Photo Credit: Christoph Burgstedt

The first results from the phase 3 PEACE-3 study demonstrated that combining enzalutamide and radium-223 treatment improved both radiological progression-free survival (PFS) and overall survival (OS) in men with metastatic castration-resistant prostate cancer (mCRPC) and bone metastases.

In patients with mCRPC progression on androgen deprivation therapy (ADT), abiraterone and enzalutamide are standard-of-care first-line treatment options^1,2. Treatment with radium-223 has also shown to increase OS in this population³. However, the combination of radium-223 and abiraterone did not show any benefit in OS or event-free survival⁴.

The randomized phase 3 PEACE-3 study (NCT02194842) investigated whether the combination of enzalutamide and radium-223 improves survival over enzalutamide alone in patients with mCRPC. The trial enrolled 446 participants (with bone metastases and no prior treatment with enzalutamide) and randomly assigned to enzalutamide plus radium-223 or enzalutamide alone. The use of bone-protecting agents was mandatory. The primary endpoint was radiological PFS. Silke Gillessen, MD, from the Oncology Institute of Southern Switzerland presented the first results⁵.

The addition of radium-223 to enzalutamide significantly improved median radiological PFS: 19.4 versus 16.4 months (HR 0.69; 95% CI 0.54–0.87; P=0.0009). The radiological PFS rate at 24 months improved from 36% to 45%. In addition, median OS was significantly improved by radium-223: 42.3 versus 35.0 months (HR 0.69; 95% CI 0.52–0.90; P=0.0031). Radium-223 also improved the time to next systemic treatment (HR 0.57; 95% CI 0.44–0.75; P<0.0001) but not the time to symptomatic skeletal event (HR 0.93; 95% CI 0.62–1.38). The combination therapy was generally well tolerated; discontinuation due to toxicity was 11%, versus 7% in the enzalutamide alone arm. Drug-related grade greater than or equal to three AE rates were 28% and 19%, respectively.

“These results support the combination of enzalutamide plus radium-223 as a potential first-line treatment option for patients with mCRPC and bone metastases who have not received a prior androgen-receptor pathway inhibitor,” Dr. Gillessen concluded.

Medical writing support was provided by Marten Dooper.
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