1. Radium-223 administration improved survival in metastatic prostate cancer patients.
2. Various other end points, such as quality of care, also favored radium-223 over standard-of-care plus placebo.
Evidence Rating Level: 1 (Excellent)
Study Rundown: In this phase-3 clinical trial, alpha emitter radium-223 significantly improved survival in patients with castration-resistant metastatic prostate cancer. Radium-223 is a calcium mimetic and selectively binds to areas with increased bone turnover. The treatment was highly effective and the trial ended early. This offers hope for patients with similar conditions who may benefit from participating in clinical trials before FDA approval. The study excluded patients with visceral metastases; as a result, we do not know at this time whether the benefits of radium-223 can be extended to this subgroup of patients. Given its mechanism of action, radium-223 may also reduce bony complications in other cancers with osteoblastic or mixed bony metastases. Future clinical trials are needed to answer this question.
Click to read the study, published today in NEJM
Relevant Reading: Bone-targeted radium-223 in symptomatic, hormone-refractory prostate cancer: a randomized, multicentre, placebo-controlled phase II study
In-Depth [phase 3, randomized trial]: This study assessed the safety and efficacy of radium-223 alpha emitter in treating castration-resistant metastatic prostate cancer. The trial enrolled 921 patients from multiple treatment centers and divided them to receive either six injections of radium-223, 50 kBq/kg q4w or placebo in a 2:1 ratio. The trial ended early due to efficacy.
The primary end point was overall survival. At the interim analysis, radium-223 group had median overall survival of 14.0 months versus 11.2 months in the placebo group. Compared to placebo, radium-223 reduced the risk of mortality by 30% (hazard ratio, 0.70; 95% confidence interval, 0.55 to 0.88). The results were similar in the updated analysis– 14.9 months of survival in the radium-223 group and 11.3 months in the placebo group; reduction in risk of death was again 30%.
Secondary end points were numerous and all favored therapy with radium-223. These end points included time to the first symptomatic skeletal event (15.6 months vs 9.8 months), time to an increase in total alkaline phosphatase levels, time to an increase in PSA levels.
In safety evaluations, radium-223 appeared generally safe with minimal myelosuppresion.
By Xiaozhou Liu and Mitalee Patil
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