ESI With EUS to Differentiate T3 and T4 ESCC (ESI)

Esophageal cancer (EC) is one of the most common malignant tumors in the world, and China has the highest incidence of esophageal squamous cell carcinoma (ESCC).According to the TNM staging system of the Union for International Cancer Control (UICC) (7th Edition, 2012), EC invades the esophageal adventitia at the T3 stage; invades the pleura, pericardium and diaphragm at the T4a stage; and involves adjacent vital organs (mainly the thoracic aorta, aortic arch, trachea, tracheal bifurcation, and spine) at the T4b stage.It is considered that T3- and T4a-stage tumors can be surgically resected, while tumors at the T4b stage are not suitable for surgical resection.Therefore, it is important for physicians and patients to know whether the tumor has metastasized to adjacent organs before considering resection. The preoperative stage is unclear in many cases of progressive disease and the involvement of vital organs is only discovered by exploratory thoracotomy, because of which the resection may need to be terminated prematurely, leading to unnecessary injuries.Therefore, accurate preoperative staging of EC, especially during the later stages, is important for deciding the appropriate therapeutic option and evaluation of the prognosis.

The imaging methods used for preoperative staging of EC include endoscopic ultrasonography (EUS). However, EUS has poor accuracy in advanced ESCC, especially in T3 and T4 stage ESCC. Therefore, it is necessary to improve the preoperative accuracy of EUS for advanced EC.

Since extraesophageal space contains loose connective tissue and saline can permeate into extraesophageal space and separate esophagus from adjacent organ; furthermore, saline serves as an EUS contrast agent (negative) and is detected by EUS.Therefore, we envisaged that if saline is directly injected into extraesophageal space, the separation between the esophageal adventitia and its adjacent organs (especially the thoracic aorta, arcus aortae, and tracheal bifurcation) can be observed by EUS. In our recent experiment in canine model, guided by EUS,extraesophageal saline injection was successfully conducted and saline separated esophageal adventitia from adjacent organs including thoracic aorta, arcus aortae, trachea and bronchial bifurcation without any complication.