Report in English with a Dutch summary (KCE reports 45A)

74 Screening for Colorectal Cancer KCE reports vol.45
(CRC mortality), however, are not published yet. Because of this the trial was
not included in the review from the NZHTA. It was however included in a
Cochrane review were the reviewers retrieved the mortality data directly from
the researchers involved 24.
Another study, the Burgundy study, a French controlled study 207, 209 published in
June 2004, was excluded for review by the NZHTA team mainly because of the
absence of random allocation. Nevertheless, in this very large population-based
study, using nonrehydrated Hemoccult without dietary restriction, all residents
of several small geographical areas (12 administrative districts in Burgundy for
the screening group and 17 other administrative districts corresponding to a
population of a similar size for the control group) were allocated either to
screening or to no screening. This involved inviting 45.642 subjects between the
ages of 50 and 74 years, while a control group of similar size was followed
without being informed of the study nor receiving any programmed screening.
Uptake in the first round was 52.8% and increased slightly in subsequent rounds
since those who clearly refused to participate were not invited again. Overall
69% of the invited population participated at least once. Screen positive
proportion was 2,1% in the first round and 1,4% on average thereafter, and the
overall colorectal cancer mortality reduction was 16% in an intention to screen
analysis and 33% in those who participated (at least once).
We need to be careful, however, when comparing these trials as there were
important differences in screening intensity (annual vs. biennial), test usage (non
rehydrated vs. rehydrated), the definition of positivity (number of samples out
of 6 that need to be positive), and ages (although all ages were between 45 and
80).
In spite of these caveats, the Cochrane review (most recent update 12 August
2005 24) estimated the colorectal cancer mortality reduction through offering a
(annual or biennial) Hemoccult screening program at 16% (95% CI: 7 - 23%) on
an intention to screen basis, and at 23% (95% CI: 11 - 43%) adjusting for
screening attendance. On a population level they estimated that if 10.000 people
were offered a biennial Hemoccult screening program, and when two-thirds
actively attend for at least one of the screening test, there would be 8,5 CRC
deaths prevented (95% CI: 3,6 - 13,5 CRC deaths) over 10 years.
The NZHTA 219 and the Cochrane systematic review 24 conclude that there is
high quality evidence of reduction in CRC mortality, possible reduction in CRC
incidence through detection and removal of colorectal adenomas and earlier
detection of cancers potentially leading to less invasive surgery. They stress
however that very little information is available from those trials, or from other
studies about the potentially harmful effects of screening other than the direct
complications of follow up colonoscopy in case of positive FOBT finding.