Central nervous system relapse in two patients with chronic myelogenous leukemia in myeloid blastic phase on imatinib mesylate therapy.

We report two patients with Philadelphia (Ph) chromosome positive chronic myelogenous leukemia (CML) in myeloid blastic phase that developed central nervous system disease while on imatinib mesylate therapy. Patient 1 presented with CML in myeloid blastic phase and responded to imatinib, cytarabine, and idarubicin-based treatment achieving complete cytogenetic remission in the marrow, but developed myeloid blasts in his cerebrospinal fluid (CSF) during treatment. Patient 2 developed CML myeloid blastic phase after initially being in hematologic and cytogenetic remission with imatinib treatment. He represented with an extramedullary mass at the base of his skull and CSF involvement. Both patients were treated with intrathecal chemotherapy and received craniospinal irradiation to clear the spinal fluid of disease. Both patients have undergone related allogeneic stem cell transplant and are in complete hematologic remission; one is in complete cytogenetic remission, the other is too early to evaluate. Central nervous system involvement with myeloid blasts is previously unreported for patients with CML in blastic phase on imatinib and warrants cautious observation and vigilance in these patients.