We treated 37 patients with polycythemia vera with imatinib mesylate (IM). The overall response rate was 49%. Thirty percent had a complete response, and 19%, a partial response. Thirty-one patients were treated for >120 days. Frequent side effects included nausea, diarrhea, edema, and skin rash. Whereas IM was effective in controlling erythropoiesis and reducing spleen size it was ineffective in controlling thrombocytosis. Normocellular marrow developed in 4 patients who had a complete response. Progression to overt myelofibrosis occurred in 3. Nevertheless, 6 patients have had a sustained complete response while on IM for >6 years. These patients were young, had high phlebotomy requirements, and only slightly elevated platelet counts. Therefore, we believe there may be a role for IM in patients with these characteristics whose disease cannot be controlled by, or as an alternative to, other myelosuppressive treatments.
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