Clinical features and prognostic factors in solitary plasmacytoma

Summary This study aimed to review the clinical features and outcome of 53 patients with solitary plasmacytoma managed at our Institution between 1976 and 2012. Thirty‐five patients had bone solitary plasmacytoma and 18 extramedullary solitary plasmacytoma. Tumour sizes were larger in patients with bone involvement ( P = 0·003). Treatment consisted of local radiotherapy ( n = 26), radiotherapy + chemotherapy ( n = 15), surgery ( n = 4) and chemotherapy ( n = 8); the local control rate was 94·3%. Progression to multiple myeloma was recorded in 20/35 (57·1%) patients with bone involvement and in 1/18 (5·5%) patients with extramedullary disease ( P = 0·0003). The 5‐year overall survival ( OS ) rate was 78·4%; bone solitary plasmacytoma patients had a significantly worse OS (71·9% vs. 88·2%, respectively; P = 0·029) and 5‐year progression‐free survival ( PFS ; 53·0% vs. 88·5%; P = 0·0003) compared to extramedullary solitary plasmacytoma patients. On univariate analysis, bone disease and size (≥5 cm) impacted negatively on PFS ( P = 0·0027 and P = 0·04, respectively). Bone disease also affected OS ( P = 0·04). In multivariate analysis bone location was the only independent prognostic factor for PFS ( P = 0·0041) and OS ( P = 0·021). Patients with bone solitary plasmacytoma have a significantly worse prognosis than extramedullary solitary plasmacytoma cases.