Prevention of thrombosis in polycythemia vera and essential thrombocythemia

Identifying the most safe and effective strategy for reducing the vascular risk of subjects with polycythemia vera and essential thrombocythemia has always been challenging. The mechanisms underlying the thrombotic diathesis of these patients are still largely elusive and, more importantly, the number of large scale studies performed in this specific setting is very limited. Thus, physicians have to rely on approximate and largely subjective estimations of the vascular risk and on consensus-based recommendations. Not surprisingly, the use of several agents is quite heterogeneous among different countries. The European Collaboration on Low-dose Aspirin in Polycythemia Vera (ECLAP), which was established to test the efficacy and safety of low-dose aspirin in polycythemia vera, involved 12 European countries.1 The participating centers, although with moderate differences among centers and countries, prescribed hydroxyurea and aspirin to a much higher percentage of their patients than that reported in a survey on polycythemia vera treatments performed in the same years among North American centers.2 After the ECLAP trial, the recommendations on the use of aspirin in polycythemia vera will likely become more uniform but debates on hydroxyurea will probably continue for a long time. In fact, a clinical trial comparing the long-term efficacy and safety of this agent with that of alternative cytoreductive strategies would be very difficult to organize