title: Advantages and pitfalls of 18F-fluoro-2-deoxy-D-glucose positron emission tomography in detecting locally residual or recurrent nasopharyngeal carcinoma: comparison with magnetic resonance imaging.
abstract: BACKGROUND
  This prospective study was designed to elucidate the advantages and pitfalls of (18)F-FDG PET in detecting locally residual/recurrent nasopharyngeal carcinoma (NPC) in comparison with MRI.
  
  
  METHODS
  We recruited NPC patients from two ongoing prospective trials. One is being performed to evaluate suspected local recurrence (group A) and the other to assess local treatment response 3 months after therapy (group B). Both groups received (18)F-FDG PET and head and neck MRI. The gold standard was histopathology or clinical/imaging follow-up. An optimal cut-off standardised uptake value (SUV) was retrospectively determined.
  
  
  RESULTS
  From January 2002 to August 2004, 146 patients were eligible. Thirty-four were from group A and 112 from group B. In all, 26 had locally recurrent/residual tumours. Differences in detection rate between (18)F-FDG PET and MRI were not statistically significant in either group. However, (18)F-FDG PET showed significantly higher specificity than MRI in detecting residual tumours among patients with initial T4 disease (p=0.04). In contrast, the specificity of (18)F-FDG PET for patients with an initial T1-2 tumour treated with intracavitary brachytherapy (ICBT) was significantly lower than that for patients not treated by ICBT (72.2% vs 98.1%, p=0.003). At an SUV cut-off of 4.2, PET showed an equal and a higher accuracy compared with MRI in groups A and B, respectively.
  
  
  CONCLUSIONS
  (18)F-FDG PET is superior to MRI in identifying locally residual NPC among patients with initial T4 disease but demonstrates limitations in assessing treatment response in patients with initial T1-2 disease after ICBT. A cut-off SUV is a useful index for aiding in the visual detection of locally residual/recurrent NPC.
authors.affiliation: Department of Nuclear Medicine, Chang Gung Memorial Hospital Linkou Medical Center, 5 Fu-Shin St, Kueishan, Taoyuan, Taiwan, 333, Republic of China.
authors.forename: Sheng-Chieh
authors.initials: SC
authors.lastname: Chan
authors.forename: Shu-Hang
authors.initials: SH
authors.lastname: Ng
authors.forename: Joseph Tung-Chieh
authors.initials: JT
authors.lastname: Chang
authors.forename: Chien-Yu
authors.initials: CY
authors.lastname: Lin
authors.forename: Yen-Chao
authors.initials: YC
authors.lastname: Chen
authors.forename: Yu-Chen
authors.initials: YC
authors.lastname: Chang
authors.forename: Cheng-Lung
authors.initials: CL
authors.lastname: Hsu
authors.forename: Hung-Ming
authors.initials: HM
authors.lastname: Wang
authors.forename: Chun-Ta
authors.initials: CT
authors.lastname: Liao
authors.forename: Tzu-Chen
authors.initials: TC
authors.lastname: Yen
mesh_terms: D000328:Adult; D001918:Brachytherapy; D003951:Diagnostic Errors; D005260:Female; D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis / Q000000981:diagnostic imaging; D049268:Positron-Emission Tomography / Q000706:statistics & numerical data; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D012680:Sensitivity and Specificity
chemical_list: D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18