The target of colorectal cancer surveillance in individuals with inflammatory bowel disease is to detect dysplasia. The pathologic classification system of dysplasia includes none, indefinite, low-grade and high-grade dysplasia. The endoscopic terminology to describe dysplastic colon lesions in IBD is based upon whether the lesion is visible and described as polypoid or non-polypoid, or invisible and detected on a random biopsy. Data demonstrates most dysplastic lesions detected in patients with IBD are visible and targeted biopsies are superior to random biopsies. The utility of dye-based or virtual chromoendoscopy to enhance the detection of visible dysplasia is controversial. In the meta-analysis presented by Rakowsky and colleagues, the investigators found the quality of evidence supporting their results was moderate to very low for the randomized controlled trials and observational studies respectively, due to imprecision.

In spite of the quality issues, I believe the findings that standard definition white light (SDWL) colonoscopy alone falls short in the detection of visible dysplasia compared to dye base chromoendoscopy. In contrast, high definition white light (HDWL) colonoscopy was not inferior to chromo-colonoscopy in the few randomized controlled trials available for the analysis. While the results of the analysis of the observational studies favored chromoendoscopy over HDWL colonoscopy, the authors convey the results are associated with a very serious risk for bias. The bottom line to optimize the detection of dysplasia is to utilize an excellent technical approach to visualizing the mucosa, ensure patients have a high-quality bowel preparation, time the exam when there is no active IBD to confound endoscopic or histologic interpretation of lesions, and use HDWL or SDWL with chromoendoscopy.   

Despite the recently published SCENIC guidelines regarding surveillance for cancer in IBD, most clinicians in the U.S. are not performing routine chromoendoscopy. As Feuerstein and colleagues found in their meta-analysis, more studies are needed to demonstrate the overall value of routine chromoendoscopy for IBD surveillance, particularly compared with high definition white light. Most studies have shown an increased detection rate with chromoendoscopy, but the clinical relevance remains to be established, in particular, evidence for reducing cancers in IBD patients has yet to be demonstrated. 

In my practice, using high-definition white light, I personalize use of chromoendoscopy based upon the status of the patient, prior endoscopic findings, the disease extent, and presence of pseudopolyps. I am also reassured by recent studies demonstrating normalization of mucosa with effective treatments – which lowers the risk of cancer – as well as database studies demonstrating that the risk for cancer in patients with UC undergoing surveillance is now comparable to the risk in the general population. The guidance for optimal adenoma screening optimizing bowel preps and increased examination time are essential as is the performance of surveillance during inactive disease.

Much of the literature looking at chromoendoscopy compared it with endoscopy prior to the introduction of high-definition, white-light endoscopy. Clearly chromoendoscopy is better than standard definition endoscopy, but evidence is not as strong when comparing it with high-definition, white-light endoscopy.

If I extrapolate – and it may be unfair in this case – from what narrow band imaging (NBI) and other electronic imaging techniques have shown us, we can infer that much of the mucosal detail is there, but we did not previously recognize it. Now that we have electronic chromoendoscopy-like imaging on all the different brands of endoscopes, we can visualize mucosal details and often see what we previously needed chromoendoscopy to see.

Chromoendoscopy has been slow to be adopted even within the IBD community, as it may be cumbersome and takes more time. It is now gaining widespread acceptance, but there is still more evidence needed.

Chromoendoscopy is clearly effective at identifying dysplasia in patients with IBD when done by providers who do it frequently. However, high-definition colonoscopy may provide reasonable detection rates and be an alternative to the use of chromoendoscopy, especially in patients with pseudopolyps, poor preps and with those with active disease.