A Prospective, Randomized, Open, Parallel-controlled, Superior-efficacy Clinical Study of Radical Sigmoidectomy for Sigmoid Cancer Versus Radical Sigmoidectomy Combined with Indocyanine Green Fluorescence Imaging Lymphatic Tracing Dissection in the Treatment of Sigmoid Cancer

Inclusion Criteria: 1. Age between 18 and 75 years old 2. Confirmed sigmoid adenocarcinoma cancer pathologically 3. Location of tumor: the sigmoid colon (descending colon from vertical to horizontal point) is the starting point of sigmoid colon, and the end point of sigmoid colon is at 15cm of anal margin. 4. CT showed sigmoid colon cancer: T3-4a N+ M0 5. Patients with non-local recurrence or distant metastasis; 6. no multiple colorectal cancer; 7. no neoadjuvant therapy; 8. physical conditions such as heart, lung, liver and kidney function can tolerate surgery. 9. Willing and able to provide written informed consent for participation in this study Exclusion Criteria: 1. Complicated with other malignant tumors or previous history of malignant tumors; 2. patients with intestinal obstruction, intestinal perforation, intestinal bleeding, etc.; 3. patients with tumor invasion or involvement of adjacent organs requiring combined organ resection; 4. patients with poor anal function and incontinence before operation; 5. patients with inflammatory bowel disease or familial adenomatous polyposis 6. ASA grade ≥ IV and / or ECOG physical status score \> 2; 7. patients with severe hepatorenal function, cardiopulmonary function, blood coagulation dysfunction or severe underlying diseases unable to tolerate surgery; 8. history of severe mental illness; 9. pregnant or lactating women; 10. patients with uncontrolled infection before operation; 11. patients with other clinical and laboratory conditions considered by some researchers should not participate in this trial.