Successful BCMA CAR-T Therapy for Multiple Myeloma With Central Nervous System Involvement Manifesting as Cauda Equina Syndrome—A Wandering Road to Remission

Multiple myeloma (MM) with central nervous system (CNS) involvement is rare with only 1% incidence. So far, there is no standard or effective treatment for CNS MM, and the expected survival time is fewer than 6 months. Here, we report a case of MM with CNS involvement presented with cauda equina syndrome (CES) who achieved complete remission after anti-B-cell maturation antigen (BCMA) chimeric antigen receptor T (CAR-T) cell therapy (Chictr.org.cn, ChiCTR1800017404). The expansion of BCMA CAR-T cells was observed in both peripheral blood (PB) and cerebrospinal fluid (CSF). The CAR-T cells peaked at 2.4 × 10(6)/l in CSF at day 8 and 4.1 × 10(9)/l in PB at day 13. The peak concentration of interleukin (IL)-6 in CSF was detected 3 days earlier, and almost five times higher than that in PB. Next, morphological analysis confirmed the elimination of nucleated cells in CSF 1 month after CAR-T cell treatment from 300 cells/μl, and the patient achieved functional recovery with regressed lesion shown in PET-CT. The case demonstrated that BCMA CAR-T cells are effective and safe in this patient population.