Study On Surgical Approach Of Robot-assisted Mediastinal Tumor Resection And Novel Genomic Aberration Sites Of Thymic Epithelial Tumors

PART Ⅰ STUDY ON SURGICAL APPROACH OF ROBOT-ASSISTED MEDIASTINAL TUMOR RESECTIONBackground: The objectives of this study were to evaluate the feasibility and safety of robot-assisted thoracic surgery(RATS)using the da Vinci robotic system for mediastinal tumor resection and to describe the surgical approaches for tumors in different mediastinal regions.Methods: We retrospectively reviewed data from 83 patients who underwent RATS for resection of a mediastinal tumor and 240 patients who underwent VATS from June 2015 to April 2019.The results were analyzed with statistics.Results: Due to the difference of the basic conditions of the patients,the propensity score matching(1:2)was used.Seventy-five cases in RATS group and 136 cases in thoracoscopic group were matched.The operation time in RATS group(median 80 minutes,interquartile range 40 minutes)was comparable to that in thoracoscopy group(median 90 minutes,interquartile range 59 minutes),P = 0.101.Importantly,the intraoperative blood loss in RATS group(Median 50 ml,interquartile range 20 ml)was less than that in thoracoscopy group(median 50 ml,interquartile range 70 ml),P <0.05,and the total thoracic drainage volume in RATS group(Median 110 ml,interquartile range 299 ml)less than that in the thoracoscopy group(median 300 ml,interquartile range 445 ml),P <0.001.Moreover,the duration of chest tube drainage in RATS group(median 2 days,interquartile range 1 day)was shorter than that in thoracoscopy group(median 3 days,interquartile range 1 day),P <0.001,and the postoperative hospital stay in RATS group(median 3 days,interquartile range 1 day)was also shorter than that in the thoracoscopy group(median 4 days,interquartile range 2 days),P <0.001;In addition,there was no statistical difference between the two groups in terms of symptoms,3 cases in RATS group and 15 cases in thoracoscopy group,P = 0.08.Further analysis of 83 cases of robotic mediastinal tumor resection showed that the choice of surgical approach depends on the location of the lesion and the scope of surgical resection.Twenty-one tumor types were involved in the pathology after the operation of robotic mediastinal tumor resection,which were scattered in the whole mediastinum.The common diagnoses were thymoma(n=16),bronchocyst(n=16)and neurilemmoma(n=12).Resection was performed in the lateral decubitus position in 29 patients with posterior mediastinal tumor,semi-lateral decubitus position in 41 patients who only need resection of anterior mediastinal tumor,and reverse Trendelenburg position in 13 patients undergoing thymectomy.There was no statistically difference in operating time,intraoperative bleeding,total postoperative drainage volume,duration of chest tube use,postoperative hospital stay and postoperative complications among these three groups.Conclusions: Our experience demonstrated that different surgical approaches of RATS are safe and feasible for mediastinal tumor resection.An appropriate approach can be selected based on the tumor pathologyand the mediastinal region in which the tumor is located.PART Ⅱ STUDY ON SURGICAL APPROACH OF ROBOT-ASSISTED MEDIASTINAL TUMOR RESECTIONThymic epithelial tumors(TET)including thymomas and thymic carcinomas are rare,but they are common primary tumors in the anterior mediastinum.The etiology and tumorigenesis of TET remain unclear.To better understand the novel aberrations of this rare tumor and provide more significant mutation sites for targeted therapy,we performed next-generation sequencing detection on 55 patients with TET.Our results showed that most genes in 12 core pathways harbored aberrations of indeterminate potential.In 4 genes(ARID1A,KMT2 C,TGFBR2 and MAP3K1),the indel frequency was above 90%.Dozens of genes,including TGFBR2,KMT2 C,PRKDC,ATR,CHD2,SDHA,KDM5 A,CHEK1,MSH6 and POLE,possessed frameshift indel with different frequencies in different hotspot sites,which could be the new targets of therapy for TET.For the first time,we revealed a strong correlation between the tumor mutational burden and single nucleotide variations,but not frameshift,on DNA mismatch repair gene MSH6 in TET.