From the AGA Journals

New algorithm for large nonpedunculated rectal polyps

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In clinical practice there is widespread variation in the utilization of endoscopic submucosal dissection (ESD) versus endoscopic mucosal resection (EMR) for resection of large nonpedunculated rectal polyps (LNPRPs).

EMR is easier to learn and faster to perform than ESD and results in fewer perforations. EMR for LNPRPs is usually performed piecemeal, as opposed to ESD in which the goal is en bloc resection. When apparently successful piecemeal EMR is followed by cancer in the pathology report, surgical resection is frequently recommended. This is because assessment of residual cancer risk in the bowel wall or lymph nodes is often considered unachievable after piecemeal resection. Conversely, patients with superficial submucosal invasion after ESD may avoid surgical resection.

Dr. Douglas K. Rex, emeritus professor of medicine, Indiana University School of Medicine, Indianapolis

Dr. Douglas K. Rex

Much controversy surrounds which LNPRPs have a high enough risk of cancer, and/or the patient has a sufficiently high operative risk, so that the inefficiency and risk of ESD is justified to reduce surgeries that may follow piecemeal EMRs of malignant LNPRP. At one extreme of the opinion spectrum, all LNPRPs justify ESD.

This study describes a selective approach to colorectal ESD based on two factors. First, consider ESD primarily in the rectum where the morbidity of surgical resection is highest. Second, consider ESD for those rectal lesions where the cancer risk is highest, including lesions with surface pit and vascular patterns indicating high cancer risk and those with a sessile or nodular component. When this policy was used, only 1% of rectal EMRs were followed by a diagnosis of submucosally invasive cancer. This selective approach to colorectal ESD seems a reasonable combination of procedural efficiency and optimal patient outcomes.

Douglas K. Rex, M.D., MACP, MACG, MASGE, AGAF, is distinguished professor emeritus of medicine, Indiana University, Indianapolis. He serves as a consultant to Olympus Corporation, Boston Scientific, Aries Pharmaceutical, Braintree Laboratories, Lumendi, Norgine, Endokey, GI Supply, Medtronic, and Acacia Pharmaceuticals. He has received research support from EndoAid, Olympus Corporation, Medivators, Erbe USA, Braintree Laboratories and is a shareholder in Satisfai Health.



Large nonpedunculated rectal polyps (LNPRPs), defined as 20 mm or larger, are associated with a high risk of submucosal invasive cancer (SMIC). Although LNPRPs can be removed by distal colorectal surgery, this approach has an increased risk of morbidity, mortality, and permanent ostomy formation.

The first-line resection technique for LNPRPs is endoscopic mucosal resection (EMR); however, for larger lesions, piecemeal removal is required. When SMIC is revealed after piecemeal resection, surgery is generally recommended, since this is the only way to determine if R0 margins and curative oncologic resection have been achieved.

In such cases, an alternative is endoscopic submucosal dissection (ESD), but there is no current algorithm to choose between the two procedures based on lesion identity.

Optical methods can determine a lesion’s pit and microvascular pattern in real time to determine if SMIC is present, but the performance is modest. Researchers sought to bolster optical detection by combining it with SMIC risk stratification to streamline the choice between EMR and ESD for LNPRPs.

In a study published online in Clinical Gastroenterology and Hepatology, researchers led by Neal Shahidi, MD, of the division of gastroenterology, St. Paul’s Hospital, Vancouver, described a selective resection algorithm (SRA) that could assist gastroenterologists in determining the best procedure to use when confronted with an LNPRP.

“Cost-effectiveness analyses have shown that an SRA using EMR and ESD is the optimal approach. However, a mechanism to facilitate modality selection has not been delineated. To our knowledge, this study is the first to show that a rectum-specific SRA, based on real-time optical evaluation and covert SMIC risk stratification, increases the frequency of curative oncologic resection and minimizes the risk of piecemeal resection of malignant LNPRPs. ... Piecemeal resection of endoscopically curable malignant LNPRPs negates the very benefit that they are intended to provide. To avoid malignant piecemeal resection, optical evaluation of the lesion’s pit and microvascular surface pattern can be used to predict SMIC prior to resection technique selection,” the authors wrote.

The researchers conducted a prospective observational study of 480 LNPRPs that were detected between July 2008 and April 2021. They compared the performance of the SRA to that of a universal EMR algorithm (UEA) for procedure determination. The SRA flagged LNPRPs with features consistent with SMIC (< 1,000 mm or Kudo pit pattern Vi) for endoscopic dissection. The latter included Paris 0-Is or 0-IIa+Is nongranular, or 0-IIa+Is granular with a dominant nodule 10 mm or larger. Other LNPRPs were designated to undergo EMR.

The median patient age was 67 years, and 54.2% were men; 90.1% of participants were ASA I-II; 290 LNPRPs were evaluated with the UEA and 190 with the SRA. The median lesion size was 40 mm. Overall, 11.7% of LPNRPs were identified as containing SMIC.

In the SRA, only 1.0% of LNPRPs removed by EMR contained SMIC, while the UEA identified cancer in 12.1%, a significant difference (P = .001). The SRA led to 33.3% as curative oncologic resections, while the UEA achieved only 5.7% (P = .010).

There were no significant differences in technical success or adverse events between the two algorithms.

Procedures determined by SRA took longer than those decided by UEA (median resection duration, 45 vs. 29 minutes; P < .001). Among LNPRPs that were removed through EMR and margin thermal ablation, there was no significant difference in recurrence whether SRA or UEA was used to determine the procedure.

Compared with UEA, SRA was associated with higher rates of en bloc resection (90.5% vs. 11.4%; P < .001), R0 resection (85.7% vs. 5.7%; P < .001), and curative oncologic resection (33.3% vs. 5.7%; P = .010).

“In this study, using analogous optical evaluation and covert SMIC risk stratification criteria, only one (1.0%) [of] malignant LNPRP underwent piecemeal resection within the SRA. This is a pivotal advance in the application of minimally invasive endoscopic resection techniques. It demonstrates an effective approach to optical evaluation; thereby, delineating which LNPRPs can be effectively, efficiently, and safely managed by EMR, compared with those which may derive benefit from ESD,” the authors wrote.

The authors recommended ESD only be used for lesions with suspected superficial SMIC or when there is a heightened risk of SMIC.

A key finding of the study is the frequency of curative resection following ESD. “At 33.3%, this represents a critical improvement in patient outcomes and the application of minimally invasive endoscopic resection techniques; especially when taking into consideration the potential negative ramifications of distal colorectal surgery and evidence showing that endoscopic resection does not impair subsequent surgical intervention,” the authors wrote.

There was no significant difference in recurrence at surveillance colonoscopy between SRA and UEA when undergoing margin thermal ablation. The finding suggests that margin thermal ablation should be considered a vital component of EMR, according to the authors.

Dr. Shahidi received speaker honorarium from Boston Scientific and Pharmascience, and one coauthor received research support from Olympus, Cook Medical, and Boston Scientific.

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