Recombinant interferon-alpha therapy of Philadelphia chromosome-negative myeloproliferative disorders with...

The clinical course of patients with myeloproliferative disorders and excessive thrombocytosis may be complicated by serious hemorrhagic or thrombotic events. We have previously reported that interferon-alpha can control severe refractory thrombocytosis in patients with advanced chronic myelogenous leukemia. Therefore, we treated a group of thrombocythemic patients with Ph-negative myeloproliferative disorders, including polycythemia vera and essential thrombocythemia, with recombinant interferon-alpha (rIFN-alpha 2a).

Eight patients with profound elevations in platelet counts received a median induction dose of 5.4 X 10(6) U/day (range, 5.0 to 10.0 X 10(6) U/day) of rIFN-alpha 2a administered intramuscularly or subcutaneously.

We observed a significant decline in platelet counts from a median baseline value of 1,929 X 10(9)/L (range, 960 to 2,960 X 10(9)/L) to a median posttreatment value of 431 X 10(9)/L (range, 71 to 1,150 X 10(9)/L) (p less than 0.01). Concomitantly, white blood cell counts declined from a median baseline value of 20.8 X 10(9)/L (range, 10.5 to 40.8 X 10(9)/L) to a median posttreatment value of 6.1 X 10(9)/L (range, 2.9 to 29.0 X 10(9)/L) (p less than 0.02). Correction of thrombocytosis was rapid, with a median of only eight days from the start of therapy to the achievement of a platelet count less than 1,000 X 10(9)/L. Six of eight patients have shown an ongoing response with a median follow-up period of 11 months (range, one to 30 months). There have been no bleeding or thrombotic events during the study. Side effects of rIFN-alpha 2a therapy consisted of fever and flu-like symptoms, with tachyphylaxis developing after one to two weeks of therapy.

Our observations suggest that alpha interferon may be a promising therapeutic agent for myeloproliferative disorders characterized by thrombocytosis.