214. THORACIC CAVITY/ CAGE RATIO IS PREDICTOR FOR SURGICAL DIFFICULTY OF MINIMALLY INVASIVE ESOPHAGECTOMY

Abstract Background Esophagectomy for esophageal cancer is highly invasive surgery. Minimally invasive esophagectomy (MIE) was introduced as a less invasive surgery, and conventional MIE (C-MIE) is being increasingly performed worldwide. Recently, robot-assisted MIE (RAMIE) was developed with the aim of further minimization of invasiveness, and is expected to spread in the future. When performing MIE, we sometimes experienced difficult cases. In this study, we aimed to clarify the factors related to surgical difficulty of MIE. Methods We evaluated 362 patients who underwent MIE (285 C-MIEs and 77 RAMIEs) for esophageal squamous cell carcinoma between April 2010 and February 2023. We used computed tomography to evaluate the occipitofrontal diameter of thoracic cavity and cage at brachiocephalic vein (BV), tracheal bifurcation (TB) and inferior right pulmonary vein (IRPV) levels, respectively. We calculated the thoracic cavity/cage ratio (TRRC) at each level. The cut-off values of TCCR at each level for thoracic procedure time were calculated using the receiver operating characteristic. Furthermore, total score consisted of four degrees (0,1,2,3) by the TCCR at three levels was calculated. We assessed clinicopathological and anatomical factors and determined the independent factors influencing the thoracic procedural time as parameter of difficulty in MIE. Results We divided the patients into C-MIE group and RAMIE group. Patients in each group were divided into two cohorts according to median thoracic procedure time (C-MIE: 307 and RAMIE: 409 minutes, respectively). In the C-MIE group, univariate analysis demonstrated that sex, body mass index (BMI), and the TCCR at BV, TB and IRPV levels were correlated with thoracic procedure time. The total TRRC score was also correlated with thoracic procedure time in univariate analysis. Next, multivariate analysis was done using sex, BMI, and the total TCCR score. Multivariate analyses demonstrated that BMI (p = 0.0005) and the total score (p = 0.0069) were independent factors for thoracic procedure time. In the RAMIE group, univariate analysis demonstrated that BMI and the TCCR at BV and TB levels were correlated with thoracic procedure time. Multivariate analyses demonstrated that the TCCR at TB level (p = 0.0187) was only independent factor for thoracic procedure time. Conclusions The TCCR and the total score based on it could be useful in assessing surgical difficulty of both C-MIE and RAMIE. C-MIE was affected by the diameter at all levels of the thoracic cavity due to restricted mobilities of thoracoscopic instruments. On the other hand, RAMIE’s articulated forceps prevent it from being affected by entire thoracic cavity. Consequently, only the TCCR at TB level, which is one of the most less flexible field, affects the difficulty in RAMIE.