title: A treatment planning and delivery comparison of volumetric modulated arc therapy with or without flattening filter for gliomas, brain metastases, prostate, head/neck and early stage lung cancer.
abstract: BACKGROUND
  Flattening filter-free (FFF) beams are an emerging technology that has not yet been widely implemented as standard practice in radiotherapy centers. To facilitate the clinical implementation of FFF, we attempted to elucidate the difference in plan quality and treatment delivery time compared to flattening filter beams (i.e. standard, STD) for several patient groups. We hypothesize that the treatment plan quality is comparable while the treatment delivery time of volumetric modulated arc therapy (VMAT) is considerably shorter using FFF beams, especially for stereotactic treatments.
  
  
  METHODS
  A total of 120 patients treated for head and neck (H&N) tumors, high-grade glioma, prostate cancer, early stage lung cancer and intra-cranial metastatic disease (both single and multiple metastases) were included in the study. For each cohort, 20 consecutive patients were selected. The plans were generated using STD- and FFF-VMAT for both 6 MV and 10 MV, and were compared with respect to plan quality, monitor units and delivery time using Wilcoxon signed rank tests.
  
  
  RESULTS
  For H&N and high-grade gliomas, there was a significant difference in homogeneity index in favor for STD-VMAT (p < 0.001). For the stereotactic sites there were no differences in plan conformity. Stereotactic FFF-VMAT plans required significantly shorter delivery time compared to STD-VMAT plans (p < 0.001) for higher dose per fraction, on average 54.5% for 6 MV and 71.4% for 10 MV. FFF-VMAT generally required a higher number of MU/Gy (p < 0.001), on average 7.0% for 6 MV and 8.4% for 10 MV.
  
  
  CONCLUSIONS
  It was generally possible to produce FFF-VMAT plans with the same target dose coverage and doses to organs at risk as STD-VMAT plans. Target dose homogeneity tended to be somewhat inferior for FFF-VMAT for the larger targets investigated. For stereotactic radiotherapy, FFF-VMAT resulted in a considerable time gain while maintaining similar plan quality compared to STD beams.
authors.affiliation: Department of Oncology, Section of Radiotherapy, Rigshospitalet, Copenhagen University Hospital , Copenhagen , Denmark.
authors.forename: Daniel
authors.initials: D
authors.lastname: Gasic
authors.forename: Lars
authors.initials: L
authors.lastname: Ohlhues
authors.forename: N Patrik
authors.initials: NP
authors.lastname: Brodin
authors.forename: Lotte S
authors.initials: LS
authors.lastname: Fog
authors.forename: Tobias
authors.initials: T
authors.lastname: Pommer
authors.forename: Jens P
authors.initials: JP
authors.lastname: Bangsgaard
authors.forename: Per
authors.initials: P
authors.lastname: Munck Af Rosenschöld
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001932:Brain Neoplasms / Q000532:radiotherapy* / Q000556:secondary; D005260:Female; D005374:Filtration / Q000295:instrumentation; D005910:Glioma / Q000532:radiotherapy*; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D008175:Lung Neoplasms / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D058958:Organs at Risk; D009959:Oropharyngeal Neoplasms / Q000532:radiotherapy; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation / Q000379:methods*; D018709:Statistics, Nonparametric; D013997:Time Factors