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Outcomes of Radium-223 and Stereotactic Ablative Radiotherapy Versus Stereotactic Ablative Radiotherapy for
Jarey H Wang1, Alexander D Sherry2, Soha Bazyar3
1Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD.
Summary
Adding radium-223 dichloride (Ra223) to stereotactic ablative radiation (SABR) metastasis-directed therapy (MDT) did not improve progression-free survival in men with bone metastatic oligometastatic castration-sensitive prostate cancer (omCSPC). High-risk mutations and T-cell receptor repertoire showed prognostic value.
Area of Science:
- Oncology
- Radiation Oncology
- Nuclear Medicine
Background:
- Metastasis-directed therapy (MDT) shows progression-free survival (PFS) benefits for oligometastatic castration-sensitive prostate cancer (omCSPC).
- Patients with bone metastatic (BM) omCSPC often experience disease recurrence after MDT.
- Radium-223 dichloride (Ra223), an alpha-emitter, targets bone metastases and may address subclinical disease.
Purpose of the Study:
- To investigate if adding Ra223 to stereotactic ablative radiation (SABR) MDT can delay disease progression in patients with BM omCSPC.
- To evaluate the efficacy and safety of SABR MDT combined with Ra223 compared to SABR MDT alone.
Main Methods:
- An investigator-initiated, multicenter, open-label phase II randomized clinical trial (RCT).
- Eligible men with recurrent omCSPC and bone metastases were randomized (1:1) to SABR MDT alone or SABR MDT with Ra223 (six cycles).
- The primary endpoint was composite PFS.
Main Results:
- The median PFS was 11.8 months for SABR MDT and 10.5 months for SABR MDT/Ra223 (aHR, 1.42; P = .24), showing no significant difference.
- Grade 3 treatment-related adverse events occurred in 6% of the SABR MDT arm and 17% of the SABR MDT/Ra223 arm.
- High-risk pathogenic mutations (ATM, BRCA1/2, RB1, TP53) were associated with worse PFS (HR, 5.95; P = .003), while T-cell receptor repertoire was prognostic for improved PFS (aHR, 0.45; P = .04).
Conclusions:
- Adding Ra223 to SABR MDT does not delay disease progression in patients with BM omCSPC.
- High-risk mutational signatures and T-cell receptor repertoire serve as prognostic biomarkers in omCSPC treated with SABR MDT.
- The study underscores the importance of collecting biological correlates in RCTs for omCSPC.
