Evaluation of the Use of Apixaban in Prevnetion of Thromboembolic Disease in Patients With Myeloma Trated With iMiDs

Inclusion Criteria: * Patients (men/women) aged more than 18 years * All consecutive patients, with myeloma, in first-line treatment or in relapse, who are treated - With IMiDs (MPT, Melphalan -Prednisone -Thalidomide ; Lenalidomide - Dexamethasone). AND \- who require prevention of venous thromboembolic events with Aspirin or Low molecular Weight Heparin (LMWH) for a minimum duration of 6 months At least, 2/3 of patients will be treated with Lenalidomide-Dexamethasone. * Written informed consent * Patients affiliated to the French social security system or equivalent Exclusion Criteria: * Patient who needs curative anticoagulant treatment (heparin, LMWH, vitamin K antagonists, Dabigatran, Rivaroxaban, Apixaban) for an associated disorder (mechanical valve, atrial fibrillation or venous thromboembolic disease in the previous 6 months). * Patient who needs preventive treatment with an anticoagulant in a post-operative context * Patient who needs anti-platelet treatment (Aspirin, Clopidogrel, Prasugrel, Ticagrelor or dual anti-platelet therapy ) * Patient with active bleeding or at a high risk of bleeding (ulcer disease, intracranial bleeding in the previous 6 months, uncontrolled hypertension) * Patient having undergone a surgical intervention within the past 30 days likely to expose them to an haemorrhagic risk * Active hepatic disease (hepatitis, cirrhosis) * Severe renal insufficiency (creatinine clearance using the Cockcroft equation \< 30 ml/mn) * Known allergic reaction to Apixaban * Contraindication to the use of an anticoagulant treatment * Prohibited concomitant treatment * inhibitors of CYP3A4 and P-gp : azole antimycotic agents (ketoconazole, itraconazole, voriconazole, posaconazole), inhibitors of HIV protease (ritonavir, indinavir, nelfinavir, atazanavir, saquinavir), specific macrolide antibiotics (clarithromycine, telithromycine) * other antithrombotic treatment : salicylate derivates (aspirin, products containing aspirin), antiplatelet therapy, heparin (unfractionated heparin, low molecular weight heparin, danaparoide sodique, fondaparinux), hirudines, oral anticoagulants (vitamin K antagonists, rivaroxaban, dabigatran) * Patient with AST or ALT rate \> 3 times upper limit of normal * Patient with Bilirubin rate \> 1.5 times upper limit of normal * Patient with Platelets rate \< 75 G/l * Patient with Creatinine Clearance (Cockcroft) \< 30 ml/mn * Incidental finding of a proximal Deep Venous Thrombosis on the screening ultrasound * Patients refusing or unable to give a written consent of information * Patient unable to comply with the protocol requirement, in the investigator's opinion * Life expectancy less than 6 months * Incarcerated patients * Pregnancy or possibility of pregnancy within 6 months * Females of childbearing potential without reliable contraception * Ecog \> 2