Lenalidomide Treatment of Isolated Central Nervous System Relapse in Acute Lymphoblastic Leukemia after Hematopoietic Stem Cell Transplantation and Chimeric Antigen Receptor T-Cell Therapy

Introduction: Hematopoietic stem cell transplantation (HSCT) and chimeric antigen receptor T (CAR-T) cell are effective treatments for acute lymphoblastic leukemia (ALL). Various forms of intra- and extramedullary relapses have been reported after HSCT and CAR-T-cell therapy for ALL; however, no reports have investigated isolated central nervous system (CNS) relapse after HSCT and CAR-T-cell therapy. Hence, no clinical treatment has been established for such rare patients. Case Presentation: An 18-year-old male patient with B-cell ALL suffered from isolated CNS relapse after HSCT and CAR-T-cell therapy. Conventional systemic intravenous and intrathecal chemotherapies were ineffective and intolerable. A unique immunosuppressive microenvironment of decreasing NK cell percentage and increasing IL-8 concentration and CAR-T-cell exhaustion had been illustrated in the cerebrospinal fluid. Finally, the patient received immunomodulatory therapy with lenalidomide and obtained complete remission. Conclusion: Lenalidomide might be a therapeutic strategy for isolated CNS relapse after HSCT and CAR-T-cell therapy.