Clinical value of 18F-FDG-PET/CT in suspected serious disease with special emphasis on occult cancer

Ann Nucl Med. 2019 Mar;33(3):184-192. doi: 10.1007/s12149-018-01322-9. Epub 2018 Dec 19.


Purpose: Suspected serious disease (SSD) is a disease designation often given to patients with one or more non-specific symptoms of severe disease that could be due to cancer; the optimal diagnostic strategy is largely left to the clinician's discretion. Being a sensitive non-invasive whole-body imaging modality 18F-FDG-PET/CT may have a potential role in this cancer-prevalent group of patients to confirm or refute suspected malignancy. We aimed to investigate the diagnostic value of 18F-FDG-PET/CT in SSD using long-term follow-up as reference.

Methods: We retrospectively studied results obtained in all SSD patients referred for 18F-FDG-PET/CT at a single institution in 2010-2011 retrieving the following clinical data in all patients: journal entries, examinations, and evaluations made from 6 months before the scan and until the latest recorded entry. A true positive PET scan was a positive scan with a subsequently biopsy-confirmed diagnosis of cancer in the same target organ, whereas a false positive scan had no subsequent cancer diagnosis. A true negative PET scan was a negative scan without a cancer diagnosis during follow-up, whereas a false negative PET scan was one with a subsequently confirmed cancer diagnosis.

Results: Ninety-three patients, aged 67 years (range 25-89) were included and followed for up to 7.3 years (median 6). Of these, 21 [22.6% (95% CI 15.3-32.1)] turned out to have cancer. With 18F-FDG-PET/CT, the sensitivity was 81.0% (95% CI 60.0-92.3), specificity 76.4% (95% CI 65.4-84.7), positive predictive value 50% (95% CI 34.1-65.9), and negative predictive value 93.2% (95% CI 83.8-97.3). Five patients with negative scans were subsequently diagnosed with cancer.

Conclusion: Cancer prevalence is substantial among patients with SSD. 18F-FDG-PET/CT is a promising option in this setting, in particular because a high negative predictive value equals a low incidence of cancer during follow-up. Further studies are needed to establish the role of 18F-FDG-PET/CT in SSD.

Keywords: FDG; Occult cancer; PET/CT; Suspected serious disease.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Diagnosis, Differential
  • Female
  • Fluorodeoxyglucose F18*
  • Follow-Up Studies
  • Humans
  • Kaplan-Meier Estimate
  • Male
  • Middle Aged
  • Mortality
  • Neoplasms, Unknown Primary / diagnostic imaging*
  • Neoplasms, Unknown Primary / epidemiology
  • Neoplasms, Unknown Primary / pathology
  • Positron Emission Tomography Computed Tomography*
  • Prevalence
  • Radiopharmaceuticals*
  • Retrospective Studies
  • Sensitivity and Specificity


  • Radiopharmaceuticals
  • Fluorodeoxyglucose F18