Detection efficacy of [89Zr]Zr-PSMA-617 PET/CT in [68Ga]Ga-PSMA-11 PET/CT-negative biochemical recurrence of prostate cancer

Abstract

Rationale In patients with biochemical recurrence of prostate cancer (BCR), preliminary data suggest that prostate-specifc membrane antigen (PSMA) ligand radiotracers labeled with zirconium-89 (89Zr; half-life ~ 78.41 h), which allow imaging≥24 h post-injection, detect suspicious lesions that are missed when using tracers incorporating short-lived radionuclides. Materials and methods To confrm [ 89Zr]Zr-PSMA-617 positron emission tomography/computed tomography (PET/CT) detection efcacy regarding such lesions, and compare quality of 1-h, 24-h, and 48-h [ 89Zr]Zr-PSMA-617 scans, we retrospectively analyzed visual fndings and PET variables refecting lesional [ 89Zr]Zr-PSMA-617 uptake and lesion-to-background ratio. The cohort comprised 23 men with BCR post-prostatectomy, median (minimum–maximum) prostate-specifc antigen (PSA) 0.54 (0.11–2.50) ng/mL, and negative [ 68Ga]Ga-PSMA-11 scans 40±28 d earlier. Primary endpoints were percentages of patients with, and classifcations of, suspicious lesions. Results Altogether, 18/23 patients (78%) had 36 suspicious lesions (minimum–maximum per patient: 1–4) on both 24-h and 48-h scans (n=33 lesions) or only 48-h scans (n=3 lesions). Only one lesion appeared on a 1-h scan. Lesions putatively represented local recurrence in 11 cases, and nodal or bone metastasis in 21 or 4 cases, respectively; 1/1 lesion was histologically confrmed as a nodal metastasis. In all 15 patients given radiotherapy based on [ 89Zr]Zr-PSMA-617 PET/CT, PSA values decreased after this treatment. Comparison of PET variables in 24-h vs 48-h scans suggested no clear superiority of either regarding radiotracer uptake, but improved lesion-to-background ratio at 48 h. Conclusions In men with BCR and low PSA, [ 89Zr]Zr-PSMA-617 PET/CT seems efective in fnding prostate malignancy not seen on [ 68Ga]Ga-PSMA-11 PET/CT. The higher detection rates and lesion-to-background ratios of 48-h scans versus 24-h scans suggest that imaging at the later time may be preferable. Prospective study of [ 89Zr]Zr-PSMA-617 PET/CT is warranted.