirmed benign colorectal polyp. We used the retrospective follow-up method to evaluate the risk of death from colorectal cancer in 2872 Rhode Island men and women who were 24 through 79 years of age at the time of surgery for benign polyps in the years 1959 through 1975. Among 2872 subjects, the mortality from colorectal cancer, standardized for age, sex, and calendar time, was estimated as 1.74 (95% confidence interval = 1.44−2.09) times the rate in the general population of Rhode Island residents. Colorectal cancer mortality was higher in the first 5 years of follow-up than it was later. There was little relationship between the numbers of polyps and colorectal cancer mortality, and there was only a modest association between the size of polyps and mortality. Colorectal cancer mortality was more than twice as high in subjects whose polyps were proximal to the sigmoid compared with those with sigmoid or rectal polyps. The observed elevation of risk of colorectal cancer was almost entirely confined to subjects who had an adenomatous polyp. The risk increased strongly with the percentage of villous features in the polyp and was about twice as high in subjects with villous adenoma than in those with other adenomatous polyps. Our results support the suspected relationship between colorectal polyps and cancer incidence and extend the association to colorectal cancer mortality. These data suggest that the orthotopic injection of human prostate cancer cells into the nude mouse may provide a valuable model to study the biology and therapy of human prostate cancer.