Clinical Outcomes Under Hydroxyurea and Impact of ELN Responses in Patients with Polycythemia Vera: A PV-NET Real World Study

Introduction: Hydroxyurea (HU) is the recommended treatment in patients (pts) with polycythemia vera (PV) at high thrombotic risk. In 2013, European LeukemiaNet (ELN) guidelines defined criteria for response to HU including hematology and clinical parameters (Barosi G, Blood 2013). Yet, estimates of ELN response rates and of their influence on clinical outcomes are lacking. Methods: The “PV-NET” is a European multicentre observational clinical study including now 530 cases of PV followed in 16 European Hematology Centers. Inclusion criteria are: 2016 WHO diagnosis of PV; availability of clinical/laboratory data at diagnosis and during follow-up; age≥18 yrs. Data cut-off was June 2019. A time-to-event (thrombosis, hemorrhage, evolution into blast phase [BP] or myelofibrosis [MF]) analysis was calculated from HU start with Fine & Gray model with death as competing risk. Overall survival (OS) was calculated from HU start to last contact/death (log-rank p). Response to HU was defined per ELN criteria: Complete (CR): Hematocrit (Hct)