Long‐term evaluation of 164 patients with essential thrombocythaemia treated with pipobroman: occurrence of leukaemic evolution

Essential thrombocythaemia (ET) is usually considered an indolent disease, but it may progress during its natural course into acute leukaemia (AL); however, an influence of myelosuppressive agents in the blastic transformation of ET cannot be excluded. We performed a retrospective study to assess the incidence of AL in ET patients treated with pipobroman (PB) as first‐line therapy. One hundred and sixty‐four patients with ET were managed with PB at a dose of 1 mg/kg/d until a stable platelet count below 400 × 109/l was achieved. Maintenance therapy was given at a planned dose ranging between 0·2 and 1 mg/kg/d according to platelet count, in all cases, with a median daily dose of 25 mg (range 7–75 mg/d). The median treatment time was 100 months (range 25–243 months). The patients were evaluated for the occurrence of AL and/or secondary malignancies and survival end‐points. AL was observed in nine patients (5·5%) after a median treatment time of 153 months (range 79–227 months). The overall survival (OS) and the event‐free survival (EFS) at 120 months were 95% and 97%, whereas at 180 months, they were 84% and 76% respectively. In conclusion, this retrospective analysis shows a low incidence of AL in a large group of patients consecutively treated with PB as first‐line chemotherapy. Therefore, an investigation of the role of myelosuppressive agents in the blastic transformation of ET would be of interest.