Effect of definitive radiotherapy on the long-term outcome in patients with solitary extramedullary plasmacytoma.

Extramedullary solitary plasmacytoma (EMP) is a rare type of malignancy. This paper presents a retrospective review of the experience with EMP at the Krakow Oncology Center. Records of 17 patients with head and neck EMP, treated with definitive radiotherapy between 1976 and 2009, were analyzed. The total tumour dose ranged from 45 to 70 Gy (median 56 Gy). In four patients with partial response after radiotherapy, adjuvant melphalan-based chemotherapy was applied. The median follow-up period was 8.6 years. The treatment was well tolerated. The estimated 10-year overall survival, disease-free survival, and multiple myeloma-free survival were 68.4%, 49.3%, and 55%, respectively. The 10-year local control rate was 90.9%. No in-field local recurrence was observed. During the follow-up, progression into multiple myeloma was observed in five patients, with a mean time to conversion of 24 months. The only factor adversely affecting overall survival on univariate analysis was the age >56 years, whereas a complete tumour regression after radiotherapy was associated with a significant improvement in both disease-free survival and multiple myeloma-free survival. Despite the high effectiveness of local radiotherapy, there is still a significant treatment failure risk due to the EMP conversion into generalized disease. An attempt to identify prognostic factors may facilitate selection of patients with a high risk of progression to multiple myeloma.