Introduction:

Prostate-specific membrane antigen (PSMA)-targeted imaging agents have recently been FDA approved for use in prostate cancer patients with suspected recurrence based on elevated PSA.  By comparison with conventional imaging modalities, PET/CT with PSMA-targeted agents has been shown to improve the ability to localize and determine the extent of recurrent disease.  Piflufolastat F 18 (PYLARIFY; previously known as ¹⁸F-DCFPyL) is a novel PET imaging agent that binds selectively to PSMA with high affinity.  Here we report the correct localization rate (CLR) in patients with biochemical recurrence based on their prior treatment regimens.

Methods:

Men (18 or older) with a rising PSA after definitive therapy (radical prostatectomy (RP) and/or radiation therapy (RT)) for histologically confirmed prostate cancer and negative or equivocal conventional imaging were enrolled.  Piflufolastat F 18 (~9 mCi (333 MBq)) was administered as a single dose followed by a whole-body PET/CT scan 1-2 hours later.  CLR, a novel primary endpoint based on PPV (TP/(TP+FP)), and defined as percentage of patients with a one-to-one correspondence between localization of at least one lesion identified on piflufolastat F 18-PET/CT and a composite standard of truth (SOT) was determined.  The SOT was comprised of histopathology, correlative imaging or PSA response following radiation therapy.  Piflufolastat F 18-PET/CT scans were centrally reviewed by three blinded independent readers.

Results:

Piflufolastat F 18 was administered to 208 men, median PSA 0.8 ng/mL (range: 0.17–98.45).  For all prior treatment regimens, the overall CLR was 84.8% to 87.0% across three blinded independent readers.  The range of CLRs across prior primary definitive treatment regimens were: 80.0 to 85.7% for RP (n=103); 90.9 to 92.0% for RT (n=31); and 84.8 to 85.4% for RP+RT (n=74). For RP only patients with no prior androgen deprivation therapy (ADT; n=97), the CLR ranged from 78.8% (26/33) to 83.9% (26/31) across the three readers.

CLR was slightly higher in patients who had received ADT as part of prior management and ranged from 90.0% to 93.8% compared to 82.4% to 83.8% in patients without prior ADT exposure (see table below).

Conclusion:

A consistently high CLR for piflufolastat F 18-PET/CT is maintained across all prior definitive treatment regimens (RP, RT or RP+RT, +/- ADT) when detecting recurrent prostate cancer at the subject level with the highest CLRs observed in the RT-only treatment group.  The strong diagnostic performance of piflufolastat F 18-PET/CT irrespective of prior treatment regimen provides further support for its use to inform treatment decisions more accurately in prostate cancer patients.  ClinicalTrials.gov identifier NCT03739684

Funding: Progenics Pharmaceuticals, Inc.