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
