Isolated central nervous system blast crisis in chronic myeloid leukemia

Chronic myeloid leukemia is a myeloproliferative disorder characterized by the presence of the Philadelphia chromosome, t(9:22). Extramedullary blast crisis is a rare event. Imatinib mesylate has become the treatment of choice, especially for patients for whom allogenic stem cell transplantation is not an option. Imatinib produces complete cytogenetic responses in excess of 80%. However, the penetration of the drug and its metabolites into the CNS (Central Nervous System) is poor. Hence for patients who are on prolonged imatinib therapy and continue to have complete cytogenetic responses, the central nervous system may become a sanctuary site. We report a patient who had a complete hematologic and cytogenetic response and presented with headache and vomiting. The MRI showed meningeal enhancement and the CSF (Cerebro Spinal Fluid) examination was positive for blasts. He was started on cranial radiotherapy and triple intrathecal chemotherapy. He showed good symptomatic improvement and cleared the blasts in the CSF. At the end of radiation, he was in complete hematological remission but had 50% marrow metaphases positive for Philadelphia chromosome. As he did not have a matched sibling donor, the dose of imatinib was increased to 600 mg daily. He continues to be in complete hematologic remission at the time of this report.