title: Prognostic relevance of (18)F-FDG PET/CT in carcinoma of unknown primary.
abstract: OBJECTIVE
  The aim of this study was to assess whether F-FDG PET combined with x-ray CT (F-FDG PET/CT) findings have a prognostic impact in patients with carcinoma of unknown primary (CUP).
  
  
  METHODS
  Seventy patients with CUP who were referred for F-FDG PET/CT were included. F-FDG PET/CT results were checked against available histologic diagnosis and follow-up data. For each patient, the SUVmax of the lesion with maximum uptake was measured.
  
  
  RESULTS
  In 26% of the patients, a primary tumor was identified. The follow-up period after F-FDG PET/CT scan ranged between 3 and 45 months. Kaplan-Meier analysis revealed 1-year survival rates of 92% in the group without evidence of malignancy on F-FDG PET/CT, 78% in the group with locoregional disease, and 34% in the group with extensive disease on F-FDG PET/CT. Three-year survival rates in these groups were 73%, 71%, and 23%, respectively (P = 0.001). There was no significant survival difference between patients with regionally confined disease without identification of the primary tumor and those in whom the primary tumor was identified on F-FDG PET/CT (P = 0.25). This was also the case for patients with extensive disease (P = 0.26). The SUVmax of the lesion with maximum uptake was not significantly related to survival (P = 0.56).
  
  
  CONCLUSIONS
  F-FDG PET/CT is a helpful tool for the identification of the primary tumor in patients with CUP; it is also able to provide an accurate assessment of prognosis based on the extent of the disease without the need for identification of the primary tumor.
authors.affiliation: From the *Department of Nuclear Medicine, University Hospital Aachen, Aachen, Germany; and †Department of Nuclear Medicine, Maastricht University Medical Center, Maastricht, the Netherlands.
authors.forename: Niklas
authors.initials: N
authors.lastname: Breuer
authors.forename: Florian F
authors.initials: FF
authors.lastname: Behrendt
authors.forename: Alexander
authors.initials: A
authors.lastname: Heinzel
authors.forename: Felix M
authors.initials: FM
authors.lastname: Mottaghy
authors.forename: Moritz
authors.initials: M
authors.lastname: Palmowski
authors.forename: Frederik A
authors.initials: FA
authors.lastname: Verburg
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001692:Biological Transport; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009382:Neoplasms, Unknown Primary / Q000000981:diagnostic imaging* / Q000378:metabolism; D049268:Positron-Emission Tomography; D011379:Prognosis; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
chemical_list: D019788:Fluorodeoxyglucose F18