Value of a repeat ¹⁸F-flotufolastat PET scan following a negative scan in patients with suspected biochemical recurrence of prostate cancer after radical prostatectomy.

Abstract

PURPOSE: To investigate the potential of a second 18F-flotufolastat positron emission tomography (PET) scan in patients with suspected biochemical recurrence (BCR) of prostate cancer (PCa) who had a previous negative 18F-flotufolastat PET, and to identify prostate-specific antigen (PSA) parameters influencing detection efficacy. METHODS: Our retrospective analysis included data from patients who underwent second 18F-flotufolastat PET between 2019 and 2024, following negative 18F-flotufolastat PET for suspected BCR of PCa (PSA ≥ 0.2 ng/mL) after radical prostatectomy. Two board-certified experts classified 18F-flotufolastat-avid lesions per miTNM categories. Patient-level detection rates were stratified by: pre-PET scan PSA; absolute/relative difference in PSA (ΔPSA) between negative first and second PET; PSA velocity (PSAvel); PSA doubling time (PSAdt). Receiver operating characteristic (ROC) curve analyses were performed. RESULTS: Of 101 patients (median age = 70 years; median PSA = 0.79 ng/mL), 58 (57%) had a positive second 18F-flotufolastat scan. Detection rates increased with PSA level, ΔPSA, PSAvel, and PSAdt. Differences in PSA level, ΔPSA, PSAvel, and PSAdt between groups with/without suspicious 18F-flotufolastat uptake were statistically significant (p < 0.05). Cut-offs for statistically optimal trade-off between negative and positive second PET (ROC analyses) were: PSA level > 0.82 ng/mL; absolute ΔPSA > 0.50 ng/mL; relative ΔPSA > + 100%; PSAvel > 0.30 ng/mL/y; PSAdt ≤ 17 months. CONCLUSION: In over half of patients presenting with BCR after radical prostatectomy and an initial negative 18F-flotufolastat PET, second 18F-flotufolastat PET identified recurrent lesions. PSA level at time of second PET, absolute/relative ΔPSA, PSAvel, and PSAdt influenced scan positivity.