Dr. Choudhury on the Rationale Behind Adding Pembrolizumab to Radium-223 in mCRPC

Atish D. Choudhury, MD, PhD, co-director of the Prostate Cancer Center and senior physician at Dana-Farber Cancer Institute, as well as an instructor in medicine at Harvard Medical School, discusses the rationale behind combining pembrolizumab (Keytruda) with radium-223 (Xofigo) in patients with metastatic castration-resistant prostate cancer (mCRPC) as part of a phase 2 clinical trial.

The radiopharmaceutical radium-223 has demonstrated a survival benefit in patients with mCRPC to the bone; however, it is not usually associated with clinical responses, Choudhury says. Due to this, patients do not typically experience radiographic responses or a reduction in prostate-specific antigen levels, Choudhury explains. Immune checkpoint inhibitors, such as the PD-L1 inhibitor pembrolizumab, have been shown to elicit rare clinical responses in this population, Choudhury adds.

In a phase 2 clinical trial, investigators set out to answer the question of whether treatment with radium-223 could result in a more immunostimulatory microenvironment in the bone that would allow for pembrolizumab to be more effective, Choudhury concludes.