Introduction

Little glucose metabolism is generally thought to occur in prostate cancer, leading to low diagnostic accuracy of 18F-fluoro-2-deoxyglucose (FDG) positron emission tomography-computed tomography (PET/CT). Nevertheless, this modality is reportedly useful for identifying high-risk local cancers. We therefore investigated whether local FDG uptake by the prostate reflects the perioperative results of robot-assisted laparoscopic radical prostatectomy (RALP).

Methods

Between November 2012 and August 2016, a total of 248 patients underwent RALP at our institution. Of these, subjects in this study comprised 116 patients in whom FDG-PET/CT was employed for preoperative staging. We retrospectively compared perioperative results between patients, stratified for local FDG uptake in the prostate. Patients who had received preoperative hormone therapy were excluded from the study. FDG uptake was rated based on clinical reports prepared by two radiation diagnosticians. Patient background characteristics, perioperative results and postoperative pathological results were compared between subjects divided into PET-positive and -negative groups.

Results

Participants comprised 40 PET-positive subjects and 76 PET-negative subjects. Among the patient background characteristics, mean age was slightly but significantly higher in the PET-positive group (66 years) than in the PET-negative group (64 years; p=0.0485). No significant differences were seen in PSA level, clinical T stage or Gleason Score (GS). Operative time, console time and volume of blood loss also showed no differences between groups, and no patients in either group suffered rectal perforation or required blood transfusion. Postoperative urethral balloon retention time and urinary continence rate at 3 months postoperatively were comparable between groups. Postoperative pathological results showed significantly higher values for the following parameters in the PET-positive group than in the PET-negative group: extraprostatic invasion (45.0% vs 22.4%; p=0.0185); positive margin (30.0% vs 13.2%; p=0.0445); and GS ?8 (52.5% vs 23.7%; p=0.00343). Multivariate analysis also showed that PET positivity tended to be associated with positive margins (odds ratio (OR), 2.45; p=0.0819) and extraprostatic invasion (OR, 2.34; p=0.0529), while GS ?8 was a significant predictor (OR, 3.08; p=0.0208).

Conclusions

In RALP, FDG uptake should be considered a predictor of high-grade disease and a risk factor for positive margins.

Funding

none