Consequences of Increasing Time to Colonoscopy Examination After Positive Result From Fecal Colorectal Cancer Screening Test

Abstract

BACKGROUND & AIMS Delays in diagnostic testing after a positive result from a screening test can undermine the benefits of colorectal cancer (CRC) screening, but there are few empirical data on the effects of such delays. We used microsimulation modeling to estimate the consequences of time to colonoscopy following a positive result from a fecal immunochemical test (FIT). METHODS We used an established microsimulation model to simulate an average-risk United States population cohort that underwent annual FIT screening (from ages 50 to 75 years), with follow-up colonoscopy examinations for individuals with positive results (cutoff, 20 μg/g) at different time points in the following 12 months. Main evaluated outcomes were CRC incidence and mortality; additional outcomes were total life-years lost and net costs of screening. RESULTS For individuals who underwent diagnostic colonoscopy within 2 weeks of a positive result from a FIT, the estimated lifetime risk of CRC incidence was 35.5/1000 persons and mortality was 7.8/1000 persons. Every month added until colonoscopy was associated with a 0.1/1000 person increase in cancer incidence risk (an increase of 0.3%/month, compared with individuals who received colonoscopies within 2 weeks) and mortality risk (increase of 1.4%/month). Among individuals who received colonoscopy examinations 12 months after a positive result from a FIT, the incidence of CRC was 27.0/1000 persons (increase of 4%, compared with 2 weeks) and mortality was 9.1/1000 persons (increase of 16%). Total years of life gained for the entire screening cohort decreased from an estimated 93.7/1000 persons with an almost immediate follow-up colonoscopy (cost savings of $208 per patient, compared with no colonoscopy), to 84.8/1000 persons with follow-up colonoscopies at 12 months (decrease of 9%; cost savings of $100/patient, compared with no colonoscopy). CONCLUSION Using a microsimulation model of an average-risk US screening cohort, we estimated that delays of up to 12 months after a positive result from a FIT can produce proportional losses of up to nearly 10% in overall screening benefits. These findings indicate the importance of timely follow-up colonoscopy examinations of patients with positive results from FITs.

Faecal immunochemical tests to triage patients with lower abdominal symptoms for suspected colorectal cancer referrals in primary care: a systematic review and cost-effectiveness analysis

“…The only published source that we found reporting delayed diagnosis was the Meester et al study. 139 This study used a microsimulation model to calculate the effect of delay to colonoscopy on an average-risk population cohort in the USA who underwent annual FIT screening (from the age of 50 to 75 years), with follow-up colonoscopy examinations for individuals with positive results in the following 12 months. For the scenario of diagnostic follow-up at 12 months from a positive FIT, diagnosed cancers shifted towards more advanced stages, but still with only 8% in stage D. Regardless of the precise delay and its effect on progression, the cost-effectiveness results did not change significantly assuming 6 months' or 1 year's delay and so we decided not to run an additional scenario for a smaller delay.…”

Interventions to Improve Follow-up of Positive Results on Fecal Blood Tests

“…However, the effectiveness of fecal screening tests depends on timely follow-up diagnostic colonoscopy of patients with positive test results; guidelines generally recommend colonoscopy within 1 to 3 months (5, 7, 8). A long interval between a positive test result and colonoscopy can have important implications for CRC prognosis (9–11). …”

Optimizing the Quality of the Colorectal Cancer Screening Continuum: A Call to Action

“…Prior work has shown that complete diagnostic colonoscopy follow-up rates after abnormal guaiac FOBT and FIT may be as low as 22% (9)(10)(11)(12). Further, a recent modeling study has suggested that delay in follow-up results in higher CRC stage at presentation, incidence, and mortality; the relative reduction in life-years gained associated with screening was estimated to be 10% lower for diagnostic colonoscopy within two weeks vs 12 months after a positive FIT (13).…”