TBA (26S167)

From Stool to Scope: A Prospective Study of Stool DNA testing for Advanced Colorectal Neoplasia

Author(s)

H Kerr, M Hanly, S Vilayil Johnson, F Donnellan, H Mulcahy, G Horgan, S O’Reilly, E McDermott, G Cullen, J Sheridan, G Doherty

Department(s)/Institutions

Department of Gastroenterology, St Vincent’s University Hospital, Elm Park, Dublin 4 UCD School of Medicine, University College Dublin, Dublin 4

Introduction

Early detection of colorectal cancer (CRC) and advanced adenomas is essential to reduce cancer-related morbidity and mortality. Stool DNA (sDNA) testing for Syndecan-2 methylation (mSDC2) is an emerging alternative method for early detection of colorectal neoplasia.

Aims/Background

To validate mSDC2 sDNA testing as an early detection tool in advanced colorectal neoplasia.

Method

We prospectively recruited patients attending our centre for a colonoscopy to undergo a sDNA test. Quantitative methylation-specific PCR was used to detect SDC2 methylation levels in stool samples. CT values corresponded inversely to SDC2 methylation levels. We analysed SDC2 stool results and pathology at colonoscopy. Advanced adenoma(AA) was defined as an adenoma size of >10mm or with high grade dysplasia.

Results

We report results of the first 65 participants. 15 positive and 50 negative sDNA SDC2 tests (positivity rate 24%). The median age of participants was 62 years. 46.7% were female. The median CT value of positive SCD2 results was 36.3. 6/15(40%) participants with positive sDNA tests for SDC2 had AA. 1 of these had high grade dysplasia with CT value of 33.8. 1/48(2.1%) participants with negative sDNA tests for SDC2 had an AA. There were no cancer cases. The sDNA test identified AAs with a sensitivity of 85.7% (95% CI 50.6-99.1). The specificity of the test for AAs was 83.9% (95% CI 72.9-91.9). The positive predictive value for detection of AAs was 40% (95% CI 18.3-64.9) and negative predictive value was 97.9% (95% CI 91.1-99.9).

Conclusions

sDNA testing shows acceptable diagnostic accuracy for colorectal neoplasia. Results support the use of mSDC2 sDNA test as an early detection tool for advanced colorectal neoplasia.