Colon Cancer Screen May
Miss One Quarter of Cases

NEW YORK (Reuters Health) - Combining two commonly used tests to detect colon cancer will still fail to identify one in four patients with the disease, according to a new report.

In the study, researchers at the Veterans Affairs Medical Center in Portland, Oregon compared the accuracy of several screening methods used to detect colon cancer to that of the 'gold standard' detection method, colonoscopy.

The two screening methods tested included the fecal occult-blood test and a procedure known as flexible sigmoidoscopy.

The fecal occult-blood test is used to detect blood in the stool. If blood is found, patients may undergo colonoscopy, during which a flexible, lighted tube is inserted into the rectum and passed through the colon. A video camera connected to the tube allows a doctor to examine the inside of the intestine for any unusual growths.

Another screening method is flexible sigmoidoscopy, a less extensive invasive procedure, similar to colonoscopy, which only examines the lower part of the colon.

Dr. David A. Lieberman and colleagues performed colonoscopy on nearly 2,900 people seen at 13 different VA medical centers. The investigators compared how many serious growths were detected by colonoscopy with the number of such growths found by fecal occult-blood testing and sigmoidoscopy, either combined or alone.

Among patients with serious precancerous growths, a one-time fecal occult-blood test detected 24% of the growths, a one-time sigmoidoscopy detected 70%, and combined testing detected 76%, according to the report in the August 23rd issue of The New England Journal of Medicine.

The combination of tests was somewhat less accurate in patients over age 60, Lieberman noted in an interview with Reuters Health.

``When fecal occult-blood test and sigmoidoscopy are performed once, they fail to detect many patients with serious precancerous growths,'' Lieberman said. ``If these tests are used, they need to be repeated at recommended intervals.''

The American Cancer Society recommends that people without risk factors such as a family history of the disease or inflammatory bowel disease begin screening at age 50 and continue the process for the next 35 years, because colon cancer tends to strike older adults.

``Colon screening can save lives and prevent cancer, if serious precancerous growths are detected and removed,'' Lieberman stated.

SOURCE: The New England Journal of Medicine 2001;345:555-560.

Reference Source 89

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