Clinical significance of prostate 18 F-labelled fluorodeoxyglucose uptake on positron emission tomography/computed tomography: A five-year review.

AIM: To determine the significance and need for investigation of incidental prostatic uptake in men undergoing 18 F-labelled fluorodeoxyglucose ( 18 F-FDG) positron emission tomography/computed tomography (PET/CT) for other indications.

METHODS: Hospital databases were searched over a 5-year period for patients undergoing both PET/CT and prostate magnetic resonance imaging (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. Forty-six (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.