CVCs are a risk factor for forming blood clots (venous thrombosis[13]) including upper extremity deep vein thrombosis.[14] It is thought this risk stems from activation of clotting substances in the blood by trauma to the vein during placement.[15] The risk of blood clots is higher in a person with cancer, as cancer is also a risk factor for blood clots. Anti-clotting drugs such as heparin and fondaparinux have been shown to decrease the incidence of blood clots, specifically deep vein thrombosis, in a person with cancer with central lines.[16] Additionally, studies suggest that short term use of CVCs in the subclavian vein is less likely to be associated with blood clots than CVCs placed in the femoral vein in non-cancer patients.[17]