Treating large flat polyps in the rectum can be quite challenging for endoscopists. Among other things, the difficult location of rectal polyps such as ones in the lower rectum or near the rectosigmoid junction may affect endoscopic accessibility and stability, and limit snare maneuverability. One method of treatment, endoscopic mucosal resection (EMR) of polyps, is especially difficult in the low rectum where the correct approach for endoscopes and snares is not always straightforward or clear. Technical challenges limit the size of each tissue resection with both conventional and advanced snares of variable sizes. Thus, piecemeal resection is often the answer to the endoscopic treatment of large rectal polyps.
We have learned to live with this imperfection. Piecemeal resection is currently the preferred method for larger polyps, with the goal of complete eradication, or at the very least, a reduced risk of perforation. We had no other methods than to cut large polyps into pieces and we accepted the risk for residual dysplasia or neoplasm. This resulted in an unclear or positive margin for cancer if a proper resection plan was not carefully sought, requiring patients to undergo additional surgery or to live with uncertainty regarding a cure. We know that surgeons would not try to cut any tumor into pieces.
Another method, endoscopic submucosal dissection (ESD), was developed for endoscopists as a new endoscopic resection technique that allows for the largeen bloc resection (removal in one piece) of polyps that are even larger than 3 centimeters in size. This method, which shares many similarities to the surgical techniques, allows us to think more like oncologic surgeons, and it is time for this paradigm shift.
First, we need to discuss and evaluate the configuration of the polyp prior to the resection. A flat polyp of 3 centimeters in size is classified as a laterally spreading type (LST) lesion.1 There are two types of LSTs, one is a granular type and the other is a non-granular type. Granular type lesions are less likely to harbor invasive cancer compared with non-granular type lesions, and it is usually easier to perform conventional endoscopic mucosal resection on granular type polyps, although usually in a piecemeal fashion.2,3 Previous attempts at removal were shown to be a significant independent risk factor for EMR failure and recurrence,3 and therefore it is important to employ the most appropriate and successful technique during the first attempt at removal. Risk for the presence of invasive cancer increases withParis classification 0-IIa+IIc, non-granular type, and loss of pit pattern (Kudos pit pattern V) 3 andloss of pit pattern (Kudos pit pattern V), large nodule>1cm, depressed area, sclerotic wall, redness and tumor size 20mm.4 Cancerous portions should be identified and removed within a negative margin (both deep and lateral margins) to ensure that a proper assessment for oncologic curative resection can be completed following removal.
We also need to develop strategic resectioning plans for both piecemeal and en bloc polyp removal. Those polyp segments that have been endoscopically identified as having the most advanced pathology, e.g. large nodules or depressed areas, should be removed first if en bloc resection is likely to be unsuccessful and piecemeal resection be performed. Then, the remaining portion of polyp can be removed subsequently. It is often difficult to remove flat or depressed polyps via EMR or through conventional fluid cushion assisted polypectomy, due to the difficulty of capturing adequate neoplastic tissue into the snare, which results in multiple, small resection pieces. Thus ESD is a better option for these types of polyps.
Recurrence after piecemeal resection was shown to be even higher if six pieces or more were removed compared with fewer than six (34 percent vs. 18 percent),3 or if the lesion was larger than 2 centimeters (especially more than 4 centimeters),5, 6 according to large multi-center studies from Australia and Japan.
Removal of polyps using the one-piece EMR technique was also more beneficial compared with the multiple piece technique (14.9 percent vs. 2.3 percent).
However, ESD offered further reduction of recurrence to 0.7 percent if the polyp was removed in one piece.6 Time and again, ESD has consistently shown its benefits through its very low recurrence rate of 0.8 to 2 percent, which is even lower when polyps are successfully removed in one piece.6,8
Another concern for removing large rectal polyps is the presence of advanced pathology in laterally spreading types. Furthermore, submucosal cancers (invasive cancer; T1) were noted in 4.3 to 5 percent within 20mm or larger LST removed by EMR5, 6 and 15.4 to 17 percent within 20mm or larger LST removed by ESD.6, 8 These differences are most likely due to a selection bias. Nevertheless, it is important for endoscopists to keep the relatively high cancer rates in mind with LSTs that are more than 20 mm in size. The risk of invasive cancer (T1) increases with the size of a lesion that is more than 3 centimeters.9 All of the patients who had invasive T1 cancer (4.3 percent underwent EMR) were recommended to undergo surgery in the Australian study.5 However, 71 to 77 percent of T1 cancers had only shallow invasion into the submucosal layer (<1000m) in the Japanese studies, which falls into the low risk criteria for lymph node metastasis and may allow those patients to avoid surgery.6,8
Appropriate planning for the resection and technique, including injection material and method, starting location, snare size and stiffness, and a sequence of resection, is of the upmost importance for optimal outcomes with EMR. Alternatively, ESD principally aims for en bloc resection of lesions with negative margins, thus always aiming for oncologic resection. In addition, en bloc resection is ideal for detailed pathological assessment for oncologic resection.
Endoscopic submucosal dissection is a better option for physicians and patients when it comes to large rectal laterally spreading tumors, especially when polyps show signs of advanced pathology.
Endoscopic resection for rectal lesions is a more beneficial option than surgery, as the location is safest for ESD and is shown to be least technically challenging for endoscopists.10 Thus, endoscopic submucosal dissection is a better option for physicians and patients when it comes to large rectal laterally spreading tumors, especially when polyps show signs of advanced pathology.
Dr. Fukami serves as a consultant for Olympus America and Boston Scientific.
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10. Yang DH, Jeong GH, Song Y, et al. The Feasibility of Performing Colorectal Endoscopic Submucosal Dissection Without Previous Experience in Performing Gastric Endoscopic Submucosal Dissection. Dig Dis Sci 2015.