Incidental Abnormal FDG Uptake in the Prostate on 18-fluoro-2-Deoxyglucose Positron Emission Tomography-Computed Tomography Scans

Abstract

18-fluoro-2-deoxyglucose positron emission tomography-computed tomography (18F-FDG PET/CT) scans arecommonly used for the staging and restaging of various malignancies, such as head and neck, breast, colorectaland gynecological cancers. However, the value of FDG PET/CT for detecting prostate cancer is unknown. Theaim of this study was to evaluate the clinical value of incidental prostate 18F-FDG uptake on PET/CT scans.We reviewed 18F-FDG PET/CT scan reports from September 2009 to September 2013, and selected cases thatreported focal/diffuse FDG uptake in the prostate. We analyzed the correlation between 18F-FDG PET/CT scanfindings and data collected during evaluations such as serum prostate-specific antigen (PSA) levels, digital rectalexamination (DRE), transrectal ultrasound (TRUS), and/or biopsy to confirm prostate cancer. Of a total of 18,393cases, 106 (0.6%) exhibited abnormal hypermetabolism in the prostate. Additional evaluations were performedin 66 patients. Serum PSA levels were not significantly correlated with maximum standardized uptake values(SUVmax) in all patients (rho 0.483, p=0.132). Prostate biopsies were performed in 15 patients, and prostatecancer was confirmed in 11. The median serum PSA level was 4.8 (0.55-7.06) ng/mL and 127.4 (1.06-495) ng/mLin the benign and prostate cancer groups, respectively. The median SUVmax was higher in the prostate cancergroup (mean 10.1, range 3.8-24.5) than in the benign group (mean 4.3, range 3.1-8.8), but the difference wasnot statistically significant (p=0.078). There was no significant correlation between SUVmax and serum PSA,prostatic volume, or Gleason score. 18F-FDG PET/CT scans did not reliably differentiate malignant or benignfrom abnormal uptake lesions in the prostate, and routine prostate biopsy was not usually recommended inpatients with abnormal FDG uptake. Nevertheless, patients with incidental prostate uptake on 18F-FDG PET/CT scans should not be ignored and should be undergo further clinical evaluations, such as PSA and DRE.