Central nervous system (CNS) leukemia after imatinib mesylate therapy for chronic myelogenous leukemia (CML)

Abstract

7042 Background: Imatinib is the standard first line treatment for CML. Imatinib penetrates the CSF poorly. We examined the incidence and outcome of CNS disease in pts with CML treated with imatinib at our institution. Methods: The clinical data for pts with early or late chronic phase and accelerated phase CML treated with imatinib between 1999 and 2006 were reviewed. Pts who were started on imatinib elsewhere and progressed to blast phase were also included. CNS disease was defined as a pathologically proven enhancing lesion (leptomeningeal or parenchymal) or presence of CSF leukemic cells. Results: Nine hundred and ten pts with chronic or accelerated phase CML were treated with imatinib. Fifty five developed blast crisis while on imatinib; another 28 pts had blast transformation while receiving imatinib elsewhere, making up a total of 83 pts. At diagnosis, their median age was 51 yrs, median Hgb, WBC and PLT counts were 10.6 g/dl, 59.7×109/L and 307×109/L, respectively. Median time from diagnosis to starting imatinib was 45.4 mts and the median duration of imatinib therapy was 17.9 mts. Fifteen pts had achieved a complete cytogenetic response and 47 had a complete hematologic response before progressing to blast phase. Their median overall survival from diagnosis was 73.2 mts. Thirty pts developed extramedullary disease; they had similar baseline characteristics as the rest with a median survival of 68.3 mts. Fifteen pts developed CNS disease (5 leptomenigeal, 5 CSF, 3 parenchymal, and 2 spinal cord); 14 had concomitant medullary blast crisis. They had a statistically significant younger age at diagnosis (41.9 vs 52.4 yrs), lower platelet counts (186 vs 334×109/L), and shorter overall survival (66.7 vs 73.2 mts) compared to the other pts with blast phase. Conclusions: CNS disease occurs infrequently in pts receiving imatinib for CML but should be suspected in pts with relevant symptoms. Pts developing CNS leukemia had a worse prognosis; this may be secondary to an inherently worse disease, poor CSF penetration of imatinib, and subsequent difficulty in eradicating CNS disease using available therapies. More potent tyrosine kinase inhibitors, such as nilotinib and dasatinib, and new agents with the ability to cross the blood-brain barrier should be evaluated in this setting. No significant financial relationships to disclose.

A Case of Isolated CNS Relapse in a CML Patient on Chronic Phase

“…Blastic phase of CML is not limited to peripheral involvement. In a review made by Sohl of 900 patients with CML being treated with Imatinib, they identified 30 patients with extramedullary involvement 15 of which is CNS [6]. Since 1980's reports regarding incidence of CML with extramedullary involvement were documented, most commonly affecting the lymph nodes and a rather small group involving the CNS [7].…”