How to optimize the detection of serrated lesions: old tools for a new story?

In the last two decades, we have witnessed impressive and very quick technological advances in colonoscopy imaging aimed at optimizing the detection of neoplastic lesions. All major colonoscope manufacturers have integrated these innovations into the latest generation colonoscopes and currently produce high definition (HD) imaging systems with one or more push-the-button electronic chromoendoscopy technologies that are able to enhance visualization of the mucosal vasculature and/or architecture, so enhancing the contrast between lesions and the surrounding normal mucosa.

“...this study clearly demonstrates that the latest generation LCI and NBI systems are comparable for both SSL and adenoma detection, basically disproving the alleged superiority of NBI that was suggested in a previously published randomized tandem colonoscopy study”

Unfortunately, expectations of reductions in the miss rate of neoplastic lesions with the use of contrast-enhanced technologies have been scaled back owing to the current evidence from randomized trials and systematic reviews and meta-analyses, which have shown inconsistent results or a rather marginal detection gain. However, most of the published studies have primarily focused on adenoma detection, although it is well known that the identification of sessile serrated lesions (SSLs) along with adenomas is of critical importance for colorectal cancer (CRC) prevention. Indeed, SSLs account for 15 %–30 % of sporadic CRCs via the serrated neoplasia pathway, and their detection has recently been demonstrated to be strongly related to the incidence of post-colonoscopy CRC [1]. Therefore, a technology with a clear positive impact on SSL detection might still play a relevant role in CRC prevention.

Endoscopic detection of SSLs is notoriously challenging and requires a different level of competence compared with that required for adenomas because SSLs have a subtle appearance, indistinct color, and vague borders. Therefore, these lesions should represent a brand-new ideal target for contrast-enhanced technologies. Several studies have evaluated new generation “bright” narrow-band imaging (NBI) and linked-color imaging (LCI) versus standard HD white-light colonoscopy for SSL detection. Overall, both NBI and LCI appear to improve SSL detection, but the results are inconsistent across the studies and the magnitude of detection gain, if any, is too small to recommend their routine use in average risk colonoscopy patients [2].

The article by Li Jun et al. [3] fits right into the groove of this technology-driven path, by testing, in a parallel randomized controlled trial, whether it is the NBI or the LCI system that can best contribute to the identification of colonic polyps, particularly SSLs. The absence of a control group, namely patients undergoing conventional HD white-light colonoscopy, prevents any further clarification of the potential role of electronic chromoendoscopy for SSL detection. However, this study clearly demonstrates that the latest generation LCI and NBI systems are comparable for both SSL and adenoma detection, basically disproving the alleged superiority of NBI that was suggested in a previously published randomized tandem colonoscopy study [4].

The debate regarding the superiority of one contrast-enhanced technology over another for adenoma or SSL detection is likely to become less relevant in the near future, with the rapid development of machine learning techniques. Indeed, it is likely that the integration of computer-aided detection systems into new generation colonoscopes will marginalize the role of chromoendoscopy.

Nevertheless, the data collected by Li Jun et al. [3] provide other interesting insights. First, the adenoma miss rate for both the LCI and NBI arms, resulting from a subgroup analysis, remains high (22.0 % and 30.3 %, respectively), and comparable to that reported for HD white-light colonoscopy. This finding emphasizes how polyp detection during colonoscopy results from a complex multistep process where an improvement in only one single step (i. e. the adoption of advanced technology) is likely to have a limited contribution. Second, the present study highlights once again the importance of procedural and technical issues (i. e. high quality bowel preparation and slower withdrawal time) for the detection of neoplastic lesions, including serrated lesions.

It is unquestionable that improving the detection of SSLs is crucial to optimize the effectiveness of colonoscopy in CRC prevention [1], and that a high quality colonoscopy that combines optimal technical performance and new advanced technologies is essential to achieve this goal. A lack of awareness about sessile lesions has however been recognized as one of the most important contributors to the highly variable, and often suboptimal, SSL detection rates. Therefore, educational interventions focused on increasing awareness of the clinical relevance of SSLs cannot be disregarded. In a large prospective trial, it was recently demonstrated that such educational interventions within an organized FIT-based screening program were associated with a substantial and sustained increase in the detection rate of serrated lesions [5]. Moreover, the implementation of SSL detection rate as a quality metric of colonoscopy, with continuous auditing and feedback to individual endoscopists, could represent a further important step in enhancing the identification of serrated lesions [6].

Large scale studies will be required to clarify whether a comprehensive approach including the implementation of a bundle of these measures will reduce the miss rate of SSLs and ultimately lead to a significant reduction in post-colonoscopy CRC.

Publication History

Article published online:
17 April 2023

• References

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