This month, Ruben Mesa, MD, discusses anticoagulation in a patient with essential thrombocythemia.
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I am caring for a 33-year-old female patient with JAK2-positive essential thrombocythemia (ET). Her platelet count has been in the range of 800−1,000 per mcL. She was initially treated elsewhere with aspirin alone (I understand that acquired von Willebrand disease was excluded) and has since relocated to my community. She was admitted to a hospital with injuries from a motor vehicle accident secondary to polysubstance abuse and required a splenectomy earlier this year. Her post-operative course was complicated by portal vein thrombosis (PVT), which may have been related to the trauma and operation rather than the ET. She is now noted to have a worsening thrombocytosis. Her previous physician started her on hydroxyurea, which she continues at this time. Her most recent complete blood count showed a white blood cell (WBC) count of 6.7×109/L, a hemoglobin level of 12.4 g/dL, mean corpuscular volume of 94.8 fL and a platelet count of 1,246 per mcL. Marrow showed typical features of ET without an increase in fibrosis, and storage iron was present. She also has a history of iron deficiency anemia, following childbirth last year, and is now on anticoagulation for the PVT. She seems quite young to be committed to hydroxyurea to control the marked thrombocytosis. I considered pegylated interferon, although she has ongoing mental health issues. What would you suggest with respect to cytoreductive therapy in this setting? How long would you continue the anticoagulation?
These are always challenging cases.
Patients with ET clearly have an increased baseline risk of thrombosis, but when they have a “provoked” event (e.g., after surgery, prolonged travel, or oral contraceptives), it is tough to say how much the ET contributed to that event. The specific thrombotic event this patient had is, unfortunately, a common complication of splenectomy, but that risk is increased in patients with myeloproliferative neoplasms (MPNs). One must assume that the thrombotic event is at least in part secondary to the MPN, and achieving a European LeukemiaNet Complete Hematological Response (ELN CHR: hematocrit level <45%, WBC <10×109/L, and a platelet count <400×109/L) is a goal that might reduce the risk of recurrence.
Pegylated interferon can reduce clone size and that is a worthy goal, but control of blood counts and decreasing risk of thrombosis is crucial; both hydroxyurea/hydroxycarbamide and pegylated interferon are appropriate options. I would not hesitate to start with hydroxyurea, which is inexpensive and readily available, and which most patients tolerate well. Even though this patient is young, I would not worry too much about long-term risks; you can stabilize the patient over a few months, then transition to pegylated interferon in the future if desired. I would aim for a platelet count of <400×109/L given the thrombotic event, though this may be too strict of a goal in the setting of splenectomy, which will increase thrombocytosis, and it may not be possible to normalize the platelet count without making the patient leukopenic or anemic.
PVT is a major event, so I would continue anticoagulation indefinitely if tolerated. If the patient does not tolerate the anticoagulation well, I would consider stopping after at least 6 months as long as counts are well controlled on cytoreduction (substituting aspirin for anticoagulation) and the patient is doing well.
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NEXT MONTH'S CLINICAL DILEMMA
I am caring for a female patient with obesity (>120 kg) who had an unprovoked saddle submassive pulmonary embolism that required thrombolytic therapy. I am wondering whether to use the maintenance dose of rivaroxaban 10 mg, or apixaban 2.5 mg twice per day. What would you recommend regarding use of the new oral anticoagulants for this patient?
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