title: Class solutions for SABR-VMAT for high-risk prostate cancer with and without elective nodal irradiation.
abstract: BACKGROUND
  The purpose of this study is to find the optimal planning settings for prostate SABR-VMAT for high-risk prostate cancer patients irradiated to prostate only (PO) or prostate and pelvic lymph nodes (PPLN).
  
  
  METHODS
  For 10 patients, plans using 6MV flattened, flattening-filter-free (FFF) 6MV (6 F) and FFF 10MV (10 F) photon beams with full and partial arc arrangements were generated and compared. The prescribed dose was 40Gy to the prostate with 25Gy to the PLN in 5 fractions. Plans were then evaluated for PTV coverage, dose fall-off, and OAR doses. The number of monitor units and the treatment delivery times were also compared. Statistical differences were evaluated using a paired sample Wilcoxon signed rank test with a significance level of 0.05%.
  
  
  RESULTS
  A total of 150 plans were generated for this study. Acceptable PO plans were obtained using single arcs, while two arcs were necessary for PPLN. All plans were highly conformal (CI ≥1.3 and CN ≥0.90) with no significant differences in the PTV dose coverage. 6MV plans required significantly longer treatment time and had higher dose spillage compared to FFF plans. Superior plans were obtained using 10 F 300° partial arcs for PO with the lowest rectal dose, dose spillage and the shortest treatment times. For PPLN, 6 F and 10 F plans were equivalent.
  
  
  CONCLUSIONS
  SABR-VMAT with FFF photon beams offers a clear benefit with respect to shorter treatment delivery times and reduced dose spillage. Class solutions using a single 10 F 300° arc for PO and two 10 F or 6 F partial 300° arcs for PPLN are proposed.
authors.affiliation: Centre of Cancer Research and Cell Biology, Queen's University Belfast, Belfast, BT7 1NN, Northern Ireland, UK. s.osman@qub.ac.uk.
authors.forename: Sarah O S
authors.initials: SO
authors.lastname: Osman
authors.affiliation: Radiotherapy Physics, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Belfast, UK.
authors.forename: Prakash
authors.initials: P
authors.lastname: Jeevanandam
authors.affiliation: Radiotherapy Physics, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Belfast, UK.
authors.forename: Nithya
authors.initials: N
authors.lastname: Kanakavelu
authors.affiliation: Radiotherapy Physics, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Belfast, UK.
authors.forename: Denise M
authors.initials: DM
authors.lastname: Irvine
authors.affiliation: Centre of Cancer Research and Cell Biology, Queen's University Belfast, Belfast, BT7 1NN, Northern Ireland, UK.
authors.forename: Ciara A
authors.initials: CA
authors.lastname: Lyons
authors.affiliation: Centre of Cancer Research and Cell Biology, Queen's University Belfast, Belfast, BT7 1NN, Northern Ireland, UK.|Clinical Oncology, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Belfast, UK.
authors.forename: Suneil
authors.initials: S
authors.lastname: Jain
authors.affiliation: Centre of Cancer Research and Cell Biology, Queen's University Belfast, Belfast, BT7 1NN, Northern Ireland, UK.|Radiotherapy Physics, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Belfast, UK.
authors.forename: Alan R
authors.initials: AR
authors.lastname: Hounsell
authors.affiliation: Centre of Cancer Research and Cell Biology, Queen's University Belfast, Belfast, BT7 1NN, Northern Ireland, UK.|Radiotherapy Physics, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Belfast, UK.
authors.forename: Conor K
authors.initials: CK
authors.lastname: McGarry
mesh_terms: D006801:Humans; D008198:Lymph Nodes / Q000528:radiation effects; D008297:Male; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods
keywords: Flattening-filter-free (FFF); High-risk prostate cancer; Pelvic lymph nodes irradiation; SABR; VMAT