Long-term incidence of hematological evolution in three French prospective studies of hydroxyurea and pipobroman in polycythemia vera and essential thrombocythemia.

Despite recent discoveries made in myeloproliferative disorders other than chronic myelogenous leukemia, which it is hoped will result in earlier diagnosis, and better evaluation and management of patients, hematological evolution to myelofibrosis, acute leukemia, and myelodysplastic syndromes (AL/MDS) remain major causes of long-term mortality in polycythemia vera (PV) and essential thrombocythemia (ET) patients. Evaluation of long-term leukemogenic risk of currently available drugs, therefore, is crucial. We report updated results of three French prospective trials of hydroxyurea and pipobroman in PV and ET patients with a median follow-up longer than 10 years. The results show that the incidence of AL/MDS is higher than previously reported with no evidence of a plateau (with approximately 40% of AL/MDS cases occurring after the 12th year of follow-up). Although hydroxyurea currently remains the first choice in the treatment of high-risk PV and ET patients, the use of nonleukemogenic drugs, such as interferon alpha (IFN-alpha) or anagrelide, should be assessed more widely in randomized trials using accurate diagnostic criteria and taking into account the presence of the JAK2 mutation, given that they may have an impact on disease evolution.