(68)Ga-PSMA-11 PET/CT interobserver agreement for prostate cancer assessments: an international multicenter prospective study

Background: The interobserver agreement for (68)Ga-PSMA-11 Positron Emission Tomography/Computed Tomography (PET/CT) study interpretations in patients with prostate cancer is unknown. Methods:(68)Ga-PSMA-11 PET/CT was performed in 50 patients with prostate cancer for biochemical recurrence (n = 25), primary diagnosis (n = 10), biochemical persistence after primary therapy (n = 5) or staging of known metastatic disease (n = 10). Images were reviewed by 16 observers who used a standardized approach for interpretation of local (T), nodal (N), bone (Mb), or visceral (Mc) involvement. Observers were classified as having low (<30 prior (68)Ga-PSMA-11 PET/CT studies; n = 5), intermediate (30 to 300 studies; n = 5), or high level of experience (>300 studies; n = 6). Histopathology (n = 25, 50%), post-external beam radiation therapy prostate-specific antigen (PSA) response (n = 15, 30%), or follow-up PET/CT (n = 10, 20%) served as standard of reference (SOR). Observer groups were compared by overall agreement (% patients matching the SOR) and Fleiss' κ with mean and corresponding 95% confidence interval (CI). Results: Agreement among all observers was substantial for T (κ=0.62, 95%CI 0.59-0.64) and N (κ=0.74, 95%CI 0.71-0.76) staging and almost perfect for Mb (κ=0.88, 95%CI 0.86-0.91) staging. Level of experience positively correlated with agreement for T (κ=0.73/0.66/0.50 for high/intermediate/low experience, respectively), N (κ=0.80/0.76/0.64), and Mc staging (κ=0.61/0.46/0.36). Interobserver agreement for Mb was almost perfect irrespective of prior experience (κ=0.87/0.91/0.88). Observers with low experience, when compared to intermediate and high experience, demonstrated significantly lower median overall agreement (54% versus 66% and 76%, P = 0.041) and specificity for T staging (73% versus 88% and 93%, P = 0.032). Conclusion: The interpretation of (68)Ga-PSMA-11 PET/CT for prostate cancer staging is highly consistent among observers with high levels of experience, especially for nodal and bone assessments. Initial training on at least 30 patient cases is recommended to ensure acceptable performance.

Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 2017 Apr 13 [Epub ahead of print]

Wolfgang Peter Fendler, Jeremie Calais, Martin Allen-Auerbach, Christina Bluemel, Nina Eberhardt, Louise Emmett, Pawan Gupta, Markus Hartenbach, Thomas A Hope, Shozo Okamoto, Christian Helmut Pfob, Thorsten D Pöppel, Christoph Rischpler, Sarah Schwarzenböck, Vanessa Stebner, Marcus Unterrainer, Helle D Zacho, Tobias Maurer, Christian Gratzke, Alexander Crispin, Johannes Czernin, Ken Herrmann, Matthias Eiber

Ludwig-Maximilians-University of Munich, Germany., Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, United States., Department of Nuclear Medicine, Julius-Maximilians-University of Würzburg, Germany., Department of Nuclear Medicine, Ulm University., Department of Diagnostic Imaging, St. Vincent's Public Hospital, Sydney., Division of Nuclear Medicine, Department of Biomedical Imaging and Image-guided Therapy, Austria., Department of Radiology and Biomedical Imaging, University of California, San Francisco, United States., Department of Nuclear Medicine, Hokkaido University Graduate School of Medicine, Japan, Japan., Department of Nuclear Medicine, Klinikum rechts der Isar, Technical University of Munich., Department of Nuclear Medicine, Medical Faculty, University Duisburg-Essen, Germany., Department of Nuclear Medicine, Rostock University Medical Centre, Germany., Department of Nuclear Medicine, Ludwig-Maximilians-University Munich, Germany., Department of Nuclear Medicine, Aalborg University Hospital, Aalborg, Denmark., Department of Urology, Klinikum rechts der Isar, Technical University of Munich., Department of Urology, Ludwig-Maximilians-University of Munich, Munich., Institute of Medical Informatics, Biometry, and Epidemiology, Ludwig-Maximilians-University Munich.