title: Evaluation of the role of 18FDG-PET/CT in radiotherapy target definition in patients with head and neck cancer.
abstract: OBJECTIVE
  As techniques for radiotherapy delivery have developed, increasingly accurate localisation of disease is demanded. Functional imaging, particularly PET and its fusion with anatomical modalities, such as PET/CT, promises to improve detection and characterisation of disease. This study evaluated the impact of (18)FDG-PET/CT on radiotherapy target volume definition in head and neck cancer (HNC).
  
  
  METHODS
  The PET/CT scans of patients with HNC were used in a radiotherapy planning (RTP) study. The gross tumour volume (GTV), clinical target volume (CTV) and planning target volume (PTV) were defined conventionally and compared to those defined using the PET/CT. Data were reported as the median value with 95% confidence intervals.
  
  
  RESULTS
  Eighteen patients were consented, 9 had known primary tumour site, 9 presented as unknown primary. In nine cases where the primary site was known, the combined primary and nodal GTV (GTVp+n) increased by a median of 6.1cm(3) (2.6, 12.2) or 78% (18, 313), p=0.008 with CTV increasing by a median of 10.1cm(3) (1.3, 30.6) or 4% (0, 13) p=0.012. In 9 cases of unknown primary the GTVp+n increased by a median 6.3 cm(3) (0.2, 15.7) or 61% (4, 210), p=0.012, with CTV increasing by a median 155.4 cm(3) (2.7, 281.7) or 95% (1, 137), p=0.008.
  
  
  CONCLUSIONS
  (18)FDG-PET revealed disease lying outside the conventional target volume, either extending a known area or highlighting a previously unknown area of disease, including the primary tumour in 5 cases. We recommend PET/CT in the RTP of all cases of unknown primary. In patients with a known primary, although the change in volume was statistically significant the clinical impact is less clear. (18)FDG-PET can also show areas within the conventional target volume that are hypermetabolic which may be possible biological target volumes for dose escalation studies in the future.
authors.affiliation: The Royal Marsden NHS Foundation Trust, Sutton, Surrey, UK. Kate.Newbold@rmh.nhs.uk
authors.forename: Katie L
authors.initials: KL
authors.lastname: Newbold
authors.forename: Mike
authors.initials: M
authors.lastname: Partridge
authors.forename: Gary
authors.initials: G
authors.lastname: Cook
authors.forename: Bhupinder
authors.initials: B
authors.lastname: Sharma
authors.forename: Peter
authors.initials: P
authors.lastname: Rhys-Evans
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Harrington
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Nutting
mesh_terms: D000328:Adult; D000368:Aged; D019788:Fluorodeoxyglucose F18; D006258:Head and Neck Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D009382:Neoplasms, Unknown Primary / Q000532:radiotherapy; D049268:Positron-Emission Tomography; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden
chemical_list: D019788:Fluorodeoxyglucose F18