Treatment of polycythemia vera: the use of hydroxyurea and pipobroman in 292 patients under the age of 65 years.

Nonradiomimetic drugs, hydroxyurea (HU) and pipobroman (Pi), were administred to relatively young subjects with polycythemia vera (PV) in an attempt to decrease the leukemogenic risk observed in patients treated with 32P. Clinical safety, hematological efficacy, risk of carcinoma or leukemia, and frequency of progression to myelofibrosis have not yet been defined in long-term studies, and no comparative studies of HU and Pi have been conducted. Since 1980, 292 patients with PV diagnosed before the age of 65 years were randomized to receive treatment with HU (25 mg/kg/d, followed by low-dose maintenance) or Pi (1.2 mg/kg/d, followed by low-dose maintenance). Patients were followed until death or until May 1997. Drug tolerance was often poor; leg ulcers and buccal aphthous ulcers (with HU) and gastric pain and diarrhea (with Pi) sometimes required treatment change, mainly in the HU arm. Hematological stability, especially in terms of platelet count, was very often insufficient with HU (45% of cases), but the risk of thrombo-embolic event was similar in both arms. Actuarial survival was similar in the two arms and shorter than that of the reference population. The risk of leukemia was approximately 10% at the 13th year, with no significant difference between the two arms. The risk of carcinoma (when excluding the skin cancers) was similar in both groups. There was a high risk of progression to myelofibrosis in the patients treated by HU, which was significantly higher than with Pi.