Endoscopic Mucosal Resection Versus Endoscopic Submucosal Dissection for Colorectal Laterally Spreading Lesions.

Endoscopic submucosal dissection (ESD) is curative for lesions with superficial submucosal invasive carcinoma (s-SMIC) and favourable histological features. The procedure is performed mainly for laterally spreading lesions (LSLs) and is the reference treatment for these neoplasms in Asian countries nowadays. LSLs can be granular (G) or non-granular (NG). Most LSLs-G homogenous type are superficial and can be resected by EMR because SMIC is often lacking. On the other hand, since LSLs-G mixed type \> 20 - 30 mm have a higher prevalence of SMIC when compared with the homogenous subtype, Asian experts now recommend ESD for this kind of tumors. However, some years ago, EMR had been suggested for LSLs-G mixed type if the largest nodule was resected first and the histological assessment was done separately. The rationale for the latter approach is that the invasive component is usually found within the large nodule. Conversely, the prevalence of SMIC is higher in LSLs-NG PD type, therefore, ESD is the preferred therapeutic intervention. In addition, LSLs-NG FE type have been associated with multifocal invasion in Japanese studies. However, in Western countries, the percentage of SMIC in LSLs-NG FE type \> 20 mm seems much lower than previously described in Asian series. Thus, the investigators do not know if EMR might be enough to remove these tumours. Furthermore, if the risk of s-SMIC is low, the recurrence rates for ESD in these kind of lesions (LSL-G mixed type \> 30 mm and LSL-NG FE type \> 20 mm) might be comparable to that of piecemeal EMR, in terms of curative resection (avoiding the need for surgery) in the mid-term. When performing an EMR, recurrences are more frequent, but they are largely inconsequential because it is usually unifocal, diminutive and easily can be managed endoscopically on subsequent sessions. In order to clarify the controversial issue of performing colorectal ESD in Western countries, the investigators aim to assess if piecemeal EMR (the older technique) for LSLs-G mixed type \> 30 mm and LSLs-NG FE type \> 20 mm is not inferior to ESD (the new treatment) for the need of additional surgery in the mid-term.