Two Colorectal Cancer Screening Tests Fail in 25 Percent of Patients

Even if doctors combine two commonly used tests to detect colon cancer, the screening process still will fail to detect one in four patients with serious precancerous growths, according to researchers.

Dr. David A. Lieberman of the Veterans Affairs Medical Center in Portland, Oregon compared the accuracy of the fecal occult-blood test and a procedure known as flexible sigmoidoscopy to what is regarded as best detection method, colonoscopy.

The fecal occult-blood test is used to detect blood in the stool. The flexible sigmoidoscopy is similar to a colonoscopy, but only examines the lower part of the colon.

Researchers performed colonoscopies on nearly 2,900 people seen at 13 different VA medical centers, and compared the number of serious growths detected by colonoscopy with the number of such growths found by fecal occult-blood testing and sigmoidoscopy, either combined or alone.

Of the total number of patients found to have serious precancerous growths, the fecal occult-blood test detected 24 percent, the sigmoidoscopy detected 70 percent, and the two tests combined detected 76 percent, the researchers reported in the New England Journal of Medicine.

"One-time screening with both a fecal occult-blood test with rehydration and sigmoidoscopy fails to detect advanced colonic neoplasia in 24 percent of subjects with the condition," the researchers concluded.

Other sources: New England Journal of Medicine