title: Volumetric modulation arc radiotherapy with flattening filter-free beams compared with static gantry IMRT and 3D conformal radiotherapy for advanced esophageal cancer: a feasibility study.
abstract: OBJECTIVE
  A feasibility study was performed to evaluate RapidArc (RA), and the potential benefit of flattening filter-free beams, on advanced esophageal cancer against intensity-modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3D-CRT).
  
  
  METHODS
  The plans for 3D-CRT and IMRT with three to seven and five to seven fixed beams were compared against double-modulated arcs with avoidance sectors to spare the lungs for 10 patients. All plans were optimized for 6-MV photon beams. The RA plans were studied for conventional and flattening filter-free (FFF) beams. The objectives for the planning target volume were the volume receiving ≥ 95% or at most 107% of the prescribed dose of <1% with a dose prescription of 59.4 Gy. For the organs at risk, the lung volume (minus the planning target volume) receiving ≥ 5 Gy was <60%, that receiving 20 Gy was <20%-30%, and the mean lung dose was <15.0 Gy. The heart volume receiving 45 Gy was <20%, volume receiving 30 Gy was <50%. The spinal dose received by 1% was <45 Gy. The technical delivery parameters for RA were assessed to compare the normal and FFF beam characteristics.
  
  
  RESULTS
  RA and IMRT provided equivalent coverage and homogeneity, slightly superior to 3D-CRT. The conformity index was 1.2 ± 0.1 for RA and IMRT and 1.5 ± 0.2 for 3D-CRT. The mean lung dose was 12.2 ± 4.5 for IMRT, 11.3 ± 4.6 for RA, and 10.8 ± 4.4 for RA with FFF beams, 18.2 ± 8.5 for 3D-CRT. The percentage of volume receiving ≥ 20 Gy ranged from 23.6% ± 9.1% to 21.1% ± 9.7% for IMRT and RA (FFF beams) and 39.2% ± 17.0% for 3D-CRT. The heart and spine objectives were met by all techniques. The monitor units for IMRT and RA were 457 ± 139, 322 ± 20, and 387 ± 40, respectively. RA with FFF beams showed, compared with RA with normal beams, a ∼20% increase in monitor units per Gray, a 90% increase in the average dose rate, and 20% reduction in beam on time (owing to different gantry speeds).
  
  
  CONCLUSIONS
  RA demonstrated, compared with conventional IMRT, a similar target coverage and some better dose sparing to the organs at risk; the advantage against conventional 3D-CRT was more evident. RA with FFF beams resulted in minor improvements in plan quality but with the potential for additional useful reduction in the treatment time.
authors.affiliation: Oncology Institute of Southern Switzerland, Medical Physics Unit, Bellinzona, Switzerland. giorgia.nicolini@eoc.ch
authors.forename: Giorgia
authors.initials: G
authors.lastname: Nicolini
authors.forename: Sarbani
authors.initials: S
authors.lastname: Ghosh-Laskar
authors.forename: Shyam Kishore
authors.initials: SK
authors.lastname: Shrivastava
authors.forename: Sushovan
authors.initials: S
authors.lastname: Banerjee
authors.forename: Suresh
authors.initials: S
authors.lastname: Chaudhary
authors.forename: Jai Prakash
authors.initials: JP
authors.lastname: Agarwal
authors.forename: Anusheel
authors.initials: A
authors.lastname: Munshi
authors.forename: Alessandro
authors.initials: A
authors.lastname: Clivio
authors.forename: Antonella
authors.initials: A
authors.lastname: Fogliata
authors.forename: Pietro
authors.initials: P
authors.lastname: Mancosu
authors.forename: Eugenio
authors.initials: E
authors.lastname: Vanetti
authors.forename: Luca
authors.initials: L
authors.lastname: Cozzi
mesh_terms: D004938:Esophageal Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D005240:Feasibility Studies; D006321:Heart / Q000000981:diagnostic imaging / Q000528:radiation effects; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000528:radiation effects; D016555:Matched-Pair Analysis; D058958:Organs at Risk / Q000000981:diagnostic imaging / Q000528:radiation effects*; D011832:Radiation Injuries / Q000517:prevention & control*; D011836:Radiation Tolerance; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D013116:Spinal Cord / Q000000981:diagnostic imaging / Q000528:radiation effects