The effect of androgen deprivation therapy on ⁶⁸Ga-PSMA tracer uptake in non-metastatic prostate cancer patients.

Abstract

To evaluate the effect of neoadjuvant androgen deprivation treatment (ADT) on prostate-specific membrane antigen (PSMA) tracer uptake demonstrated in ⁶⁸Ga-PSMA-positron emission tomography (PET/CT) in non-metastatic hormone-naïve prostate cancer (PC) patients. The clinical data of 108 PC patients who received neoadjuvant ADT were retrospectively analyzed. All patients had a baseline ⁶⁸Ga-PSMA-PET/CT scan, and a second scan was delivered median of 2.9 months after the initiation of ADT. The maximum standardized uptake value (SUV_max) of primary tumor (SUV_p) and metastatic lymph nodes (SUV_ln) as well as PSA response were assessed between pre- and post-ADT ⁶⁸Ga-PSMA-PET/CT scans. There were significant decreases in posttreatment serum PSA, SUV_p, and SUV_ln. A decrease in SUV_p was seen in 91 patients (84%) with a median value of 66% (range, 5-100%), while 17 patients (16%) had no change in or an increase in PSMA tracer uptake with a median value of 24% (range, 0-198%). Patients with Gleason score (GS) of 7 had significantly higher metabolic response rates compared to other patients. The disease progression was significantly higher only in patients with GS > 7 disease compared to GS 7 disease. The PSA response to ADT was the lowest in patients with ISUP high-grade tumors. A total of 16 patients (15%) had progressive disease, and in 9 patients (8%), radiotherapy decisions were modified according to posttreatment ⁶⁸Ga-PSMA-PET/CT scans. The current study includes the largest number of patients analyzed to date and demonstrates that ADT causes a significant decrease in serum PSA values and SUV_p and SUV_ln. The authors demonstrate that ⁶⁸Ga-PSMA-PET/CT may be used as a quantitative imaging modality after neoadjuvant ADT in hormone-naïve non-metastatic PC patients.