The impact of population based faecal occult blood screening on colorectal cancer
A series of studies were carried out to assess the impact of guaiac faecal occult blood test (gFOBT) screening on colorectal cancer (CRC) mortality and associated outcomes in a true population based screening programme. Using data from the Scottish arm of the UK demonstration pilot of gFOBT screening for CRC, all residents in the three Scottish pilot NHS board areas invited for gFOBT screening were compared to controls individually matched by age, gender and deprivation and resident in one of the remaining Scottish NHS boards where screening had not been introduced. A reduction in CRC mortality was shown for those invited for screening and a further reduction in those who completed the test. Screening participants also benefited from reductions in emergency admissions to hospital, length of hospital stay and stoma formation. It was estimated that nine people had died during the pre-clinical stage of disease from a cause which may have been associated with the process initiated by the screening test. In additional studies, a randomised controlled trial (RCT) showed that a pre-notification letter was an effective method of increasing participation in gFOBT screening. In an examination of national trends in CRC survival in Scotland, an effect of gFOBT was apparent even in an all age cohort. An impact of gFOBT screening on all cause mortality could not be assessed due to a biased study cohort. In conclusion, the reduction in CRC mortality with gFOBT screening previously demonstrated in RCTs can be matched at the population level and these results justify the introduction of gFOBT screening to all four UK countries following the successful completion of the demonstration pilot. However, the studies showed that the benefits of screening were limited to those who participated. It is likely that a greater impact of screening would be realised with greater participation and increasing this is a priority.
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