[Hydroxyurea--is it a harmless drug in Vaquez disease?]].

The frequent side effects of Hydroxy-Urea and the non-exceptional risk of leukemia and cancer in Polycythemia Vera treated for a long time by Hydroxy-Urea allow to conclude that Hydroxy-Urea is not an innocent drug. In a prospective trial of 150 patients with a median follow up of nine years, Hydroxy-Urea given alone induced side effects in 29% of patients necessitating to stop treatment in half of cases. The percentage of leukemia or myelodysplasia is 6.7% with an actuarial risk of leukemic transformation of 10% at 13 years. In an other prospective trial in 181 aged patients Hydroxy-Urea was given as maintenance therapy after 32P treatment. The median follow-up in that study is also of nine years. Side effects are observed in 13% of cases. A two fold increase of the leukemic risk was observed in the maintenance arm of the trial: 11 versus 19% at ten years, 14 vs 30% at 12 years, 16 vs 35% at 15 years because of the leukemogenic effect of Hydroxy-Urea in maintenance therapy we stopped including new patients in this arm of the trial.