@article {Hagens1531, author = {Marinus J. Hagens and Daniela E. Oprea-Lager and Andr{\'e} N. Vis and Maurits Wondergem and Maarten L. Donswijk and Dennie Meijer and Louise Emmett and Pim J. van Leeuwen and Henk G. van der Poel}, title = {Reproducibility of PSMA PET/CT Imaging for Primary Staging of Treatment-Na{\"\i}ve Prostate Cancer Patients Depends on the Applied Radiotracer: A Retrospective Study}, volume = {63}, number = {10}, pages = {1531--1536}, year = {2022}, doi = {10.2967/jnumed.121.263139}, publisher = {Society of Nuclear Medicine}, abstract = {Our purpose was to determine and compare the interobserver variability of 3 clinically frequently used radiotracers targeting the prostate-specific membrane antigen (PSMA), namely 18F-DCFPyL, 18F-PSMA-1007, and 68Ga-PSMA-11, in primary prostate cancer (PCa) staging. Methods: Patients with newly diagnosed PCa in whom PSMA PET/CT was performed for primary staging purposes were retrospectively included. All PSMA PET/CT images were centrally overread within a high-volume PCa center, and original reports (from referring hospitals) were compared with overread reports (from the overreading hospital). To assess the interobserver variability, a Cohen κ analysis was used. To study possible differences in interobserver variability between the 3 applied PSMA radiotracers, multivariate logistic regression analyses were used. Results: In total, 584 patients with newly diagnosed PCa were included in the analysis. 18F-DCFPyL, 18F-PSMA-1007, and 68Ga-PSMA-11 were used in 205 (35.1\%), 168 (28.8\%), and 211 (36.1\%) patients, respectively. The overall agreement (Cohen κ analysis) for locoregional lymph node metastases, distant lymph node metastases, bone metastases, and visceral metastases was 0.86, 0.86, 0.80, and 0.46, respectively. 18F-PSMA-1007 showed a significantly increased interobserver variability regarding bone metastases, compared with 18F-DCFPyL and 68Ga-PSMA-11 (P = 0.001 and 0.03, respectively). Additionally, 18F-PSMA-1007 showed a significantly increased interobserver variability regarding overall agreement and locoregional lymph node metastases, compared with 18F-DCFPyL (P \< 0.001 and P = 0.01, respectively). Conclusion: Interobserver variability differs among the 3 clinically frequently used PSMA radiotracers (18F-DCFPyL, 18F-PSMA-1007, and 68Ga-PSMA-11) in patients with newly diagnosed PCa. The agreement in bone metastases is significantly worse for 18F-PSMA-1007, mainly due to nonspecific tracer uptake in osseous structures. On the basis of our findings, PSMA PET/CT scans undertaken with 18F-PSMA-1007 in primary staging should be interpreted carefully, and training on interpreting this specific PSMA radiotracer is strongly advised.}, issn = {0161-5505}, URL = {https://jnm.snmjournals.org/content/63/10/1531}, eprint = {https://jnm.snmjournals.org/content/63/10/1531.full.pdf}, journal = {Journal of Nuclear Medicine} }