A Prospective, Multicenter Randomized Controlled Study of the Application of Preoperative FOLFOXIRI Chemotherapy Combined With Lateral Lymph Node Dissection in Low- and Medium-lying Rectal Cancer With Lateral Lymph Node Metastasis

Inclusion Criteria:

* Age 18-70 years old, gender is not limited;
* The clinical stage based on magnetic resonance imaging (MRI) is cT1-4aN+M0 (according to AJCC Cancer Staging Manual, 8th Edition, 2018).
* Meet the criteria for lateral lymph node metastasis (lymph node short diameter ≥7mm, or lymph node short diameter ≥5cm with uneven internal signals and no chemical shift effect, or irregular boundaries);
* The primary tumor was located in the rectum (hard tube proctoscopy indicated that the lower margin of the lesion was less than 10cm from the anus);
* Kastler score ≥70, ECOG score 0 or 1;
* Meet the following laboratory diagnostic indicators: hemoglobin ≥100g/L, white blood cells ≥3.5×109

  /L, neutrophil ≥1.5×109/L, platelet ≥100×109/L; Creatinine ≤1.5× upper limit of normal (UNL); Urea nitrogen (BUN) ≤1.5 upper limit of normal (UNL) alanine aminotransferase (ALT), aspartate aminotransferase (AST) ≤2.5×UNL, alkaline phosphatase (ALP) ≤2.5×UNL, total bilirubin (Tbil) ≤2.5×UNL; Urinary protein (-); Clotting time is normal.
* Patients with primary locally advanced rectal cancer required that they had not received surgery, radiotherapy, chemotherapy or other antitumor therapy from diagnosis to enrollment; No previous pelvic radiation;
* Subjects voluntarily join the study and sign the informed consent.

Exclusion Criteria:

* A history of malignancy at other sites, excluding curable non-melanic skin cancer and carcinoma in situ of the cervix;
* Unable to complete MRI;
* Preoperative examination indicated the need for combined organ resection;
* Allergic to 5-Fu and platinum drugs; Inability to swallow oral medications;
* The patient is under thrombolytic or anticoagulant therapy, has bleeding diathesis or coagulation dysfunction, or has occurred in the past year Aneurysm, stroke, transient ischemic attack, arteriovenous malformation;
* After renal history, urine test found proteinuria or clinical renal function was obviously abnormal;
* History of digestive tract fistula, perforation or severe ulcer;
* Active infection is present; Clinically significant cardiac disease (e.g., uncontrolled hypertension (160/110) mm Hg blood pressure, any history of myocardial infarction, unstable angina), NYHA class Ⅱ congestive heart failure, unstable symptomatic arrhythmias, or class II peripheral vascular disease. Myocardial infarction and cerebrovascular accident occurred within 6 months before enrollment;
* Participating in other clinical trials currently or within 4 weeks prior to enrollment;
* long-term adverse drug history, drug addiction history of mental disorders;
* Other cases where the examiner considers from the registration study that there are good reasons for non-conformity: if there are potential inconsistencies with the clinical protocol.