New Guidelines for Colorectal Cancer Screening

Laurie Barclay, MD

February 03, 2003

Feb. 3, 2003 — New guidelines published in the February issue of Gastroenterology by the U.S. Multisociety Task Force on Colorectal Cancer differ from previous guidelines in several important ways. They still emphasize the importance of starting screening at age 50 years but reduce the frequency of follow-up for those with positive findings. The task force generally favors colonoscopy over barium enemas, and it updates screening recommendations for familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC).

Although the future of screening looks bright, with Medicare and other insurance carriers covering the costs, and new procedures and tests under development, the task force reminds doctors that they must recommend the tests.

"It takes a team to ensure colorectal cancer screening is successful. Physicians must recommend the tests, patients must accept this advice, and insurers must pay for screening and follow-up tests," Robert Fletcher, MD, co-chair of the task force, from Harvard Medical School in Boston, Massachusetts, says in a news release.

Initial colorectal cancer screening appears to be most effective at detecting the largest, most invasive polyps, which can be removed during colonoscopy and polypectomy. Previous guidelines recommended follow-up colonoscopy every three years after polypectomy, but studies show little additional benefit from follow-up colonoscopies after three years, because precancerous polyps are very unlikely to develop in that brief time period.

The new guidelines recommend that patients with one or two tubular adenomas less than 1 cm have their first follow-up colonoscopy at five years, while patients with advanced or multiple adenomas (at least three) should have their first follow-up colonoscopy at three years, as recommended in the previous guidelines.

"Planning follow-up surveillance of patients according to their risk for advanced adenomas is an especially important point in the new guidelines," says lead author Sidney Winawer, MD, from Memorial Sloan-Kettering Cancer Center in New York City. "If adopted nationally, this would shift critical resources from surveillance to screening, helping us screen more people, which would in turn decrease incidence and mortality rates."

Other differences from the earlier guidelines include an emphasis on colonoscopy rather than barium enema in screening and surveillance. Indications for colonoscopy include diagnostic evaluation, screening for those with family history of colorectal cancer or of adenomatous polyps occurring before age 60 years, screening people with two affected close relatives, screening in those with genetic mutations linked to colorectal cancer, and surveillance after polypectomy and after colorectal cancer resection.

"Colonoscopy allows us to visualize the entire colon, and to detect and remove polyps in one procedure," says task force member Douglas Rex, MD, from the Indiana University School of Medicine. "It's invaluable in patients who are at high risk of developing colorectal cancer."

For those with family history of FAP, genetic counseling should address genetic testing and considerations of colectomy, because risk of colorectal cancer approaches 100% in FAP. Those testing positive for FAP should be followed with sigmoidoscopy, and colectomy should be considered once polyps develop. Genetic testing in children can be delayed until age 10 years.

Those with HNPCC should have colonoscopy annually or biannually beginning at the earlier time point of age 20 to 25 years, or 10 years earlier than the youngest age of colon cancer diagnosis in the family. First-degree relatives of persons with a known inherited gene mutation should be offered genetic testing for HNPCC.

As an alternative to colonoscopy, those who have the genetic mutation could be screened with double contrast bariumenema (DCBE) every five years rather than every 10 years as recommended previously, because this test is less sensitive than colonoscopy and detects only about half of colon polyps.

Annual fecal occult blood test (FOBT) is recommended for people older than 50 years who are at average risk for colorectal cancer. The guaiac-based slides should not be rehydrated even though this increases sensitivity, because it has an unpredictable effect on test readability and substantially increases the false-positive rate.

Thanks to national prevention campaigns and Medicare reimbursement for screening, awareness of colorectal cancer has increased. However, colorectal cancer screening rates remain low.

Future developments in colorectal cancer screening include virtual colonoscopy, a thin-section, helical computed tomography followed by off-line processing. Although this procedure can yield high-resolution, three-dimensional images and is less invasive than colonoscopy, its ability to detect colon polyps is not well established. Further drawbacks include the same patient preparation as for colonoscopy, air insufflation, and inability to perform biopsy or polypectomy.

Trials are ongoing for a new DNA stool test, which offers greater sensitivity than the FOBT but less than that of colonoscopy. "Colorectal cancer screening should take place with the tests available now, and not wait until something better comes along," Dr. Rex says. "The colorectal cancer screening tests we have today are very effective compared to screening tests for other cancers that are more widely used."

Gastroenterology. 2003;124(2):544-560

Reviewed by Gary D. Vogin, MD

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