Outcome and prognostic factors in solitary plasmacytoma.

Abstract

e18512 Background: Solitary plasmacytoma is a rare plasma-cell neoplasm. We wanted to assess the outcome and prognostic factors in patients with solitary plasmacytoma. Methods: The data from 79 patients with bone (n=55), and/or extramedullary (n=25) solitary plasmacytoma with no evidence of multiple myeloma treated with definitive radiation at a single institution from 1988-2007 were collected. The median follow-up time was 56 months. A serum myeloma protein was present in 36 patients (46%), and Bence Jones proteinuria was present in 24 patients (31%). The median radiation dose was 45 Gy. Overall-survival, local control, and freedom from multiple-myeloma progression were calculated actuarially. Results: The five-year overall survival rate was 78%. The median overall survival was 11 years. Local control was achieved in 72 patients (91%). Radiation dose above or below 45 Gy was not a predictor of local control (p=0.452). The five-year probability of progression to multiple myeloma in all patients was 47%. The five-year probability of progression to multiple myeloma was higher in patients with bone plasmacytoma than extramedullary plasmacytoma (57% versus 27%, p = 0.008). In patients with solitary plasmacytoma of the bone, the 5-year probability of progression to multiple myeloma was 47% in patients with resolution of serum or urine myeloma protein, versus 75% in patients without resolution of myeloma protein (p =0.056). Conclusions: Local control is excellent in this disease. Progression to multiple myeloma remains the main problem. Patients with extramedullary plasmacytoma had the best outcomes. There was a trend towards a lower rate of progression to multiple myeloma in patients with bone plasmacytoma that had resolution of myeloma protein. No significant financial relationships to disclose.