Newly Diagnosed Multiple Myeloma Is Associated with Enhanced TF Pathway Activation, Thrombin Generation and Increased Concentration of Procoagulant Microparticles

Background: Multiple myeloma (MM) and plasma cell dyscrasias (PCD) are associated with increased risk of venous thromboembolism (VTE) which is further enhanced by treatments with immunomodulatory agents, melphalan or steroids. The optimization of VTE prevention in patients with MM is an unmet need. According to Virchow's triad, blood hypercoagulabilty is one of the three conditions required for thrombosis. Elaboration of a risk assessment model, which includes biomarkers of hypercoagulability, could lead to better identification of MM patients eligible for pharmacological thromboprophylaxis.

Aims: We conducted a longitudinal observational study, to explore the relationship of MM with cellular and plasma hypercoagulability aiming to identify the most relevant biomarkers which could be used in the RAM for VTE.

Materials and Methods: Newly diagnosed patients (n=72) with PCD were recruited from July 2014 to May 2015. The control group (CG) was consisted of 30 healthy age and sex-matched individuals. A systematic compression ultrasound was performed at baseline and 6 months post-therapy. Blood samples were obtained at time of diagnosis and at 3-6 months post therapy. Samples of platelet poor plasma were assessed for thrombin generation (TG) with the PPP-Reagent® (5pMTF and 4μM phospholipids), P-selectin, D-dimers (D-Di), activated FVII (FVIIa), Tissue Factor (TFa), fibrin monomers (FM), and procoagulant phospholipid dependent clotting time (PPL-ct). The upper and lower normal limits (UNL and LNL) were calculated by the mean±2sd. We present herein the data obtained at the inclusion of the patients.

Results: Forty-three patients had MM, 16 had asymptomatic MM (AMM), 13 had MGUS. The median age was 68 years (40-84 years); 44% of patients were males. The median time to follow up was 6 months (range: 2-12 months). Patients with PCD as compared to the CG had significantly shorter PPL-ct, which it has been shown that it is inversely correlated with the concentration of platelet derived procoagulant microparticles. PCD patients had also lower Endogenous thrombin potential (ETP), shorter time to thrombin Peak (ttPeak) and lower mean rate index (MRI) of the propagation phase of TG as compared to the controls. The levels of P-selectin were not significantly different between the two groups. Patients with MM as compared to MGUS and AMM patients had significantly higher levels of TFa, FVIIa, FM, D-Di, Peak and MRI (Table 1). Among MM patients 72% had PPL-ct below the LNL, 62% and 28% had TFa and FM above the UNL respectively, 4% had MRI above the UNL and 29% had MRI below the LNL. Among patients who received therapy, 46% also received thromboprophylaxis with either aspirin (76%, n=22) or LMWH (24%, n=5); all were MM patients who received IMiD-based therapies. During the follow-up period the rate of VTE events in MM patients was 7% (all MM patients under treatment).

Conclusion: In patients with PCD increased procoagulant microparticles of cellular origin is a generalized phenomenon. In addition, patients with MM present significant TF pathway activation and increased in vivo TG. A significant part, but not all of the patients present strong signs of plasma hypercoagulability. The finding of high inter-individual variability of TG underlines the heterogeneity of blood coagulation alterations in MM patients. The data of the prospective part of this study will allow to validate the clinical significance of this finding.