Aug. 16, 2019
Wide-field endoscopic mucosal resection (EMR) is an advanced resection technique that has been shown to be an effective and relatively safe approach for the removal of large (> 20 mm), laterally spreading colorectal polyps.
During this procedure, the endoscopist injects a lifting fluid medium submucosally and then resects the lesion with a snare device. As with other endoscopic approaches, EMR has several advantages over surgical management. These advantages include lower morbidity and mortality rates, rapid recovery, preservation of normal gut function, lower costs, and higher patient satisfaction scores.
The most significant limitation associated with EMR is the potential for recurrence of adenoma. Up to 20% of patients will have a recurrence detected at their first surveillance colonoscopy, and 4% will experience the same after 12 months.
To detect the presence of recurrent neoplastic tissue, the current standard of care is to perform surveillance of the site, via biopsy or resection, four to six months after the initial procedure. Optimizing the accuracy of optical diagnosis of recurrent neoplastic tissue requires the use of enhanced imaging techniques.
Researchers from Mayo Clinic's campus in Jacksonville, Florida, and colleagues from universities throughout the United States and in Europe and Australia recently conducted the EMR Scar Assessment Project for Endoscope (ESCAPE) trial. This large study prospectively analyzed the efficacy of various endoscopic modalities in the diagnosis of recurrent neoplasia after EMR. The results of that trial were published in Gut in 2019.
Study methods and design
The research team conducted a prospective study of 230 patients undergoing colonoscopy after EMR of large (≥ 20 mm) colorectal neoplasia. Endoscopists predicted recurrence and confidence level with four imaging modes: high-definition white light (WL) and narrow band imaging (NBI) with and without near focus. A group of 26 experienced endoscopists assessed offline images separately.
The study included results obtained from 230 patients with 255 EMR scars. Within that group, the prevalence of recurrent adenoma was 24%. Diagnostic values were high for all diagnostic modalities, with negative predictive value ≥ 97%, positive predictive value ≥ 81%, sensitivity ≥ 90%, specificity ≥ 93% and accuracy ≥ 93%.
Relevant findings include the following:
- In high-confidence cases, combined use of NBI with near focus had a negative predictive value of 100%, with 95% confidence interval (CI), 98% to 100%; and sensitivity of 100%, with 95% CI, 93% to 100%.
- Use of clips at initial EMR increased diagnostic inaccuracy, with an adjusted odds ratio = 1.68; 95% CI, 1.01 to 2.75.
- In offline assessment, specificity was high for all imaging modes: mean ≥ 93%, range 55% to 100%.
- Sensitivity was significantly higher for NBI with near focus: mean, 82% (range 72% to 93%), when compared with WL: 69% (38% to 86%), p < 0.001; WL with near focus: 68% (55% to 83%), p < 0.001; and NBI: 71% (59% to 90%), p < 0.001.
According to lead author Michael B. Wallace, M.D., a gastroenterologist and interventional endoscopist at Mayo Clinic's campus in Jacksonville, Florida, these study findings offer a number of important takeaways for clinicians. The ESCAPE trial helped answer two important questions related to endoscopic assessment of scars after colorectal EMR:
- Does this assessment have to include biopsies, even if endoscopy is negative?
- Does endoscopic diagnosis of recurrent adenoma require biopsy before endoscopic re-interventions?
Dr. Wallace and co-authors note that appropriate use of these tools can help clinicians maximize the accuracy of optical diagnosis. "Our study demonstrates very high sensitivity and accuracy for all four imaging modalities, especially with the use of narrow band imaging with near focus, for diagnosis of recurrent neoplasia after EMR," explains Dr. Wallace.
"Furthermore, our data strongly suggest that in cases of high confidence, the use of narrow band imaging with near focus for the optical diagnosis eliminates the need for biopsy to confirm absence of recurrence during colorectal EMR follow-up," says Dr. Wallace. "And a high-confidence positive optical diagnosis can lead to immediate resection of any suspicious area. In all cases of low confidence, biopsy is still required."
"We typically perform biopsies of large post-EMR scars even if they appear unremarkable, but our practice has changed as a result of this study," states Louis M. Wong Kee Song, M.D., an interventional endoscopist at Mayo Clinic's campus in Rochester, Minnesota. "These data provide reassurance that one can omit biopsy when the level of confidence for residual or recurrent adenoma/dysplasia is high using the aforementioned optical techniques, resulting in cost savings," says Dr. Wong Kee Song.
Although the study involved the participation of endoscopists with experience in EMR and optical diagnosis, Dr. Wong Kee Song believes the study results are translatable to endoscopists in the community at large, since the NBI International Colorectal Endoscopic (NICE) classification of images utilized in the study is relatively simple to learn. "One caveat is the interpretation of polypoid tissue surrounding retained clips at the EMR site, which can be benign granulation/reactive tissue or residual adenoma, a difficult issue to sort out even with enhanced imaging techniques. Biopsies are recommended in this setting," says Dr. Wong Kee Song.
The research team is optimistic that this new knowledge will help clinicians avoid performing unnecessary biopsies when disease is absent. And, in cases where recurrence is detected, it can offer more-precise guidance about when it's necessary to repeat resection.
For more information
Kandel P, et al. Endoscopic scar assessment after colorectal endoscopic mucosal resection scars: When is biopsy necessary (EMR scar assessment project for endoscope (ESCAPE) trial). Gut. In press.