Pulmonary embolism, the second leading cause of death in cancer patients, is effectively treated with anticoagulants. In patients with cancer-associated thrombosis (CAT), the use of anticoagulants is associated with 10 to 15% of bleeding in the first 6 months. Most of the guidelines propose to integrate the bleeding risk in the choice of therapies. Thrombin generation assay (TGA) reflects an overall hemostatic response and could be a useful biomarker. Proven on the thrombotic side in the CAT population, useful in the assessment of the bleeding risk of hemophiliac patients, the TGA is emerging as a tool. The investigators to measure TGA in cancer patients included prospectively, having recently developed a CAT and to evaluate the association between the measurement and the risk of hemorrhagic complication under anticoagulant during the first 6 month of treatment.

Pulmonary embolism, the second leading cause of death in cancer patients, is effectively treated with anticoagulants. In patients with cancer-associated thrombosis (CAT), the use of anticoagulants is associated with 10 to 15% of bleeding in the first 6 months. Most of the guidelines propose to integrate the bleeding risk in the choice of therapies. Existing models for predicting anticoagulant associated bleeding risk applied to the CAT patients are not very predictive (AUC<0.60). Thrombin generation assay (TGA) reflects an overall hemostatic response and could be a useful biomarker. Proven on the thrombotic side in the CAT population, useful in the assessment of the bleeding risk of hemophiliac patients, the TGA is emerging as a tool. The investigators wish to measure TGA in cancer patients included prospectively, having recently developed a CAT and to evaluate the association between the measurement and the risk of hemorrhagic complication under anticoagulant during the first 6 month of treatment.

Inclusion Criteria:

• Patients with active cancer, as defined by current French recommendations (Mahé I et al Rev Mal Respir 2021)
• Presenting acute proximal deep vein thrombosis of the lower limb (DVT) and/or proximal pulmonary embolism (at least segmental) (PE), confirmed by objective tests (Doppler ultrasound in the event of DVT; lung scintigraphy or CT scan in the event of PE)
• No contraindication for anticoagulant treatment at a curative dose at the time of inclusion

Exclusion Criteria:

• Patients participating in a therapeutic clinical trial with a blinded therapy or an open-label therapeutic trial who are included in the experimental treatment group.
• Patients already on anticoagulant at a curative dose for valvular or rhythmic embolic disease or a history of venous thromboembolic disease
• Hematological malignancies
• Patients with a contraindication to anticoagulant treatment on inclusion
• Patient whose relay by DOAC has already been carried out.