Knowing risk can determine what kind of colon cancer screening is best

Oct 29 2007

While colonoscopy has become widely used for colorectal cancer screening, nearly two-thirds of screening colonoscopies show no cancer or pre-cancerous polyps.

In an editorial in the October issue of the journal Gastroenterology, Thomas F. Imperiale, M.D., professor of medicine at the Indiana University School of Medicine and a Regenstrief Institute, Inc. research scientist, says that studies that can help determine who is at risk for colorectal cancer as well as who is not at risk and how to stratify risk for each group can help determine which screening test is best for each individual and will better serve both patients and the healthcare system.

"If we knew more about risk factors for advanced neoplasia [cancer and advanced, precancerous polyps] and could effectively stratify risk, then screening and surveillance could be tailored—that is, targeted to persons with high risk and away from those at low risk, who could either be examined with less invasive methods or perhaps not at all. Risk stratification and tailoring would improve the overall efficiency and effectiveness of colonoscopic screening and surveillance," Dr Imperiale wrote.

Dr. Imperiale is the lead investigator of the Risk Assessment in Colon Cancer Study, which is investigating whether using easily accessible factors such as age, family medical history, race, smoking history, body mass index, and other candidate factors can help determine who is and who is not at risk. That study also focuses on whether more sophisticated tools such as blood tests that look at genes, proteins or other markers of risk, would be effective.

Colonoscopy has become a common tool for screening partly by default, according to Dr. Imperiale.

"Colonoscopy is the 500-pound gorilla. It has evolved into an acceptable screening test in part because many people believe that there are no other good options. To increase screening rates for colorectal cancers, we need to stress convenient and less invasive screening tests for those who are not at high risk for colorectal cancer and advanced, precancerous polyps," said Dr. Imperiale. "First, however, we need a way to stratify risk among the nearly 90 percent of persons who are considered to be "average-risk." Certainly, a hundred years from now - perhaps even 10 years from now – screening colonoscopy will likely be looked upon as overkill," said Dr. Imperiale, who is a gastroenterologist and clinical epidemiologist.

Colorectal cancer is the third most common cancer and the third leading causing of cancer related deaths in the United States. The National Cancer Institute estimates that more than 52,000 Americans will die of colorectal cancer in 2007.