The impact of concomitant use of androgen deprivation therapies (ADT) on the efficacy of piflufolastat F 18-PET/CT in patients with prostate cancer: a sub-group analysis of OSPREY Cohort B

Introduction: Piflufolastat F 18 is a PSMA-targeted PET radiopharmaceutical approved for imaging in men with suspected prostate cancer metastasis who are candidates for initial definitive therapy and in patients with suspected recurrence based on elevated PSA levels. Here we report on the impact of ADT on the performance of piflufolastat F 18-PET/CT including sensitivity and positive predictive value (PPV) in patients with prostate cancer recurrence or metastases on conventional imaging on ADT compared to patients in the same cohort not receiving ADT (OSPREY Cohort B).

Methods: Piflufolastat F 18-PET/CT (previously described as ¹⁸F-DCFPyL-PET/CT) was evaluated in 117 men with elevated PSA and radiologic evidence of local recurrence or metastatic disease on baseline anatomical imaging (CT, MRI) or whole-body bone scintigraphy and in whom at least one lesion was deemed amenable to biopsy. A single dose of 9 mCi (333 MBq) of piflufolastat F 18 was administered via intravenous injection, followed by PET/CT acquisition 1 to 2 hours thereafter. Three central, blinded, and independent readers evaluated the piflufolastat F 18 scans. Sensitivity (TP/TP+FN) and PPV (TP/TP+FP) at the patient level were determined for all patients with evaluable pathology. TP = true positive; FN = false negative; FP = false positive

Results: In OSPREY Cohort B, 34.4% of patients (32/93) were receiving concurrent ADT therapy, with start dates of medications prior to and ongoing at the time of piflufolastat F 18 dosing. The median PSA and testosterone levels for patients on concurrent ADT therapy (n=32) were 31.59 ng/mL and 0.31 ng/dL, respectively. For patients not on concurrent ADT therapy (n=61), PSA and testosterone levels were 6.08 ng/mL and 11.0 ng/dL, respectively. Sensitivity and PPV of piflufolastat F 18 PET/CT by ADT status as determined by each of the three independent readers is shown in the table below.

The n’s in the table represent the number of patients with positive histopathology for sensitivity and the number of positive scans reported for PPV.

Conclusions: In this post-hoc, sub-group analysis, piflufolastat F 18-PET/CT in men with recurrent PCa and elevated serum PSA levels showed comparable sensitivity and PPV in patients who received concomitant ADT when compared to patients not receiving ADT. Clinicaltrials.gov: NCT02981368.