Interferon and the treatment of polycythemia vera, essential thrombocythemia and myelofibrosis.

Recombinant IFN-α (rIFN-α) induces complete hematologic remissions in patients with myeloproliferative neoplasms (MPNs), but its use has been limited by side effects owing to the relatively high doses used. Now, low-dose rIFN-α is stressed, starting relatively early in the course of the MPNs. In polycythemia vera, this has resulted in a significant clinical, hematologic, morphologic and molecular response manifested by reduction in the JAK2(V617F) allele burden, sustained even after discontinuation of recombinant IFN. In essential thrombocythemia, platelet count reduction is prompt and durable without treatment for varying periods. In hypercellular primary myelofibrosis, rIFN-α has restored normal blood counts, reduced splenomegaly and induced morphologic marrow remissions. This article highlights our current use of rIFN-α in MPNs.