Solitary plasmacytoma (SP) is characterized by a localized mass of clonal plasma cells with no or minimal bone marrow plasmacytosis. It can present either as EMP or SBP. Radiotherapy is the first-line treatment with high response rate. However, 65-84% SBP patients and 25-35% EMP patients progress at 10 years. We aimed to investigate whether adjuvant bortezomib based chemotherapy with radiotherapy could prolong event-free survival in treatment-naive SP patients compared to that with radiotherapy alone.