Clinical analysis of 36 multiple myeloma patients with extramedullary plasmacytoma invasion of the spinal canal.

Few physicians are familiar with extramedullary plasmacytoma (EMP) invasion of the spinal canal in multiple myeloma (MM) patients, and little information about this rare disease is available. The purpose of the present study was to investigate the clinical features, prognosis and treatment of MM patients with EMP invasion of the spinal canal. We evaluated 36 MM patients with EMP invasion of the spinal canal. EMP invasion was confirmed by magnetic resonance imaging, computed tomography and/or histopathological analysis of bone marrow biopsy samples. Patients underwent surgery followed by chemotherapy or received chemotherapy alone. Chemotherapy consisted of bortezomib-containing regimens and other combination therapies. The patients' median age was 58.6 years (range, 31-78 years). Eight patients had negative immunofixation electrophoresis results, and nine patients had a bone marrow plasma cell infiltration rate of less than 5%. Of the 36 MM patients with EMP invasion of the spinal canal that we identified, 19 had thoracic spinal cord involvement, 10 had lumbar spinal cord involvement, 2 had sacral spinal cord involvement and 5 had both lumbar and thoracic spinal cord involvement. The findings of our study, which is the largest study in MM patients with EMP spinal canal invasion conducted to date, suggest the importance of the early detection of spinal invasion in MM patients. Extramedullary disease was resistant to conventional treatments but responded well to regimens containing novel drugs such as bortezomib. In patients with symptoms of nerve root involvement, the tumour should be resected as soon as possible to relieve spinal cord compression.