Impact of Concomitant Hormone Therapy on the Diagnostic Performance of ¹⁸F-Piflufolastat PET/CT in Prostate Cancer Patients: A Sub-Group Analysis of OSPREY Cohort B

Background: This study investigates the impact of hormone therapy (HT) on the diagnostic performance of ¹⁸F-piflufolastat PET/CT in OSPREY (NCT02981368) cohort B patients with recurrent or metastatic prostate cancer. Methods: ¹⁸F-piflufolastat PET/CT was evaluated in OSPREY cohort B patients (n = 117 men) with elevated prostate-specific antigen (PSA) levels and suspected local recurrence or metastatic disease on baseline conventional imaging. Patients were stratified based on HT status, and sensitivity and positive predictive value (PPV) were determined for the subset of 93 patients with evaluable pathology. Baseline serum PSA and testosterone levels were determined within 30 days before dosing using standardized laboratory methods. Results: In OSPREY cohort B, 34.4% of patients (32/93) were on at least one concomitant HT with a median exposure duration of 15.5 months. The median baseline PSA and testosterone levels for patients on concurrent HT (n = 32) were 31.6 ng/mL and 9 ng/dL, respectively. For patients not on concurrent therapy (n = 61), median PSA and testosterone levels were 6.1 ng/mL and 317.35 ng/dL, respectively. The median sensitivity of ¹⁸F-piflufolastat PET/CT across three readers was 96.4% (95%CI: 80.8%–100%) in patients receiving concurrent HT and 95.4% (95%CI: 83.7%–99.6%) in patients not receiving concurrent HT. A modest increase in median PPV was observed in patients receiving concomitant HT (median of three readers: 90.0% [95%CI: 73.6, 97.3]) compared to patients not receiving concomitant therapy (median of three readers: 77.4% [95%CI: 66.1, 88.6]). Conclusions: The diagnostic performance of ¹⁸F-piflufolastat PET/CT was unaffected by concomitant HT in OSPREY cohort B patients with recurrent and/or metastatic prostate cancer.