PREVALENCE OF DISTAL COLONIC NEOPLASIA ASSOCIATED WITH PROXIMAL COLONCANCERS

Background: The number, size, and histologic features of distal colore ctal adenomatous polyps have been reported to correlate with the risk of developing proximal colon cancer. To investigate this putative rela tionship further, we evaluated the frequency of distal colorectal neop lastic polyps in patients with colon cancer located proximal to the sp lenic flexure. Methods: All cases of colorectal adenocarcinomas treate d at a tertiary referral center and Veterans Affairs hospital between 1979 and 1992 were identified by International Classification of Disea ses coding and review of pathology and colonoscopy reports. The medica l records of patients with documented cancers proximal to the splenic flexure were examined for the presence, location, size, and histopatho logic features of synchronous neoplastic lesions found at colonoscopy. Results: Among 634 patients with colorectal cancer identifiable by lo cation, 172 had proximally located tumors. Of these, 60 patients were excluded because of lack of complete colonoscopy or because surgical r esection was performed elsewhere. Forty percent of the remaining 112 p atients for whom data could be evaluated demonstrated neoplastic lesio ns in addition to the proximal cancer. The colon was devoid of ''senti nel'' neoplasia distal to the splenic flexure and descending colon-sig moid colon junction in 69% and 72% of patients, respectively. Conclusi ons: The majority of proximal colon cancers are not associated with di stal sentinel lesions. We surmise that flexible sigmoidoscopy will fai l to find evidence of neoplasia in at least 25% of patients with preva lent colon cancers.