Incidental diagnosis of prostate cancer in FDG PET/CT: An initial experience

2218 Objectives: PET/CT with 18F-FDG has proven to be effective in detecting and assessing various types of cancers. However, sensitivity of FDG PET is suboptimal in prostate cancer (PC) because of interfering urine activity as well as FDG accumulation in benign prostatic hypertrophy and prostatitis. The purpose of this study was to evaluate frequency of incidental detection of PC in routine FDG PET/CT of patients with no history of PC. Methods: True Whole-Body FDG-PET/CT scans, covering from the top of skull to the bottom of the feet, of 773 male patients > 50 years old were retrospectively selected and reviewed. Images were acquired on a PET/CT scanner (Phillips Medical Systems) 60 minutes after an intravenous injection of a weight-adjusted dose of 0.14 mCi/kg FDG with a maximum dose of 14 mCi. A log was kept to record cases of intense FDG uptake, defined as Standard Uptake Value max (SUVmax) > 3.5, in the prostatic bed suspicious for PC. The presence or absence of PC was subsequently assessed using all available clinical and pathologic follow-up information. Results: PET/CT scans revealed an incidental finding of focal intense FDG uptake in the prostate in 11 (1.42%) of the 773 studies. Of those 11 patients: follow-up data are pending in one; no follow-up data were available for four; three had false-positive findings (two cases of uptake in the urethra and one case of probable inflammation), and cancerous primary PC lesions were confirmed by biopsy in three cases (Mean Gleason score and SUVmax of 5.6 and 4.7, respectively). Conclusions: We conclude that 1.42% of male cancer patients above the age of 50 had an incidental focal intense metabolic activity in the region of the prostate detected on a routine PET/CT exam. When present, this focal intense FDG uptake represented a previously unknown PC in at least 3/11 (27%). Therefore, an incidental finding of an intense FDG uptake in the prostate requires further investigation in order to rule out or diagnose PC. We continue to accrue more data to investigate the relationship between metabolic activity (SUV), Gleason score and/or PSA level in the incidentally discovered PC cases.