RT Journal Article SR Electronic T1 The Impact of Baseline PSMA PET/CT Versus CT on Outcomes of 223Ra Therapy in Metastatic Castration-Resistant Prostate Cancer Patients JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 541 OP 547 DO 10.2967/jnumed.123.266654 VO 65 IS 4 A1 Bosch, Dianne A1 van der Velden, Kim J.M. A1 Oving, Irma M. A1 Wyndaele, Dirk N.J. A1 Weijs, Leo E. A1 van Schelven, W. Dick A1 Oyen, Wim J.G. A1 te Beek, Erik T. A1 van de Luijtgaarden, Addy C.M. A1 Somford, Diederik M. A1 Nagarajah, James A1 Hermsen, Rick A1 Mehra, Niven A1 Gerritsen, Winald R. A1 van der Doelen, Maarten J. A1 van Oort, Inge M. YR 2024 UL http://jnm.snmjournals.org/content/65/4/541.abstract AB Imaging before 223Ra-dichloride (223Ra) therapy is crucial for selecting metastatic castration-resistant prostate cancer (mCRPC) patients with bone-only disease. The purpose of this study was to evaluate if baseline prostate-specific membrane antigen (PSMA) PET/CT (bPSMA) versus CT is associated with outcomes of 223Ra therapy. Methods: A secondary analysis of the data of a prospective observational study (NCT04995614) was performed. Patients received a maximum of 6 223Ra cycles and were retrospectively divided into the bPSMA or baseline CT (bCT) groups. All patients received baseline bone scintigraphy. Primary endpoints were alkaline phosphatase and prostate-specific antigen response. Secondary endpoints were overall survival (OS) and radiologic response. Results: Between 2017 and 2020, 122 mCRPC patients were included: 18 (14.8%) in the bPSMA group and 104 (85.2%) in the bCT group. All baseline characteristics were comparable. No significant differences in alkaline phosphatase or prostate-specific antigen response were found. The bCT group showed an OS significantly shorter than that of the bPSMA group (12.4 vs. 19.9 mo, P = 0.038). In 31 of 76 patients (40.1%) in the bCT group who also received posttherapy CT, lymph node or visceral metastases (soft-tissue involvement [STI]) were detected after 223Ra therapy, compared with 0 of 15 patients in the bPSMA group who received posttherapy PSMA PET/CT or CT. No significant difference in OS was found between patients in the bCT or posttherapy CT subgroup without STI (46/76) and the bPSMA group. Conclusion: bPSMA versus CT does not seem to impact biochemical response during 223Ra therapy in mCRPC patients. Nevertheless, patients in the bCT group had a significantly shorter OS, most likely due to underdetection of STI in this group. Therefore, replacing bCT with PSMA PET/CT appears to be a valuable screening method for identifying patients who will benefit most from 223Ra therapy.