Incidence of cancer in the colon and rectum among polyp-free patients

Summary

Over 4,000 patients, found to be polypfree at sigmoidoscopy, have been followed for five years to determine the incidence of cancer of the colon and rectum. If the study group had been subject to the same risk of cancer as the general population, about 22 new cancers should have been found; 19 were in fact discovered. These results are compared with those reported by Weakley and Swinton, who followed a corresponding group of 307 patients with benign adenomatous polyps of the rectum and sigmoid flexure. In their sample, the incidence of new cancers of the colon and rectum also was close to that of the general population. Thus, in the samples studied there was neither a high cancer incidence rate among patients with treated polyps nor a significantly low incidence rate among polyp-free patients. Because of the small number of cancers observed and expected, these findings must be accepted cautiously. It does seem clear, however, that if patients with benign adenomatous polyps have an increased risk of developing cancer of the lower intestinal tract, the increase must be relatively small for at least the first five years after discovery of the first polypoid lesion.