title: The radiosurgery fractionation quandary: single fraction or hypofractionation?
abstract: Stereotactic radiosurgery (SRS), typically administered in a single session, is widely employed to safely, efficiently, and effectively treat small intracranial lesions. However, for large lesions or those in close proximity to critical structures, it can be difficult to obtain an acceptable balance of tumor control while avoiding damage to normal tissue when single-fraction SRS is utilized. Treating a lesion in 2 to 5 fractions of SRS (termed "hypofractionated SRS" [HF-SRS]) potentially provides the ability to treat a lesion with a total dose of radiation that provides both adequate tumor control and acceptable toxicity. Indeed, studies of HF-SRS in large brain metastases, vestibular schwannomas, meningiomas, and gliomas suggest that a superior balance of tumor control and toxicity is observed compared with single-fraction SRS. Nonetheless, a great deal of effort remains to understand radiobiologic mechanisms for HF-SRS driving the dose-volume response relationship for tumors and normal tissues and to utilize this fundamental knowledge and the results of clinic studies to optimize HF-SRS. In particular, the application of HF-SRS in the setting of immunomodulatory cancer therapies offers special challenges and opportunities.
authors.affiliation: Duke University, Durham, North Carolina, NC, USA.
authors.forename: John P
authors.initials: JP
authors.lastname: Kirkpatrick
authors.affiliation: Stanford University, Stanford, California, USA.
authors.forename: Scott G
authors.initials: SG
authors.lastname: Soltys
authors.affiliation: University of Washington, Seattle, Washington, USA.
authors.forename: Simon S
authors.initials: SS
authors.lastname: Lo
authors.affiliation: Memorial Sloan Kettering Cancer Center, New York, USA.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Beal
authors.affiliation: University of Utah School of Medicine, Salt Lake City, Utah, UT, USA.
authors.forename: Dennis C
authors.initials: DC
authors.lastname: Shrieve
authors.affiliation: Mayo Clinic, Rochester, Minnesota, MN, USA.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Brown
mesh_terms: D001932:Brain Neoplasms / Q000532:radiotherapy* / Q000556:secondary; D002986:Clinical Trials as Topic; D019583:Dose Fractionation, Radiation; D005909:Glioblastoma / Q000532:radiotherapy; D006801:Humans; D008577:Meningeal Neoplasms / Q000532:radiotherapy; D008579:Meningioma / Q000532:radiotherapy; D009464:Neuroma, Acoustic / Q000532:radiotherapy; D000069473:Radiation Dose Hypofractionation; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D016896:Treatment Outcome
keywords: brain metastases; hypofractionated stereotactic radiosurgery; normal tissue injury; radiobiology; stereotactic radiosurgery