The indications for colorectal ESD are, presently, intramucosal or superficial submucosal (SM) (T1a: invasion depth < 1000μm) colorectal cancers (CRC) with a large tumor size ≧2cm, in which conventional en bloc EMR is predicted to be difficult. Endoscopic treatment is local resection without lymph node dissection, and therefore, considered appropriate when the following conditions have been satisfied: a lesion is determined to be well or moderately differentiated adenocarcinoma; invasion depth < T1a; and the lesion is histopathologically negative for both lymphovascular invasion and poorly differentiated component.
Consequently, it is clinically important to accurately diagnose the depth of invasion before treatment. Endoscopic depth diagnosis is clinically based on endoscopic findings of the JNET classification, and invasive pit pattern by magnified colonoscopy, or fullness by conventional colonoscopy rather than the non-lifting sign.
Based on previous clinicopathological analyses of laterally spreading tumors (LSTs), LST non-granular type (LST-NG) lesions have a higher rate of SM invasion. Approximately 30–56 % of LST-NGs have multifocal SM invasion, which is primarily T1a and can be difficult to predict endoscopically. In addition, LST-NGs >20 mm in diameter are quite difficult to resect en bloc by conventional EMR; therefore, these tumors are definite candidates for ESD.
In contrast, LST granular type (LST-G) lesions have a lower rate of SM invasion, which is generally found under the largest nodule or depression. These lesions are easier to predict endoscopically. LST-Gs >20 mm can be treated by elective piecemeal EMR rather than ESD. LST-Gs >30 mm are, however, possible candidates for ESD since such lesions are more difficult to treat by piecemeal EMR. A high SM invasion rate and 25 % rate of multifocal invasion were recently reported.
0-IIc lesions >20 mm, intramucosal tumors with non-lifting sign and large sessile lesions, all of which are difficult to resect en bloc by conventional EMR, are also potential candidates for colorectal ESD.