Published online Dec 7, 2018. doi: 10.3748/wjg.v24.i45.5179
Peer-review started: August 20, 2018
First decision: October 14, 2018
Revised: October 18, 2018
Accepted: November 16, 2018
Article in press: November 16, 2018
Published online: December 7, 2018
Endoscopic mucosal resection of colon polyps in a piecemeal fashion (EPMR) requires a first close follow-up at 3-6 mo. In addition, the European Society of Gastrointestinal Endoscopy recommends the use of advanced endoscopic imaging for the detection and differentiation of residual neoplasia at the polypectomy scar, but with low quality of evidence.
There are limited data on the best approach with the use of narrow band imaging (NBI) compared with white light endoscopy (WLE) to review a polypectomy scar.
This study was designed to assess the incremental benefit of NBI and WLE, randomizing the initial technique for the detection of residual neoplasia at the polypectomy scar after an EPMR.
We conducted an observational study of 120 polypectomy scars in 111 patients who had undergone a baseline colonoscopy with piecemeal polyp resection regardless of size and prospectively assigned to follow-up colonoscopy with random application of NBI and WLE 1:1 at the proximity of the scar. Patients were distributed in two groups (NBI-WLE or WLE-NBI). Five experienced endoscopists used Olympus 190 series for the assessment. Any macroscopically suspicious lesion was recorded as positive, with high confidence of a definitive diagnosis, or as negative. After the first examination, the endoscopist switched to the second technique and reviewed the polypectomy scar again, making a second prediction. After both evaluations, all of the sites were biopsied, including apparently normal scars. All resected specimens were blinded to the three specialized pathologists. The primary outcome was the accuracy of NBI and WLE in detecting residual neoplasia in the polypectomy scar, with pathological analysis as the gold standard. Receiver operating characteristic (ROC) curve analyses were performed to reveal the relationship between the sensitivity and specificity of NBI and WLE, and Kappa statistics were used to assess interobserver agreement between endoscopists for each technique and with histology.
After randomization, 8 lesions were excluded from the final assessment because the scar was not found, and therefore 112 scars were finally included to the analysis. In the WLE-NBI group, a first inspection with WLE showed 78.9% sensitivity, 84.2% specificity, 71.4% positive predictive value (PPV) and 88.9% negative predictive value (NPV). The addition of a second review with NBI slightly increased sensitivity to 89.5% and NPV to 94.1%, without modifying specificity (84.2%) or PPV (73.9%). The addition of NBI was followed by a slight but non- significant increase in accuracy, shown by the area under the ROC curve (AUC): WLE 81.6% vs NBI 86.8% (P = 0.15). In the NBI-WLE group, which underwent the first review with NBI, the results in terms of sensitivity and specificity were almost equivalent. There were no differences in the AUC with NBI (81.1%) vs WLE (81.4%) (P = 0.9). There was a high degree of interobserver agreement between WLE and NBI (Kappa value, 0.91) and good concordance with histology (WLE: Kappa 0.62 and NBI: Kappa, 0.65). Of the 112 scars detected at the endoscopic follow-up, 39 (34.8%) had residual neoplastic lesions on histologic assessment.
We found that NBI and WLE showed high sensitivity, specificity and very good accuracy in detecting residual neoplasia. Sensitivity and NPV were improved only when NBI was performed after WLE but this difference was not statistically significant. In our study we identified a higher rate of patients with residual neoplasia. Due to the primary outcome of the study, we did not undertake a second follow-up. Despite the use of NBI after WLE, we found a false negative rate of 11%. These lesions could have been missed if we had not taken biopsies from the scar. For this reason, we believe that biopsies are still required in the first review of the scars in all cases, even if there are no macroscopically evident lesions, although we recognize that this is an imperfect gold standard. Monitoring EPMR at 3 to 6 mo is mandatory to detect and resect residual tissue.
The future direction in this field will probably focus on the use of optical magnification or other digital improvements in image enhancing techniques.