Multitarget Stool DNA Testing Has High Positive Predictive Value for Colorectal Neoplasia on the Second Round of Testing

BACKGROUND & AIMS: Multitarget stool DNA (mt-sDNA) testing is a stool-based screening test for colorectal cancer (CRC). In a single instance of testing, the pivotal Food and Drug Administration-approval study (NCT01397747) found that 16% of mt-sDNA tests were positive, and the positive predictive value (PPV) for CRC or advanced precursor lesions (APL) was 27.3%. We aimed to examine real world longitudinal performance by determining the test-positive rate and PPV of mt-sDNA on the second round of testing.METHODS: Colonoscopy and pathology reports were reviewed retrospectively for patients with a negative mt-sDNA on the first round of screening and a positive mt-sDNA on the second round. The test positivity rate and PPV for CRC, APL, and any colorectal neoplasia were calculated for the second mt-sDNA and compared with baseline PPVs from a previously published cohort of patients from our institution who tested positive on the first round of screening. RESULTS: A total of 2758 patients completed a second test at a median of 3.2 years after the first test. Of these, 422 (15%) had a positive second mt-sDNA. The PPV was 0.25% for CRC, 24% for APL, and 67% for any colorectal neoplasia. There was no significant difference in PPV on the second mtsDNA test compared with the first round (24% vs 28% for APL; P [ .12).CONCLUSIONS: mt-sDNA test positive rate and PPV were similar between the first and second rounds of screening. These observations confirm the utility of a second round of mt-sDNA screening and may inform estimates of mt-sDNA effectiveness for CRC screening.

Automated summary

Multitarget stool DNA (mt-sDNA) testing is an effective screening method for colorectal cancer. The positive rate and positive predictive value (PPV) of mt-sDNA were examined in a second round of testing and found to be similar to those in the first round. These findings confirm the usefulness of mt-sDNA for CRC screening.