Response to imatinib therapy in patients with hypereosinophilic syndrome. Median follow-up for all patients was 13 weeks (range, 6 to 36+ weeks). One of the patients who achieved CR underwent splenectomy before starting treatment with imatinib; he died in CR of pneumococcal sepsis after 9 weeks of therapy. The other 3 patients who achieved CR continue on therapy and are in remission 13+,25+, and 36+ weeks from the start of therapy. None of these patients has had any objective evidence of residual or recurrent tissue infiltration.