title: Target delineation in stereotactic body radiation therapy for recurrent head and neck cancer: a retrospective analysis of the impact of margins and automated PET-CT segmentation.
abstract: BACKGROUND
  Few guidelines exist on stereotactic body radiation therapy (SBRT) treatment planning for recurrent head and neck cancer. We assessed the impact of retrospectively adding margins/automated PET volumes to the gross tumor volume (GTV) in patients with post-SBRT recurrences.
  
  
  METHODS
  We reviewed 89 patients with recurrent head and neck cancer treated with SBRT using no margin around the GTV. GTVs were recontoured with 1-5mm margins. PET-CT planned GTVs were also recontoured by adding PET-standardized uptake value (SUV)(3.5), SUV(4.5), SUV(40% max), and signal/background ratio (SBR) to the original GTV. We deformably registered recontoured GTVs to post-SBRT scans and assessed fraction of recurrence volume (RV) falling within the GTV, the "RV-GTV overlap."
  
  
  RESULTS
  With non-PET-CT planning, median RV-GTV overlap increased from 11.7% to 48.2% using 5mm margins, and median GTV size increased by 41.8 cc (156%). With PET-CT planning, RV-GTV overlap increased from 45% to 93.6% using 5mm margins, and GTV size increased by 34.8 cc (140%). Adding SUV(3.5) and SBR increased RV-GTV overlap from 45% to 73.3% and 73.6%, with GTV size increases of 0.8 (3%) and 3.1 cc (11%), respectively.
  
  
  CONCLUSIONS
  Recontouring increased recurrence coverage and also GTV size. Margins up to 5mm may reduce failures but could possibly increase toxicities. Automated PET contours may reduce near-miss failures with smaller increases in GTV size.
authors: Department of Radiation Oncology, University of Pittsburg Cancer Institute, Pittsburg, PA, USA.
authors: Kyle
authors: K
authors: Wang
authors: Dwight E
authors: DE
authors: Heron
authors: David A
authors: DA
authors: Clump
authors: John C
authors: JC
authors: Flickinger
authors: Gregory J
authors: GJ
authors: Kubicek
authors: Jean-Claude M
authors: JC
authors: Rwigema
authors: Robert L
authors: RL
authors: Ferris
authors: James P
authors: JP
authors: Ohr
authors: Annette E
authors: AE
authors: Quinn
authors: Cihat
authors: C
authors: Ozhasoglu
authors: Barton F
authors: BF
authors: Branstetter
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D049268:Positron-Emission Tomography; D016634:Radiosurgery; D011880:Radiotherapy Planning, Computer-Assisted; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed