A randomized controlled trial for assessing the effectiveness and safety of patients with malignant abdominal or pelvic tumors receiving prolonged postoperative thromboprophylaxis

INTERVENTION: Control group:???;Experimental group:???; CONDITION: venous thromboembolism PRIMARY OUTCOME: VTE occurrence in the 4th week after operation;VTE occurrence in the 8th week after operation;all‐cause mortality in the 4th week after operation;VTE occurrence in the 8th week after operation;all‐cause mortality in the 4th week after operation;all‐cause mortality in the 8th week after operation;duration from operation to VTE occurrence;bleeding events; INCLUSION CRITERIA: 1. Patients are clearly pathologically diagnosed abdominal or pelvic malignant tumors (from general surgery department, gynecology department, urology department, etc.; including laparoscopic and open surgery); 2. Caprini score >=5 points; 3. Expecting life span >=6 months; 4. Patients need to receive routine VTE prophylaxis during hospitalization after operation (physical prevention and pharmaceutical prevention); 5. Tumor stage >=2.