Advanced Endoscopic Techniques for Preoperative Assessment of Early Gastric Cancer before ESD

ESD is the standard treatment for early gastric cancer in Japan and its gaining acceptance in Western countries in the last years. After detection accurate endoscopic characterization and delineation of the tumor should be performed before ESD because only superficial lesions with low risk of lymph node metastasis can be endoscopically removed. Basically preoperative assessment of the lesion involves determining size, tumor margins, depth of invasion, histological type and presence or absence of ulceration. Advanced endoscopic techniques, including, high-magnification (HME) and narrow-band imaging (NBI) endoscopy has been developed to enhance staging of early gastric cancer. Recent studies showed possibility of HME with NBI in effective detection, evaluation of lateral extent of the cancer, histology prediction and even diagnosing the depth of invasion on the basis of microvascular architecture and microsurface structure changes. However HME with NBI requires a time consuming, and the interpretation of the patterns, or inter-observer agreement, remains a challenge in clinical practice. Newly developed computer-aided decision support systems in endoscopy are designed to detect and/or classify abnormalities and thus assist a medical expert in improving the accuracy of medical diagnosis. The specific goals of these systems in HME are pathology prediction, marking of areas with high cancer risk, and determination of its margins. Thus, an accurate preoperative endoscopic assessment of early gastric cancer plays a key role in effective endoscopic treatment.