Clinical Significance of 18F-Fluorodeoxyglucose Avid Prostate Gland Incidentalomas on Positron Emission Tomography/Computed Tomography

OBJECTIVE The aim of this study was to evaluate the clinical significance of incidental focal uptake of 18F-fluorodeoxyglucose (18F-FDG) on positron emission tomography/computed tomography (PET/CT) in the prostate glands of cancer patients. METHODS A retrospective review of 3122 consecutive male patients who underwent 18F-FDG PET/CT studies with an oncologic indication, over the course of four years, was performed. Studies with incidental 18F-FDG uptake in the prostate gland were further analyzed. RESULTS Incidental 18F-FDG uptake in the prostate gland was identified in 65/3122 men (2.1%). Sufficient follow-up data (≥12 months) were available in 53 patients, of whom 11 had a biopsy and 42 had clinical and imaging follow-up. Malignancy was histologically diagnosed in 4 out of 53 patients (7.5%). There was no statistically significant difference in 18F-FDG uptake values between benign prostate lesions [maximum standardized uptake value (SUVmax) 7.3] and malignant ones (SUVmax 7.2, p=0.95). There was a statistically significant difference between the serum prostate specific antigen (PSA) of the benign group (n=24, PSA=2.7 ng/mL) and the malignant group (n=4, PSA=9.2 ng/mL, p<0.001). There was a direct correlation between SUVmax and Gleason score. CONCLUSION 18F-FDG positive prostate incidentalomas were detected in 2.1% of oncologic PET/CT scans and of these 7.5% were malignant. SUVmax was not useful for distinguishing between benign and malignant incidental prostate lesions. 18F-FDG avid prostate incidentalomas on PET/CT should prompt a recommendation for obtaining a serum PSA and further investigation if serum PSA is elevated.