How I Prevent and Treat Central Nervous System Disease in Adults with Acute Lymphoblastic Leukemia

The central nervous system (CNS) is the most important site of extramedullary disease in adults with acute lymphoblastic leukemia (ALL). While CNS disease is identified only in a minority of patients at the time of diagnosis, subsequent CNS relapses (either isolated or concurrent with other sites) will occur in some patients, even after delivery of prophylactic therapy targeted to the CNS. Historically, prophylaxis against CNS disease has included intrathecal (IT) chemotherapy and radiotherapy (RT), although the latter is being used with decreasing frequency. Treatment of a CNS relapse usually involves intensive systemic therapy and cranial or craniospinal RT along with IT therapy, and consideration of allogeneic hematopoietic cell transplant (HCT). However, short- and long-term toxicities can make these interventions prohibitively risky, particularly for older adults. As new antibody-based immunotherapy agents have been approved for relapsed/refractory B-cell ALL, their use specifically in patients with CNS disease is an area of keen interest, both because of the potential for efficacy but also concerns of unique toxicity to the CNS. In this review, we discuss data-driven approaches for these common and challenging clinical scenarios, as well as highlight how recent findings potentially support the use of novel immunotherapeutic strategies for CNS disease.