Management of patients with a low burden of JAK2 mutation and a history of thrombosis

Dr Chris Hillis is an assistant professor in the Division of Oncology at McMaster University and hematologist at the Juravinski Hospital and Cancer Centre.

What is your approach in a patient with a low burden of JAK2 mutation without other diagnostic criteria for myeloproliferative neoplasms (MPNs)? Does this approach change if the patient has a history of thrombosis?

Chris Hillis, MD, MSc: We do not have great evidence in this area on what to do. If it is found by chance—meaning there is no clinical event that has led to the testing of JAK2 and the allele burden is very low—we may see that patient back in a year, redo their JAK testing, and see if the allele burden has gone up with no pharmaceutical intervention in the meantime.

If there are blood count abnormalities that warrant therapy or if there has been a thromboembolic event, then we will of course treat that patient differently.

In a patient who has had a thromboembolic event and the JAK2 testing comes back as positive, but it is weakly positive or with a low allele burden, they have had a thromboembolic event so you want to make sure that appropriate anticoagulation is instituted. Where the presence of the low burden of JAK2 may influence your thought process would be how long to continue the anticoagulant for. In a strictly provoked event, where you are thinking of a short-term therapy—for example, after an orthopedic surgery—you may wish to repeat the JAK2 mutation testing to determine if the allele burden has increased. Certainly you would also want to repeat the blood counts at the time that you are considering stopping the antithrombotic agent and perhaps switching to an antiplatelet agent at that stage.

If it is a weakly provoked event or an unprovoked event and the person has a low burden of JAK2 mutation, I would actually advocate that they should continue on lifelong anticoagulants while it is safe to do so and monitor the blood counts as they may have an evolving MPN or you may actually start to get blood findings that warrant cytoreductive therapy or other actions.