Endoscopic resection is safe, effective alternative to surgery
Endoscopic management of colorectal polyps and early tumors has progressed rapidly in the last few years. Endoscopic mucosal resection (EMR) has been widely adopted for removal of large lesions from the superficial layer (mucosa) of the gut wall, and en bloc resection of very large neoplasms using endoscopic submucosal dissection (ESD) and submucosal tunneling techniques has proved to be a safe, less invasive alternative to surgery.
The evolution from relatively simple endoscopic procedures to the full spectrum of endosurgical approaches has been driven by many factors, including recently developed endoscopic devices and techniques for resection as well as novel clips and suturing devices for defect closure that have made endoscopic resection safer, easier and more effective.
Timothy A. Woodward, M.D., a gastroenterologist at Mayo Clinic's campus in Jacksonville, Florida, notes that many techniques that are now standard of care started as trial and error and then proved advantageous in clinical practice. The current armamentarium of snares for EMR is an example.
"Snares with different stiffness and configurations allow operators to pick and choose, depending on the situation," he says. "A flat polyp growing along a colonic fold is difficult to grasp with an oval snare; a duck-billed snare may be more convenient in this setting because its shape orients along the axis of the fold, so you're no longer struggling to grasp tissue. This illustrates how one can adapt a specific snare to a particular lesion in order to make resecting difficult mucosal lesions more efficient and effective."
Viscous solutions for submucosal injection such as hydroxypropyl methylcellulose also may aid in the resection of difficult lesions by providing a longer lasting fluid cushion than normal saline. Adding a staining dye — either indigo carmine or methylene blue — to the injection solution can help delineate the border of the lesion and assess for the presence of the target sign in the resection defect — a reliable marker of injury to the muscularis propria and potential perforation.
Pushing the envelope
Despite technical enhancements, EMR has limitations that often result in piecemeal resections, especially in the case of large lesions, leading to an increased risk of local recurrence. When snare resection en bloc is difficult or infeasible, endoscopic submucosal dissection is an alternative to EMR.
In ESD, after thermal marking of the lesion boundary and submucosal injection, the lesion is dissected directly along the submucosal layer using an electrosurgical knife, resulting in en bloc resection of even the largest polyps. This makes it possible to assess deep and lateral margins — something not offered by piecemeal EMR techniques. ESD is more accurate for histological analysis than EMR, and lesion recurrence rates are lower.
According to Louis M. Wong Kee Song, M.D., a gastroenterologist at Mayo Clinic's campus in Rochester, Minnesota, the ESD approach makes it possible to remove lesions that were not previously amenable to complete resection endoscopically.
"Some lesions that we were not able to snare resect in the past due to lack of accessibility, we now can remove effectively," he says. "For example, rectal polyps growing at the dentate line were once only within the purview of the surgeon, but with ESD, we can resect low-lying rectal lesions in intimate contact with the dentate line in one piece as effectively as surgery.
"We also have the advantage of characterizing and better delineating the lesion border with enhanced endoscopic imaging modalities, including chromoendoscopy — the spray application of dye to the colonic mucosa. The en bloc resection leads to high cure rates and low recurrence rates of premalignant and early superficial malignant lesions.
"Thus, many patients with these lesions are now referred to gastroenterologists for endoscopic resection. With endoscopic resection, post-procedure recovery is faster, with fewer adverse events compared with transanal surgical excision."
Dr. Woodward explains further: "Previously there was a great deal of emphasis on trying to be more conservative with resections because of concern about perforation. But now we feel we have more latitude; novel endoscopic suturing devices and clips such as the over-the-scope clip system allow us to close perforations or deep defects in the rectum and other sites."
At Mayo Clinic, success with more-aggressive approaches in the rectum has led to increasing use of endoscopic resection in the duodenum and elsewhere.
"Large duodenal neoplasms are very challenging to resect and are prone to procedure-related bleeding and perforation. But we've been more aggressive at taking on larger duodenal lesions," Dr. Wong Kee Song explains. "We have experience with successfully managing perforations in the colon and rectum, and now with the availability of effective full-thickness closure devices, we are more comfortable pushing the envelope.
"We are resecting more duodenal lesions every year and are becoming more aggressive in pursuing very large lesions that would once have required major surgery. But doing so requires careful inspection with high-definition endoscopy and enhanced imaging techniques — similar to the evaluation of colorectal lesions — to characterize the lesion and assess its suitability for endoscopic resection. If malignant invasion is suspected, then endoscopic resection is not suitable."
Select subepithelial lesions, including gastrointestinal stromal lesions (GISTs) can also be resected endoscopically using ESD, endoscopic full thickness resection or submucosal tunneling endoscopic resection. These advanced resection techniques are pushing the boundaries of resection beyond mucosal-based neoplasms, but evaluating lesion size and location and careful staging with endoscopic ultrasound are essential.
Rahul Pannala, M.D., a gastroenterologist and therapeutic endoscopist at Mayo Clinic's campus in Arizona, stresses the importance of careful patient selection and counseling.
"There are many early esophageal, gastric and rectal tumors and subepithelial lesions that can be treated with endoscopic resection techniques," he says. "Many of these lesions require intentional breach of the gut wall, but with the availability of endoscopic devices for defect closure, we have a greater ability to manage the majority of them endoscopically. Still, counseling patients about treatment options and the pros and cons of endoscopic resection versus surgery is also important."