Association of Reducing the Recommended Colorectal Cancer Screening Age With Cancer Incidence, Mortality, and Costs in Canada Using OncoSim

Key Points Question What are the potential effects of earlier colorectal cancer (CRC) screening on disease incidence, mortality, and health care costs in Canada? Findings This modeling study followed simulated individuals representative of the Canadian population. Beginning screening by biennial fecal immunochemical test (FIT) at age 45 or 40, rather than 50 years, was associated with decreased CRC incidence, mortality, and overall CRC-related health care costs. Meaning Lowering the screening initiation age in Canada from the current start age of 50 years may be justified.

OncoSim's Base Case contains a separate stream for screening in individuals with a family history of CRC (at least one first degree relative diagnosed) which we kept consistent in all scenarios.This involves screening with colonoscopy every 5 years and is made available to a random subset of 50% of individuals with family history of CRC, with 100% of invited individuals participating in a first screen: the other 50% can enter the FIT screening stream.We made no changes to this screening stream in our scenarios.

Sensitivity Analyses
In addition to the main analysis, we carried out two sensitivity analyses: one demonstrating an aspirational screening participation rate of 60% with the same adenoma rate multiplier applied to birth cohorts, and a second conservative estimate with no adenoma incidence rate multiplier and 43% participation.These two scenarios were carried out in the same way as the main analysis as outlined in eTables 1 and 2.

eResults: Sensitivity Analyses Sensitivity Analyses -Effect on CRC Incidence and Mortality
Using an aspirational estimate of 60% screening participation predicts decreases in CRC incidence and mortality of greater magnitude than the main analysis using 43% participation.Screening initiation at age 45 yields 16,590 fewer CRC cases and 7,288 fewer CRC deaths compared to screening initiation at age 50 (total among the four birth cohorts studied).This represents 4,402 CRC cases and 2,027 CRC deaths avoided compared to our analysis using 43% participation.
Screening beginning at age 40 with 60% participation yields 25,046 fewer CRC cases and 11,030 fewer CRC deaths compared to initiation at age 50 (total for all birth cohorts).This is 6,911 fewer CRC cases and 3,042 fewer CRC deaths compared to the 43% participation scenario.As in the main analysis, the 60% participation scenario shows higher incidence and mortality reductions in younger birth cohorts (eTable 3).
In our conservative estimate using no adenoma rate multiplier and 43% participation, we observe more modest benefit compared to our main analysis.

Input Parameter Screening initiation at age 50 (base case) Screening initiation age lowered to 45 in 2022 Screening initiation age lowered to 40 in 2022
Abbreviations: FIT, fecal immunochemical test.a All costs in 2019 Canadian dollars.eTable 2.

Cumulative Outcomes of Modeled Scenarios for CRC Screening Initiation at age 45 or 40 When Screening Participation Set to 60% a,b
The results of the sensitivity analyses are also expressed as cumulative values over 40 years from the year a cohort's oldest subjects turn 40 to the year the youngest turn 75.All costs are in 2019 Canadian dollars.Screening test results include screening done by FIT and colonoscopy (for eligible individuals with family history).c Cost of CRC management includes screening, diagnosis, treatment, management of recurrence, palliative and end-of-life care.
eTable3.Abbreviations: CRC, colorectal cancer.a Values are cumulative over the 40-year period from the year the oldest subjects of the cohort turn age 40 to when the youngest subjects turn age 75.b eTable4.

Sensitivity Analyses -Quality-Adjusted Life-Years The
The model predicts 7,468 fewer CRC cases and 2,811 fewer deaths with screening beginning at age 45 and 10,274 fewer cases and 4,235 fewer deaths with screening beginning at age 40.The 60% participation scenario predicts a cumulative additional screening and treatment cost of $423 million with screening initiation at age 45 and an additional $912 million with initiation at age 40, both cumulative over 40 years and relative to screening starting at age 50.We again observe savings in the overall cost of CRC management (including cost of diagnosis, treatment, cancer recurrence, palliative and end-of-life care for all CRC cases, diagnosed by screening or not) of $999 million for screening initiation at 45 and $1.5 billion for initiation at age 40 (total for all birth cohorts over 40 years).60%participationscenariopredicts a total gain of 128,490 quality-adjusted life-years (QALYs) in the four birth cohorts for screening initiation at age 45 and 209,515 QALYs gained by screening from age 40 (eTable 4).Compared to 43% screening participation, this is 36,378 more QALYs for screening initiation at age 45 and 59,142 more QALYs for initiation at age 40.In the youngest birth cohort (born 1988-92) the cost per QALY is $780 and $2,574 for screening initiation at age 45 and 40 respectively, in keeping with our main analysis with 43% participation (eTable 4).The conservative model predicts a total gain of 49,613 quality-adjusted life-years (QALYs) in the four birth cohorts for screening initiation at age 45 and 77,098 QALYs gained by screening from age 40.In the youngest birth cohort(born 1988-92)the cost per QALY is $13,090 and $15,995 for screening initiation at age 45 and 40 respectively (eTable 6).While the costs per QALY are higher in this sensitivity analysis than in scenarios using the adenoma rate multiplier, this is still cost effective compared to other accepted health care interventions.