title: Post-treatment surveillance of head and neck cancer: pitfalls in the interpretation of FDG PET-CT/MRI.
abstract: OBJECTIVE
  We investigated non-malignancy-associated (¹⁸F)fluoro-deoxy-D-glucose (FDG) uptake in the head and neck cancer (HNC) post-treatment follow-up with positron emission tomography - computed tomography / magnetic resonance imaging (PET-CT/MRI). A retrospective study on HNC patients undergoing follow-up or re-staging PET-CT/MRI examinations was performed. Thereby, FDG-positive regions were morphologically correlated to the CT and MRI images and a statement regarding tumour persistence/recurrence.
  
  
  METHODS
  FDG-positive lesions were assessed according to their anatomical localisation and categorised as true positive, true negative, false positive or false negative findings. The gold standard for verification of an FDG-positive lesion was the cytological or histopathological examination of the region of interest. The most likely aetiology was assessed according to the following categories: (1.) physiological uptake (2.) post-surgical, inflammatory uptake, (3.) post-irradiation, inflammatory uptake and (4.) reactive, not otherwise specified.
  
  
  RESULTS
  Tumour recurrence / tumour persistence was found in 14/87 patients (16.1%). A total of 159 non-malignancy-associated FDG-positive lesions were found. Every PET-CT/MRI examination revealed 2.1 ± 1.5 FDG-positive lesions in the head and neck. A total of 107 FDG-positive lesions (67.3%) were categorised as physiological, 52 FDG-positive lesions (32.7%) as inflammatory (post-surgical: n = 14, 8.8%; post-irradiation: n = 9, 5.7%; reactive, not otherwise specified: n = 29, 18.2%). Eight patients (11.8%) underwent invasive diagnostic procedures to clarify indistinct findings.
  
  
  CONCLUSIONS
  Post-treatment follow-up of HNC patients requires interdisciplinary management and familiarity with the patient's past medical history. Awareness of common confounders of FDG positivity often allows clarification of indistinct lesions. However, a substantial number of approximately 12% of FDG-positive lesions remain unclear unless invasive diagnostic procedures are performed.
authors.affiliation: Department of Otorhinolaryngology, University Hospital Zurich, Switzerland.
authors.forename: Christian Martin
authors.initials: CM
authors.lastname: Meerwein
authors.affiliation: Department of Medical Imaging, University Hospital Zurich, Switzerland.
authors.forename: Marcelo  A
authors.initials: M
authors.lastname: Queiroz
authors.affiliation: Department of Neuroradiology, University Hospital Zurich, Switzerland.
authors.forename: Spyros
authors.initials: S
authors.lastname: Kollias
authors.affiliation: Department of Medical Imaging, University Hospital Zurich, Switzerland.
authors.forename: Martin
authors.initials: M
authors.lastname: Hüllner
authors.affiliation: Department of Medical Imaging, University Hospital Zurich, Switzerland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Veit-Haibach
authors.affiliation: Department of Otorhinolaryngology, University Hospital Zurich, Switzerland.
authors.forename: Gerhard Frank
authors.initials: GF
authors.lastname: Huber
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018450:Disease Progression; D005260:Female; D019788:Fluorodeoxyglucose F18; D006258:Head and Neck Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000628:therapy; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis*; D011159:Population Surveillance / Q000379:methods*; D049268:Positron-Emission Tomography / Q000379:methods; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18