The cost-effectiveness of screening for colorectal cancer

Background

Published decision analyses show that screening for colorectal cancer is cost-effective. However, because of the number of tests available, the optimal screening strategy in Canada is unknown. We estimated the incremental cost-effectiveness of 10 strategies for colorectal cancer screening, as well as no screening, incorporating quality of life, noncompliance and data on the costs and benefits of chemotherapy.

Methods

We used a probabilistic Markov model to estimate the costs and quality-adjusted life expectancy of 50-year-old average-risk Canadians without screening and with screening by each test. We populated the model with data from the published literature. We calculated costs from the perspective of a third-party payer, with inflation to 2007 Canadian dollars.

Results

Of the 10 strategies considered, we focused on three tests currently being used for population screening in some Canadian provinces: low-sensitivity guaiac fecal occult blood test, performed annually; fecal immunochemical test, performed annually; and colonoscopy, performed every 10 years. These strategies reduced the incidence of colorectal cancer by 44%, 65% and 81%, and mortality by 55%, 74% and 83%, respectively, compared with no screening. These strategies generated incremental cost-effectiveness ratios of $9159, $611 and $6133 per quality-adjusted life year, respectively. The findings were robust to probabilistic sensitivity analysis. Colonoscopy every 10 years yielded the greatest net health benefit.

Interpretation

Screening for colorectal cancer is cost-effective over conventional levels of willingness to pay. Annual high-sensitivity fecal occult blood testing, such as a fecal immunochemical test, or colonoscopy every 10 years offer the best value for the money in Canada.Colorectal cancer is the fourth most common cancer diagnosed in North America and the second leading cause of cancer death.^1,2 An effective population-based screening program is likely to decrease mortality associated with colorectal cancer^3–6 through earlier detection and to decrease incidence by allowing removal of precursor colorectal adenomas.^7,8 Professional societies and government-sponsored committees have released guidelines for screening of average-risk individuals for colorectal cancer by means of several testing options.^9–12 These tests vary in sensitivity, specificity, risk, costs and availability. With no published studies designed to directly compare screening strategies, decision analysis is a useful technique for examining the relative cost-effectiveness of these strategies.^13–21 Previous studies have shown that screening for colorectal cancer is cost-effective at conventional levels of willingness to pay, but no single strategy has emerged as clinically superior or economically dominant.²² The interpretations of economic evaluations in this area have been limited because investigators have not simultaneously accounted for the positive effects of screening on quality of life, the effect of noncompliance with screening schedules, and the greater efficacy and cost of more modern chemotherapy regimens for colorectal cancer. Furthermore, no study has included all of the strategies recommended in the 2008 guidelines of the US Multi-Society Task Force on Colorectal Cancer.¹⁰Our objective was to estimate the incremental cost-effectiveness of 10 strategies for colorectal cancer screening, as well as the absence of a screening program. The current study is more complete than earlier studies because we included information on quality of life, noncompliance with screening and the efficacy observed in recent randomized trials of colorectal cancer treatments. The complete model is available in Appendix 1 (available at www.cmaj.ca/cgi/content/full/cmaj.090845/DC1). This article focuses on the comparison of no screening and three screening strategies:¹ low-sensitivity guaiac fecal occult blood test,² performed annually; fecal immunochemical test,³ performed annually; and colonoscopy, performed every 10 years. These three tests are currently being used or considered for population-based screening of average-risk individuals in some Canadian provinces.     

Effectiveness of population-based colorectal cancer screening programme in down-staging

BackgroundThis is the first evaluation study to assess the demographic characteristics of the colorectal cancer (CRC) cases detected in the prevalent round of the population-based Colorectal Cancer Screening Programme (CRCSP) in Hong Kong and to explore the effectiveness of the programme on the stage distribution of CRC.MethodsThis study covered the period between 28 September 2016 and 31 December 2018. Information on CRC diagnosis, age and stage at diagnosis were retrieved and reviewed by the Hong Kong Cancer Registry (HKCaR). The CRC detection rate among CRCSP-screened participants and incidence rate among the Hong Kong general population were calculated respectively. The odds ratio (OR) was calculated to measure the strength of association and quantify the effect of CRCSP on stage shift between CRCSP-detected CRC cases and an age-matched cohort of CRC cases diagnosed outside the programme.ResultsThe CRC detection rate among participants of the CRCSP during the study period was 736.0/100,000, whereas the overall CRC incidence rate among general population of similar age groups was 393.7/100,000. For all ages and both sexes, the OR of stage I CRCSP-detected CRC compared to the CRC from the age-matched cohort was 3.91 (95%CI=3.41–4.48) and the OR dropped to 0.54 (95%CI=0.41–0.70) at stage IV. Meanwhile, the overall OR of CRCSP-detected CRC compared to CRC from the age-matched cohort dropped from 2.24 (95%CI=1.97–2.56) to 1.62 (95%CI=1.40–1.87) with increasing age.ConclusionThe present study has demonstrated the initial impact of the CRCSP on shifting the stage at diagnosis towards earlier stage. The benefit of stage-shift was similar for all ages from 60 to 77 in both sexes and seems to increase with younger age. Given the stage-dependent survival outcomes, this stage-shift could lead to a reduction in CRC-associated mortality in Hong Kong in future.     

Randomised trial of compliance with screening for colorectal cancer.

A randomised trial of compliance with screening for colorectal cancer by means of the haemoccult test was conducted in Farnborough and Basingstoke districts. In each of the 14 participating practices (41 general practitioners) 25 852 men and women aged between 40 and 70 years were randomly allocated by household to one of six groups. The group determined the method of invitation to screening: a letter and the test were sent to the patient, or a letter with an appointment to attend the surgery was sent, or during a routine consultation the general practitioner invited patients to participate, and some patients received an educational booklet about bowel disorders and screening. Of the 17 824 people who were offered screening, 7545 (42%) complied. Compliance was significantly affected by the method of invitation, but not by whether an educational booklet was received, and was highest (57%) in the group that was offered the haemoccult test during a routine consultation (the "opportunistic" approach). In this group the compliance rate achieved by individual general practitioners ranged from 26% to 82%. Compliance was significantly higher in Farnborough, in the older (55-70) age group, in women, and in households in which two or more people were offered screening. The higher compliance in Farnborough may be explained by the higher proportion of older people and by the higher proportion of people living in households of two or more in the population that was offered screening. The fact that the screening programme in Farnborough was offered to the whole community and that the researcher may have acted as a facilitator were probably also important. One per cent of the patients screened had a positive test, and 24 (38%) of the 63 patients who were positive and were investigated in hospital had neoplastic disease. The yield was 1.2 cancers and 1.2 benign adenomas (1 cm or larger in size) per 1000 people screened. This low yield is likely to be a consequence of the relatively young age group screened.     

Evaluating the long-term effect of FOBT in colorectal cancer screening

BackgroundCancer screening has been effective in detecting tumors early before symptoms appear. However, the effectiveness of the regular fecal occult blood test (FOBT) in colorectal cancer in the long term has not been quantified.MethodsWe applied the statistical method developed by Wu and Rosner [1] using data from the Minnesota Colon Cancer Control Study (MCCCS). All initially asymptomatic participants were classified into four mutually exclusive groups: true-early-detection, no-early-detection, over-diagnosis, and symptom-free life; human lifetime was treated as a random variable and is subject to competing risks. All participants in the screening program will eventually fall into one of the four outcomes above. Predictive inferences on the percentages of the four outcomes for both genders were made using the Minnesota study data.ResultsDepending on gender, screening frequency and age at the initial screening, for all participants the probability of “symptom-free-life” varies between 95.3% and 96.6%; the probability of “true-early-detection” is 1.9–3.8%; the probability of no-early-detection is 0.3–2.0%; the probability of over-diagnosis is 0.16–0.3%. Among those with colorectal cancer detected by regular FOBT, the probability of over-diagnosis is lower than expected and is between 6% and 9%, with 95% CI (2.5%, 21.3%) for females and (1.9%, 44.7%) for males. The probability of true-early-detection increases as screening interval decreases. The probability of no-early-detection decreases as screening interval decreases.ConclusionThe probability of over-diagnosis among the screen-detected cases is not as high as previously thought. We hope this outcome can provide valuable information on the effectiveness of the FOBT in colorectal cancer detection in the long term.