Impact of linked color imaging on the proximal adenoma miss rate: useful or not?

In this issue of Endoscopy, Karsenti et al. present an impressive randomized controlled trial investigating the impact of linked color imaging (LCI) on the proximal adenoma miss rate in a multicenter tandem setting [1]. The study examined whether LCI could detect more adenomas than white-light imaging (WLI) in the right-sided colon. The detection and resection of colorectal adenomas by colonoscopy is performed worldwide because it helps prevent colorectal cancer deaths. Routine colonoscopy is mainly performed under WLI. However, in a meta-analysis of 51 reports, the adenoma miss rate (AMR) of WLI was 26% (95%CI 23%–30%) [2].

“In a clinical setting, attention should be paid to various factors to ensure maximum benefit of LCI, such as patient age, endoscopist experience, observation sites, observation time, histopathology, and tandem observation.”

Narrow-band imaging (NBI), blue-laser imaging or blue-light imaging (BLI), and LCI are narrow-band light observation modalities that may be useful for improving the detection of colorectal polyps in routine colonoscopy [3]. NBI and BLI make lesions brownish for lesion detection. However, endoscopic views of NBI and BLI become reddish and are dark, especially when bowel preparation is poor, limiting their use in some situations. On the other hand, LCI makes lesions appear more reddish and the surrounding mucosa more whitish, providing good contrast for tumor detection. The endoscopic views of LCI are brighter than those of NBI and BLI, and the residual fluid becomes yellowish with LCI [3]. A recent meta-analysis including 17 randomized control trials (RCT) showed that the adenoma detection rate (ADR) of LCI was significantly higher than that of WLI (relative risk [RR] 1.18, 95%CI 1.11–1.25; P < 0.01) [4]. The analysis included mainly parallel and tandem studies, and the AMR was examined in only four studies (three of which were tandem studies), showing that the AMR was lower with LCI than with WLI (RR 0.54, 95%CI 0.41–0.73; P < 0.01) [4]. However, in the current study by Karsenti et al., there was no significant reduction in AMR with LCI compared with WLI [1]. The authors mentioned some limitations of the study, including a nonuniform distribution of patients across the participating centers, with more than half of patients treated at 3 (2 academic and 1 nonacademic) of the 10 centers. In addition, it was a tandem study rather than a parallel study as recommended by some authors, and in fact, only the right colon was studied in the tandem setting.

Regarding the efficacy of LCI in the right-sided colon, a study conducted at a Japanese center on LCI showed no significant difference in ADR between LCI and WLI for observation of the whole colorectum, although the number of adenomas per colonoscopy was significantly higher with LCI [5]. This study showed that the superiority of LCI over WLI was evident only in the descending colon and sigmoid colon. Thus, this result supports the result of the current study. Regarding the experience of the endoscopists, the current study by Karsenti et al. was conducted at 10 institutions and included only experienced endoscopists. However, a recent post hoc analysis of a previous large-scale international RCT showed that LCI significantly improved ADR in both experts and nonexperts [6]. In addition, the current study by Karsenti et al. included 686 patients and their mean age was 59.5 (SD 11.8) years; this was a little younger than other studies and this affected the number of adenomas detected in the study and the sample size calculation to achieve sufficient power for statistical calculation [7].

The current study by Karsenti et al. also showed that the miss rate of sessile serrated lesions (SSLs) was not significantly higher with LCI than with WLI, although the authors suggested the potential for reducing the SSL miss rate. Suzuki et al. reported that LCI showed significantly better SSL detection than WLI (4.8% vs. 2.8%; P < 0.01) [7]. On the other hand, Miyaguchi et al. reported no difference in SSL detection between LCI and WLI (3.2% vs. 3.4%; P = 0.84) [5]. A recent RCT directly evaluated SSL detection in LCI and WLI and there was a significant difference between the LCI and WLI groups (11.3% vs. 5.9%; P < 0.01) [8]. Thus, more studies should be performed to determine whether LCI is useful for detecting SSL.

LCI observation shows promise for improving colorectal polyp detection and decreasing AMR, and many studies have shown positive results [5]. However, the current study by Karsenti et al. showed negative results [1]. I think the current study is important as it highlights the need for a better understanding of LCI observations. I mentioned some possible reasons for the result. In a clinical setting, we should pay attention to various factors to ensure maximum benefit of LCI, such as patient age, endoscopist experience, observation sites, observation time, histopathology, and tandem observation. I also suggest that LCI observations require some experience for accurate interpretation. Tandem observations of WLI and LCI in the right-sided colon, as in the current study, would be good practice until endoscopists get used to the new observation mode (e.g. WLI observation first, new observation mode second).

WLI observation alone may results in some polyps being missed by both experts and nonexperts. I suggest that endoscopists need to know and learn more about each modality for clinical use. New observation modalities are appearing each year as improvements in electronics materialize. As demonstrated by this impressive paper by Karsenti et al., each modality should be studied in different ways before it is adopted into clinical settings. Thus, we continue to search for the best observation modality to improve polyp detection.

Publication History

Article published online:
09 August 2024

• References

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