Researchers make colorectal screening a little easier

Mar 25 2008

Colon cancer screening is a tough sell. It's icky, uncomfortable and the thought of a colonoscopy, especially the prep, can be intimidating, to say the least.

But here's what clinches the sale: Colon cancer can be largely prevented through proper screening.

Researchers, including those at the University of Michigan Comprehensive Cancer Center, are working to make colorectal screening a little easier, through a combination of more choices and less-invasive procedures.

Colorectal cancer is the second biggest cancer killer in both men and women, surpassed only by lung cancer. Some 148,810 Americans will be diagnosed with colorectal cancer this year, and 49,960 people will die from the disease.

U-M colorectal cancer specialists are working to raise awareness of the disease and the importance of prevention. March is Colon Cancer Awareness Month.

In recent years, efforts to increase awareness have led to slow and steady climbs in screening rates. New data released this month by the Centers for Disease Control and Prevention showed 60.8 percent of adults were current with colorectal cancer screening recommendations in 2006, compared with 53.9 percent in 2002. But these numbers lag significantly in comparison with other cancer screening tests, such as mammography or Pap smears.

“It's important to be screened routinely for colon cancer, and there are a variety of tests available to help do that. If we reached full compliance with colon cancer screening, we could prevent more than 90 percent of colon cancers,” says D. Kim Turgeon, M.D., clinical associate professor of internal medicine in the division of gastroenterology at the U-M Medical School.

Turgeon and other researchers are continuing to look for less-invasive screening methods to encourage more people to get the test. One potential option researchers are looking at is a test to look for markers in blood or stool that might suggest colon cancer. Then only those with suspicious results would be referred for further tests, such as colonoscopy.

In separate research, Thomas D. Wang, M.D., Ph.D., assistant professor of internal medicine and biomedical engineering at U-M, reports this week in Nature Medicine on a potential new technique to screen for colon cancer. The method involves topically applying a type of probe called a peptide, that is labeled with a fluorescent agent. The peptide is designed to target pre-cancerous changes in the colon. Then, using a special microscope that fits through a standard medical endoscope, a doctor can spot these suspicious lesions.

“There's been a lot of effort behind screening patients for polyps that you can see with a white light endoscope. But if the cancerous or precancerous lesions are flat, you can't see them with standard screening techniques. We are using advanced imaging to look at molecular targets rather than structural changes. We hope this approach will allow us to find more lesions than with conventional colonoscopy,” says Wang, who conducted the research while at Stanford University.

The researchers found that the peptide bound to pre-cancerous tissue 81 percent of the time. They hope to identify additional peptides that would bind to other targets to increase this method's promise.

Currently, screening guidelines include a choice of four different tests:

• Fecal occult blood test, which checks for blood in the stool
• Colonoscopy, the gold standard, in which an instrument is inserted into the colon through the rectum
• Flexible sigmoidoscopy, which examines the rectum and lower colon using a different instrument
• Double contrast barium enema, a series of X-rays of the colon and rectum

This month, experts added two new screening tools to the arsenal: Virtual colonoscopy, which uses a CT scan to look for abnormalities; and a stool test that looks for DNA markers associated with cancer. Neither test is currently covered by insurance, although experts hope the CT colonography will be covered within a year.