Venous thromboembolism (VTE) has emerged as a major adverse event of primary induction therapy with thalidomide (thal) and dexamethasone (dex) for newly diagnosed multiple myeloma (MM). Aim of the present study was to investigate the relationship between thrombophilic alterations and the risk of VTE in 266 patients who received four months of therapy with thal (200 mg/d) and pulsed high-dose dex in preparation for double autologous transplantation. The rate of VTE in the whole group of patients was 11.6%. The risk of VTE was 26.3% (86.2% patient-years) among the first 19 patients who entered the study and did not received any prophylaxis against thrombosis. The corresponding value among the remaining 247 patients who received thromboprophylaxis with fixed low-dose (1.25 mg/d) warfarin during the four months of thal-dex therapy was 10.6% (35.5% patient-years) (P=0.04). Episodes of VTE occurred at a median of 53 days from the start of thal therapy and, with the exception of 3 patients, were observed after at least a partial response to thal-dex was documented. No VTE events were recorded during the first two months after the end of the induction phase. After VTE occurrence, the majority of patients went on with thal treatment plus full anticoagulation, without evidence of progression of thrombosis. One hundred and ninety patients were evaluated for the presence of thrombophilic alterations at baseline and at the end of thal-dex therapy. The prevalence of factor V Leiden (3.2%) or g20210A prothrombin (2.1%) polymorphism in patients with MM was similar to that observed in 183 healthy controls (3.3%, P= 0.81; 3.8%, P= 0.50, respectively). The relative risk of VTE for patients carrying one of these thrombophilic alterations was 20% compared with 9.4% for patients who lacked both of them (P= 0.58). Reduced protein C and S activities or acquired activated protein C resistance (aAPCR) were recorded at baseline in 11% and 7.4% of MM patients, respectively. Abnormal values at baseline normalized almost completely at the end of treatment. Carriers of aAPCR and/or of reduced levels of natural anticoagulants at baseline did not have a significantly higher risk of VTE compared with normal patients (15.2% vs 9.3%; P=0.49). In conclusion, no significant relationship was found between baseline thrombophilic alterations, including aAPCR, and the risk of thal-related VTE. Prophylaxis with fixed low-dose warfarin was associated with an apparent decrease in the rate of VTE in comparison with a subgroup of patients who did not receive any thromboprophylaxis. A prospective phase III study comparing low molecular weight heparin with fixed low-dose warfarin with aspirin is currently ongoing in Italy to evaluate the best prophylaxis against the risk of thal-related VTE for patients with newly diagnosed MM.

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