Model shows lower age of screening initiation, stool tests improve CRC outcomes
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Moving the age of first colorectal cancer screening to 45 years – even when recognizing real-world imperfect adherence – showed improved incidence and outcomes in a model presented at the American College of Gastroenterology annual meeting.
“The take homes were that starting screening at age 45 resulted in increases in life-years gained and decreases in in cancer incidence and cancer death compared to starting at age 50,” Deborah A. Fisher, MD, MHS, of Duke University, said in an interview. “This was true with perfect adherence to screening, but it was also true looking at examples of published adherence rates from clinical practice, real-world data. Even without 100% participation in screening, starting at age 45 resulted in better population-level outcomes that starting at age 50.”
Based on the Colorectal Cancer and Adenoma Incidence & Mortality (CRC-AIM) microsimulation model, Fisher and colleagues simulated screening strategies for people without a previous diagnosis of colorectal cancer. The strategies started at age 40 and looked at CRC incidence, mortality and life-years gained from ages 50 years to 75 years as well as ages 45 years to 75 years. They predicted outcomes of screening vs. no screening per 1,000 individuals. Adherence rates were assumed to be as previously reported, which is 71% for multitarget-stool DNA (mt-sDNA) vs. 43% for fecal immunochemical test (FIT) test or perfect (100%).
“The idea was that if we had our own model that was validated and started with the initial assumptions of the Cancer Intervention and Surveillance Modeling Network (CISNET) model, we could make step-wise changes and examine outcomes under different conditions,” Fisher said. “One of the conditions that we’ve been exploring is what is the impact of not assuming 100% adherence to screening or any screening follow-up ... how does that affect the model and the predicted outcomes?”
Using reported adherence for mt-sDNA every 3 years and FIT tests every year, Fisher and colleagues reported starting screening at age 45 would result in 23.9 more life-years gained for mt-sDNA and 24.4 more life-years gained for FIT vs. starting screening at 50 years.
With the same parameters, CRC incidence fell by 64.5% if screening started at 45 and 61.1% if it started at 50 with mt-sDNA. With FIT, the reductions were 53.7% at 45 years and 49.9% at 50 years (P < .0001).
“There’s accumulating data that the outcomes are better starting earlier and that we can potentially impact the rising rates among individuals younger than age 50 by starting screening earlier,” Fisher said. “There are many caveats to starting early and the continued trend of younger people getting cancer. ... Nonetheless this provides additional data that if we do this, we will get better patient outcomes.”
Similarly, researchers showed a reduction in CRC mortality with mt-sDNA screening – 71.7% reduction starting at age 45 years and 68.7% reduction starting at age 50 years. With FIT, the reductions were 62.7% at 45 years and 59% at 50 years (P < .0001).
Fisher and colleagues reported reduced CRC cases and deaths in both pre-Medicare and Medicare populations and, using real-world adherence numbers, the number of CRC cases and deaths were lower with mt-sDNA every 3 years vs. annual FIT, regardless of screening age initiation.
Overall, improvements were seen with earlier screening when utilizing real-world reported adherence or assumed perfect adherence, according to Fisher.
“This study looks at stool-based screening, which has a much higher access and availability,” Fisher said. “Earlier screening at 45 does not necessarily have to mean earlier colonoscopy. Younger people – or everybody – could be screened by one of the other recommended methods and then the impact on colonoscopy resources would be lessened because of course it would be for people who had a positive test and not everyone.”
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Fisher DA. P0723. Presented at: The American College of Gastroenterology Annual Scientific Meeting (Virtual). Oct. 26-28, 2020.
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