What’s the Best Way to Examine Lynch Colons?
Because of the more rapid transformation of adenomas to cancer in Lynch syndrome, one often sees recommendations that colonoscopists performing Lynch examinations should be proven high-level detectors who employ special techniques, such as double-right colon examination, chromoendoscopy, or electronic chromoendoscopy.
What is the state-of-the-art for examination of Lynch colons? Two recent studies are relevant to this question.
One study is a meta-analysis of 4 eligible trials on chromoendoscopy versus white-light endoscopy. Chromoendoscopy was superior to white-light endoscopy for detection of adenomas (pooled ratio of lesion detection rates [RR], 1.53), flat lesions (RR, 3.4), and proximally located lesions (RR, 2.93).
The second study is a multicenter trial in which 138 patients underwent double colonoscopy, first with narrow-band imaging (NBI) using the 190 series brighter illumination NBI, followed by a second examination using chromoendoscopy with indigo carmine (ICC). The adenoma detection rates were 20.3% after the NBI examination and 30.4% after ICC. ICC detected additional adenomas in 25 patients (18.1%). The total number of adenomas increased from 39 after NBI to 75 after ICC, for a calculated miss rate of 48% for NBI, which was higher than the authors expected from second-pass effect alone. Median withdrawal time with NBI was 8 minutes versus 13 minutes with ICC.
Comment:
The second study gets at the current major question in color highlighting for detection, which is not whether electronic chromoendoscopy or chromoendoscopy is better than white-light endoscopy (they both are better than white-light endoscopy), but whether chromoendoscopy is better than electronic chromoendoscopy. Because patients in a tandem study can’t be randomized to chromoendoscopy versus electronic chromoendoscopy first (if chromoendoscopy is done first, the dye will affect the electronic chromoendoscopy examination), then this question will need to be solved by straight, randomized, controlled trials. These trials will have to be controlled for bowel preparation quality and inspection time. Despite the results of this tandem study, I believe the jury is still out on whether traditional dye-sprayed chromoendoscopy can beat new generation Olympus and Fujinon electronic chromoendoscopy, and the simplicity and speed of electronic chromoendoscopy means the question is important.
Note to readers: At the time we reviewed this paper, its publisher noted that it was not in final form and that subsequent changes might be made.
Douglas K. Rex, MD, FASGE
Citation(s):
Har-Noy O, Yung DE, Koulaouzidis A, et al. Chromoendoscopy or white light endoscopy for neoplasia detection in Lynch syndrome, a meta-analysis. Dig Liver Dis 2019 Sep 13. (Epub ahead of print) (https://doi.org/10.1016/j.dld.2019.07.018)
Cellier C, Perrod G, Colas C, et al. Back-to-back comparison of colonoscopy with virtual chromoendoscopy using a third-generation narrow-band imaging system to chromoendoscopy with indigo carmine in patients with Lynch syndrome. Am J Gastroenterol 2019 Sep 9. (Epub ahead of print) (https://doi.org/10.14309/ajg.0000000000000386)
