[Successful treatment with lenalidomide-containing regimen of plasma cell leukemia accompanied by meningeal involvement]

The central nervous system (CNS) is rarely involved in plasma cell neoplasms (PCN), especially in patients with advanced disease, harboring poor prognostic chromosomal abnormalities. The prognosis after development of CNS is poor, with a median survival of 2-6 months. Here, we present a 56-year-old woman with isolated CNS relapse of plasma cell leukemia who was admitted to our hospital with back pain, thigh pain, and dysuria. Morphological examination of the cerebrospinal fluid (CSF) confirmed the presence of relapsed plasma cell leukemia, whereas active myeloma lesions were not detectable outside the CNS. Her symptoms did not improve with high doses of methotrexate or intrathecal chemotherapy. However, one cycle of combination therapy with lenalidomide and dexamethasone led to the improvement in clinical symptoms, with complete response seen in the CSF morphology. After 13 cycles, she developed a hematological relapse but maintained complete response in the CSF. The efficacy of lenalidomide in CSF PCN was sporadically reported, and the CNS penetrance of lenalidomide was demonstrated in animal models; however, its efficacy in CNS PCN has not been established. The current case supports the efficacy of combination therapy with lenalidomide as a new therapeutic strategy for CNS PCN.