Radium-223 Treatment Outcomes in Patients with Metastatic Castration-Resistant Prostate Cancer: A Taiwan-Japan Collaborative Cohort Study.

BACKGROUND

This study examined oncologic outcomes associated with Radium-223 (Ra-223) administered at different treatment lines in patients with metastatic castration-resistant prostate cancer (mCRPC) with bone metastases, and evaluated the prognostic implications of biomarker responses-particularly prostate-specific antigen (PSA) and alkaline phosphatase (ALP)-during Ra-223 therapy.

MATERIAL AND

METHODS

Patients with mCRPC treated with Ra-223 between August 2016 and March 2023 were identified from the multi-institutional Chang Gung Research Database (Taiwan) and Hirosaki University Hospital (Aomori, Japan). The primary endpoint was the changes in biomarkers during Ra-223 treatment. Secondary endpoints included hematologic adverse events and survival outcomes. Multivariable Cox regression and sensitivity analyses were performed to adjust for baseline clinical factors and potential selection bias.

RESULTS

Among 306 included patients, earlier use of Ra-223 was associated with more favorable biomarker dynamics, including smaller post-treatment PSA increase and greater ALP reductions (p=0.003). Post-treatment PSA velocity was significantly lower, and post-Ra-223 survival was longer (both p<0.001), particularly in patients with ALP decreases or PSA increases <100% after Ra-223 treatment (p<0.01), corresponding to survival risk levels (low, intermediate, high). Although overall survival from mCRPC diagnosis differed by treatment line, survival from Ra-223 initiation was more strongly associated with biomarker dynamics than treatment line itself.

CONCLUSIONS

In this multicenter cohort, earlier use of Ra-223 in patients with mCRPC was associated with more favorable biomarker responses (PSA and ALP) and longer post-treatment survival. Decreases in ALP levels and limited PSA increases (<100%) were associated with distinct overall and post-treatment survival risk profiles and may serve as clinically useful prognostic indicators.