Options for screening for colorectal cancer in the Royal Air Force: a cost-effectiveness evaluation

Colorectal cancer (CRC) is the second most common form of malignancy, causing death after late presentation in two-thirds of cases. Early detection makes curative treatment likely. Faecal occult blood tests (FOBTs) detect some pre-symptomatic CRCs and their precursor lesions, adenomatous polyps. A trial showed reduced mortality in USA volunteers aged 50-80 with regular FOBTs; both this and the Nottingham population-based trial detected earlier-stage CRCs. Current US guidelines recommend annual digital rectal examination and FOBTs from age 40. FOBTs have been included in the USAF examination of aircrew for several years. Day-case colonoscopy, with appropriate biopsy-excision, is the first-choice follow-up investigation. This study aims to investigate the design of any programme to introduce FOBTs as part of the RAF's existing schedule of Periodic Medical Examinations (PMEs) and Screenings, and the age groups to be included, rather than the decision as to whether or not it should be commenced. The analysis therefore examines the cost per cancer detected. The information required to evaluate subsequent outcomes, such as cost per life-year saved, is not available for the RAF population so speculative extrapolation from other data is not attempted. Over a third of RAF personnel are under the age of 25, nearly three-quarters under 35 and over four-fifths under 40. Over a quarter of the 4 RAF CRC cases pa occur under age 40 and two-thirds under 50. The most cost-effective age at which to introduce FOBTs in the RAF is 40, regardless of the following parameters. Assuming FOBT sensitivity of 55% and positivity 5%, FOBT costing 23p and colonoscopy 175 pounds, starting FOBTs RAF-wide at age 40 would cost annually 35,968 pounds and 15,881 pounds per CRC case detected. The FOBT contribution to the costs is extremely small and the importance of maximising sensitivity and specificity very great. Hence dietary modification, and using a test or combination of tests with higher sensitivity and/or lower false-positivity, even if much more expensive, would be highly cost-effective, reducing the above costs substantially. Counting as "cases" persons with adenomas reduces the cost per "case" detected by about 75%. A pilot study is proposed concerning the introduction on selected stations of FOBTs with RAF PMEs/Screenings, from age 40, to determine: sensitivity and false-positivity rates for single and serial FOBTs, and the predictive value of positive tests, in RAF screenees; the annual cost; the costs per CRC case, and per CRC-plus-adenoma case, detected; possibly, an estimate of the cost per life-year saved; and, hence, whether the programme should be extended to all RAF personnel. FOB screening from age 40 would miss the quarter of RAF CRC cases which occur in personnel under 40. Identification is therefore recommended now of personnel at high risk for CRC, because of personal or family history, at all PMEs/Screenings, regardless of age, with the subsequent offer of serial FOBTs annually and regular colonoscopy. 2 1/2 yearly [corrected] FOBTs, done with PMEs/Screenings and half-way through the 5 year interval, would detect almost as many CRCs as annual testing, missing only half as many as 5-yearly testing. This analysis provides information on the costs and consequences of various FOB screening strategies for the RAF and other Services. Similar principles can be applied to develop informed strategies for other screening.