title: ¹⁸F-FDG-PET imaging in radiotherapy tumor volume delineation in treatment of head and neck cancer.
abstract: OBJECTIVE
  To determine the impact of (18)F-fluorodeoxyglucose positron emission tomography (PET) in radiotherapy target delineation and patient management for head and neck squamous cell carcinoma (HNSCC) compared to computed tomography (CT) alone.
  
  
  METHODS
  Twenty-nine patients with HNSCC were included. CT and PET/CT obtained for treatment planning purposes were reviewed respectively by a neuroradiologist and a nuclear medicine specialist who were blinded to the findings from each other. The attending radiation oncologist together with the neuroradiologist initially defined all gross tumor volume of the primary (GTVp) and the suspicious lymph nodes (GTVn) on CT. Subsequently, the same radiation oncologist and the nuclear medicine specialist defined the GTVp and GTVn on (18)F-FDG-PET/CT. Upon disagreement between CT and (18)F-FDG-PET on the status of a particular lymph node, an ultrasound-guided fine needle aspiration was performed. Volumes based on CT and (18)F-FDG-PET were compared with a paired Student's t-test.
  
  
  RESULTS
  For the primary disease, four patients had previous diagnostic tonsillectomy and therefore, FDG uptake occurred in 25 patients. For these patients, GTVp contoured on (18)F-FDG-PET (GTVp-PET) were smaller than the GTVp contoured on CT (GTVp-CT) in 80% of the cases, leading to a statistically significant volume difference (p=0.001). Of the 60 lymph nodes suspicious on PET, 55 were also detected on CT. No volume change was observed (p=0.08). Ten biopsies were performed for lymph nodes that were discordant between modalities and all were of benign histology. Distant metastases were found in two patients and one had a newly diagnosed lung adenocarcinoma.
  
  
  CONCLUSIONS
  GTVp-CT was significantly larger when compared to GTVp-PET. No such change was observed for the lymph nodes. (18)F-FDG-PET modified treatment management in three patients, including two for which no curative radiotherapy was attempted. Larger multicenter studies are needed to ascertain whether combined (18)F-FDG-PET/CT in target delineation can influence the main clinical outcomes.
authors: Department of Radiation Oncology, Centre Hospitalier de l'Université de Montréal, Montréal, Canada. g.delouya@gmail.com
authors: Guila
authors: G
authors: Delouya
authors: Levon
authors: L
authors: Igidbashian
authors: Annie
authors: A
authors: Houle
authors: Manon
authors: M
authors: Bélair
authors: Luc
authors: L
authors: Boucher
authors: Christian
authors: C
authors: Cohade
authors: Sylvain
authors: S
authors: Beaulieu
authors: Edith J
authors: EJ
authors: Filion
authors: Geneviève
authors: G
authors: Coulombe
authors: Martin
authors: M
authors: Hinse
authors: Charles
authors: C
authors: Martel
authors: Philippe
authors: P
authors: Després
authors: Phuc Félix
authors: PF
authors: Nguyen-Tan
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D019788:Fluorodeoxyglucose F18; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D061089:Radiotherapy, Image-Guided; D012189:Retrospective Studies; D000077195:Squamous Cell Carcinoma of Head and Neck; D014057:Tomography, X-Ray Computed
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18