The Utility of Multitarget Stool DNA Testing for Colorectal Cancer Screening After a Normal Colonoscopy

Multitarget stool DNA (MT-sDNA) tests (here, Cologuard®) are currently used in average-risk patients as a primary method of screening for colorectal cancer. However, MT-sDNA testing has also been used in patients who previously underwent colonoscopy who wish to avoid repeat colonoscopy. Here, in a large primary care practice setting, our aim was to evaluate the diagnostic performance of MT-sDNA testing in patients with a previously normal colonoscopy.

This retrospective cohort study included 5827 patients from 35 different primary locations in South Carolina. Patients aged 45 and above with a previously documented normal, high-quality colonoscopy prior to the MT-sDNA test date were included. High-risk patients and those with a previous negative MT-sDNA result were excluded.

Of 5827 ordered MT-sDNA tests, 248 patients had a prior normal colonoscopy. The average time from initial colonoscopy to MT-sDNA testing was 7.3 years. Of the 63 patients who had a positive MT-sDNA test, 41 patients (65%) completed follow-up colonoscopy and 40 patients had complete colonoscopy data. Of these 40 patients, 12 patients (30%) had advanced adenomas and none had colorectal cancer. Compared to patients without a previous colonoscopy, patients with prior colonoscopies had fewer adenomas of all types (1.6 vs 2.4) and fewer advanced adenomas (1.4 vs 2.0).

Patients with a previously negative colonoscopy and subsequent positive MT-sDNA test were found to have a high rate of advanced adenomas on follow-up colonoscopy (30%). Thus, in patients with a previously negative colonoscopy, MT-sDNA testing may be a reasonable alternative screening option.