Patients with multiple myeloma and other blood cancers have a high risk of venous thromboembolism, or blood clotting, according to a recent study published in the Journal of Clinical Oncology. The rate of this complication is influenced by multiple factors, including the type of disease, the type of chemotherapy, and the use of catheters.

Venous thromboembolism (VTE) is a condition in which a blood clot forms in a vein, limiting the blood flow in the affected vein. Additionally, a piece of the clot can break off, travel through the vein, and block an artery to the lungs. VTE occurs in 0.5 percent of cancer patients, compared with just 0.1 percent of the general population.

Historically, VTE has been associated with solid tumor cancers; however, recent evidence has indicated that the VTE rate in patients with blood-related tumors is similar to that in patients with solid tumors. VTE can occur at any point in the disease progression. General risk factors include immobility, age, history of blood clotting, slow blood flow in the veins, and infections. Treatment-related risk factors include chemotherapy, hormone therapy, and the use of catheters.

Myeloma patients frequently experience complications due to VTE, with ten percent of newly diagnosed myeloma patients developing VTE while undergoing chemotherapy treatment. The risk of VTE is further increased for those patients who are given a combination regimen of chemotherapy, steroids, and immunomodulatory agents, which include Revlimid ^[1] (lenalidomide) and thalidomide ^[2] (Thalomid).

Among patients receiving thalidomide alone, up to 4 percent experience VTE. When thalidomide is administered with the steroid dexamethasone ^[3] (Decadron), 26 percent of newly diagnosed patients and 8 percent of relapsed patients experience VTE. Up to 58 percent of patients can experience VTE when thalidomide is administered with dexamethasone and doxorubicin ^[4] (Adriamycin).

Approximately 3 percent of patients receiving Revlimid alone experience VTE. Newly diagnosed patients using Revlimid experience VTE 6 percent of the time, but this rate increases to 75 percent when these patients receive Revlimid in combination with dexamethasone. Among relapsed myeloma patients, 4 percent experience VTE when Revlimid is administered alone, and 15 percent experience VTE when dexamethasone is added to their treatment. However, low rates of VTE have been reported for patients taking Revlimid in combination with Velcade ^[5] (bortezomib).

Because VTE complications significantly increase morbidity and mortality, the authors of the study say that it is extremely important for high-risk patients to adhere to preventative measures. The American Society of Clinical Oncology recommends that cancer patients take low molecular weight heparin and warfarin (Coumadin), two blood thinners, prior to chemotherapy to help prevent clots.

The administration of heparin reduced the VTE rate from 58 percent to 10 percent for patients treated with a combination of thalidomide, dexamethasone, and doxorubicin. Reduced VTE rates were also observed when heparin was administered to patients treated with Revlimid and dexamethasone.

The administration of low-dose warfarin reduced the VTE rate from 26 percent to 13 percent in patients treated with thalidomide and dexamethasone. Clinical trials are still needed to evaluate the effectiveness of these blood thinner regimens.

For more information, please read the article in the Journal of Clinical Oncology ^[6] (abstract).