In a recent literature review, Canadian researchers confirmed that the use of aspirin, warfarin, and heparin decreases the risk for blood clots in multiple myeloma patients receiving thalidomide treatment.

However, the authors of the review pointed out that they were unable to recommend a specific strategy for blood clot prevention due to inconsistent reporting of blood clotting events among the trials. 

They pointed out that randomized, controlled trials directly comparing the different medications are needed in order to determine the true efficacy of the preventative medications.

In addition, the authors of the review pointed out that the rate of major bleeding events, a complication associated with medications preventing blood clots, was not reported in the majority of the reviewed trials. They concluded that the risk-benefit ratio of these medications, therefore, remains unclear.

Research has shown that patients with blood cancers, including multiple myeloma, are at high risk for developing blood clots in the veins, or venous thromboembolism. If a deep vein is blocked (called deep vein thrombosis), patients may experience redness, pain, and swelling. Additionally, if the clot breaks off and travels through the vein, it may block an artery to the lungs (called pulmonary embolism).

The risk of developing blood clots is higher for patients treated with thalidomide ^[1] (Thalomid) or Revlimid ^[2] (lenalidomide). The risk increases further when patients also receive dexamethasone ^[3] (Decadron).

Patients on thalidomide and Revlimid, therefore, frequently receive prophylactic (preventative) medications, such as aspirin, warfarin (Coumadin), and heparin, to reduce the risk of blood clots. A recent study has shown that all three agents are equally effective in reducing blood clots in myeloma patients who received thalidomide treatment (see related Beacon ^[4] news). 

In order to establish the best blood clot prevention strategy, the authors of the review pointed out that it is important to know what the absolute blood clot rates are with the different prophylactic agents in newly diagnosed and previously treated myeloma patients who receive thalidomide or Revlimid treatment.

The researchers performed a retrospective analysis of clinical trials evaluating either thalidomide-based or Revlimid-based regimens. They included 71 studies in their review, 61 of which were studies involving thalidomide and 10 of which were studies involving Revlimid.

The researchers reported that newly diagnosed patients treated with thalidomide alone had a blood clotting risk of 1.3 percent per treatment cycle. This risk increased to 4.1 percent when patients were also treated with dexamethasone. However, the risk was lowered to 2.6 percent per treatment cycle if patients received preventative medications. According to the authors of the review, both warfarin and heparin were most effective in reducing blood clots.

The risk of developing blood clots was lower in previously treated myeloma patients on thalidomide treatment. The rate of blood clots was 0.8 percent per treatment cycle for patients who received thalidomide in combination with dexamethasone. The majority of reviewed studies did not report on the use of different preventative treatments.

Newly diagnosed patients treated with Revlimid and dexamethasone had a blood clotting risk of 0.8 percent per treatment cycle. This risk did not change significantly when patients received aspirin as a prophylactic treatment (0.9 percent). Previously treated patients treated with Revlimid and dexamethasone had a blood clotting risk of 0.7 percent per treatment cycle. Once again, this risk was comparable when patients received aspirin as a prophylactic treatment (0.6 percent).

For more information, please see the study in the Journal of Thrombosis and Haemostasis ^[5] (abstract).