F-florastamin positron emission tomography/computed tomography in men with clinical suspicion of prostate cancer: A phase I prospective study.

[UNLABELLED] Research on prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) and pending Food and Drug Administration (FDA) approval are predominantly aimed at biochemical recurrence rather than presurgical staging. Studies on the latter indication have almost exclusively investigated biopsy-proven cancers. We herein present the first-in-man clinical evaluation of a novel F-labeled PSMA ligand, florastamin, in screening for prostate cancer.

[METHODS] We recruited twenty men with prostate-specific antigen (PSA) levels between 3 (the threshold for biopsy) and 20 n/mL. A dose of 267-370 MBq (8-10 mCi) F-Florastamin was administered. Whole-body images were acquired at 90 minutes postinjection, followed by an additional pelvic PET/CT acquisition at 30 minutes. Conventional imaging (MRI) was performed within one week of, usually preceding, the PET/CT. PET/CT findings were compared to preoperative diagnostic magnetic resonance imaging (MRI) and correlated with final biopsy pathology. Diagnostic performance of the two modalities and both timepoints were compared on a per-patient, per-lobe, and per-segment basis. Inter-rater agreement was also measured for three readers.

[RESULTS] Twenty patients, who had a median PSA of 8.02 ng/mL (range 3.24-18.6), were enrolled in this study. Twelve patients were biopsy-proven with prostate cancer, of which four were low-risk and eight were intermediate risk. PET/CT visual analysis identified abnormal F-Florastamin uptake in at least one primary prostatic tumor focus in 10/12 patients at 90 minutes and 11/12 patients at 120 minutes. The per-segment sensitivity, specificity, and accuracy was 50%, 99.3%, and 93.1% for MRI with the best-performing threshold of ≥4, and 85%, 99.3% and 97.5% for F-Florastamin at 60 minutes, respectively. Delayed imaging showed comparable accuracy, with detection an additional true-positive lesion. The inter-rater agreement was substantial to almost perfect.

[CONCLUSION] F-Florastamin is a promising PET tracer that correctly identifies foci of cancer within the prostate with a higher accuracy than conventional imaging (MRI), and may be helpful in stratifying patients with low to intermediate PSA levels to better assess the need for an invasive biopsy. Our cohort study suggests triage with F-Florastamin PET/CT has the potential to reduce unnecessary biopsies in 9/20 (45%) patients.

[CLINICAL TRIAL NUMBER] (CRIS) KCT0004609.