The Impact of Baseline PSMA PET/CT Versus CT on Outcomes of 223Ra Therapy in Metastatic Castration-Resistant Prostate Cancer Patients.

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.

Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 2024 Feb 29 [Epub ahead of print]

Dianne Bosch, Kim J M van der Velden, Irma M Oving, Dirk N J Wyndaele, Leo E Weijs, W Dick van Schelven, Wim J G Oyen, Erik T Te Beek, Addy C M van de Luijtgaarden, Diederik M Somford, James Nagarajah, Rick Hermsen, Niven Mehra, Winald R Gerritsen, Maarten J van der Doelen, Inge M van Oort

Department of Urology, Radboud University Medical Center, Nijmegen, The Netherlands., Department of Medical Oncology, Ziekenhuisgroep Twente, Almelo, The Netherlands., Department of Nuclear Medicine, Catharina Hospital, Eindhoven, The Netherlands., Department of Radiology and Nuclear Medicine, Ziekenhuisgroep Twente, Almelo, Netherlands., Department of Nuclear Medicine, Medical Center Leeuwarden, Leeuwarden, The Netherlands., Department of Radiology and Nuclear Medicine, Rijnstate Hospital, Arnhem, The Netherlands., Department of Nuclear Medicine, Reinier de Graaf Gasthuis, Delft, The Netherlands., Department of Medical Oncology, Reinier de G raaf Gasthuis and Reinier Haga Prostate Cancer Center, Delft, The Netherlands., Department of Urology, Canisius-Wilhelmina Hospital, Nijmegen, The Netherlands., Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands., Department of Nuclear Medicine, Canisius-Wilhelmina Hospital, Nijmegen, The Netherlands; and., Department of Medical Oncology, Radboud University Medical Center, Nijmegen, The Netherlands., Department of Urology, Radboud University Medical Center, Nijmegen, The Netherlands; .