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

Abstract

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.

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