MCNU in the treatment of essential thrombocythemia--a pilot study.

The efficacy of a single dose of MCNU 150 mg was evaluated in nine symptomatic patients with essential thrombocythemia (ET). As the platelet counts increased during the following 4 weeks, an extra dose of 100 mg of MCNU was administered to three patients. All patients had thrombotic or hemorrhagic complications. Seven patients responded. The mean platelet count decreased to below 1.0 x 10(12)/l within 5 weeks; it reached its lowest level (0.35 x 10(12)/l) at 6 weeks and became stable at less than 1.0 x 10(12)/l without further therapy for 12 weeks in all patients. Thrombotic and hemorrhagic complications ameliorated within 4 weeks in all patients. Our study indicates that MCNU acts as a platelet-reducing agent in patients with ET.