Effect of faecal occult blood testing on colorectal cancer mortality in the surveillance of subjects at moderate risk of colorectal neoplasia: a case-control study

Colonoscopy is the established method of surveillance of subjects at high r isk of developing colorectal neoplasia. Its role in the surveillance of a p opulation at moderate risk is less clear, however, as the procedure is expe nsive, time consuming and occasionally hazardous. The aim of this study was to estimate by case-control methods the effect of faecal occult blood (FOB ) screening on colorectal cancer (CRC) mortality in a population at moderat e risk of developing CRC. Screening by FOB testing prior to diagnosis in pa tients over the age of 45 years who died of CRC diagnosed in 1989-1998 was compared with screening in controls matched with the case for age and sex. Information about episodes of FOB testing and potential confounders was obt ained from the data collection system of the screening programme. Cases wer e less likely than controls to have ever been screened, with an odds ratio of 0.64 (95% confidence interval 0.34-1.15) for exposure to at least one FO B testing. There was no significant difference between the sub-groups according to gen der, age at diagnosis or location of the cancer. The inverse association be tween screening for faecal occult blood and fatal colorectal cancer suggest s that screening in a population at moderate risk of CRC can reduce mortali ty from CRC in this group.