EMR can replace the surgery in the treatment of early colon cancer without lymph node metastasis. Most colorectal polyps can be treated using simple snaring or EMR, although large sessile colorectal tumors exceeding 20 mm can’t be removed by traditional EMR procedure. For these tumors, piecemeal resection is recommended [6]. The merit of piecemeal resection is that it is safe for resecting large sessile polyp . LSTs with granular homogenous type can be safely treated by EPMR, even it is larger than 30 mm. However, the fragmentation of specimens during conventional polypectomy or EMR prevents the evaluation of the resection margin involvement or the depth of tumor invasion, making it difficult to plan further treatment. In addition, any tumor cells remaining after piecemeal polypectomy can grow on the polypectomy scar and invade the submucosal layer more rapidly. Thus care should be used to remove suspicious malignant tumor including pseudo-depressed type LSTs by EPMR [6–8]. ESD introduced to overcome these limitations is now widely used for excising various gastrointestinal tumors, including colorectal tumors. ESD results in higher rates of en-bloc tumor resection, reducing local recurrences and providing more accurate pathologic information for planning further treatment. However, the procedure time is much longer and the complication rate is much higher for ESD than for EMR, limiting the use of ESD in the removal of colorectal tumors [9, 10].

According to several studies reported the outcomes of ESD, en-bloc resection rate is 84.9% (95% CI, 77.8–90.8), curative resection rate is 75.4% (95% CI, 66.7–82.2). A study on the long term outcomes of colorectal ESD found that the local recurrence rate was 2%, and the 3 and 5 year disease free survival rates were 97% and 95%, respectively. Safety outcomes of colorectal ESD are also important, in as much as perforation associated with this procedure was reported in 3.3–20.4%, with tumor size and the presence of fibrosis being independent risk factors for perforation [11–14]. Although many cases showing perforation have been improved with conservative treatment without surgery, using endoscopic clipping, it make to prolonged hospitalization and to need additional treatments.

In summary, both EPMR and ESD techniques can be used for large sessile polyps or LSTs. EPMR technique has merits of safety, ease and demerits of the difficulty of pathologic evaluation, high rates of local recurrences. ESD technique has merits of en-bloc resection, low rate of recurrence and demerits of long operation time, high rates of complications. Thus, ESD should be recommended for LSTs with suspected malignancy or lesions are technically difficult to treat with conventional EMR, and EPMR should be recommended for adenomatous lesions, LSTs with granular homogenous type [12, 15–18].

Basically, all endoscopic treatment is recommended only for lesions diagnosed as non-invasive tumors with a low metastatic potential. The risk factors for lymph node metastasis are poorly differentiated, signet-ring cell, and mucinous adenocarcinoma, massive submucosal invasion, lymphovascular invasion and tumor budding.

Current indications for colorectal ESD include (1) early colorectal cancer, (2) laterally spreading tumors ≥2 cm in diameter, (3) submucosal tumors, and (4) colorectal polyps with fibrosis. In detail, ESD study group in Japan announced the indication of colorectal ESD include LSTs with non-granular pseudo-depressed type, mucosal lesions with fibrosis caused by inflammation or scar change after biopsy, the tumor with underlying ulcerative colitis, recurred tumors after EMR resection, etc. They excluded the size criteria, more than 20 mm, in ESD indication, because depressed-type tumors with less than 20 mm in size can invade submucosal layer. And they also commented the submucosal infiltration of tumors should be shallow (Table 3.1).

Before procedure, malignant potential and margins should be clearly identified. Tumor morphology including color, unevenness, depression, fold convergence also carefully evaluated. Malignant tumors have the loss of the surface pattern of pits or the structure of micro-vessels. Dye spraying, magnifying endoscopy, narrow band image can be helpful to identifying it. For predicting the malignant polyps, the accuracy of conventional endoscopy is about 80%, and that of chromo-magnifying endoscopy is up to 96–98%. Endoscopic ultrasonography (EUS) is also helpful to diagnose the submucosal invasive cancer, however it is still not popular because the additional equipment is required.