title: Stereotactic body radiotherapy of bone metastases in oligometastatic disease: prognostic factors of oncologic outcomes.
abstract: BACKGROUND
  To evaluate the safety of stereotactic body radiotherapy (SBRT) of bone metastases in oligometastatic disease and to investigate prognostic factors of local control (LC), progression/disease-free survival (PDFS), and overall survival (OS).
  
  
  METHODS
  Eligibility criteria were number of metastates ≤5, controlled primary tumor without evidence of progression under systemic therapy, exclusion of surgery, and no previous radiotherapy of the lesion of interest. Oligometastatic status was classified into only bone (BOD) and outside bone disease (OBOD), whereas SBRT was delivered to bone lesions using 2 different schedules: 24 Gy/1 fraction or 27 Gy/3 fractions. A positron emission tomography study of the lesion of interest was performed at baseline and at 3 months after SBRT to evaluate metabolic response according to European Organization for Research and Treatment of Cancer (EORTC) criteria. A Cox regression model was used for univariate and multivariate analysis.
  
  
  RESULTS
  Between January 2010 and December 2013, 40 patients were enrolled. Only 1 patient experienced severe late toxicity (radiation-related fracture). Local control was longer among responders' than nonresponders' lesions (94.2% and 91.2% versus 63% and 35% at 1 and 2 years, respectively) (p = 0.004; hazard ratio = 9.958). The multivariate analysis of PDFS showed a significant correlation with planning target volume (PTV) size (p = 0.003) and oligometastatic status (p = 0.002). The multivariate analysis of OS confirmed a statistically significant value of the oligometastatic status (p = 0.002) and a significant trend for PTV size (p = 0.065).
  
  
  CONCLUSIONS
  Stereotactic body radiotherapy is safe with a low incidence of severe toxicity. Positron emission tomography response was a strong prognostic factor of LC whereas BOD status and small PTV size could identify a subset of oligometastatic patients at better prognosis.
authors.affiliation: Department of Radiation Oncology, S. Chiara University Hospital, Pisa - Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Ursino
authors.affiliation: Department of Radiation Oncology, S. Chiara University Hospital, Pisa - Italy.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Montrone
authors.affiliation: Department of Radiation Oncology, S. Chiara University Hospital, Pisa - Italy.
authors.forename: Martina
authors.initials: M
authors.lastname: Cantarella
authors.affiliation: Department of Radiation Oncology, S. Chiara University Hospital, Pisa - Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Menghini
authors.affiliation: Department of Radiation Oncology, S. Chiara University Hospital, Pisa - Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Matteucci
authors.affiliation: Department of Radiation Oncology, S. Chiara University Hospital, Pisa - Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Mazzotti
authors.affiliation: Department of Radiation Oncology, University Hospital of Ferrara, Ferrara - Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Fiorica
authors.affiliation: Radiotherapy of Casa di Cura San Rossore, Pisa - Italy.
authors.forename: David
authors.initials: D
authors.lastname: Fedele
authors.affiliation: Department of Nuclear Medicine, S. Chiara University Hospital, Pisa - Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Erba
authors.affiliation: Biostatistical Consulting, Department of Oncology, University Hospital S. Chiara, Pisa - Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Morganti
authors.affiliation: Department of Radiation Oncology, S. Chiara University Hospital, Pisa - Italy.
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Fabrini
authors.affiliation: Department of Radiology, S. Chiara University Hospital, Pisa - Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Caramella
mesh_terms: D000328:Adult; D000368:Aged; D001859:Bone Neoplasms / Q000401:mortality / Q000556:secondary* / Q000601:surgery*; D018572:Disease-Free Survival; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D007558:Italy; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D011379:Prognosis; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D016019:Survival Analysis; D016896:Treatment Outcome