Fecal occult blood testing and the incidence of colorectal cancer.

OBJECTIVE

The objective of this abstract is to demonstrate by life table methodology a significant reduction in the mean annual incidence rate of colorectal cancer in randomized groups with annual or biennial screening for fecal occult blood, as compared with the annual incidence rate in the control group.

BACKGROUND

Testing for the presence of fecal occult blood has long been used for the early detection of colorectal polyps and potential cancers. The Minnesota Colon Cancer Study, in an earlier report, has shown that colorectal cancer mortality was significantly reduced, but a 12% reduction in incidence of colorectal cancer was not statistically significant. Follow-up in the Minnesota Study has now been extended to 18 years for augmented incidence results, which have now been reported in the source article and in this morbidity abstract.

RESULTS

Subjects in Minnesota were recruited in 1975-1978 and randomized into annual or biennial screening for fecal occult blood, and a control group receiving "usual care." Screening was continued 1976-1982, discontinued, then resumed 1986-1992. During 18 years of follow-up, about 235,000 person-years of exposure were accumulated in each randomized group, with 417 and 435 cases of colorectal cancer in each of the screening groups and 507 cases in the control group.

CONCLUSION

Aggregate mean annual incidence rates of colorectal cancer were significantly lower in both screening groups than in the control group, as shown in Table 1. In the source article the same was true for the 18-year cumulative incidence rates, which were also significantly reduced (p < 0.001 for the annual screening group and p = 0.002 for the biennial screening group).