Linked Color Imaging vs. High-definition White Light Endoscopy for the Evaluation of Post-polypectomy Scars of Non-pedunculated Polyps. A Randomized Controlled Cross-over Trial. (LCI-Scar Study).

Polypectomy is highly effective in reducing cancer risk by resection of colon cancer precursors: adenomas and serrated lesions1. Despite expertise and good technique, up to 20% of non-pedunculated colorectal polyps larger than 20 mm resected by piecemeal endoscopic mucosal resection (EMR) show scar recurrence2. High recurrence rate implies a higher burden of subsequent surveillance and therapeutic colonoscopies, resulting in patient medicalization and increased costs.

Careful inspection and evaluation of the post-polipectomy scars looking for residual polyp is mandatory. In the past few years several techniques have been developed to improve optical diagnosis. One of them, virtual chromoendoscopy have been developed to overcome laboriousness of conventional chromoendoscopy. A recently a well-designed randomized controlled trial has demonstrated the accuracy of high definition white light endoscopy (WLE) and narrow band imaging (NBI) with or without magnification for diagnosis of scar recurrence after an endoscopic mucosal resection3. High diagnostic values were found for all the modalities but the diagnosis accuracy was higher in NBI with near focus. In cases of high confidence, if the optical diagnosis with NBI plus near focus for scar recurrence is negative, no biopsies are needed3. In view of these findings, the European Society of Gastrointestinal Endoscopy (ESGE) recommends the use of virtual or dye-based chromoendoscopy in addition to WLE for the detection of residual neoplasia in the polypectomy scar after a piecemeal resection.

Fujifilm® (HDTV, ELUXEOTM 700 System, Fujifilm® Tokyo, Japan) has developed a new generation of electronic endoscopy system that employs 4 different-wavelength LEDs as light sources. By changing the intensity of each of 4 LEDs, a white light mode and a Linked Color Imaging (LCI) and Blue Light Imaging (BLI) mode can be obtained. The white light mode is similar to conventional endoscopy using a Xenon lamp while LCI and BLI are the new technologies incorporated the system allowing a bright image-enhanced chromoendoscopy. In both BLI and LCI mode, the peak intensity of the LEDs is set at 410nm±10nm. As this is the peak absorption of light of hemoglobin, microvascular structures at the surface of the mucosa can be distinguished more clearly from blood vessels in the deep mucosa. In contrast to BLI, LCI also acquires the white light in an appropriate balance. The acquired color information is reallocated to differentiate the colors close to the mucosal color, i.e. information for several colors is simultaneously expanded so that the reddish and whitish colors become redder and whiter, respectively. Thereby, mucosal surface patterns are better visualized and this could potentially increase the detection of polyps by improving the visibility of colorectal lesions.

LCI has demonstrated to improve polyp and adenoma detection rate in previous studies5-7. However, to our knowledge no previous studies have been made for validation of LCI for optical diagnosis of a scar looking for residual neoplasia after a previous polypectomy. We hypothesize that LCI will improve the optical diagnosis of polyp recurrence compared to WLE. Therefore, the aim of this study is to evaluate the efficacy of LCI for optical diagnosis of post-polypectomy scar recurrence compared with WLE.