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Update: Danish Fecal Occult Blood Testing Trial

Three randomized studies have demonstrated that screening with fecal occult blood tests (FOBTs) is associated with reduced mortality from colorectal cancer. In the Danish Fecal Occult Blood Testing Trial (the only 1 of the 3 still in progress; others are in follow-up phases), biennial screening with Hemoccult-II was associated with an 18% reduction in colorectal cancer mortality compared with no screening after 10 years and 5 screening rounds (Lancet 1996; 348:1467). Now, the investigators report extended results after 13 years and 7 screening rounds. In contrast with results from the Minnesota Colon Cancer Control Study (N Engl J Med 1993; 328:1365), the results from the Danish study are population-based and reflect screening without slide rehydration.

The proportion of screened patients with positive tests at each screening round ranged from 0.8% to 3.8%, with more patients testing positive at later screenings. The cumulative risk for a positive test was 5.1% after 7 rounds; 4.8% of patients underwent at least 1 colonoscopy. The mortality reduction from colorectal cancer after 7 rounds was 15% (down from 18% at 10 years after 5 rounds); the downward trend was attributed to the decreasing proportion of the study group who actually were being screened. The relative risk for death from colorectal cancer in participants who adhered to all 7 screening rounds was reduced by 30% compared with controls. The reduction in mortality from colorectal cancers proximal to the sigmoid colon was 28%; it was only 8% for cancers of the rectum and sigmoid colon.

Comment: FOBT is important because some patients will not undergo invasive testing and it likely will be used to evaluate the effectiveness of new noninvasive tests, such as stool molecular marker tests. Based on these study results, patients who inquire about the relative effectiveness of colorectal cancer screening methods can be informed that compliance with biennial Hemoccult-II screening without rehydration and with colonoscopy for positive tests will reduce their chance of colorectal cancer death by about 30%. The data also indicate that flexible sigmoidoscopy is an appropriate adjunct to FOBT, because the mortality reduction from FOBT was better in the proximal colon than from the rectosigmoid. However, in the Nottingham randomized controlled trial of FOBT (Lancet 1996; 348:1472), researchers reported mortality reductions of 13% for cancer proximal to the sigmoid colon and 16% for distal cancers. Further, recent data from the Veterans Affairs Cooperative Study suggest that FOBT has little incremental benefit when added to flexible sigmoidoscopy (JW Gastro Oct 2001, p. 84, accession number 01091201, and N Engl J Med 2001; 345:555).

— Douglas K. Rex, MD

Published in Journal Watch Gastroenterology January 29, 2002

Citation(s):

Jorgensen OD et al. A randomised study of screening for colorectal cancer using faecal occult blood testing: Results after 13 years and 7 biennial screening rounds. Gut 2002 Jan; 50:29-32.

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