Colonoscopy Crowned Best for Detecting Colon Cancer
The second study in the journal attempted to determine whether the presence of polyps in the lower area of the colon is a marker for cancers higher in the colon. The researchers thought that if a lower polyp predicts the presence of a cancer higher up, then flexible sigmoidoscopy may be an adequate screening tool. The scientists analyzed almost 2,000 patients with no symptoms over the age of 50 who underwent initial colonoscopy. Twelve cancers -- eight in men -- were detected by the screening.
The scientists found that the presence of a polyp in the lower colon does increase the likelihood that the person has a colon cancer farther up. However, one of the study's authors, Thomas F. Imperiale, MD, tells WebMD that more than half of the people with cancer high in the colon -- beyond the range of the flexible sigmoidoscope -- had no polyps close to the rectum.
Because colonoscopy is expensive -- about $1,000 -- and requires that patients be given anesthesia, some experts have suggested that it should be reserved for those patients who have polyps detected using the far less expensive flexible sigmoidoscope. But Imperiale says that strategy would miss nearly half of the polyps that could lead to cancer, as he found in his study. Having said that, Imperiale, who is an assistant professor of medicine at Indiana University School of Medicine in Indianapolis, says he doesn't favor colonoscopy for everyone.
"My take is that there should be a more balanced approach. I do think we need to be more liberal in the use of colonoscopy, but our long-term goals should be to find ways to estimate risk more accurately," Imperiale says. He says that abandoning flexible sigmoidoscopy in favor of colonoscopy is "going to the other extreme ... remember, the vast majority of patients in our study and other studies had no polyps." Imperiale says he differs from many of his colleagues in that he takes a conservative approach to colonoscopy. "We don't have high enough numbers to say with great confidence who does and who doesn't need colonoscopy," he says.