The utilization of flexible sigmoidoscopy as a screen for colorectal cancer has been shown to be cost effective for patients with average risk factors for this cancer. The impact of variables on the location of colon cancer has not been completely studied. Nelson and colleagues explored age, gender and race as variables that may influence the site for colorectal cancer.

The site for colorectal cancer was defined as distal (sigmoid, rectosigmoid and rectum) or proximal (cecum through descending colon). The study consisted of a review of 38,391 patients with colorectal cancer enrolled in the tumor registry in one state. When controlled for age, the incidence of proximal colorectal cancer was higher in the black population than in the white population. Distal colorectal cancer rates were higher for male patients than for female patients in both races.

The authors conclude that offering flexible sigmoidoscopy as a screen is appropriate for white male patients. However, in black female patients, a barium enema would be a better screen because of the increased incidence in that population of proximal colorectal cancers that are beyond the range of a sigmoidoscope. The authors also conclude that the poorer survival rate for colorectal cancer in the black population might be explained by the tendency for these patients to have a higher incidence of proximal tumors.