The goal of this observational study is to learn about the long-term efficacy and safety of extended anticoagulant treatment in patients with cancer associated thrombosis. (CAT) The main question it aims to answer is:
• Does extended prophylactic dose anticoagulant provide comparable efficacy and safety to therapeutic dosing after 6-month treatment of anticoagulant? The medical record data of participants who's already received for at least 6-month anticoagulant treatment upon regular medical care for CAT will be collected and analyzed about their recurrent thrombosis, anticoagulant related bleeding, and survival outcome.