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

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122 Screening for Colorectal Cancer KCE reports vol.45 even in a small percentage of cases, death. Both the influence on benefits and costs should be taken into account. A very important problem concerns the participation rate and compliance. First of all, some studies, based on their sensitivity analysis, argue compliance did not have a major influence on the ICERs. However, this was due to omitting campaign costs from the analysis. If fixed costs would be included in the analysis, having a high participation and/or compliance would have a positive influence on results because these relatively large fixed costs would be divided over a larger population participating in the screening. Moreover, the values for participation/compliance rates incorporated in the studies may be questioned. Many studies used 100% compliance in their base case analysis. This obviously does not reflect reality and therefore results should be interpreted with caution. From the studies comparing FOBT to no screening, the core scenario was characterized by biennial screening with a 60-67% participation in the first screening round and about 90% participation in subsequent screening rounds and compliance follow-up by colonoscopy. These numbers are based on population based randomized controlled trials. It is difficult to assess, however, how participation and compliance with an advertised national screening program could be expected to behave. As mentioned by Flanagan, participation rates in organized breast cancer screening programs in Canada in 1997 98 were well below the target of 70%, with estimates ranging from 12% to 55% across provinces after as much as 10 years of program implementation 516. Also Helm referred to a review which concluded that even the most intensive strategies in well defined populations rarely increase FOBT participation to more than 50% of the eligible population 403. This uncertainty has not been tackled extensively in most studies. Uncertainty in general was handled poorly. The models tried to reproduce mean estimates but did not take into account the full uncertainty on the input data as for example reported in the original RCTs. In addition, almost all studies performed one-way sensitivity analysis. As a result, the influence of combined uncertainty in the input variables (test characteristics, compliance, test costs, campaign costs, health benefits, etc ) was not taken into account. A few multiway sensitivity analyses were presented and show the major influence of changing several factors at the same time. Unfortunately, none of the studies performed probabilistic sensitivity analysis applied on all input variables at the same time, which should be part of an economic evaluation according to the Belgian guidelines 517. Another problem relates to the comparability of study results: differences in cost items included, country variations in cost levels, possibly different cost estimation methods, year of pricing, different discount rates, etc. Costs for the included variables in the US studies are, for example, much higher than in the Singapore, Israeli or Taiwanese studies. Special attention should be paid at the costs of testing and discount rates on benefits since, according to the one-way sensitivity analysis, they have a large impact on results. Fortunately, almost all studies discounted health benefits and costs. With regard to transferability to the Belgian situation, cost data are within the ranges mentioned in most of the studies, i.e. 539 for diagnostic colonoscopy, 568 for colonoscopy and biopsy, and 656 for colonoscopy in combination with polypectomy. FOBT costs in Belgium are 2,06 for the test kit or 44,47 with inclusion of development cards and two GP visits. The studies included in the first part of our overview, comparing FOBT with no screening, based compliance rates on RCT data. All results indicate that
KCE reports vol.45 Screening for Colorectal Cancer 123 screening individuals in a target population between 50/55 and 74 years of age is cost effective. Results may, however, overestimate cost effectiveness in realworld conditions. First of all, as mentioned before, participation and compliance in real-world settings are often lower than in RCTs. Secondly, several studies have not explicitly included campaign costs and/or impact of complications (Whynes, 1998, 1999, 2004; Gyrd-Hansen, 1998, 1999; Helm, Lejeune). From the studies comparing guaiac FOBT and immunochemical FOBT, the US study 499 cannot have direct policy implications. The major limitation of this study is the use of a hypothetical immunochemical FOBT with properties that do not currently exist amongst immunochemical FOBTs 219. This hypothetical immunochemical FOBT was assumed to have comparable sensitivity to Hemoccult SENSA but with higher specificity. Furthermore, 100% compliance was assumed. Based on other aspects such as compliance and including campaign costs the French study 504 is the most complete one. Both the Danish and French study (Gyrd-Hansen, 1998b; Berchi, 2004), however, provide better cost effectiveness results for gFOBT than for iFOBT. From the studies in the third part, i.e. assessing both FOBT and colonoscopy as a screening strategy, Sonnenberg, Leshno and Wong applied a 100% compliance rate in the base case which does not reflect real-world conditions. Furthermore, all but one, i.e. O Leary, did not explicitly include campaign costs thereby overestimating cost effectiveness of screening campaigns. The costeffectiveness estimates presented by Maciosek focus only on the average ICER of offering patients a choice of CRC screening tools rather than on the incremental value of each screening tool relative to another or compared with no screening. Compliance levels were also assumed to be the same, whatever the strategy chosen. Only O Leary both included program administration costs and reasonable compliance levels, i.e. 60% for FOBT and 42% for colonoscopy. Looking at other aspects of the study, they have also included costs of complications and distinguished treatment costs according to stage of colorectal cancer. The only major problem with this study is that they evaluated against rehydrated FOBT, as most studies in this part did, while it is clear from the studies on gFOBT that cost effectiveness results are in favour of unrehydrated FOBT. 6.5 CONCLUSION Which screening test is most appropriate is function of several factors such as the acceptability and safety of a test, the evidence for its clinical effectiveness, as well as economic considerations. Until now, only guaiac based FOBT has been the subject of large RCTs with published results on clinical outcomes and on costs. Based on the point estimates from economic studies, unrehydrated Hemoccult II test, followed by colonoscopy for subjects with positive FOBT results, is a cost effective option. Results also show that a screening program based on gFOBT is likely to be more cost effective than iFOBT. The high specificity, which avoids unnecessary colonoscopies, seems to be a determining factor for cost effectiveness. If more favourable evidence is provided for other types of FOBT, they may become an alternative in the future. Concerning the periodicity of the program, biennial screening is more cost effective than annual screening and the implication of periodicity on logistic requirements should not be underestimated. With respect to the target population, CRC screening is mostly proposed to subjects aged 50-74 years. It should be mentioned, however, that a screening program starting later, for
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KCE reports 1. Effectiviteit en kos
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