Detection Efficacy of 18F-rhPSMA-7.3 PET/CT and Impact on Management in Patients with Biochemical Recurrence of Prostate Cancer After Radical Prostatectomy and Before Potential Salvage Treatment

Abstract

Radiohybrid prostate-specific membrane antigen (rhPSMA) ligands are a new class of 18F-labeled PSMA-targeting agents. 18F-rhPSMA-7.3 is a lead compound that is currently under investigation in 2 multicenter phase III trials for PET imaging. Here, we report the first retrospective data on its detection efficacy and potential impact on clinical management in a homogeneous cohort of patients with biochemical recurrence after radical prostatectomy and before any salvage therapy. Methods: In total, 242 patients (median prostate-specific antigen [PSA], 0.60 ng/mL; range, 0.2-60.8 ng/mL) who underwent 18F-rhPSMA-7.3 PET/CT were retrospectively selected from the institution's database. Images were reread by an experienced nuclear medicine physician. Lesion detection rates were stratified by PSA. Further, potential management before and after PET was assessed by an interdisciplinary simulated tumor board and categorized (major vs. minor vs. no therapeutic change). The distribution of management change identified in each PSA subgroup was determined. Results: In total, 176 of 242 (72.7%) patients showed PSMA-ligand-positive findings. 18F-rhPSMA-7.3 detection rates were 61.8% (63/102), 67.9% (38/56), 81.1% (30/37), and 95.7% (45/47) for PSA levels of 0.2 to less than 0.5 ng/mL, 0.5 to less than 1 ng/mL, 1 to less than 2 ng/mL, and at least 2 ng/mL, respectively. 18F-rhPSMA-7.3 PET/CT revealed local recurrence, pelvic lymph node metastases, retroperitoneal lymph nodes metastases, supradiaphragmatic lymph nodes, bone metastases, and visceral metastases in 48.8% (n = 118), 28.9% (n = 70), 6.6% (n = 16), 1.2% (n = 3), 13.2% (n = 32), and 1.2% (n = 3) of patients, respectively. Notably, bone lesions were identified in 8.8% of patients (9/102) with a PSA of less than 0.5 ng/mL. Results from the tumor board indicated a change in therapeutic management in 153 of 242 patients (63.2%), with 54 (22.3%) considered major and 99 (40.9%) minor. 18F-rhPSMA-7.3 PET/CT did not prompt any therapeutic changes in 64 patients (26.4%). Conclusion: 18F-rhPSMA-7.3 PET offered high detection efficacy in patients with biochemical recurrence after radical prostatectomy and before potential salvage therapy and resulted in a potential change in treatment plan in nearly two thirds of patients.