Aspirin and low molecular weight heparin (LMWH) are both commonly employed pharmacologic methods of venous thromboembolism (VTE) prophylaxis after orthopaedic surgery. Data comparing these two methods of VTE prophylaxis in patients undergoing pelvic/lower extremity orthopaedic surgery for malignancy are lacking, however, as compared to the data and guidelines present for VTE chemoprophylaxis after joint arthroplasty and hip fracture surgery. In this clinical trial, our specific aim is to compare the post operative incidence of VTE between patients receiving aspirin and LMWH after pelvic/lower extremity orthopaedic oncology procedures.