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Chronic Myeloproliferative Disorders Treatment (PDQ®): Treatment - Health Professional Information [NCI] - Primary Myelofibrosis


Ruxolitinib, an inhibitor of JAK1 and JAK2, can reduce the splenomegaly and debilitating symptoms of weight loss, fatigue, and night sweats for patients with JAK2-positive or JAK2-negative primary myelofibrosis, post–essential thrombocythemia myelofibrosis, or post–p. vera myelofibrosis.[27] In two prospective, randomized trials, 528 higher-risk patients were randomly assigned to ruxolitinib or to best available therapy or placebo; at 48 weeks, patients on ruxolitinib had a decrease of 40% to 60% in mean palpable spleen length or in spleen volume compared with an increase of 1% to 4% with best available therapy.[28][Level of evidence: 1iiDiv]; [29][Level of evidence: 1iDiv] Ruxolitinib also improved overall quality-of-life measures with low toxic effects in both studies but with no benefit in overall survival. Discontinuation of ruxolitinib results in a rapid worsening of splenomegaly and recurrence of systemic symptoms.[28,29,30] Other JAK2 inhibitors are currently being studied in clinical trials.[31]

Painful splenomegaly can be treated temporarily with ruxolitinib, hydroxyurea, thalidomide, lenalidomide, cladribine, or radiation therapy, but sometimes requires splenectomy.[19,32,33] The decision to perform splenectomy represents a weighing of the benefits (i.e., reduction of symptoms, decreased portal hypertension, and less need for red blood cell transfusions lasting for 1 to 2 years) versus the debits (i.e., postoperative mortality of 10% and morbidity of 30% caused by infection, bleeding, or thrombosis; no benefit for thrombocytopenia; and accelerated progression to the blast-crisis phase that was seen by some investigators but not others).[4,32]

After splenectomy, many physicians use anticoagulation therapy for 4 to 6 weeks to reduce portal vein thrombosis, and hydroxyurea can be utilized to reduce high platelet levels (>1 million).[34] However, data from a retrospective review of 150 patients who underwent surgery provided documentation that 8% of the patients had a thromboembolism and 7% had a major hemorrhage with prior cytoreduction and postoperative subcutaneous heparin used in one-half of the patients.[35]

Hydroxyurea is useful in patients with splenomegaly but may have a potential leukemogenic effect.[4] In patients with thrombocytosis and hepatomegaly after splenectomy, cladribine has shown responses as an alternative to hydroxyurea.[36] The use of interferon-alpha can result in hematologic responses, including reduction in spleen size in 30% to 50% of patients, though many patients do not tolerate this medication.[37,38] Favorable responses to thalidomide and lenalidomide have been reported in about 20% to 60% of patients.[17,18,19,39,40,41][Level of evidence: 3iiiDiv]

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