Interferon alpha-2a to control thrombocytosis in chronic myelogenous leukemia and essential thrombocythemia.

Four patients with chronic myelogenous leukemia and thrombocytosis and one patient with essential thrombocythemia were treated with purified recombinant human interferon alpha-2a (IFN-alpha 2a). Significant decline in platelet counts, from a mean ( +/- SE) of 1.396 +/- 0.265 x 10(6)/mm3 to a mean of 0.396 +/- 0.04 x 10(6)/mm3 (p less than 0.05), was observed in all patients. The platelet count remained normal for 15, 21 and 30 days after discontinuation of IFN-alpha 2a in 3 patients. In 2 patients the platelet count began to rise slowly two weeks after discontinuation of IFN-alpha 2a. Our preliminary observations suggest that purified recombinant human IFN-alpha 2a may effectively control progressive thrombocytosis in advanced chronic myelogenous leukemia and essential thrombocythemia.