Noriko Matsuura, MD; Noriya Uedo, MD; and Rajesh Puri, MD, DNB, MNAMS
Since its introduction, endoscopic mucosal resection (EMR) has evolved from being a diagnostic procedure for obtaining large areas of mucosa to a minimally invasive, organ-sparing treatment method for superficial neoplasms in the gastrointestinal (GI) tract. EMR can be curative for superficial neoplasm in which the risk of lymph node metastasis is none. Moreover, EMR, particularly when performed with en bloc resection, enables accurate histological diagnosis and staging to ascertain curability of the resection.
To date, various EMR techniques, including simple injection EMR, lift and cut EMR using double-channel endoscope and grasping forceps, cap- and band-assisted EMR, and underwater EMR have been described. Cap- and band-assisted EMR uses suctioning to create a “pseudopolyp” to facilitate placement of a snare or band around the lesion. Compared to endoscopic submucosal dissection (ESD), EMR is a time-saving and easy procedure for any operator. In this chapter, we provide an overview of the techniques of cap- and band-assisted EMR.
Cap Endoscopic Mucosal Resection
Inoue et al1 first reported a simple EMR technique using a cap (EMR-C) in 1992. At first, a straight plastic cap was fitted to the endoscope, and the mucosa was suctioned into the snare, which was inserted though working channel and opened inside the cap. Later, a wide, soft, oblique cap with a rim was developed to enable constant removal of a large area of the mucosa (Figure 16-1A). Torii and colleagues2 have also reported endoscopic aspiration mucosectomy in which a snare sheath is attached outside the scope and the snare wire is opened outside the cap (Figure 16-1B). The usefulness of EMR-C has been widely reported for the treatment of superficial neoplasia throughout the GI tract.
EMR-C can be performed in the hypopharynx but clear resection is often difficult because of the 3-dimensional anatomical structure of the laryngopharynx. Based on observational studies,3,4 the en bloc and R0 resection rates of pharyngeal EMR (37% and 26%) were inferior to pharyngeal ESD (79% and 98%).
EMR-C is a useful technique for the treatment of superficial esophageal squamous cell carcinoma (SCC) and early Barrett’s neoplasia. Ishihara et al showed the overall R0 resection rate of ESD was significantly higher than that of EMR-C and 2-channel EMR. However, for lesions smaller than 15 mm, the R0 resection rate of EMR-C (86%) was significantly better than that of 2-channel EMR (51%) and approached that of ESD5 (100%). A meta-analysis including 8 Asian retrospective studies comparing ESD and EMR for superficial esophageal carcinoma (mostly SCC) indicated that ESD had a significantly higher en bloc resection rate (odds ratio [OR] 52.76; 95% confidence interval [CI], 25.57 to 108.84) and a lower recurrence rate (OR 0.08; 95% CI, 0.03 to 0.23) than EMR. However, the difference in recurrence rate was negligible6 when small (≤ 20 mm) lesions were selected (OR 0.34; 95% CI, 0.06 to 2.08). In aggregate, these data suggest that EMR-C provides similar outcomes to that of ESD for small (≤ 1.5 to 2.0 cm) esophageal SCC lesions, with the potentially added benefit of being a less complex and time-consuming procedure. With larger lesions, the number of piecemeal resections increase, which in turn is associated with higher risk of local recurrence with EMR-C.7,8 Indeed, local recurrence has been reported to develop in 15% to 20% of lesions after piecemeal esophageal EMR at a median follow-up period of 32 to 35 months.9
Application of EMR for Barrett’s esophageal lesions varies from focal removal of nodular lesions plus ablation for the adjunct mucosa to complete eradication of the entire Barrett’s esophagus.10 At present, endoscopic eradication of nondysplastic Barrett’s esophagus is not recommended because the number needed to treat to prevent one cancer is high and the risk associated with the endoscopic procedure outweighs the benefits.11 On the other hand, endoscopic treatment is preferred to surveillance for management of Barrett’s neoplasm.12 An international guideline recommends EMR with or without ablation therapy for management of visible Barrett’s neoplasm (≥ high-grade dysplasia),12 and the effectiveness of the practice is validated in a multicenter prospective cohort study.13
EMR-C has also been used for the treatment of early gastric cancer (EGC).14 Unlike esophageal SCC, which can be well delineated under iodine chromoendoscopy, EGC can be difficult to fully characterize given its unclear margins. Hence, EMR of EGC often result in R1 (positive-margin) resection leading to the development of local recurrence. A meta-analysis of 9 retrospective observational studies on ECG demonstrated that ESD is associated with a 5-fold higher R0 resection rate (OR 5.66; 95% CI, 2.92 to 10.96) and a one-tenth lower local recurrence rate (OR 0.10; 95% CI, 0.06 to 0.18) when compared with EMR.15 In spite of its potentially longer procedure time and risk for adverse events when compared with EMR, given its favorable oncological outcomes, ESD is the preferred approach in most Asian countries where gastric cancer is highly endemic.
Duodenum and Colorectum
EMR-C has been used to treat sporadic duodenal adenomas16,17 and sessile colorectal neoplasms.18,19 Given the relative thinness of the duodenal wall compared to the rest of the GI tract, full suction should be refrained to avoid inadvertently grasping and resecting the muscularis propria. The safety of these reports must be justified by the large amount of submucosal fluid injection and the judicious suction of the mucosa with the cap.
In addition to adenomas, EMR-C can be potentially curative for the resection of small neuroendocrine tumors (NET) (≤ 1 cm) given their low risk for metastasis.20 Conventional EMR (injection-lift method) of rectal NET is commonly associated with positive resection margins because 76% of these tumors extend into the submucosa.21 Conversely, the EMR-C sucks the tumor up into the cap and effectively removes the rectal NET.22
Currently, various distal caps of various shapes and sizes are available (Figure 16-2). The larger the cap diameter, the larger the specimen that can be potentially removed en bloc. The type of cap should be chosen according to the lesion size and scope diameter. The largest cap (D-206-series) can be used for the removal of lesions between 2 and 2.5 cm in size. A thin crescent snare (SD-7P-1, Olympus) is recommended for these cases. EMR kits (Olympus), which contain a spraying catheter, an injection needle, a cap, and a crescent snare, are commercially available in some countries.23
Pretreatment Evaluation and Marking
Similar to other resection procedures, accurate preprocedural staging (lesion characterization) is as important as the resection technique itself. Theoretically, if the extent of a lesion is accurately diagnosed and delineated, and the lesion is confined to the mucosa, even piecemeal resection with EMR-C can be curative. Careful inspection with high-definition endoscopy using dye-based or equipment-based, image-enhanced endoscopic assessment is essential. For esophageal SCC, the European guidelines recommend using iodine chromoendoscopy to help delineate the extent of the lesion.24
Electrocoagulation markings are made around the lesion with the tip of the snare using forced coagulation (effect 3, 30 W) or soft coagulation mode (effect 4, 40 W). Only the tip of the snare should be projected from the sheath to focus the current to conduct in a small area. The use of a conventional, short, distal attachment cap may help stabilize the scope for accurate marking, which is key as subsequent visualization of the margins may be impaired during EMR as a result of thermal effect from electrocautery, bleeding, etc. In our experience, as opposed to the markings usually placed up to 5 to 10 mm outside the lesion margins for ESD, markings for EMR-C should be placed closer to the lesion margin (within 1 mm or on the edge) to increase en bloc resection rate and to avoid excessive resection.
For resection procedures, an endoscope with water-jet irrigation is preferred for cleansing the mucosal surface and in case of bleeding. Endoscopes with a large working channel (GIF-Q260J, 3.2 mm and GIF-1TH190, 3.7 mm, Olympus) can facilitate suctioning of fluid even with a device inserted through the working channel.
An EMR cap is fitted onto tip of an endoscope. For an oblique-type cap, the notch is placed along the axis of the working channel. In preparation for resection, saline or a lifting solution is injected into the submucosa beneath the lesion with an injection needle until enough elevation of the entire lesion is achieved. A crescent snare is then opened fixed inside of the rim of the cap (prelooping). At this time, the spiked part of the snare should be located at the tip of the sheath (Figure 16-3). Successful prelooping is strongly associated with successful resection, thus it is worth spending the necessary time and effort to ensure adequate fitting and preloop position.
As opposed to the management of variceal bleeding, suctioning of the target lesion prior to resection can be performed repeatedly for “test suctioning” to ascertain the optimal position prior to removal.25 With this maneuver, the endoscopist can adjust the position of the cap (both longitudinal and circumferential), the amount of suction, and the way to maneuver the cap during suctioning the tissue. Moreover, repeated suctioning helps separate the mucosa and submucosa away from the muscularis propria, which further facilitates suctioning and lifting large target lesions. With EMR-C, the distal margin of the lesion is not always seen during suction and resection, and the amount of resection at the distal part cannot be easily controlled. Therefore, the proximal edge of the cap is always adjusted to suction the proximal marking into the cap, then the target lesion is fully aspirated until the endoscopic image is “red-out.” When the lesion suctioning is inadequate or is not enough, the cap can be readjusted and the lesion is suctioned again. Once maximum suctioning has been achieved and the lesion is aspirated into the cap, the snare is slowly closed, and the captured pseudopolyp is resected using coagulation and ENDO CUT mode (VIO300D, Erbe) (Figure 16-4). If the assistant controlling the snare feels that too much tissue has been entrapped, the snare should be opened to release some tissue followed by recapturing to avoid resection of the muscularis propria.