title: Evaluation of unified intensity-modulated arc therapy for the radiotherapy of head-and-neck cancer.
abstract: Recently our group developed a unified intensity-modulated arc therapy (UIMAT) technique which allows for the simultaneous inverse-optimization and the combined delivery of volume-modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT). The aim of this study was to evaluate the dosimetric benefits of UIMAT plans for radiation treatment of complex head-and-neck cancer cases.
  
  
  
  A retrospective treatment planning study was performed on 30 head-and-neck cases, 15 of which were treated clinically with VMAT while the other 15 were treated with step-and-shoot IMRT. These cases were re-planned using our UIMAT technique and the results were compared with the clinically delivered plans. Plans were assessed in terms of clinically relevant metrics describing target volume coverage, dose conformity, and the sparing of organs at risk.
  
  
  
  When compared to stand-alone VMAT or IMRT, UIMAT plans offered slightly better tumor volume coverage (Median D95: 98.1% vs. 97.5%, p=0.01) and similar dose conformity (Median CI: 0.69 vs. 0.69, p=0.09). More significantly, UIMAT plans had substantially lower doses to all organs at risk, including the spinal cord (Median D2%: 29.9Gy vs. 35.6Gy, p<0.01), brainstem (Median D2%: 21.2Gy vs. 25.6Gy, p<0.01), left parotid (Median DMean: 26.1Gy vs. 28.0Gy, p<0.01), and right parotid (Median DMean: 23.6Gy vs. 27.2Gy, p<0.01). The reduction in OAR doses did not result from the redistribution of dose to unspecified tissue. Furthermore, UIMAT plans can be delivered with comparable delivery times to VMAT (Median time: 135s vs. 168s, p=0.394) but with fewer monitor units (Median MU: 486 vs. 635, p<0.01).
  
  
  
  Compared to stand-alone IMRT or VMAT, UIMAT was demonstrated to have a dosimetric advantage for the radiation treatment of head-and-neck cancer.
authors.affiliation: Department of Medical Biophysics, Western University, London, Canada; London Regional Cancer Program, London Health Science Center, LondonCanada. Electronic address: mmacfar4@uwo.ca.
authors.forename: Michael
authors.initials: M
authors.lastname: MacFarlane
authors.affiliation: Department of Medical Biophysics, Western University, London, Canada; London Regional Cancer Program, London Health Science Center, LondonCanada; Department of Oncology, Western University, London, Canada.
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Hoover
authors.affiliation: Department of Medical Biophysics, Western University, London, Canada; Department of Oncology, Western University, London, Canada; Department of Physics & Astronomy, Western University, London, Canada.
authors.forename: Eugene
authors.initials: E
authors.lastname: Wong
authors.affiliation: London Regional Cancer Program, London Health Science Center, LondonCanada; Department of Oncology, Western University, London, Canada.
authors.forename: Nancy
authors.initials: N
authors.lastname: Read
authors.affiliation: Department of Medical Biophysics, Western University, London, Canada; London Regional Cancer Program, London Health Science Center, LondonCanada; Department of Oncology, Western University, London, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Palma
authors.affiliation: London Regional Cancer Program, London Health Science Center, LondonCanada; Department of Oncology, Western University, London, Canada.
authors.forename: Varagur
authors.initials: V
authors.lastname: Venkatesan
authors.affiliation: London Regional Cancer Program, London Health Science Center, LondonCanada; Department of Oncology, Western University, London, Canada.
authors.forename: Alex
authors.initials: A
authors.lastname: Hammond
authors.affiliation: Department of Medical Biophysics, Western University, London, Canada; London Regional Cancer Program, London Health Science Center, LondonCanada; Department of Oncology, Western University, London, Canada.
authors.forename: Jerry J
authors.initials: JJ
authors.lastname: Battista
authors.affiliation: Department of Medical Biophysics, Western University, London, Canada; London Regional Cancer Program, London Health Science Center, LondonCanada; Department of Oncology, Western University, London, Canada.
authors.forename: Jeff Z
authors.initials: JZ
authors.lastname: Chen
mesh_terms: D006258:Head and Neck Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D058958:Organs at Risk; D010306:Parotid Gland / Q000528:radiation effects; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies; D047368:Tumor Burden
keywords: Head-and-neck cancer; IMRT; Radiotherapy optimization; UIMAT; VMAT