Combined FDG-PET/CT for the detection of unknown primary tumors: systematic review and meta-analysis

Eur Radiol. 2009 Mar;19(3):731-44. doi: 10.1007/s00330-008-1194-4. Epub 2008 Oct 17.


The aim of this study was to systematically review and meta-analyze published data on the diagnostic performance of combined 18F-fluoro-2-deoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in the detection of primary tumors in patients with cancer of unknown primary (CUP). A systematic search for relevant studies was performed of the PubMed/MEDLINE and Embase databases. Methodological quality of the included studies was assessed. Reported detection rates, sensitivities and specificities were meta-analyzed. Subgroup analyses were performed if results of individual studies were heterogeneous. The 11 included studies, comprising a total sample size of 433 patients with CUP, had moderate methodological quality. Overall primary tumor detection rate, pooled sensitivity and specificity of FDG-PET/CT were 37%, 84% (95% CI 78-88%) and 84% (95% CI 78-89%), respectively. Sensitivity was heterogeneous across studies (P = 0.0001), whereas specificity was homogeneous across studies (P = 0.2114). Completeness of diagnostic workup before FDG-PET/CT, location of metastases of unknown primary, administration of CT contrast agents, type of FDG-PET/CT images evaluated and way of FDG-PET/CT review did not significantly influence diagnostic performance. In conclusion, FDG-PET/CT can be a useful method for unknown primary tumor detection. Future studies are required to prove the assumed advantage of FDG-PET/CT over FDG-PET alone and to further explore causes of heterogeneity.

Publication types

  • Meta-Analysis
  • Systematic Review

MeSH terms

  • False Positive Reactions
  • Fluorodeoxyglucose F18 / pharmacology*
  • Humans
  • Medical Oncology / methods
  • Neoplasm Metastasis
  • Neoplasms, Unknown Primary / diagnosis
  • Neoplasms, Unknown Primary / diagnostic imaging*
  • Neoplasms, Unknown Primary / pathology
  • Positron-Emission Tomography / methods*
  • Radiology / methods
  • Radiopharmaceuticals
  • Sensitivity and Specificity
  • Tomography, X-Ray Computed / methods*


  • Radiopharmaceuticals
  • Fluorodeoxyglucose F18