Reducing False-Positives Due to Urinary Stagnation in the Prostatic Urethra on 18 F-DCFPyL PSMA PET/CT With MRI

Area of Science:

• Nuclear Medicine
• Radiology
• Urology

Background:

• Prostate-specific membrane antigen (PSMA)-targeting PET radiotracers show physiologic uptake in the urinary system.
• This uptake can be misinterpreted as intraprostatic lesions, specifically in the prostatic urethra.

Purpose of the Study:

• To investigate the correlation between midline 18F-DCFPyL activity in the prostate and T2-weighted MRI hyperintensity.
• To assess retained urine in the prostatic urethra as a cause of false-positive PSMA PET findings.

Main Methods:

• Retrospective analysis of 85 patients who underwent both 18F-DCFPyL PSMA PET/CT and prostate MRI.
• Evaluation for midline radiotracer activity and retained urine on postvoid T2W MRIs.
• Statistical comparison of urethral and prostatic characteristics between patients with and without midline activity.

Main Results:

• Midline PSMA PET activity was observed in 14 patients (case group), while 71 had no midline activity (control group).
• Urethral hyperintensity on T2W MRI was significantly higher in the case group (71.4%) compared to the control group (29.6%) (P < 0.01).
• Patients with midline activity had larger urethral dimensions, prostate volumes, and higher rates of urethral curvature.

Conclusions:

• Stagnated urine in the prostatic urethra is a confounding factor in PSMA PET imaging.
• Integrating PSMA PET/CT with T2W MRI can reduce false-positive interpretations of prostate cancer.