WHEN TO START, WHEN TO STOP WITH COLORECTAL CANCER SCREENING: A COST-EFFECTIVENESS ANALYSIS

Background
In the Dutch colorectal cancer (CRC) screening program, individuals aged 55 to 75 years are invited biennially for fecal immunochemical test (FIT)-based screening using a positivity cut-off of 47 microgram Hemoglobin per gram feces (µg Hb/g). The start age is higher than advised within several screening guidelines: the United States guideline advises to start screening at age 45; the European guideline advises to start screening at age 50. Being one option to extend the screening program, lowering the start age should be weighed against other possibilities to further optimize the program. We aimed to investigate the cost-effectiveness of several adjustments to the current Dutch CRC screening program.

Methods
The Microsimulation Screening Analysis model for CRC (MISCAN-Colon) was used to simulate CRC screening while varying four parameters: 1) screening interval between 1, 2 or 3 years, 2) FIT cut-off between 15, 20, 30, 40, 47, 50 or 60 µg Hb/g, 3) start age between 50, 52, 54, 55, 56, 58 or 60 years, and 4) stop age between 70, 72, 74, 75, 76, 78 or 80 years. This resulted in 1029 different screening strategies. For each of these strategies, quality-adjusted life-years gained (QALYs), costs and colonoscopy demand were calculated. Efficient screening strategies, i.e. strategies that yield the highest number of QALYs for a given cost level, were identified. In sensitivity analyses, colonoscopy capacity was restricted to the capacity required for the current strategy, as well as an additional 20% extra capacity. A willingness-to-pay threshold of €20,000 was assumed for all analyses.

Results
Without restrictions on colonoscopy capacity, only strategies with the lowest cut-off considered (i.e. 15 µg Hb/g) were efficient, and almost all efficient strategies had a stop age of 80 (Figure). The cheapest efficient strategies had a screening interval of three years and start age 60, whereas the most costly strategies had an interval of one year and start age 50. Costs and effects of efficient strategies ranged from 164 QALYs and cost-saving per 1,000 individuals to 281 QALYs at €240,403 per 1,000 individuals. The optimal screening strategy comprised annual screening at a cut-off of 15 µg Hb/g from age 50 through 80. When colonoscopy capacity was restricted to the capacity required for the current screening strategy, the current strategy (biennial screening from 55-75 years at cut-off 47 µg Hb/g) was optimal. With 20% extra colonoscopy capacity, triennial screening from 50-74 years at a cut-off 20 µg Hb/g was optimal.

Conclusion
From a cost-effectiveness perspective, increasing the stop age of CRC screening should precede over decreasing the start age. However, with limited colonoscopy capacity, it is better to lower the FIT cut-off and start age of screening, while increasing the screening interval.