title: Coplanar VMAT vs. noncoplanar VMAT in the treatment of sinonasal cancer.
abstract: BACKGROUND
  Previous studies showed that noncoplanar intensity-modulated radiotherapy (NC-IMRT) for sinonasal cancer is superior to coplanar intensity-modulated radiotherapy (IMRT). Volumetric-modulated arc therapy (VMAT) is a newly introduced treatment modality, and the performance of noncoplanar VMAT for sinonasal cancer has not been well described to date.
  
  
  OBJECTIVE
  To compare the dosimetry difference of noncoplanar VMAT (NC-VMAT), coplanar VMAT (co-VMAT), and NC-IMRT for sinonasal cancer.
  
  
  METHODS
  Ten postoperative patients with sinonasal cancer were randomly selected for planning with NC-VMAT, co-VMAT, and NC-IMRT. Two planning target volumes (PTVs) were contoured representing high-risk and low-risk regions set to receive a median absorbed dose (D50%) of 68 Gy and 59 Gy, respectively. The homogeneity index (HI), conformity index (CI), dose-volume histograms (DVHs), and delivery efficiency were all evaluated.
  
  
  RESULTS
  Both NC-VMAT and co-VMAT showed superior dose homogeneity and conformity in PTVs compared with NC-IMRT. There was no significant difference between NC-VMAT and co-VMAT in PTV coverage. Both VMAT plans provided a better protection for organs at risk (OARs) than NC-IMRT plans, and NC-VMAT showed a small improvement over co-VMAT in sparing of OARs. For peripheral doses, the doses to breast, thyroid, and larynx in the NC-IMRT plans were significantly higher than those in both VMAT plans. Compared to NC-VMAT, co-VMAT significantly reduced peripheral doses. NC-VMAT and co-VMAT reduced the average delivery time by 63.2 and 64.2%, respectively, in comparison with NC-IMRT. No differences in delivery efficiency were observed between the two VMAT plans.
  
  
  CONCLUSIONS
  Compared to NC-VMAT, co-VMAT showed similar PTV coverage and comparable OAR sparing but significantly reduced peripheral doses and positioning uncertainty. We propose to give priority to coplanar VMAT in the treatment of sinonasal cancer.
authors.affiliation: Department of Radiation Oncology, The Third Affiliated Hospital, Soochow University, 185 Juqian Road, 213003, Changzhou, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Zhong-Hua
authors.forename: Jiang
authors.initials: J
authors.lastname: Jing-Ting
authors.forename: Li
authors.initials: L
authors.lastname: Xiao-Dong
authors.forename: Mu
authors.initials: M
authors.lastname: Jin-Ming
authors.forename: Mo
authors.initials: M
authors.lastname: Jun-Chong
authors.forename: Jin
authors.initials: J
authors.lastname: Jian-Xue
authors.forename: Gao
authors.initials: G
authors.lastname: Ming
authors.forename: Li
authors.initials: L
authors.lastname: Qi-Lin
authors.forename: Gu
authors.initials: G
authors.lastname: Wen-Dong
authors.forename: Chen
authors.initials: C
authors.lastname: Lu-Jun
authors.forename: Pei
authors.initials: P
authors.lastname: Hong-Lei
mesh_terms: D065638:Absorption, Radiation; D000368:Aged; D001822:Body Burden; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D059351:Organ Sparing Treatments / Q000379:methods*; D058958:Organs at Risk / Q000528:radiation effects*; D010255:Paranasal Sinus Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D016896:Treatment Outcome