Relative risk of colorectal cancer decreases with age among individuals with a family history of colorectal cancer.
However, no screening recommendations specify less frequent screening with increasing age.
Dr Steffie Naber and her team of doctors from Rotterdam, The Netherlands, aimed to determine whether such a refinement would be cost effective.
The researchers determined the relative risk for colorectal cancer for individuals based on age and number of affected first-degree relatives using data from publications.
For each number of affected first-degree relatives, the team used the Microsimulation Screening Analysis model to estimate costs and effects of colonoscopy screening strategies with different age ranges and intervals.
Screening was then optimized sequentially, starting with the youngest age group, and allowing the interval of screening to change at certain ages.
Strategies with an incremental cost effectiveness ratio below $100,000 per quality-adjusted life year were considered cost effective.
For people with 1 affected first-degree relative screening every 3 years beginning at an age of 40 years is most cost effective.
The team reported that if no adenomas are found, the screening interval can gradually be extended to 5 and 7 years, at ages 45 and 55 years, respectively.
From a cost-effectiveness perspective, individuals with more affected first-degree relatives should start screening earlier and at shorter intervals.
However, frequency can be reduced if no abnormalities are found.
Dr Naber's team commented, "Using a microsimulation model for individuals with a family history of colorectal cancer, it is cost effective to gradually increase the screening interval, if several subsequent screening colonoscopies have negative results and no new cases of colorectal cancer are found in family members."