Jack S. Mandel, PhD, MPH, and colleagues said even biennial (every two years) screening could reduce mortality by 21 percent. The researchers followed 46,551 patients aged 50 to 80 for 18 years, and addressed several inconsistencies that were found in other studies regarding mortality reduction with biennial testing. Participants were randomly assigned to one of three groups: annual FOBT, biennial FOBT, or a control group.

Cancerous tumors, and occasionally polyps, can be a source of bleeding in the intestine. The FOBT detects the presence of hidden, or "occult" blood in a sample of stool. The sample can be collected at home, and then sent to the physician or lab for examination.

Three consecutive fecal samples were taken and two occult blood tests were done on each sample. Participants who had at least one positive sample out of the six were asked to undergo a diagnostic examination that included colonoscopy. The participants were followed annually to determine the number of new cases of colorectal cancer, as well as the number of deaths from the disease.

Colorectal mortality was 33 percent lower in the annual group than in the control group and the biennial group had 21 percent lower colorectal cancer mortality than the control group.

"This report clearly and convincingly confirms that colorectal cancer screening saves lives," said Gabriel Feldman, MD, director of prostate and colorectal cancer for the American Cancer Society. "While the study found screening every two years was of some benefit, yearly screening was more effective."

The evidence supporting the effectiveness of population-based screening using fecal occult blood testing and flexible sigmoidoscopy continues to mount, said Bernard Levin, MD, University of Texas M.D. Anderson Cancer Center, and chair of the American Cancer Society National Advisory Group on Colorectal Cancer.

"While other strategies, such as chemoprevention or lifestyle changes, may ultimately surpass the effectiveness of periodic screening, for the present, screening with FOBT remains the only proven strategy for randomized prospective trials," he said in an accompanying editorial. As science continues to grapple with issues related to the primary prevention of colorectal cancer using dietary intervention and chemoprevention, the report by Mandel et al., substantiates the important and clear finding that screening of men and women more than 50 years of age for colorectal cancer can save lives."

"Based on the results of this and previous studies, we feel even more lives can be saved by following one of the American Cancer Society?s options for early detection of colorectal cancer," Dr. Feldman concluded. The ACS screening options are more sensitive that FOBT alone in detecting colorectal cancer.

The American Cancer Society (ACS) recommends men and women at average risk begin screening for colorectal cancer at the age 50, and follow one of the following examination schedules: a FOBT every year and a flexible sigmoidoscopy every five years; colonoscopy every 10 years; or a double-contrast barium enema every five to 10 years. A digital rectal examination (DRE) should be done at the same time as sigmoidoscopy, colonoscopy, or double-contrast barium enema.

People who are at moderate or high risk for colorectal cancer should talk with their doctor about a different testing schedule.

More than 129,000 Americans are diagnosed with this disease each year. Approximately 56,000 will die from it, making it the second leading cause of cancer deaths.

• Colon and Rectum Cancer Resource Center
• Few Americans Screened for Colorectal Cancer