S0280 Lowering the Colorectal Cancer Screening Age Improves Predicted Outcomes in Pre-Medicare and Medicare Populations in the CRC-AIM Microsimulation Model

Abstract

INTRODUCTION: Most US guidelines recommend average risk colorectal cancer (CRC) screening for ages 50–75. An increasing CRC incidence among younger populations renders critical the need to evaluate the potential benefit of earlier CRC screening initiation. Using the validated CRC-AIM microsimulation model, we estimated the impact of lowering the CRC screening initiation age on outcomes for triennial multitarget stool DNA (mt-sDNA) or annual fecal immunochemical test (FIT) screening strategies. METHODS: Screening strategies were simulated for individuals free of diagnosed CRC at age 40 and screened from ages 50–75 or 45–75. CRC incidence, mortality, and life-years gained (LYG) were assessed for pre-Medicare eligible and Medicare eligible years (ages 65–75). Adherence rates were assumed to be as previously reported (71% for mt-sDNA vs 43% for FIT) or perfect (100%). Predicted outcomes of screening vs no screening are per 1000 individuals. Statistical differences between ages 45 and 50 were assessed by McNemar’s test. RESULTS: For individuals who initiated screening at age 45 with reported adherence, triennial mt-sDNA and annual FIT resulted in 23.9 and 24.4 more predicted LYG, respectively, versus starting screening at age 50 (Figure 1). With reported adherence, reductions in CRC incidence with mt-sDNA were 64.5% and 61.1% at screening start ages of 45 and 50, respectively, and with FIT were 53.7% and 49.9% (both P < 0.0001). Reductions in CRC mortality with mt-sDNA were 71.7% and 68.7% at screening start ages of 45 and 50, respectively, and with FIT were 62.7% and 59.0% (both P < 0.0001). Reductions in CRC cases and deaths were observed for both pre-Medicare and Medicare populations (Figures 2-3). With reported adherence, the number of CRC cases and deaths were lower with triennial mt-sDNA than annual FIT regardless of screening start age. Improvement in outcomes with earlier screening initiation were greater when assuming reported versus perfect adherence. CONCLUSION: Non-invasive stool-based screening tests may serve as effective early screening tools among younger populations. LYG and reductions in CRC incidence and mortality are greater when beginning screening at age 45 vs age 50, with gains applying to both pre-Medicare and Medicare populations. CRC outcomes were improved with a lower initiation age for both reported and perfect adherence model assumptions. When assuming reported adherence rates, mt-sDNA confers greater benefits than FIT.Figure 1.: Life-years gained (LYG) with triennial mt-sDNA and annual FIT assuming reported or perfect adherence and screening start ages of 45 or 50 years.Figure 2.: CRC cases per 1000 individuals with triennial mt-sDNA and annual FIT assuming reported or perfect adherence and screening start ages of 45 or 50 years. Results are shown for the pre-Medicare eligibility years (ages 45– or 50–64) or during Medicare eligibility (ages 65–75).Figure 3.: CRC deaths per 1000 individuals with triennial mt-sDNA and annual FIT assuming reported or perfect adherence and screening start ages of 45 or 50 years. Results are shown for the pre-Medicare eligibility years (ages 45– or 50–64) or during Medicare eligibility (ages 65–75).