[Successful induction of complete cytogenetic response with low-dose imatinib mesylate in an accelerated phase chronic myelogenous leukemia patient who developed severe bone marrow aplasia following standard-dose imatinib mesylate therapy].

A 58-year-old female presented with massive splenomegaly, leukocytosis and anemia. Bone marrow appearance was consistent with CML-AP, and t (9;22) (q34;q11) was detected on karyotyping. 600 mg daily imatinib mesylate (imatinib) was started and achieved complete hematological remission. However, pancytopenia was evident. Despite dose reduction and subsequent drug withdrawal, the pancytopenia worsened and she became transfusion dependent. Grade 4 pancytopenia persisted for 8 months after discontinuing imatinib. Bone marrow biopsy showed severe bone marrow aplasia with no morphological evidence of disease progression. Karyotyping showed minor cytogenetic response with no clonal evolution. Signs of hematological recovery appeared 8 months after stopping imatinib. The patient was re-started on imatinib at a dose of 100 mg/day. The dose was increased to 200 mg/day without hematological toxicity. Complete cytogenetic response (CCyR) was achieved 5 months after the re-administration of imatinib. The patient maintained CCyR with 200 mg of imatinib per day. Prolonged severe bone marrow aplasia has rarely been reported as a complication of imatinib therapy. This case also suggests that low-dose imatinib would be tolerable and effective for some CML patients who are intolerant of a standard dose of imatinib.