Dr. Antonarakis on Sipuleucel-T Plus Radium-223 in Bone-Metastatic CRPC

Emmanuel S. Antonarakis, MBBCh, professor of oncology, Johns Hopkins Medicine, discusses a phase II trial evaluating the combination of sipuleucel-T (Provenge) plus radium-223 dichloride (Xofigo) versus sipuleucel-T alone in patients with asymptomatic bone-metastatic castration-resistant prostate cancer (mCRPC).

In a phase II study, investigators theorized that radium-223 plus sipuleucel-T would enhance immune response, and lead to an improvement in clinical outcomes in this patient population. Synergy was observed in the combination arm, which was evidenced by prostate-specific antigen (PSA) responses, Antonarakis says. There were 5 confirmed PSA responses (50%) with the combination compared with 0 PSA responses (50%) in the control arm.

Moreover, there was a prolongation of radiographic progression-free survival (PFS) with the combination at 9.3 months versus 3.1 months with sipuleucel-T alone. This was a statistical difference, Antonarakis explains. While the study had limitations and comprised a small number of patients, these data are expected to lead to a larger study evaluating this combination in a broader patient population with longer follow-up, he concludes.

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