MP53-14 THE CLINICAL SIGNIFICANCE OF INCIDENTAL PROSTATE AVIDITY ON FDG-PET IMAGING

Abstract

INTRODUCTION AND OBJECTIVES: Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) imaging is increasingly used for the initial staging and surveillance of multiple malignancies. Its utility in prostate cancer, however, is unclear as it does not appear to improve existing clinical staging. Accordingly, the significance of incidental prostate avidity on FDG-PET scan remains unclear. We sought to review our experience with incidental prostate avidity on FDGPET imaging. METHODS: We identified patients from January 2000 to August 2013 who were found to have incidentally-noted prostate avidity on FDG-PET scan during the diagnosis or monitoring of unrelated disease processes. We evaluated patients who underwent prostate biopsy prompted by the FDG-PET findings. RESULTS: We identified 65 patients with findings on FDG-PET concerning for primary prostate malignancy who underwent a prostate biopsy prompted by these findings. The median age at the time of biopsy was 68. Median pre-biopsy PSA was 4.02 (range 0.34 21). 40 of 65 patientswere cT1c (61.5%),while 25were cT2 (38.5%). The indication for FDG-PET was solid tumors in 30 (46%), hematologic malignancy (leukemia, lymphoma) in 21 (32%), and evaluation for benign lesions in 14 (22%). Prostate biopsy was positive for malignancy in 25 patients (38%) and negative formalignancy in 40 patients (62%). In patients with positive biopsy findings, low risk disease was identified in 13 (52%), intermediate risk disease in 9 (36%), and high risk disease in 3 (12%), as definedby the National Comprehensive Cancer Network (NCCN). Thirteen patients (52%) diagnosed with prostate cancer underwent treatment with radical prostatectomy, radiation, or androgen deprivation, while the remainder underwent active surveillance. With a median follow up of 15 months, no patients progressed to metastatic prostate cancer and there were no prostate cancer deaths. One patient progressed on surveillance and underwent proton beam therapy. One patient who initially had a negative prostate biopsy was diagnosed with intermediate risk prostate cancer 17 months later and underwent radical prostatectomy. CONCLUSIONS: Approximately 38% of patients with incidental FDG avidity in the prostate will be diagnosed with prostate cancer, with 18% of all FDG-PET avid prostates harboring intermediate or high risk malignancy. This risk warrants further evaluation to determine the need for prostate biopsy, in concert with other factors, such as age, family history, comorbidity, PSA and clinical examination.