[Basics and Clinics of Cancer-Associated Venous Thromboembolism]

Cancer patients, especially active cancer patients have high risk of cancer-associated venous thromboembolism(VTE). Virchow's triad, hyper-coagulability, endothelial cell damage, and blood stasis are often found during cancer treatment. Tissue factor expressed on tumor cells activate coagulation, and decrease in antithrombotic activity by topical inflammation and platelet activation increase the risk of VTE. The risk of VTE is further enhanced by surgical intervention and chemotherapy. Anticoagulation is the most important treatment, however warfarin is not suitable for active cancer patients due to drug- drug interaction and gastrointestinal toxicity. In the Western countries, low molecular weight heparin (LMWH) is the standard choice for cancer-associated VTE. During anticoagulation, risk of recurrence of VTE and major bleeding is very high. Recently, direct oral anticoagulant(DOAC)has been introduced and widely used in Japan after the evidence of DOACs in cancer patients. Gastrointestinal bleeding is one of the frequent adverse events during DOAC treatment. Drug-drug interaction such as P-glycoprotein and CYP3A4 must be considered for safety treatment.