TBA (16S167)

WHAT ARE THE LONGTERM SURVEILLANCE IMPLICATIONS FOR A NORMAL COLONOSCOPY (NEGATIVE SCREENING) IN A HIGH RISK POPULATION?

Author(s)

M. Walshe, C. Kiat, J Leyden, P. MacMathúna

Department(s)/Institutions

Department of Gastroenterology, Mater Misericordiae University Hospital

Introduction

Absence of adenomas at screening colonoscopy has been shown to be predictive of absence of adenomas at follow up colonoscopy. Positive family history (FHx) of colorectal cancer (CRC) is associated with increased risk of CRC, resulting in a significant increased demand for screening full colonoscopy (FC). However, the implications of surveillance interval of a ‘polyp-free’ index FC in this cohort have not been clearly defined.

Aims/Background

To assess the long term surveillance implications for a normal index FC (negative screening) in a high risk population attending a Family Colorectal Cancer Clinic.

Method

We identified patients undergoing more than one screening FC from a group of 2242 patients attending the High-Risk Family CRC Screening clinic. Polyps found during FC were characterized into simple adenoma (SA) and advanced adenoma (AA). A total 1510 FC's were performed in 589 patients: median age at index FC was 46.9 years (range 18.5-75.3), a median of FC's performed was 2 (range 2-12) and the median interval to subsequent FC was 4.9 years (range 0.33-10.2). 

Results

At index FC , 465 (78.9%) had no adenoma while 124 (21.1%) had an adenoma. Of the 124 patients with adenoma at index colonoscopy, 47 (37.9%) had AA and 77(63.1%) had a SA.

In the normal FC cohort, follow up colonoscopy was normal in 404 (86.9%) while adenomas were only detected in 61 (13.1%). This is in contrast to 48 (38.7%) patients with adenoma found on subsequent colonoscopy in the adenoma at index FC group (P<0.001).

47 patients had AA at index colonoscopy and on subsequent follow-up, 8 (17.0%) patients had AA. Of the 542 patients who had no adenomas or SA only at index colonoscopy, only 14 (2.6%) had AA at follow-up (P<0.001, VS AA at index colonoscopy).

Conclusions

This study demonstrates that patients who are polyp free or SA only at index colonoscopy have lower risk of having an AA at subsequent colonoscopies. This could justify extending screening intervals within a high risk cohort with associated savings in resources within a limited capacity health service.