Efficacy of radiotherapy and role of adjunctive immunochemotherapy in POEMS syndrome with solitary plasmacytoma.

Radiotherapy is a definitive treatment for polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, skin changes (POEMS) syndrome with solitary plasmacytoma. However, data on its efficacy and the role of immunochemotherapy are limited. This study evaluated the treatment outcomes of patients with POEMS syndrome receiving radiotherapy as their primary therapy and compared the results of those treated with adjunctive immunochemotherapy with those without. A retrospective analysis of patients with POEMS syndrome referred to the University College London Hospital from 1998 to 2023 was conducted. Among 150 patients with POEMS syndrome, 30 (20%) presented with solitary plasmacytoma. Sixteen patients (53%) received radiotherapy alone, whereas 14 (47%) had combined treatment with radiotherapy and immunochemotherapy, predominantly lenalidomide, and dexamethasone. Treatment responses were greater in the combined treatment group, with clinical, vascular endothelial growth factor, hematological, and radiological responses of 100%, 92%, 100%, and 100%, respectively, compared with 87%, 92%, 85%, and 79% in patients receiving radiotherapy only. The median follow-up for the entire cohort was 124 months, with a 5-year overall survival rate of 100% and a progression-free survival (PFS) rate of 82%. For those receiving radiotherapy alone, the median follow-up was 124 months, with a 3-year PFS rate of 69%. In contrast, no progression was observed among patients treated with combined therapy during the follow-up period (range, 7-54 months). Six patients experienced disease progression, with all having received radiotherapy alone as their first-line treatment. This study demonstrated the high efficacy of radiotherapy in patients with POEMS syndrome and solitary plasmacytoma and highlighted the potential benefits of combining radiotherapy with immunochemotherapy.