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.