title: Prognostic factors in solitary plasmacytoma of the bone: a multicenter Rare Cancer Network study.
abstract: BACKGROUND
  Solitary plasmacytoma (SP) of the bone is a rare plasma-cell neoplasm. There are no conclusive data in the literature on the optimal radiation therapy (RT) dose in SP. Therefore, in this large retrospective study, we wanted to assess the outcome, prognostic factors, and the optimal RT dose in patients with SP.
  
  
  METHODS
  Data from 206 patients with bone SP without evidence of multiple myeloma (MM) were collected. Histopathological diagnosis was obtained for all patients. The majority (n = 169) of the patients received RT alone; 32 chemotherapy and RT, and 5 surgery. Median follow-up was 54 months (7-245).
  
  
  RESULTS
  Five-year overall survival, disease-free survival (DFS), and local control was 70%, 46%, and 88%; respectively. Median time to MM development was 21 months (2-135) with a 5-year probability of 51%. In multivariate analyses, favorable factors were younger age and tumor size < 5 cm for survival; younger age for DFS; anatomic localization (vertebra vs. other) for local control. Older age was the only predictor for MM. There was no dose-response relationship for doses 30 Gy or higher, even for larger tumors.
  
  
  CONCLUSIONS
  Younger patients, especially those with vertebral localization have the best outcome when treated with moderate-dose RT. Progression to MM remains the main problem. Further investigation should focus on adjuvant chemotherapy and/or novel therapeutic agents.
authors: Department of Radiation Oncology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland. david.knobel@chuv.ch
authors: David
authors: D
authors: Knobel
authors: Abderrahim
authors: A
authors: Zouhair
authors: Richard W
authors: RW
authors: Tsang
authors: Philip
authors: P
authors: Poortmans
authors: Yazid
authors: Y
authors: Belkacémi
authors: Michel
authors: M
authors: Bolla
authors: Fazilet Dinçbas
authors: FD
authors: Oner
authors: Christine
authors: C
authors: Landmann
authors: Bernard
authors: B
authors: Castelain
authors: Mahmut
authors: M
authors: Ozsahin