Isolated central nervous system relapse in two patients with BCR-ABL-positive acute leukemia while receiving a next-generation tyrosine kinase inhibitor.

We describe two patients with break point cluster region-Abelsen (BCR-ABL)-positive acute leukemia who had an isolated relapse in the central nervous system (CNS) while receiving a next-generation BCR-ABL inhibitor. The first had B-cell acute lymphoblastic leukemia which relapsed in the CNS while maintaining molecular remission in the bone marrow on nilotinib. The second patient had an isolated CNS myeloid blast crisis of chronic myeloid leukemia while maintaining complete cytogenetic remission in the bone marrow on dasatinib. Mutation analysis of the kinase domain revealed 35 base pair insertion (35INT) between exon 8 and 9 in both cases.