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Chronic Myeloproliferative Neoplasms 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.[29]

In two prospective, randomized trials, 528 higher-risk patients were randomly assigned to ruxolitinib or to either placebo (COMFORT-I [NCT00952289]) or best available therapy (COMFORT-II [NCT00934544]). At 48 weeks, patients on ruxolitinib had a decrease of 30% to 40% in mean spleen volume compared with an increase of 7% to 8% in the control patients.[30][Level of evidence: 1iiDiv]; [31][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 in the initial reports. Additional follow-up in both studies (1 year in COMFORT-I and 2 years in COMFORT-II) showed a survival benefit among ruxolitinib-treated patients compared with control patients (COMFORT-I hazard ratio [HR], 0.58; 95% confidence interval [CI], 0.36-0.95; and COMFORT-II HR, 0.48; 95% CI, 0.28-0.85).[32,33][Level of evidence: 1iiA] Clinical benefits were observed across a wide variety of clinical subgroups.[34,35] Discontinuation of ruxolitinib results in a rapid worsening of splenomegaly and the recurrence of systemic symptoms.[30,31,36] Ruxolitinib does not reverse bone marrow fibrosis or induce histologic or cytogenetic remissions. More selective JAK inhibitors are currently being evaluated in clinical trials.[37,38]

Painful splenomegaly can be treated temporarily with ruxolitinib, hydroxyurea, thalidomide, lenalidomide, cladribine, or radiation therapy, but sometimes requires splenectomy.[21,39,40] 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).[4,39]

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).[41] 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.[42]

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