RA07.04: DIAGNOSTIC UTILITY OF ENDOBRONCHIAL ULTRASONOGRAPHY FOR THE TRACHEOBRONCHIAL INVASION OF ESOPHAGEAL CANCER

Background Preoperative precise diagnosis of invasion to the trachea and bronchi from advanced esophageal cancer is important to estimate the prognosis and resectability. But it is difficult to diagnose the invasion to the tracheobronchial adventitia by conventional examination, like CT scan, MRI, bronchoscopy, etc. The purpose of this study is to clarify the diagnostic utility of endobronchial ultrasonography (EBUS) for the invasion to the trachea and bronchi of esophageal cancer. Methods We examined the diagnostic utility of EBUS in cadaver, by comparing echoic image and actual tracheobronchial structure using tracheal invasion model. The model was made by cauterizing adventitia with the electrical scalpel. The cancer image model was made by injecting the agarose gel into esophageal muscular layer. And we also examined for clinical T3 or T4b esophageal cancer cases using EBUS for the diagnosis of tracheobronchial invasion. Results Normal image of tracheal wall was shown as three layers (high-low-high echoic layers) by EBUS. Echoic image of the tracheal invasion model in cadaver showed disappearance of the deepest high echoic layer. Histological examination proved interruption of tracheal adventitia by cauterization. Echoic image of tumor image model showed disappearance of the deepest high echoic layer and clearly observed tumor like agarose gel through the tracheal wall. These indicated the deepest high echoic layer correspond with the tracheal adventitia layer. EBUS could be visualized esophageal cancer invasion to the tracheobronchial adventitia. We performed EBUS for 32 cases of T3 or T4b esophageal cancer had been suspected the tracheobronchial invasion. 9 cases were diagnosed as T3 without invasion to the trachea or bronchi and received neo-adjuvant therapy following surgery, and all cases of these were confirmed precise diagnosis of EBUS in histological findings. 23 cases were diagnosed as T4b with invasion to the trachea or bronchi and received definitive chemo-radiation, and one patient received esophagectomy and pharyngolaryngectomy for salvage surgery and also confirmed accuracy of preoperative diagnosis using EBUS in histological findings. Conclusion EBUS is useful to diagnose the tracheobronchial invasion of esophageal cancer. Precise diagnosis of the tracheobronchial invasion using EBUS will help us to perform R0 resection and improve the prognosis of cT4b esophageal cancer. Disclosure All authors have declared no conflicts of interest.