Prospective determination of distal colon findings in average-risk patients with proximal colon cancer

Background: Recent guidelines indicate that colonoscopy and sigmoidoscopy are both acceptable options for screening average-risk patients for colorectal cancer. Retrospective studies have found that a majority of patients with cancer proximal to the splenic flexure have a normal screening flexible sigmoidoscopy. Methods: This was a multicenter, prospective description of colonoscopic findings and family history in consecutive patients with proximal colon cancer. Results: Among 116 prospectively identified average-risk patients with cancer proximal to the splenic flexure, 40 (34.5%) had neoplasia distal to the splenic flexure. The prevalence of patients with adenomas greater than or equal to 1 cm, with only one tubular adenoma less than 1 cm, and with only hyperplastic polyps were 16.4%, 8.6%, and 6.9%, respectively. Conclusions: Most average-risk patients with cancer proximal to the splenic flexure will have a normal screening flexible sigmoidoscopy. These patients have an unexpectedly high prevalence of large distal adenomas, but the prevalence of both single small tubular adenomas and hyperplastic polyps alone is similar to that expected during screening of the general population. Clinicians and payers should continue to seek methods to improve the cost-effectiveness and availability of screening colonoscopy in average-risk persons.