Oral (15W172)

FIT-positive Colorectal Cancer (CRC) screening colonoscopy: High sensitivity or just serendipity?

Author(s)

David J Gibson1, Blathnaid Nolan1, Joanna Rea1, Sarah Collins2, Maire Buckley1, Gareth Horgan1, Kieran Sheahan1, Glen A Doherty1, Hugh E Mulcahy1, Alan Smith3, Garret Cullen1

Department(s)/Institutions

1Centre for Colorectal Disease, St Vincent’s University Hospital; 2MedLab Pathology; 3Bowelscreen –The National Bowel Screening Programme, Ireland

Introduction

Approximately 65% of FIT positive clients in BowelScreen have colonic polyps identified at colonoscopy. It is not known if these polyps are the cause of the positive FIT, particularly when they are less than 10mm in size.

Aims/Background

The aim of this study is to determine if polypectomy in BowelScreen clients is associated with a negative FIT on follow up.

Method

A single centre prospective observational study of consecutive patients attending for first round screening colonoscopy who had a positive FIT (>225ng/ml buffer) as part of the Bowel Screen program. Subjects were consented at the time of their colonoscopy and were sent a further FIT 6-8 weeks later. Pre and post-colonoscopy FITs were compared, and this was correlated with clinical findings and endoscopic intervention.

Results

112 consecutive first round clients were recruited. Eight patients (7%) had a colonic tumour, 75 had adenomatous polyps (67%), 17 had a normal colonoscopy (15%) and 12 (11%) had other pathology. There was a clear difference in median FIT levels between the 4 groups (p=0.006). Advanced pathology (tumour or adenomatous polyp>10mm) was associated with higher FIT than non-advanced pathology (median FIT 1728 vs 443 p=0.0003). 83% (86/104) of subjects completed a follow-up FIT. Follow-up FIT remained positive in 20% (17/86). Polypectomy was associated with a reduction in FIT from a median of 498ng/ml to 25ng/ml (p<0.0001). Polypectomy was the only factor independently associated with a negative follow-up FIT on multivariate analysis (OR 3.9 (1.3-11.9, p=0.017)).

Conclusions

Adenomatous polyps cause a positive FIT test and polypectomy is associated with a negative follow-up FIT in the Bowel Screen programme. This may indicate a role for FIT in surveillance of clients with polyps identified at index colonoscopy.