Short-Term Androgen Deprivation Therapy and 18F-flotufolastat PSMA PET/CT Imaging for Prostate Cancer Staging: A Pilot Study

Rationale: This pilot study evaluates the impact of short-term Androgen Deprivation Therapy (ADT) on the findings on 18F-flotufolastat PSMA PET/CT scan when used for staging prostate cancer prior to a Robot-Assisted Radical Prostatectomy (RARP) and bilateral Pelvic Lymph Node Dissection (PLND). Methods: Ten patients with unfavorable intermediate, high or very-high risk prostate cancer were assigned to one of two cohorts, A and B (n=5 each). Baseline serum Prostate-Specific Antigen (PSA) and testosterone were measured, followed by an 18F-flotufolastat PSMA PET/CT. All patients then underwent either 3 weeks (cohort A) or 6 weeks (cohort B) of relugolix therapy. A second PSMA PET/CT was performed immediately upon ADT completion. Quantitative and qualitative changes in PSMA PET/CT findings were analyzed. Results: All patients reached castrate levels of testosterone (<20 ng/dL) within 3 weeks of the initiation of ADT. Only 1 patient (10%) exhibited a 16.1% increase in the maximum standardized uptake value (SUVmax) of the primary intraprostatic lesion. No new clinically significant findings were detected on the post-ADT PSMA PET/CT compared to pre-ADT scans and no pre-existing findings were obscured post-ADT. No serious adverse events related to ADT were reported. Conclusion: Short-term ADT (3 and 6 weeks) did not alter PSMA PET/CT findings in a manner that would impact surgical planning or management.