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

2024; Society of Nuclear Medicine and Molecular Imaging; Volume: 65; Issue: 4 Linguagem: Inglês

10.2967/jnumed.123.266654

1535-5667

D. Andries Bosch, K.J.M. van der Velden, Irma M. Oving, Dirk Wyndaele, L. 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,

Bone health and treatments

Imaging before 223 Ra-dichloride ( 223 Ra) 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 223 Ra therapy. Methods: A secondary analysis of the data of a prospective observational study (NCT04995614) was performed. Patients received a maximum of 6 223 Ra 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 223 Ra 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 223 Ra 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 223 Ra therapy.