Cardiovascular Events and Intensity of Treatment in Polycythemia Vera
What is the efficacy of conventional treatment aimed at maintaining the recommended hematocrit target of <45%, as compared with a level of 45-50%, for the prevention of thrombotic events in patients with polycythemia vera?
The investigators randomly assigned 365 adults with JAK2-positive polycythemia vera who were being treated with phlebotomy, hydroxyurea, or both to receive either more intensive treatment (target hematocrit, <45%) (low-hematocrit group) or less intensive treatment (target hematocrit, 45-50%) (high-hematocrit group). The primary composite endpoint was the time until death from cardiovascular causes or major thrombotic events. The secondary endpoints were cardiovascular events; cardiovascular hospitalizations; incidence of cancer; progression to myelofibrosis, myelodysplasia, or leukemic transformation; and hemorrhage. An intention-to-treat analysis was performed.
After a median follow-up of 31 months, the primary endpoint was recorded in 5 of 182 patients in the low-hematocrit group (2.7%), and 18 of 183 patients in the high-hematocrit group (9.8%) (hazard ratio [HR] in the high-hematocrit group, 3.91; 95% confidence interval [CI], 1.45-10.53; p = 0.007). The primary endpoint plus superficial-vein thrombosis occurred in 4.4% of patients in the low-hematocrit group, as compared with 10.9% in the high-hematocrit group (HR, 2.69; 95% CI, 1.19-6.12; p = 0.02). Progression to myelofibrosis, myelodysplasia, or leukemic transformation, and bleeding were observed in six, two, and two patients, respectively, in the low-hematocrit group, as compared with two, one, and five patients, respectively, in the high-hematocrit group. There was no significant between-group difference in the rate of adverse events.
The authors concluded that in patients with polycythemia vera, those with a hematocrit target of <45% had a significantly lower rate of cardiovascular death and major thrombosis than did those with a hematocrit target of 45-50%.
This randomized study suggests that in patients with polycythemia vera who were receiving conventional treatment (including phlebotomy, hydroxyurea, or both), maintaining a hematocrit target of 45-50% was associated with four times the rate of death from cardiovascular causes or major thrombosis, as was maintaining a hematocrit target of <45%. The benefit of intensive hematocrit reduction was consistent in the examined subgroups, and no significant heterogeneity of results was found according to age, previous thrombosis, platelet or white-cell counts, splenomegaly, previous cytoreductive treatment, or antiplatelet or anticoagulant medication. The results validate current treatment recommendations for patients with polycythemia vera that call for maintaining a hematocrit of <45%.
Keywords: Hematocrit, Myelodysplastic Syndromes, Follow-Up Studies, Phlebotomy, Polycythemia Vera, Thrombosis, Hospitalization, Hemorrhage
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