Efficacy trial of pipobroman in polycythemia vera and incidence of acute leukemia.

ABSTRACT

A trial was conducted between 1970 and 1981 with pipobroman (PB) in 100 consecutive patients with polycythemia vera (PV), followed for a median time of 60 months, to evaluate the efficacy of this drug and assess the risk of acute leukemia. Phlebotomy was not done before PB was given. Hematologic remission was achieved in 92% of previously untreated patients in a median time of 12 weeks (range, 6-48 weeks) and maintained for a median of 48 months. Acute hematologic toxicity was absent. The median overall survival was 140 months with 65% five-year complication-free survival; the overall death rate at 12 years was 23% (6% of patients died of thrombotic complications). The actuarial risk of acute leukemia was 6% and 9% at five and seven years, and the time from the diagnosis of PV to leukemia ranged from 14 to 81 months. Myelofibrosis occurred in three patients and lung carcinoma in one. All leukemias were nonlymphoid with prominent monocytic component and dyserythropoiesis. One patient had erythroleukemia, two cases were heralded by preleukemia with chromosomal abnormalities, one involving the chromosomes 5 and 7. PB is effective in PV; however, despite an easy induction of remission, continuous low-dose maintenance is necessary and the risk of subsequent acute leukemia is still significant.