In ten patients with essential thrombocythemia and polycythemia Vera with thrombocytosis we have investigated the therapeutic effect of recombinant a-2a interferon (Roceron-A@) given subcutaneously in a maintenance dosage of 3 million units three times weekly.
The aim was to normalize the platelet count ( ~4 0 0 x 109/L). One of the secondary aims was to study platelet activity measured as p-thromboglobulin (p-TG) in urine.
All but one patient could administer the injections and in all patients a significant reduction in platelet values was seen. The treatment was discontinued in three patients due to side effects of interferon, two because of hair loss (one with irreversible alopecia), and one because of depression. Three patients developed antibodies to a-2a interferon and a concomitant rise in the platelet level; in one patient therapy was switched to leukocyte a-interferon with an excellent response. The initial levels of p-TG were elevated in 9/10 patients and were significantly reduced at 6 months in 4/5 patients not developing antibodies. Six patient are still on a-interferon therapy with a long-term follow-up of 3-3.5 years. We conclude that dnterferon therapy may be an alternative in patients with thrombocytosis and/or complications necessitating treatment.