Central nervous system (CNS)

At diagnosis, approximately 3% of patients have CNS3 disease (defined as cerebrospinal fluid specimen with ≥5 white blood cells/μL with lymphoblasts and/or the presence of cranial nerve palsies). However, unless specific therapy is directed toward the CNS, most children will eventually develop overt CNS leukemia whether or not lymphoblasts were detected in the spinal fluid at initial diagnosis. CNS-directed treatments include intrathecal chemotherapy, CNS-directed systemic chemotherapy, and cranial radiation. Some or all of these treatments are included in current regimens for ALL. For more information, see the CNS-Directed Therapy for Childhood ALL section.