Clinical significance of prostate $^{18}$F-FDG uptake on PET/CT: A five-year review

Abstract

AIM: To determine the significance and need for investigation of incidental prostatic uptake in men undergoing $^{18}$F-FDG PET/CT for other indications. METHODS: Hospital databases were searched over a 5-year period for patients undergoing both PET/CT and prostate MRI. For the initial analysis, the prostate was divided into six sectors and suspicious or malignant sectors were identified using MRI and histopathology reports respectively. Maximum and mean $^{18}$F-FDG standardised uptake values were measured in each sector by an investigator blinded to the MRI and histopathology findings. Two age-matched controls were selected per case. Results were analysed using a paired t-test and one-way ANOVA. For the second analysis, PET/CT reports were searched for prostatic uptake reported incidentally and these patients were followed up. RESULTS: Over a 5-year period, 15 patients underwent both PET/CT and MRI and had biopsy-proven prostate cancer. Malignant prostatic sectors had a trend to higher $^{18}$F-FDG uptake than benign sectors, however this was neither clinically nor statistically significant (3.13 ± 0.58 vs 2.86 ± 0.68, P > 0.05). $^{18}$F-FDG uptake showed no correlation with the presence or histopathological grade of tumour. $^{18}$F-FDG uptake in cases with prostate cancer was comparable to that from age-matched controls. 46 (1.6%) of 2846 PET/CTs over a 5-year period reported incidental prostatic uptake. Of these, 18 (0.6%) were investigated by PSA, 9 (0.3%) were referred to urology, with 3 (0.1%) undergoing MRI and/or biopsy. No cases of prostate cancer were diagnosed in patients with incidental $^{18}$F-FDG uptake in our institute over a 5-year period. CONCLUSION: $^{18}$F-FDG uptake overlaps significantly between malignant and benign prostatic conditions. Subsequent patient management was not affected by the reporting of incidental focal prostatic uptake in this cohort.