Science Spotlight

Model Based Estimation of Colorectal Screenings during COVD-19

From the The Issaka Group, Division of Public Health Sciences

In the US, colorectal cancer (CRC) is the second leading cause of cancer deaths.  Currently, CRC screening is below 80% (67% for adults aged 50-75); the National Colorectal Roundtable recommends at least 80% adherence for colorectal screening in the US.  During the COVID-19 pandemic, the Centers for Medicare and Medicaid Services recommended delaying all nonurgent medical procedures, which delayed CRC screenings, especially by colonoscopy. Because of this delay, by mid-April 2020 compared to the prior year, there had been a 90% reduction in CRC screenings, 32% reduction in CRC diagnoses, and 52% reduction in CRC surgical procedures. Unfortunately, the restrictions caused by COVID-19 have limited or deferred CRC screenings, which have led to deferments in diagnoses, further stage progression in patients with cancer, and increased the CRC mortality rate. Around the world, the fecal immunochemical test (FIT) is the most common CRC screening method but in the US, colonoscopies are more commonly used. As a result of the pandemic, there is an increased interest in stool-based screening tests in the US, particularly in populations where resources have been limited.

FIT has the potential to curb the public health effects of COVID-19 on CRC mortality.  The annual test is cost-effective and can be performed at home. It checks for blood in the stool and can be sent and received by mail. FIT has an overall diagnostic accuracy of 95% for CRC. The Issaka group, in the Division of Public Health Sciences, estimated how expanding FIT-based CRC screening would affect screening participation during the pandemic. Within four scenarios, CRC screening decreased for different amounts of times with or without the utilization of FIT-based screening.  The Issaka group’s objective was to assist medical professionals as they determined the clinical tradeoffs of approaches to increase CRC screening. The paper is published in JAMA Network Open.  

In order to complete the model estimations, the researchers used a simulation model in Excel to estimate the 3-year CRC outcomes for all eligible individuals according to the US Preventive Services Task Force. The researchers’ approach was amalgamated from previous colonoscopy studies, FIT-based screening tests, and screening statistics from the American Cancer Society.  The decision modeling approach utilized in the study was adopted from the methods of budget impact presented by the International Society for Pharmacoeconomics and Outcomes Research.  The population consisted of the US pre-COVID population who were eligible to be screened either by colonoscopy or FIT based on American Cancer Society CRC Facts and Figures.  Gender and age were based on the 2016 projection of the 2010 US Census.  The researchers also assumed that screening percentages for 2020-2023 would be similar to the 2017 to 2020 trends.

The four COVID-19 scenarios varied with regard to the COVID-19 dispersion profile (whether COVID-19 cases led restrictions in election procedures, locally or nationally) and the researchers response to improve CRC screening during the pandemic (whether FIT-based screening programs will increase in response to other CRC screening method reductions). In order to predict the stages of CRC cases for each screening method, the population prevalence estimates were multiplied by the reported stage-detection rates. To predict nonadherent and false-negative patients, the Issaka group used the Surveillance, Epidemiology, and End Results incidence rates from 1975 to 1979.  The decision model framework was used to estimate those who completed CRC screening, newly diagnosed CRC patients, or CRC detected at an early stage (stages I and II). The outcomes from each scenario were compared with the baseline or referent scenario (scenario 1 vs. 3 and scenario 2 vs. 4).

Graphical Representation of Number of people screened for colorectal cancer (CRC) and early stage CRC cases detected across modeled COVID-19 scenarios
Number of people screened for colorectal cancer (CRC) and early stage CRC cases detected across modeled COVID-19 scenarios Image from Dr. Rachel Issaka

In the baseline scenario, a total of 4,690,668 eligible adults completed CRC screening by colonoscopy or FIT per year, for the next 3 years (2020-2023). Assuming there were 34,323 cases, 98% were detected by both screening methods, the rest by symptoms.  In Scenario 1, COVID-19 related declines in colonoscopy screenings were limited during a 9-month period, there would be 37.6% fewer screenings and 32.6% fewer cancer diagnoses. In Scenario 2, COVID-19 related declines remained for 18 months, there were 42.9% fewer colonoscopy screenings and 37.6% fewer diagnoses. In Scenario 3 (compared to scenario 1), not only were colonoscopy screening limited during a 9-month period, FIT based screening was increased by 20% over the 3-year period. There was a 20% increase in adults completing CRC screening and a 12.3% increase of CRC diagnoses in which 68.9% was detected at an early stage. In Scenario 4 (compared to scenario 2), COVID-19 related declines remained for 18 months and FIT based screening was increased by 22% over the 3-year period. There was a 24.5% increase in adults completing CRC screening and a 12.7% increase of CRC diagnoses in which 71.6% was detected at an early stage. 

Dr. Issaka, the first author, concluded that “COVID-19 significantly disrupted colorectal cancer screenings. Our study found that modestly increasing the use of stool-based screening tests, such as the fecal immunochemical test (FIT), from 15% to 22% during a 3-year period, was associated with a 25% increase in colorectal cancer (CRC) screening and detection of 2715 additional cancers, the majority of which would be diagnosed at an early stage.” In research and clinical practice, Dr. Issaka continues to offer her patients options for CRC screening and stresses the importance of continuing preventive care, even during the pandemic. These findings raised the following questions:  will health systems across the country adopt programmatic stool-based CRC screening for disease prevention? What long-term effects will the COVID-19 pandemic have on the landscape of CRC screening in the U.S.?

This research was supported by National Cancer Institutes of Health.

Fred Hutch/UW Cancer Consortium member Rachel Issaka, Scott Ramsey, Joshua Roth contributed to this work.

Issaka RB, Taylor P, Baxi A, Inadomi JM, Ramsey SD, Roth J. Model-Based Estimation of Colorectal Cancer Screening and Outcomes During the COVID-19 Pandemic. JAMA Network Open. 2021 Apr 1;4(4):e216454-. doi:10.1001/jamanetworkopen.2021.6454