Multiple myeloma patients are at an increased risk of developing deep vein blood clots, and several myeloma treatments further increase the risk. However, blood clots can often be prevented with the use of blood thinners, according to Dr. Todd Zimmerman of the University of Chicago during a myeloma education session on June 7 at the annual American Society of Clinical Oncology (ASCO) meeting.

Dr. Zimmerman reported that there is a nine-fold increase of deep vein thrombosis (a blood clot in a deep vein) among multiple myeloma patients, even before they begin treatment. According to Dr. Zimmerman, researchers are not sure why.

Treatment with high-dose dexamethsone ^[1] (Decadron) or other multi-agent therapies can significantly increase the risk of blood clots.

As benefits of long-term, continuous maintenance therapy are becoming clear, it is good news that there is only a 3 percent risk or less of developing a blood clot on Revlimid maintenance therapy.

The risk of blood clots can be minimized with the use of aspirin, warfarin (Coumadin), and low-molecular weight heparin.

Recent studies have shown that aspirin, which is most often used for the prevention of arterial clots as compared to venous clots, is sufficient for preventing deep vein blood clots in myeloma patients.

There are a few exceptions: patients receiving a high-dose regimen or high-risk patients who have already had blood clots should receive heparin or warfarin. For patients with low platelet counts, no blood thinner should be given. For patients with kidney failure, heparin is generally not recommended, so their myeloma therapy should be carefully considered.

“The good news in all of this, though, is that even when these patients do have a venous thromboembolic event, it does not seem to impact their overall or progression-free survival,” said Dr. Zimmerman. “But it is clearly important to prevent these complications from occurring in patients with myeloma.”

It is still not yet clear how long after an event or discontinuation of myeloma therapy a patient should stay on anti-coagulation medication.

“It is important to educate our patients about what symptoms to look for so that they can notify us of any symptoms they have that may be suggestive of [a blood clot],” said Dr. Zimmerman.

Symptoms of a deep vein blood clot include leg pain, accumulation of fluid, redness of the skin, and warmth in the affected limb.