The Challenge of Myeloma-Related Thromboembolic Disease: Can Thrombin Generation Assay May Detect Disease-Related Hypercoagulability?

RATIONAL/BACKGROUND: Venous thromboembolism (VTE) is a major complication of multiple myeloma (MM). Mortality and morbidity related to VTE in multiple myeloma patients remain a challenging health problem. The incidence of deep venous thrombosis with thalidomide plus dexamethasone therapy is 15-17%. The reported incidence of thrombosis with lenalidomid treatment in MM is 9 – 17.5%. The risk is higher when lenalidomid is used in combination with high dose of dexamethasone. The guidelines therefore recommend thromboprophylaxis but serious uncertainties remain concerning the optimal thromboprophylaxis. The optimal dose of LMWH for thromboprophylaxis, the potential interest of aspirin as an alternative strategy in these patients have not been clearly established. Thus, antithrombotic prophylaxis remains underused also due to the lack of a laboratory assay which can reliably detect hypercoagulability and predict the VTE risk in each patient with MM. Thrombin generation assay is a global haemostasis assay reflecting the overall function of the blood clotting system. Both platelet-poor and platelet-rich plasma samples can be tested. In platelet rich plasma, the test also reveals the role played by platelets in supporting haemostasis.

With this pilot study, we aimed to evaluate thrombin generation assay (TGA) measuring the overall coagulation capacity of each patient, as a reliable, standardized over-all hemostasis assay for the detection of MM-related hypercoagulability.

PATIENTS/MATERIALS & METHODS:

Patients: Hundred and three adult patients, 62 males and 41 females, with MM followed in Lyon and Nantes University Hospitals were included in the study, after obtaining informed consent. The control group included 100 healthy adult volunteers with no personal history of bleeding or thrombosis and with no treatment which may interfere on hemostasis. Fifty three patients were included at the diagnosis before any treatment, 9 patients had a treatment with lenalidomid only, 41 patients were on lenalidomid and anti-thrombotic treatment e.g. 15 warfarin, 9 low molecular weight heparin (LMWH) and 20 aspirin.

TGA: TG was measured using the calibrated automated TGA (CAT; Thrombinoscope bv) as previously described by Hemker et al, using TF1pM and phospholipids 4µM (final concentrations) in platelet poor plasma (PPP). Platelet Rich Plasma (PRP) samples were tested with TF1pM only.

RESULTS & DISCUSSION:

Our results showed that patients with MM had significantly higher thrombin generation capacity in PPP (p=0.01, Mann Whitney test) and in PRP (p<0.0001, Mann Whitney test). The in vitro addition of increasing concentrations of lenalidomid and dexamethasone had no significant effect on thrombin generation capacity of patients (p=0.99, Anova). In vivo thrombin generation results of patients treated with lenalidomid was significantly higher in PRP compared to untreated MM patients (p=0.04, Mann Whitney test). In the presence of platelets, prophylaxis with aspirin induced a significant reduction of thrombin generation (p=0.003) which was similar to that observed with LMWH, whilst patients on warfarin had very low thrombin generation results compared to prophylactic doses of LMWH (p<0.0001). These results are in line with clinical studies showing a similar prophylaxis efficacy of aspirin and LMWH in MM patients treated with lenalidomid. Our results emphasize a crucial role of platelets in the hypercoagulability induced by MM and immunomodulatory therapy. Platelet flow cytometry analysis showed that platelets were more activated in patients treated with lenalidomid and dexamethasone compared to untreated myeloma patients, with a statistically significant higher expression of platelet CD 62P (n=6; p=0.03 Mann Whitney test).

CONCLUSIONS: TGA can be an interesting biomarker to detect hypercoagulability induced by MM. Our results suggest that platelets are involved in the pathophysiology of MM and lenalidomid-related hypercoagulability. In PRP of patients treated by lenalidomid, aspirin and LMWH have similar antithrombotic effect on thrombin generation. Warfarin induces the highest inhibition of thrombin generation in this population. The mechanisms involving platelets in the hypercoagulability of MM are currently further explored in our laboratory. The correlation between thrombin generation capacity and clinical VTE events needs to be investigated in further clinical studies.