18F-PSMA-11 Versus 68Ga-PSMA-11 Positron Emission Tomography/Computed Tomography for Staging and Biochemical Recurrence of Prostate Cancer: A Prospective Double-blind Randomised Cross-over Trial

Abstract

BackgroundFluorine-18 (18F)-labelled prostate-specific membrane antigen (PSMA) offers several advantages over gallium-68 (68Ga) in terms of costs, yield, transport/distribution, and image resolution. ObjectiveThis trial investigates the new radiotracer 18F-PSMA-11 via a prospective, intraindividual crossover design. The trial was powered for noninferiority of 18F-PSMA-11 over 68Ga-PSMA-11 positron emission tomography (PET)/computed tomography (CT) in terms of the number of positive PET scans. Secondary endpoints were as follows: (1) superiority of 18F-PSMA-11 over 68Ga-PSMA-11 with respect to the number of positive PET scans, the total number of suspicious prostate cancer lesions, and the miPSMA expression score of corresponding lesions; (2) correlation of the PET/CT images with available follow-up data for 18F-PSMA-11 and 68Ga-PSMA-11; and (3) assessment of the interobserver variability. Design, setting, and participantsProstate cancer patients (primary or biochemical recurrence) were randomised in a double-blind crossover design whereby each patient received both 18F-PSMA-11 and 68Ga-PSMA-11 PET/CT. Outcome measurements and statistical analysisAll scans were reviewed and scored by three independent experienced nuclear physicians following the proposed guideline for the interpretation of PSMA-ligand PET/CT, as described by Eiber et al. Results and limitationsIn total, 82 patients were included for scan analyses. The primary endpoint was met: per patient, the proportions of positive scans rated by the three readers were 67%/67%, 65%/65%, and 73%/70% for 18F-PSMA-11/68Ga-PSMA-11 PET/CT. The miPSMA expression score was higher for 18F-PSMA-11 than for 68Ga-PSMA-11 for the reference reader. Follow-up data showed identical estimated sensitivity for both the 18F-PSMA-11 and the 68Ga-PSMA-11 scan (0.92, 0.83, and 0.92 for the three readers). A fair to good agreement among readers (at patient level) was obtained, which was demonstrated by a Light’s kappa value of 0.59 for both tracers. ConclusionsThe tracer 18F-PSMA-11 is noninferior to68Ga-PSMA-11. Superiority of 18F-PSMA-11 was limited to the miPSMA expression score, given by the reference reader. Inter-rater agreement was fair to good, and equal for both radiotracers. Patient summaryIn this study, we compared two radiotracers: 18F-PSMA-11 and 68Ga-PSMA-11. We proved that 18F-PSMA-11 is not inferior to 68Ga-PSMA-11 for detecting prostate cancer and thus can be used as an alternative. Possible superiority of this tracer should be further investigated in specific subpopulations.