Radium-223 May Add Small Benefit in Bone-Metastatic Breast Cancer

Patricia McKnight

December 20, 2022

The study covered in this summary was published on researchsquare.com as a preprint and has not yet been peer reviewed.

Key Takeaway

  • 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

  • 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.

  • Radium-223 selectively targets areas of bone metastases.

Study Design

  • 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.

  • Patients in study A received investigator's choice of single-agent endocrine therapy; patients in study B received exemestane plus everolimus.

  • Overall, 382 patients were randomly assigned to receive either radium-223 or placebo every 4 weeks for a total of six doses.

Key Results

  • 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).

  • However, patients in the radium-223 group did experience significant improvements in time to bone alkaline phosphatase progression (HR, 0.593; P = .0195).

  • 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).

  • 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%).


  • There were differences in study design between the two groups, including differences in endocrine regimens and variations in the duration of follow-up.

  • Enrollment was stopped early in both studies, which decreased the sample size.

  • Alkaline phosphatase measurements may have been missed.


  • 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.

For more news, follow Medscape on Facebook, Twitter, Instagram, and YouTube.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.