N36: Back To Back Comparison Of Colonoscopy With Virtual Chromoendoscopy Using Third Generation Narrow Band Imaging System To Chromoendoscopy With Indigo Carmine In Lynch Syndrome Patients

E. Samaha1, C. Colas2, M. Dhooge3, J. C. Saurin4, T. Lecomte5, E. Coron6, G. Rahmi1, G. Perrod1, C. Savale1, S. Chaussade3, J. Bellanger2, N. Benech4, J. P. Barbieux5, M. Le Rhun6, H. Pereira1, G. Chatellier1, C. Cellier1

1 – European Georges Pompidou Hospital. 2 – Saint Antoine Hospital. 3 – Cochin Hospital. 4 – Edouard Heriot Hospital. 5 – CHU Tours. 6 – CHU Nantes.


Aim: Colonoscopic screening with indigo carmine chromoendoscopy (ICC) in Lynch Syndrome (LS) patients improves adenoma detection rate and is widely used nowadays. Nevertheless, it is a time- and-money-consuming technique which requires a dedicated training. Narrow band imaging (NBI) is a well-known virtual chromoendoscopy technique that highlights superficial mucosal vessels and improves contrast for adenomas. We conducted a prospective multicenter study in a back-to-back fashion to compare 3rd generation NBI to ICC for detecting colonic adenomas in LS patients.

Method: One hundred and thirty eight patients underwent a double colonoscopy, first with NBI, followed by ICC, in a back-to-back fashion. All polyps detected in either pass were removed for histopathological analysis. The primary outcome measure was the number of patients with at least one adenoma after NBI compared with the number of patients with at least one adenoma after NBI and ICC. Proportions were compared with the paired exact test (McNemar’s test). Continuous variables were compared with the Wilcoxon signed-rank test.

Results: All of the 138 patients were proven MMR mutation carriers (MLH1 = 33%, MSH2 = 47%, MSH6 = 15%, PMS2 = 4%, EPCAM = 1%). Mean age (standard deviation [SD]) was 40.5 (14.7) years, 64 (46.4%) were male. The median time for an NBI procedure was 8 minutes (interquartile range [IQR] 6–11) compared to 13 minutes (IQR 8–17) for ICC. At least one adenoma was detected during the initial NBI pass in 28 (20.3%) of 138 patients. ICC detected additional adenomas in 25 (18.1%) of 138 patients. Forty-two patients (30.4%) had at least one adenoma detected after both NBI and ICC; this represents an increase of 50.0% of the adenoma detection rate (ADR) (p=0.0001). The total number of adenomas increased from 39 after NBI pass to 75 after ICC pass with a mean number of adenomas detected per patient of 0.3 (0.7) after NBI pass vs 0.5 (1.1) after both NBI and ICC passes (p<0.0001). The ADR for flat adenomas was 10.9% after NBI vs 23.2% after ICC (p<0.0001). The ADR increased for right sides adenomas (10.9% after NBI vs 16.7% after ICC, p=0.0078) as well as for diminutive adenomas ≤5mm (16.7% after NBI vs 28.3% after ICC, p<0.0001). Detection of both sessile adenomas (11.6% NBI vs 13.8% ICC, p=0.25) and adenomas > 5mm (6.5% NBI vs 8.0% ICC, p=0.5) did not differ significantly between the 2 techniques. After adding white light detected adenomas, the total ADR of the study was 33.3%.

Conclusion: Colonoscopy with indigo carmine chromoendoscopy detects significantly more adenomas than 3rd generation NBI in LS patients, whereas sessile and > 5mm adenomas are equally detected. Although less time consuming, NBI colonoscopy cannot be recommended to replace indigo carmine chromoendoscopy in LS patients.