Isolated central nervous system (CNS) relapse of multiple myeloma 11 years after autologous stem cell transplantation: a case report.

Background: Multiple myeloma (MM) relapse in the central nervous system (CNS) confers an adverse prognosis, usually occurring in a short period after stem cell transplant and with a short overall survival. Isolated CNS relapse is so rare that there is no current standard treatment. Case Description: We present a 59-year-old male with an isolated CNS MM relapse, who had received autologous stem-cell transplant (ASCT) and thalidomide maintenance 11 years prior. He returned to our clinic with cauda equina syndrome and a nuclear magnetic resonance (NMR) identified a spinal lesion, a lumbar puncture was performed and plasma cells were identified in his cerebrospinal fluid (CSF). He was initially treated with intrathecal (IT) chemotherapy with methotrexate and steroid + radiotherapy and plasma cells disappeared after a few bi-weekly doses. Later on, treatment with pomalidomide/dexamethasone was given for 12 cycles with good clinical response with 80% recovery of his motor function. Conclusions: In this rare case of a very late CNS MM relapse, we demonstrate that IT chemotherapy complemented with a systemic pomalidomide-based treatment is safe and effective. This is particularly important in contexts where newer therapies such as bispecifics, chimeric antigen receptor-T (CAR-T) cells or even daratumumab or selinexor are not widely available. Further clinical experience in this particular scenario will be required to confirm this observation and define overall the best strategy for this rare group of patients.