title: A quantitative comparison of gross tumour volumes delineated on [18F]-FDG PET-CT scan and CECT scan in head and neck cancers.
abstract: OBJECTIVE
  To compare quantitatively Gross tumor volume (GTV), both primary and nodal areas of head and neck cancers, delineated on [18F]-2fluoro, 2deoxy d-glucose-positron emission tomography/computed tomography ([18F]-FDG-PET-CT) scan to those delineated on Contrast-enhanced CT scan (CECT scan).
  
  
  METHODS
  A total of 26 consecutive patients with squamous cell cancers of head and neck were included in this study. The primary sites were oropharynx (n = 7), hypopharynx (n = 6), paranasal sinus (n = 6), nasopharynx (n = 4), oral cavity (n = 2), and one with unknown primary and secondary neck node. All patients underwent routine staging work-up. FDG-PET and CECT scans were performed with dedicated PET-CT scanner in single session as a part of the radiotherapy treatment planning for Intensity modulated radiotherapy/Image-guided radiotherapy.
  
  
  RESULTS
  All patients had abnormal increased uptake in PET-CT scans. PET-CT resulted in changes of CT-based staging in 8 of 26 patients (up-staged in 7 and down-staged in 1). The mean primary and nodal GTV volumes on PET-CT and CT were significantly different (primary: PET-GTV: 48.43 ± 53.21 cc vs. CT 54.78 ± 64.47 cc, P < 0.001; nodes: PET-GTV: 12.72 ± 15.46 cc vs. 11.04 ± 14.87 cc, P < 0.001). The mismatch between two target volumes was statistically significant (P = 0.03 for GTV primary, P = 0.04 for GTV node).
  
  
  CONCLUSIONS
  Accuracy of delineation of GTV can be improved along with functional imaging using [18F]-FDG. These metabolically active volumes are significantly smaller than CT-based volumes and could be missed during conventional CT-based target delineations of GTVs.
authors.affiliation: Department of Radiation, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India.
authors.forename: Manickam G
authors.initials: MG
authors.lastname: Venkada
authors.forename: Sheh
authors.initials: S
authors.lastname: Rawat
authors.forename: Ps
authors.initials: P
authors.lastname: Choudhury
authors.forename: T
authors.initials: T
authors.lastname: Rajesh
authors.forename: Sa
authors.initials: S
authors.lastname: Rao
authors.forename: Pooja
authors.initials: P
authors.lastname: Khullar
authors.forename: Anjali
authors.initials: A
authors.lastname: Kakria
keywords: [18F]-fluoro-d-glucose; gross tumor volume; radiotherapy