title: Tumor volume threshold for achieving improved conformity in VMAT and Gamma Knife stereotactic radiosurgery for vestibular schwannoma.
abstract: OBJECTIVE
  Recent advances in multileaf collimator field shaping technology and inverse planning software have resulted in highly conformal LINAC based stereotactic radiosurgery (SRS) plans with minimal dose to critical structures. This modeling study compares Gamma Knife (GK) and LINAC SRS for vestibular schwannoma (VS).
  
  
  METHODS
  76 treatment plans from nineteen patients with VS were planned using GK forward planning and volumetric arc therapy (VMAT) inverse planning software. VMAT plans were generated with 1 coplanar, 3 and 5 non-coplanar arcs. Dose to normal structures and beam-on time (dose rate 600MU/min) were compared using Kruskal-Wallis and Dunn's post hoc test.
  
  
  RESULTS
  Median tumor volume was 1.2cm(3) (range 0.1-4.8cm(3)). A peripheral tumor dose of 12Gy was prescribed. Tumor coverage was >99.8%. VMAT plans had lower target D2% and mean dose, as well as decreased beam-on time, compared to GK plans (p<0.0001). Paddick conformity index in VMAT 5 arc plans was superior to that of GK plans for targets >0.5cm(3) (p=0.002). Similar dose to cochlea, normal brain tissue and brainstem was observed.
  
  
  CONCLUSIONS
  VMAT should be considered as a safe, alternative modality to GK for VS SRS treatment, especially for tumors larger than 0.5cm(3).
authors.affiliation: Department of Radiation Oncology, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, United States.
authors.forename: Hyun
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, United States.
authors.forename: Peter
authors.initials: P
authors.lastname: Potrebko
authors.affiliation: Department of Radiation Oncology, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, United States.
authors.forename: Amanda
authors.initials: A
authors.lastname: Rivera
authors.affiliation: Department of Neurological Surgery, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, United States.
authors.forename: Haisong
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Radiation Oncology, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, United States.
authors.forename: Harriet B
authors.initials: HB
authors.lastname: Eldredge-Hindy
authors.affiliation: Department of Neurological Surgery, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, United States.
authors.forename: Vickie
authors.initials: V
authors.lastname: Gunn
authors.affiliation: Department of Radiation Oncology, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, United States.
authors.forename: Maria
authors.initials: M
authors.lastname: Werner-Wasik
authors.affiliation: Department of Neurological Surgery, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, United States.
authors.forename: David W
authors.initials: DW
authors.lastname: Andrews
authors.affiliation: Department of Neurological Surgery, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, United States.
authors.forename: James J
authors.initials: JJ
authors.lastname: Evans
authors.affiliation: Department of Neurological Surgery, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, United States.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Farrell
authors.affiliation: Department of Neurological Surgery, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, United States.
authors.forename: Kevin
authors.initials: K
authors.lastname: Judy
authors.affiliation: Department of Radiation Oncology, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, United States. Electronic address: Wenyin.Shi@jefferson.edu.
authors.forename: Wenyin
authors.initials: W
authors.lastname: Shi
mesh_terms: D001932:Brain Neoplasms / Q000532:radiotherapy* / Q000601:surgery*; D006801:Humans; D009464:Neuroma, Acoustic / Q000532:radiotherapy* / Q000601:surgery*; D016634:Radiosurgery / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated; D012984:Software; D047368:Tumor Burden
keywords: Gamma knife; Radiosurgery; VMAT; Vestibular schwannoma