A retrospective study on 226 polycythemia vera patients: impact of median hematocrit value on clinical outcomes and survival improvement with anti-thrombotic prophylaxis and non-alkylating drugs

The clinical impact of polycythemia vera (PV) diagnostic and therapeutic guidelines is still undetermined. In particular, the recommended target of hematocrit (Hct) < 0.45 has been recently questioned and alkylating drugs are still used for elderly patients. We revised, according to WHO criteria, 300 PV diagnosis and evaluated the impact on clinical outcome of median Hct and of the strategy to administer anti-thrombotic prophylaxis and to avoid alkylating chemotherapy in almost all patients. Of 226 patients with WHO-confirmed diagnosis (median age 66), 91.3% survived at the median follow-up of 5.84 years and 77.5% are projected alive at 13 years. Eighteen percent had major thrombosis and 2.7% acute myeloid leukemia. Twenty-two percent of patients maintained an Hct < 0.45: their overall and thrombosis-free survival are similar to those of patients with a 0.45-0.48 value. Conversely, an Hct > 0.48 and a "high thrombotic risk" according to ECLAP criteria were both significantly associated to shorter survival and higher thrombosis risk. Chemotherapy reduced thrombotic events without affecting survival. Our study revealed suboptimal compliance to published guidelines. However, in our casistic characterized by wide use of anti-platelet- and avoidance of alkylating drugs, patients' survival, although analyzed retrospectively, seemed to have improved compared to old literature data. The optimal Hct target was not clearly defined, although a value < 0.48 looks highly advisable.