Prostate-specific membrane antigen (PSMA) PET has a higher accuracy than CT and bone scans to stage patients with prostate cancer. We do not understand how to apply clinical trial data based on conventional imaging to patients staged using PSMA PET. Therefore, we aimed to evaluate the ability of bone scans to detect osseous metastases using PSMA PET as a reference standard. Methods: In this multicenter retrospective diagnostic study, 167 patients with prostate cancer, who were imaged with bone scans and PSMA PET performed within 100 d, were included for analysis. Each study was interpreted by 3 masked readers, and the results of the PSMA PET were used as the reference standard. Endpoints were positive predictive value (PPV), negative predictive value (NPV), and specificity for bone scans. Additionally, interreader reproducibility, positivity rate, uptake on PSMA PET, and the number of lesions were evaluated. Results: In total, 167 patients were included, with 77 at initial staging, 60 in the biochemical recurrence and castration-sensitive prostate cancer setting, and 30 in the castration-resistant prostate cancer setting. In all patients, the PPV, NPV, and specificity for bone scans were 0.73 (95% CI, 0.61-0.82), 0.82 (95% CI, 0.74-0.88), and 0.82 (95% CI, 0.74-0.88), respectively. In patients at initial staging, the PPV, NPV, and specificity for bone scans were 0.43 (95% CI, 0.26-0.63), 0.94 (95% CI, 0.85-0.98), and 0.80 (95% CI, 0.68-0.88), respectively. Interreader agreement for bone disease was moderate for bone scans (Fleiss κ, 0.51) and substantial for the PSMA PET reference standard (Fleiss κ, 0.80). Conclusion: In this multicenter retrospective study, the PPV of bone scans was low in patients at initial staging, with 57% of positive bone scans being false positives. This suggests that a large proportion of patients considered low-volume metastatic by the bone scan actually had localized disease, which is critical when applying clinical data from trials such as the STAMPEDE M1 radiation therapy trial to patients being staged with PSMA PET.
Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 2023 Aug 17 [Epub ahead of print]
Thomas A Hope, Matthias Benz, Fei Jiang, Daniel Thompson, Francesco Barbato, Roxana Juarez, Miguel Hernandez Pampaloni, Martin Allen-Auerbach, Pawan Gupta, Wolfgang P Fendler, Jeremie Calais
Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California; ., Ahmanson Translational Theranostics Division, Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, UCLA, Los Angeles, California., Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, California; and., Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California., Department of Nuclear Medicine, University of Duisburg-Essen and German Cancer Consortium, University Hospital Essen, Essen, Germany.