A team from the USA followed participants in the Minnesota Colon Cancer Control Study for 18 years. A total of 46,551 people, mostly 50- to 80-year olds, were enrolled between 1975 and 1978.
Individuals were randomly assigned to annual screening, biennial screening, or usual care (the control group).
Those assigned to the screening groups submitted 2 samples from each of 3 consecutive stools for detection of occult blood. Those with at least 1 positive slide in the set of 6 were offered a diagnostic examination that included colonoscopy.
Annual and biennial fecal occult-blood testing reduces colorectal cancer incidence
Study participants were followed with respect to newly diagnosed cases of colorectal cancer and deaths. Follow-up was more than 90 per cent complete.
1359 new cases of colorectal cancer were identified during the 18-year follow-up period: 417 in the annual-screening group, 435 in the biennial-screening group, and 507 in the control group.
The cumulative incidence ratios for colorectal cancer in the screening groups, as compared with the control group, were 0.80 and 0.83 for the annual-screening and biennial-screening groups, respectively.
For both screening groups, the number of positive slides was associated with the positive predictive value both for colorectal cancer and for adenomatous polyps at least 1 cm in diameter.
Team member Dr Jack Mandel concluded from the study that, "The use of either annual or biennial fecal occult blood testing significantly reduces the incidence of colorectal cancer."