Clinicopathological Characteristics as Predictive Factrs for Lymph Node Metastasis in Submucosal Gastric Cancer

DISCUSSION

The significant achievements of gastric surgeons in the last century in establishing radical surgery with extensive lymph node dissection for gastric cancer, deserve unequivocal respect. However, we now have to proceed to the next stage by improving post-operative function and quality of life after gastric cancer surgery without impairing long-term outcome^[5,6].

MIS, such as EMR or ESD, for gastric cancer is frequently performed in many institutions^[7]. These techniques do preserve gastric function and maintain a high quality of life. However, the treatment strategy for early tumors should therefore be based on a complete cure, and limited surgery must thus have clear indications^[7]. The following indications for EMR for early gastric cancer have generally been accepted: differentiated-type of mucosal cancers without ulcerative findings, with ≤ 2 cm in size if elevated or ≤ 1 cm in size if depressed or flat^[8]. At present, the indications for ESD are still controversial. It has extended through expansion of both theoretical and technical conditions^[9]. In fact, the indication for ESD is strictly confined by two aspects: the possibility of nodal metastases and technical difficulty^[10].

ESD is a highly effective technique enabling surgeons to resect much larger and difficult lesions, which cannot be resected by conventional EMR techniques. ESD is a new endoscopic technique using cutting devices to remove the tumor by the following three steps: 1) injecting fluid into the submucosa to elevate the tumor from the muscle layer; 2) precutting the surrounding mucosa of the tumor; and 3) dissecting the connective tissue of the submucosa beneath the tumor. So the tumors are resectable in an enbloc fashion, regardless of the size, shape, coexisting ulcer, and location^[9-11]. ESD is gaining acceptance among endoscopists because of its efficacy^[12].

To identify clinicopathological characteristics predictive of lymph node metastasis, definite criteria for predicting lymph node metastasis can lay a foundation for ESD. Still now, some studies thus far have demonstrated that tumor size, gross appearance of the tumor, histological type, and depth of tumor invasion could be predictors of lymph node metastasis in early gastric cancer^[13-15]. In our study, a tumor size of 2 cm or more and an undifferentiated histologic type were significantly associated with a higher rate of lymph node metastasis. No lymph node metastases were observed in patients who had neither of the two risk clinicopathological characteristics, whereas the positive rate of lymph node metastasis was calculated to be 61.1% in patients who had both clinicopathological characteristics.

Reguarding the clinical implications on our study, ESD can be performed for the patients without both risk clinicopathological characteristics. As a result, patients without lymph node metastasis do not have to endure possible operative complications and thus are able to avoid risks owing to stomach resection and lymph node dissection. However, the patients with the two risk clinicopathological characteristics have a high potential for lymph node metastasis, and they should receive a lymph node dissection.

In conclusion, knowledge of the risk clinicopathological characteristics provides a simple and useful criterion to indicate ESD for the patients with submucosal gastric cancer. ESD is applicable with promising results, but the technique is still at a developmental stage. Therefore when conducting an endoscopic resection, we must consider the approach to treatment, in terms of the situation and skills of the endoscopist^[16]. Future clinical studies are required to fully develop the indications for, and technique of ESD.