P1294 - Predictive Value of a Positive Multi-Target Stool DNA Test in Patients Evaluated for an Off-Label Indication

Raj I. Narayani, MD, FACG, Kaden R. Narayani,
Gastrointestinal Associates, PC, Knoxville, TN

Introduction: Multi-target stool DNA (mt-sDNA) analysis is approved for colorectal cancer (CRC) screening in average risk patients. For various reasons, providers may order mt-sDNA in patients with underlying CRC risk factors (off-label use). Whether this practice affects the predictive value of mt-sDNA has not been well-studied. We analyzed colonoscopy and polyp histology findings for all consecutive positive mt-sDNA referrals to compare predictive value for adenomatous polyps and CRC between average risk patients and off-label referrals.

Methods: We reviewed charts for all positive mt-sDNA referrals between January 2017 and December 2020. Referrals were classified as off-label if patients had CRC risk factors in the form of a personal history of adenomatous polyps or family history of colon cancer in a first degree relative. On subsequent diagnostic colonoscopy, detection rates for any adenoma, multiple adenomas (3 or more), advanced adenoma, and adenocarcinoma were calculated and compared between average risk and off-label referrals.

Results: 917 patients were referred for positive mt-sDNA during the query period. Of these, 829 (90%) completed a diagnostic colonoscopy. Colonoscopy data was reviewed in 670 average risk patients (81%) and 159 patients (19%) in whom mt-sDNA was obtained off-label. Table 1 shows positive predictive value of mt-sDNA in each neoplastic category for the entire cohort and a comparison between average risk and off-label subgroups. Notably, the detection rates for advanced adenomatous polyps and CRC were lower for off-label mt-sDNA referrals compared to average risk patients (21% vs 31%, 1.9% vs 2.8%).

Discussion: Among positive mt-sDNA referrals, nearly 20% were ordered off-label in relation to pre-existing CRC risk factors. Having risk factors for CRC at baseline significantly lowered predictive value of a positive mt-sDNA for discovery of advanced adenomatous polyps, but not simple or multiple adenomatous polyps. Predictive value for CRC was also lower for off-label referrals, but did not meet statistical significance, though this was likely related to small sample size. These results reinforce the need to educate primary care providers regarding the proper indication for mt-sDNA testing.



Disclosures:


Raj I. Narayani, MD, FACG, Kaden R. Narayani, . P1294 - Predictive Value of a Positive Multi-Target Stool DNA Test in Patients Evaluated for an Off-Label Indication, ACG 2021 Annual Scientific Meeting Abstracts. Las Vegas, Nevada: American College of Gastroenterology.