Can SUVmax values of Ga-68-PSMA PET/CT scan predict the clinically significant prostate cancer?

The intensity of prostate-specific membrane antigen (PSMA) expression increases as the tumor grade increases and the uptake of Ga-68-PSMA is higher in high-grade tumors. The aim of the present study was to evaluate the correlation of preoperative tracer uptake of primary tumor to Gleason Score in patients who underwent prostatectomy.

We retrospectively evaluated 141 patients who had Ga-68-PSMA positron emission tomography/computed tomography (PET/CT) imaging and who underwent prostatectomy. All patients had a diagnosis of prostate cancer on the basis of 10-24 cores transrectal ultrasound-guided biopsy (TRUS-Bx). Histological assessment was performed according to the New Contemporary Prostate Cancer Grading System. All patients had a prostate-specific antigen (PSA) level measurement within maximum of 28 days before Ga-68-PSMA PET/CT. Region of interests were drawn manually around the prostate gland, avoiding the bladder activity, to calculate the maximum standardized uptake values (SUVmax) values.

The median PSA values for all patients were 10.0 ng/ml. PSA values for low-risk patients were significantly lower than those of high-risk patients (P<0.001). There were 41.1% upgrades and 7.8% downgrades following prostatectomy in terms of Grade Groups. According to the final pathology reports, 21% (n=16) of patients moved from a low-risk level (grade groups 1+2) to a high-risk level (grade groups 3+4+5). The median SUVmax value was 8.8, ranging from 2.1 to 62.4. There was a strong correlation between SUVmax values and grade groups (Pearson ρ=0.66) (P<0.001). The mean SUVmax values of high-risk patients were significantly higher than those of low-risk patients (18.9±12.1 vs. 7.16±6.2, respectively) (P<0.001). Receiver operation characteristic curve analysis of SUVmax at the cut-off value of 9.1 showed a high sensitivity (78%) and specificity (81%) for detection of high risk disease.

SUVmax values correlate significantly with the grade groups of the primary tumor. The intraprostatic accumulation sites may predict clinically significant cancer and potentially serve as a target for biopsy sampling in conjunction with mpMRI in selected patients.