S352 Implementation of Blood-Based Colorectal Cancer Screening Demonstrates High Adherence: Real-World Clinical Experience

Introduction: Colorectal cancer (CRC) remains a leading cause of cancer-related death in the United States. Overall CRC screening adherence is 58% in screen-eligible individuals. Blood-based CRC screening tests have been shown to yield adherence rates upwards of 90% and the ability to access previously unscreened populations. We describe adherence to a commercially available blood-based CRC screening test between May 2022 and June 2024. A version of this laboratory developed test (LDT) was recently approved by the FDA. Methods: Shield LDT (Guardant Health) was intended for screening in eligible individuals aged 45-84 years, who were not up to date with CRC screening. Providers ordered the blood-based CRC screening test commercially for patients they determined were eligible. Retrospective review of the first 20,000 age-eligible (≥45 years) clinical orders was performed to determine patient demographics and adherence rate, defined as the number of unique blood samples received at the laboratory out of the number of unique clinical test orders. Test turnaround time was assessed as time from placement of an order to blood sample receipt in the laboratory and time from blood sample receipt to results report. This research was conducted under Institutional Review Board approval for the generation of deidentified data sets for research purposes. Results: In the first 20,000 age-eligible clinical orders received, 61% were female and 39% were male; median age was 59 years (range, 45–99). Out of 20,000 unique orders, 18,901 samples were received by the laboratory, resulting in an adherence rate of 94.5%. Demographics of patients who completed the test were similar to those of the overall order population. Among the samples received at the laboratory, 91% (17,195/18,901) had a results report delivered. The 9% (1,706/18,901) of completed test orders without a results report were due to patient/provider cancellations or administrative/laboratory reasons. There were 1,585 test reports with an abnormal result reported, resulting in a positivity rate of 9.2%. Median time from placement of a test order to blood sample receipt in the testing laboratory was 1 day (range 0–182); median time from blood sample receipt to results report was 15 days (range, 0–83). Conclusion: This summary of real-world clinical ordering of a commercially available blood-based CRC screening test yields a 95% adherence rate, far higher than current rates for stool-based tests and colonoscopy.