Date Published: August 16, 2018
Publisher: Public Library of Science
Author(s): Mary Dillon, Louisa Flander, Daniel D. Buchanan, Finlay A. Macrae, Jon D. Emery, Ingrid M. Winship, Alex Boussioutas, Graham G. Giles, John L. Hopper, Mark A. Jenkins, Driss Ait Ouakrim, Steven D. Shapiro
Abstract: BackgroundThe Australian National Bowel Cancer Screening Programme (NBCSP) was introduced in 2006. When fully implemented, the programme will invite people aged 50 to 74 to complete an immunochemical faecal occult blood test (iFOBT) every 2 years.Methods and findingsTo investigate colorectal cancer (CRC) screening occurring outside of the NBCSP, we classified participants (n = 2,480) in the Australasian Colorectal Cancer Family Registry (ACCFR) into 3 risk categories (average, moderately increased, and potentially high) based on CRC family history and assessed their screening practices according to national guidelines. We developed a microsimulation to compare hypothetical screening scenarios (70% and 100% uptake) to current participation levels (baseline) and evaluated clinical outcomes and cost for each risk category. The 2 main limitations of this study are as follows: first, the fact that our cost-effectiveness analysis was performed from a third-party payer perspective, which does not include indirect costs and results in overestimated cost-effectiveness ratios, and second, that our natural history model of CRC does not include polyp sojourn time, which determines the rate of cancerous transformation.Screening uptake was low across all family history risk categories (64%–56% reported no screening). For participants at average risk, 18% reported overscreening, while 37% of those in the highest risk categories screened according to guidelines. Higher screening levels would substantially reduce CRC mortality across all risk categories (95 to 305 fewer deaths per 100,000 persons in the 70% scenario versus baseline). For those at average risk, a fully implemented NBCSP represented the most cost-effective approach to prevent CRC deaths (AUS$13,000–16,000 per quality-adjusted life year [QALY]). For those at moderately increased risk, higher adherence to recommended screening was also highly cost-effective (AUS$19,000–24,000 per QALY).ConclusionInvesting in public health strategies to increase adherence to appropriate CRC screening will save lives and deliver high value for money.
Partial Text: Australia has one of the highest incidences of colorectal cancer (CRC) in the world . CRC is currently the second most common malignancy diagnosed in Australians, accounting for 13.4% of all new cancer diagnoses and causing 8.7% of all cancer-related deaths . These figures have remained stable over the last 30 years in Australia. But with a growing and aging population and escalating cost of new therapeutics, the cost of treating CRC has been rapidly increasing and was estimated at $1.2 billion per year in 2011, a 4-fold increase from 2001 .
We developed a Markov microsimulation to assess the expected clinical and economic impact of appropriate, under-, and overscreening. The analysis extends a model previously developed by Ait Ouakrim and colleagues  that simulates a hypothetical population of 100,000 individuals and their progression through 9 mutually exclusive health states representing CRC progression—from normal bowel to adenoma, CRC bowel states, and death from CRC or other causes. Given that only 70% to 80% of CRCs develop via the transformation of an adenomatous polyp [13,14] commonly referred to as the adenoma–carcinoma sequence, the model allows for a small proportion of CRCs to develop via an alternative pathway. Therefore, individuals in the health states “normal bowel” and “small adenoma” can progress to CRC Dukes A without having to pass through the modelled adenoma–carcinoma pathway (see Fig 1). Movement between states was determined by state transition probabilities identified in the literature.
Our first objective was to investigate CRC screening practices in the Australian population and characterise them according to national screening guideline recommendations and CRC risk categories based on family history. Our results provide a complex picture of CRC screening in Australia. Absence of, or inappropriate, screening concerns the vast majority of the population. Of eligible people in risk category 1—being at or slightly above average risk, which is the case for 98% of the population—approximately two-thirds had never undergone a CRC screening test, while 10% to 15% had been screened according to guideline recommendations and 16% to 21% had been overscreened given their risk category (by undergoing colonoscopies). A total of 2% to 6% engaged in CRC screening but less often than recommended.
This study provides a reference to which the performance of the national programme can be compared. A fully implemented NBCSP appears as both the cheapest and most effective approach to prevent death from CRC in the general population compared with colonoscopy-based screening. According to our model, this performance holds even with the 2017 NBCSP participation level, which is around 39%. Currently, opportunistic screening—i.e., screening outside of the existing organised programme—despite its high cost appears to be the most appropriate way to access screening for those at higher risk of CRC due to their family history as long as the specific needs of people in this category are not taken into account by the NBCSP. A programmatic approach to offering appropriate colonoscopy-based screening to the highest-risk group may provide further benefits in terms of cost and CRC deaths prevented.