Changes in planned disease management after piflufolastat F18 PET/CT in men with biochemically recurrent prostate cancer and low PSA levels: A secondary analysis of results from the CONDOR study.

Abstract

61 Background: Piflufolastat F 18 is a PSMA-targeted radiopharmaceutical approved in the US for imaging prostate cancer (PCa) patients both at the time of initial staging and at disease recurrence. In a phase 3 study of patients with biochemically recurrent (BCR) PCa, we reported that nearly two-thirds (63.9%; 131/205) of participants had a change in their intended disease management plan based on pre- and post-piflulfolastat F 18 PET/CT management questionnaires (MMQs) completed by the treating physicians. The clinical utility of piflufolastat F 18 scanning in men with very low/low PSA levels (<0.5 ng/mL) and a detection rate of ~36% has not been previously described. Here we report the changes in intended management in this subset of patients. Methods: Men ≥18 years of age with a rising PSA after definitive PCa therapy and negative or equivocal imaging were enrolled. A single ~9 mCi (333 MBq) dose of piflufolastat F 18 was administered followed by PET/CT from mid-thigh through skull vertex 1-2 hours later. Prior to scanning, the treating physicians completed a pre-PET MMQ to document the initial intended management plan for their patients based on available clinical information including baseline conventional imaging results. After PET, they completed a post-PET MMQ and recorded the management plan in light of PET findings. Treatment recommendations that differed from the pre-scan recommendations were reported as changes in the intended management plan. Results: 208 men (median PSA 0.8 ng/mL [range 0.17-98.45], n=202) underwent piflufolastat F 18-PET/CT. 200 evaluable patients had both a baseline PSA value and completed MMQs. Of 131 patients with a recorded change in intended management, 127 had an evaluable baseline PSA level. Of the 69 patients with baseline PSA levels ≤0.5ng/mL, 27 (39.1%) recorded a change in intended disease management based on positive (n=20) or negative (n=7) PET, including salvage local to systemic therapy (n=15); systemic to local therapy (n=3); observation to treatment (n=5); and treatment to observation (n=4). An additional 15 patients (21.7%) had recommended bidirectional change in management (e.g., salvage RT+ADT) and are excluded in this report. Specific treatment intensification/de-intensification plans are under investigation. Conclusions: The frequency of changes in intended disease management observed in BCR PCa patients with low baseline PSA levels (≤0.5ng/mL) was 39.1%. Both negative and positive PET/CT results impacted treatment recommendations and can provide useful and actionable information. Clinical trial information: NCT02981368 .