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00925njm 22002777a 4500 dc Alvarez-Larrán, Alberto author Pérez-Encinas, Manuel author Ferrer-Marín, Francisca author Hernández-Boluda, Juan Carlos author Ramírez, María José author Martinez-Lopez, Joaquin author Magro, Elena author Cruz, Yasmina author Mata, María Isabel author Aragües, Pilar author Fox, María Laura author Cuevas, Beatriz author Montesdeoca, Sara author Hernández-Rivas, José Angel author García-Gutiérrez, Valentín author Gómez-Casares, María Teresa author Steegmann, Juan Luis author Durán, María Antonia author Gómez, Montse author Kerguelen, Ana author Bárez, Abelardo author García, Mari Carmen author Boqué, Concepción author Raya, José María author Martínez, Clara author Albors, Manuel author García, Francesc author Burgaleta, Carmen author Besses, Carlos author 2017 Hematocrit control below 45% is associated with a lower rate of thrombosis in polycythemia vera. In patients receiving hydroxyurea, this target can be achieved with hydroxyurea alone or with the combination of hydroxyurea plus phlebotomies. However, the clinical implications of phlebotomy requirement under hydroxyurea therapy are unknown. The aim of this study was to evaluate the need for additional phlebotomies during the first five years of hydroxyurea therapy in 533 patients with polycythemia vera. Patients requiring 3 or more phlebotomies per year (n=85, 16%) showed a worse hematocrit control than those requiring 2 or less phlebotomies per year (n=448, 84%). There were no significant differences between the two study groups regarding leukocyte and platelet counts. Patients requiring 3 or more phlebotomies per year received significantly higher doses of hydroxyurea than the remaining patients. A significant higher rate of thrombosis was found in patients treated with hydroxyurea plus 3 or more phlebotomies per year compared to hydroxyurea with 0-2 phlebotomies per year (20.5% vs. 5.3% at 3 years; P<0.0001). In multivariate analysis, independent risk factors for thrombosis were phlebotomy dependency (HR: 3.3, 95%CI: 1.5-6.9; P=0.002) and thrombosis at diagnosis (HR: 4.7, 95%CI: 2.3-9.8; P<0.0001). The proportion of patients fulfilling the European LeukemiaNet criteria of resistance/intolerance to hydroxyurea was significantly higher in the group requiring 3 or more phlebotomies per year (18.7% vs. 7.1%; P=0.001) mainly due to extrahematologic toxicity. In conclusion, phlebotomy requirement under hydroxyurea therapy identifies a subset of patients with increased proliferation of polycythemia vera and higher risk of thrombosis. Alvarez-Larran A, Perez-Encinas M, Ferrer-Marin F, Hernandez-Boluda JC, Ramirez MJ, Martinez-Lopez J, et al. Risk of thrombosis according to need of phlebotomies in patients with polycythemia vera treated with hydroxyurea. Haematologica. 2017 Jan;102(1):103-9. 10.3324/haematol.2016.152769 1592-8721 0390-6078 Haematologica http://hdl.handle.net/20.500.13003/17457 27686377 L617380486 2-s2.0-85008420111 http://hdl.handle.net/20.500.12105/7081 392921800023 Factores de Tiempo Risk of thrombosis according to need of phlebotomies in patients with polycythemia vera treated with hydroxyurea