title: Effects of full-neck volumetric-modulated arc therapy vs split-field intensity-modulated head and neck radiation therapy on low neck targets and structures.
abstract: OBJECTIVE
  While split-field intensity-modulated radiation therapy (SF-IMRT) decreases dose to low neck (LAN) structures such as the glottic larynx compared with full-neck intensity-modulated radiation therapy (IMRT), it is unknown whether SF-IMRT affords superior dose avoidance to organs than whole neck-field volumetric-modulated arc therapy (WF-VMAT).
  
  
  METHODS
  10 patients treated definitively with radiation for oropharyngeal, oral cavity or nasopharyngeal carcinoma were compared. Only patients ideally suited for SF-IMRT plans were included. The glottic larynx, supraglottic larynx, arytenoids, pharyngeal constrictors, oesophagus, brachial plexus and target volume coverage in the LAN were compared between WF-VMAT and SF-IMRT.
  
  
  RESULTS
  Volumetric-modulated arc therapy (VMAT) yielded statistically significant decreases in maximum dose to the arytenoids and mean dose to the oesophagus. There was no difference in dose to the glottic larynx, supraglottic larynx, pharyngeal constrictors and brachial plexus. WF-VMAT led to improved coverage to 50/2 Gy fraction equivalent in LAN compared with SF-IMRT using an anteroposterior (AP) LAN field but no difference to the 60/2 Gy fraction equivalent between SF-IMRT and WF-VMAT using AP/posterior-anterior LAN boost.
  
  
  CONCLUSIONS
  WF-VMAT affords equivalent glottic and supraglottic larynx dose and lower dose to the arytenoids and oesophagus. WF-VMAT better covers most LAN target structures. Given these findings as well as concerns with matchline cold spots or hotspots with SF-IMRT, patients requiring comprehensive elective nodal irradiation should typically be treated with WF-VMAT.
  
  
  CONCLUSIONS
  SF-IMRT for larynx sparing has better dosimetric results to normal structures than whole-neck IMRT, but with increased matchline recurrence risk. We show dosimetric equivalence or superiority of WF-VMAT compared with SF-IMRT.
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA.
authors.forename: Shibu J
authors.initials: SJ
authors.lastname: Anamalayil
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA.
authors.forename: Boon-Keng K
authors.initials: BK
authors.lastname: Teo
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Lin
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Lustig
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA.
authors.forename: Peter H
authors.initials: PH
authors.lastname: Ahn
mesh_terms: D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D009333:Neck / Q000528:radiation effects*; D059351:Organ Sparing Treatments / Q000379:methods*; D058958:Organs at Risk / Q000528:radiation effects; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D016896:Treatment Outcome