This study is a retrospective real-world research initiated by the Chinese Academy of Medical Sciences Cancer Hospital, including Cancer Hospital of the Chinese Academy of Medical Sciences, Shenzhen Hospital and Peking University First Hospital. The study aims to retrospectively analyze the clinical data of approximately 2,000 patients who underwent laparoscopic surgery with preoperative imaging staging of cT1-4aNanyM0 and pathological diagnosis of adenocarcinoma or high-grade intraepithelial neoplasia from April 2016 to April 2020. The patients will be divided into the intracorporeal anastomosis group (IA) and extracorporeal anastomosis group (EA) based on the surgical records. The primary endpoints of the study are 3-year disease-free survival (DFS) and 3-year overall survival (OS). The secondary endpoints include overall complication rate within 30 days, postoperative pain score, time to first flatus after surgery, time to first bowel movement after surgery, time to first oral intake after surgery, length of hospital stay, and postoperative quality of life.
