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

112 Screening for Colorectal Cancer KCE reports vol.45
3300 (baseline 2150) for screening based on the Funen-1 protocol, and
1000 to 3300 (baseline 1975) for screening based on the Nottingham
protocol. Also in the Canadian study 498, the cost effectiveness ratio remained
favourable even under high-cost scenarios, i.e. 12.900 ($18.445) instead of
8335 ($11.907).
With respect to which cost items have the largest impact on results, Whynes
and colleagues (2004) doubled testing, investigation, and treatment costs which
increased the ICER with 59,6, 27,5, and 12,9 percent respectively. In the initial
study, doubling FOBT costs raised the ICER by 30 percent relative to the base
estimate.(Whynes, 1998, 1999) The French study results are relatively similar.
Colorectal cancer treatment costs did not influence the ICERs, but, changes in
the costs of FOBT and colonoscopy had a stronger impact. A decrease in the
FOBT cost from 3,20 to 1,60 led to an 11,1 percent reduction in the ICER.
According to the lowest and highest value of the colonoscopy costs, i.e. 225
and 830, ICERs ranged from 2929 to 3817 per LYG. Finally, also Gyrd-
Hansen found that the cost of colonoscopy had a significant effect on the
estimated cost per life year saved. Tripling this cost, i.e. from 130 to 390
(3000DKK), increased the ICERs by 40-45 percent (Gyrd-Hansen, 1998, 1999).
Concerning the influence of discounting, results are not surprising. In the study
of Whynes (2004), results were found to be relatively insensitive to plausible
variations in the assumed discount rate for costs but more sensitive to
variations in the discount rate for benefits. Discounting benefits by the same
rate as costs, i.e. 6 percent instead of 2 percent, raised the ICER by 77,4
percent. When benefits are undiscounted, the ratio falls by 25,5 percent. The
fact that changing the discount rate on costs does not influence results greatly is
due to the fact that these occur mainly in the short term. Benefits of screening
programs, on the contrary, occur in the future which is the reason why
discounting them has a greater impact on results.
Regarding the periodicity of the screening test a biennial screening program is
favoured. The study of Gyrd-Hansen (1998, 1999) provided six efficient
screening programs. The biennial screening program provided better ICERs
than the annual screening program. For example, in a target population of 55-74
year old persons, the incremental cost effectiveness ratio was 2990
(23.012DKK) and 4610 (35.471DKK) for respectively biennial and annual
screening. The cost per life-year gained from biennial screening was 8335
(CAD11.907) and this increased to 9450 (CAD13.497) under annual screening
(discounted at 5%). Both biennial and annual screening remained cost-effective
under the high-cost sensitivity analysis, respectively 12.900 (CAD18.445) and
13.925 (CAD19.893).(Flanagan) In the Australian study, annual screening was
associated with an ICER of 12.000 (AUD20,000) per DALY gained instead of
10.200 (AUD17.000) for biennial screening.(Stone) However, annual screening
was found to increase both the cost and yield of screening compared with the
biennial approach, and Whynes (1998, 1999) concluded these two effects
compensated for each other and as a result had little impact on the ICER.
Two studies (Gyrd-Hansen (1998, 1999) and Stone estimated the influence of
changing the age of the target population in the main analysis (see above). With
regard to cost effectiveness, older age groups had better outcomes than
younger ones (45-49 and/or 50-54). Other studies explored the influence of
changing target groups as part of their sensitivity analysis. In the Canadian study,
the increased cost of screening before age 50 was not warranted, given the
small gain in life expectancy, and screening after age 75 showed no significant
gains in life expectancy. Starting to screen at age 50 and ending at age 74 was
shown to be more cost-effective than starting later or ending earlier (Flanagan).