The study covered in this summary was published on researchsquare.com as a preprint and has not yet been peer reviewed.
Key Takeaway
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In patients with HR-positive bone-metastatic breast cancer, a pooled analysis of two trials showed a trend favoring radium-223 plus endocrine therapy compared with endocrine therapy alone for bone-related endpoints but not for progression-free or survival endpoints.
Why This Matters
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Most women with advanced breast cancer experience skeletal metastases, which puts them at increased risk for bone-related events that can impair quality of life.
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Radium-223 selectively targets areas of bone metastases.
Study Design
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Researchers pooled analyses from two double-blind, placebo-controlled studies that explored whether adding radium-223 to endocrine therapy for women with HR-positive bone-metastatic breast cancer improved bone-related endpoints.
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Patients in study A received investigator’s choice of single-agent endocrine therapy; patients in study B received exemestane plus everolimus.
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Overall, 382 patients were randomly assigned to receive either radium-223 or placebo every 4 weeks for a total of six doses.
Key Results
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The median skeletal event-free survival was 22.2 months in the radium-223 arm, vs 19.9 months in the placebo arm — a nonsignificant difference (hazard ratio [HR], 0.81; P = .1389).
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However, patients in the radium-223 group did experience significant improvements in time to bone alkaline phosphatase progression (HR, 0.593; P = .0195).
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Radiographic progression-free survival and overall survival were not significantly different between the two groups (HR, 0.956; P = .704; and HR, 0.89; P = .441, respectively).
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Treatment-emergent adverse events were reported in more than half of patients in the radium-223 arm (50.3%), vs more than one third (35%) of patients in the placebo arm. The rate of grade 3 and 4 events was also higher in the radium-223 arm (25.7% vs 8.5%).
Limitations
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There were differences in study design between the two groups, including differences in endocrine regimens and variations in the duration of follow-up.
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Enrollment was stopped early in both studies, which decreased the sample size.
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Alkaline phosphatase measurements may have been missed.
Disclosures
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The study was supported by Bayer HealthCare.
This is a summary of a preprint research study, “Radium-223 in Women With Hormone Receptor-Positive Bone-Metastatic Breast Cancer Receiving Endocrine Therapy: Pooled Analysis of Two International, Phase 2, Randomized, Double-Blind, Placebo-Controlled Trials.” The study has not been peer reviewed. The full text can be found at researchsquare.com.
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