Multicentre study of 18F-FDG-PET/CT prostate incidental uptake

The purpose of our study was to establish the prevalence and pathological nature of fluorine-18-fluorodeoxyglucose (18F-FDG) prostate incidental uptake (PIU) among patients studied for non-prostate-malignant purposes in three nuclear medicine centres.

We retrospectively evaluated 20,422 scans performed on male patients; all patients underwent 18F-FDG-PET/CT for purposes not related to prostate disease.

Among 20,422 patients PIU was identified for 280 (1.4 %) with an average age of 70 ± 10.7 years. Sixty-three of the 280 patients with PIU (22.5 %) underwent PSA dosage and biopsy to determine the nature of the incidental uptake. Thirty-five of the 63 (55.5 %) PIU were malignant whereas 28/63 (44.5 %) were benign. The average value of PSA for patients with benign PIU was 3.7 ± 2.8 ng/ml whereas it was 7.8 ± 8.2 ng/ml in patients with malignant PIU; this difference was statistically significant. For malignant lesions, the average lesion-to-liver SUVmax ratio was 2.9 ± 2.5 and the average lesion-to-blood-pool SUVmax ratio was 3.7 ± 2.5. For benign lesions, the average lesion-to-liver SUVmax ratio was 2.5 ± 1.7 and the average lesion-to-blood-pool SUVmax ratio was 3.5 ± 2.4; there was no statistically significant difference between lesion-to-liver and lesion-to-blood-pool SUVmax ratios for benign and malignant lesions.

Because PIU values are indicative of malignancy for a substantial percentage of patients, further investigation is required.