More investment than payoff
Most large colorectal polyps are best managed by endoscopic mucosal resection (EMR) and do not require endoscopic submucosal dissection (ESD). EMR can provide complete, safe, and effective removal, preventing colorectal cancer while avoiding the risks of surgery or ESD. EMR has several advantages over ESD. It is minimally invasive, low cost, well tolerated, and allows excellent histopathologic examination. It is performed during colonoscopy in an outpatient endoscopy lab or ambulatory surgery center. There are several techniques that can be performed safely and efficiently using accessories that are readily available. It is easier to learn and perform, with lower risks and fewer resources. Endoscopists can effectively integrate EMR into a busy practice, without making significant additional investments.
Dr. Sumeet K. Tewani
EMR of large adenomas has improved morbidity, mortality, and cost compared to surgery.1-3 I first carefully inspect the lesion to plan the approach and exclude submucosal invasion, which should be referred for ESD or surgery instead. This includes understanding the size, location, morphology, and surface characteristics, using high-definition and narrow-band imaging or Fujinon intelligent chromoendoscopy. Conventional EMR utilizes submucosal injection to lift the polyp away from the underlying muscle layer before hot snare resection. Injection needles and snares of various shapes, sizes, and stiffness are available in most endoscopy labs. The goal is en bloc resection to achieve potential cure with complete histological assessment and low rate of recurrence. This can be achieved for lesions up to 2 cm in size, although larger lesions require piecemeal resection, which limits accurate histopathology and carries a recurrence rate up to 25%.1 Thermal ablation of the resection margins with argon plasma coagulation or snare-tip soft coagulation can reduce the rate of recurrence. Additionally, most recurrences are identified during early surveillance within 6 months and managed endoscopically. The rates of adverse events, including bleeding (6%-15%), perforation (1%-2%), and postpolypectomy syndrome (< 1%) remain at acceptable low levels.1,4
For many polyps, saline injection is safe, effective, and inexpensive, but it dissipates rapidly with limited duration of effect. Alternative agents can improve the lift, at additional cost.4 I prefer adding dye, such as methylene blue, to differentiate the submucosa from the muscularis, demarcate the lesion margins, and allow easier inspection of the defect. Dilute epinephrine can also be added to reduce intraprocedural bleeding and maintain a clean resection field. I reserve this for the duodenum, but it can be an important adjunct for some colorectal polyps. Submucosal injection also allows assessment for a “nonlifting sign,” which raises suspicion for invasive carcinoma but can also occur with benign submucosal fibrosis from previous biopsy, partial resection, or adjacent tattoo. In these cases, effective management can still be achieved using EMR in combination with avulsion and thermal ablation techniques.
Alternative techniques include cold EMR and underwater EMR.1,4 These are gaining popularity because of their excellent safety profile and favorable outcomes. Cold EMR involves submucosal injection followed by cold-snare resection, eliminating the use of cautery and its associated risks. Cold EMR is very safe and effective for small polyps, and we use this for progressively larger polyps given the low complication rate. Despite the need for piecemeal resection of polyps larger than 10 mm, local recurrence rates are comparable to conventional EMR. Sessile serrated polyps are especially ideal for piecemeal cold EMR. Meanwhile, underwater EMR eliminates the need for submucosal injection by utilizing water immersion, which elevates the mucosal lesion away from the muscularis layer. Either hot or cold snare resection can be performed. Benefits include reduced procedure time and cost, and relatively low complication and recurrence rates, compared with conventional EMR. I find this to be a nice option for laterally spreading polyps, with potentially higher rates of en bloc resection.1,4
ESD involves similar techniques but includes careful dissection of the submucosal layer beneath the lesion. In addition to the tools for EMR, a specialized electrosurgical knife is necessary, as well as dedicated training and mentorship that can be difficult to accommodate for an active endoscopist in practice. The primary advantage of ESD is higher en bloc resection rates for larger and potentially deeper lesions, with accurate histologic assessment and staging, and very low recurrence rates.1,4,5 However, ESD is more complex, technically challenging, and time and resource intensive, with higher risk of complications. Intraprocedural bleeding is common and requires immediate management. Additional risks include 2% risk of delayed bleeding and 5% risk of perforation.1,5 ESD involves an operating room, longer procedure times, and higher cost including surgical, anesthesia, and nursing costs. Some of this may be balanced by reduced frequency of surveillance and therapeutic procedures. While both EMR and ESD carry significant cost savings, compared with surgery, ESD is additionally disadvantaged by lack of reimbursement.
Regardless of the technique, EMR is easier to learn and perform than ESD, uses a limited number of devices that are readily available, and carries lower cost-burden. EMR is successful for most colorectal polyps, with the primary disadvantage being piecemeal resection of larger polyps. The rates of adverse events are lower, and appropriate surveillance is essential to ensuring complete resection and eliminating recurrence. Japanese and European guidelines endorse ESD for lesions that have a high likelihood of cancer invading the submucosa and for lesions that cannot be removed by EMR because of submucosal fibrosis. Ultimately, patients need to be treated individually with the most appropriate technique.
Dr. Tewani of Rockford Gastroenterology Associates is clinical assistant professor of medicine at the University of Illinois, Rockford. He has no relevant conflicts of interest to disclose.
References
1. Rashid MU et al. Surg Oncol. 2022 Mar 18;101742.
2. Law R et al. Gastrointest Endosc. 2016 Jun;83(6):1248-57.
3. Backes Y et al. BMC Gastroenterol. 2016 May 26;16(1):56.
4. Thiruvengadam SS et al. Gastroenterol Hepatol. 2022 Mar;18(3):133-44.
5. Wang J et al. World J Gastroenterol. 2014 Jul 7;20(25):8282-7l.
