title: Role of 18F-FDG PET-CT imaging for the detection of an unknown primary tumour: preliminary results in 21 patients.
abstract: OBJECTIVE
  Metastatic cancer of unknown primary origin is a syndrome characterised by a poor prognosis, with a typical survival rate from diagnosis of no longer than 1 year. Only 20-27% of primary tumours are identified by conventional radiological imaging. By contrast, it has been reported that 18F-fluorodeoxyglucose positron emission tomography (FDG PET) allows the identification of 24-40% of otherwise unrecognised primary tumours. To our knowledge, the studies on this topic have been conducted using 18F-FDG PET imaging alone. The aim of this study was to evaluate the potential additional diagnostic role of fused 18F-FDG PET-CT imaging for the detection of metastatic occult primary tumours.
  
  
  METHODS
  The study population consisted of 21 consecutive patients with biopsy-proven metastatic disease and negative conventional diagnostic procedures. Each patient underwent a PET scan, carried out according to a standard procedure (6 h of fasting, i.v. injection of 370 MBq of 18F-FDG and image acquisition with a dedicated PET-CT scanner for 4 min per bed position).
  
  
  RESULTS
  18F-FDG PET-CT detected the occult primary tumour in 12 patients (57% of cases), providing a detection rate higher than that reported with any other imaging modality, including conventional 18F-FDG PET.
  
  
  CONCLUSIONS
  The favourable results of this study need to be confirmed in larger patient populations with long-term follow-up.
authors.affiliation: Nuclear Medicine Service-PET Unit, S. Orsola-Malpighi Bologna Hospital, Bologna, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Nanni
authors.forename: D
authors.initials: D
authors.lastname: Rubello
authors.forename: P
authors.initials: P
authors.lastname: Castellucci
authors.forename: M
authors.initials: M
authors.lastname: Farsad
authors.forename: R
authors.initials: R
authors.lastname: Franchi
authors.forename: S
authors.initials: S
authors.lastname: Toso
authors.forename: C
authors.initials: C
authors.lastname: Barile
authors.forename: L
authors.initials: L
authors.lastname: Rampin
authors.forename: O
authors.initials: O
authors.lastname: Nibale
authors.forename: S
authors.initials: S
authors.lastname: Fanti
mesh_terms: D000230:Adenocarcinoma / Q000175:diagnosis* / Q000556:secondary*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000175:diagnosis* / Q000556:secondary*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009382:Neoplasms, Unknown Primary / Q000175:diagnosis*; D010865:Pilot Projects; D049268:Positron-Emission Tomography / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D014057:Tomography, X-Ray Computed / Q000379:methods*
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