title: The impact of radiosurgery fractionation and tumor radiobiology on the local control of brain metastases.
abstract: OBJECTIVE
  Experience with whole-brain radiation therapy for metastatic tumors in the brain has identified a subset of tumors that exhibit decreased local control with fractionated regimens and are thus termed radioresistant. With the advent of frameless radiosurgery, fractionated radiosurgery (2-5 fractions) is being used increasingly for metastatic tumors deemed too large or too close to crucial structures to be treated in a single session. The authors retrospectively reviewed metastatic brain tumors treated at 2 centers to analyze the dependency of local control rates on tumor radiobiology and dose fractionation.
  
  
  METHODS
  The medical records of 214 patients from 2 institutions with radiation-naive metastatic tumors in the brain treated with radiosurgery given either as a single dose or in 2-5 fractions were analyzed retrospectively. The authors compared the local control rates of the radiosensitive with the radioresistant tumors after either single-fraction or fractionated radiosurgery.
  
  
  RESULTS
  There was no difference in local tumor control rates in patients receiving single-fraction radiosurgery between radioresistant and radiosensitive tumors (p = 0.69). However, after fractionated radiosurgery, treatment for radioresistant tumors failed at a higher rate than for radiosensitive tumors with an OR of 5.37 (95% CI 3.83-6.91, p = 0.032).
  
  
  CONCLUSIONS
  Single-fraction radiosurgery is equally effective in the treatment of radioresistant and radiosensitive metastatic tumors in the brain. However, fractionated stereotactic radiosurgery is less effective in radioresistant tumor subtypes. The authors recommend that radioresistant tumors be treated in a single fraction when possible and techniques for facilitating single-fraction treatment or dose escalation be considered for larger radioresistant lesions.
authors.affiliation: Departments of Neurosurgery and.
authors.forename: Eric K
authors.initials: EK
authors.lastname: Oermann
authors.forename: Marie-Adele S
authors.initials: MA
authors.lastname: Kress
authors.forename: Jonathan V
authors.initials: JV
authors.lastname: Todd
authors.forename: Brian T
authors.initials: BT
authors.lastname: Collins
authors.forename: Riane
authors.initials: R
authors.lastname: Hoffman
authors.forename: Huma
authors.initials: H
authors.lastname: Chaudhry
authors.forename: Sean P
authors.initials: SP
authors.lastname: Collins
authors.forename: David
authors.initials: D
authors.lastname: Morris
authors.forename: Matthew G
authors.initials: MG
authors.lastname: Ewend
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001932:Brain Neoplasms / Q000145:classification / Q000601:surgery*; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis / Q000473:pathology / Q000628:therapy*; D009364:Neoplasm Recurrence, Local / Q000473:pathology*; D016634:Radiosurgery / Q000379:methods*; D012189:Retrospective Studies; D016896:Treatment Outcome