EMBARK Subgroup Analysis: Enzalutamide With Prior Radiotherapy for BCR Prostate Cancer

A new subgroup analysis of the EMBARK study was presented as a late-breaking abstract at the American Society for Radiation Oncology 2023 Annual Meeting.

The primary analysis of EMBARK—a phase 3 study of patients with high-risk biochemical recurrence (BCR) randomized (1:1:1) to receive enzalutamide plus leuprolide acetate, placebo plus leuprolide acetate, or enzalutamide monotherapy—demonstrated that after a median follow-up of 60.7 months, metastasis-free survival (MFS) was clinically meaningful and statistically superior for enzalutamide plus leuprolide acetate and enzalutamide monotherapy compared with placebo plus leuprolide acetate.

Swetha Sridharan, MBBS, and colleagues’ latest look at the data was dedicated to a subgroup analysis of MFS by prior radiotherapy. A total of 804 patients were reported to have received prior radiotherapy (enzalutamide plus leuprolide acetate, n=265; placebo plus leuprolide acetate, n=283; enzalutamide monotherapy, n=256). External beam radiotherapy was the most common prior radiotherapy received (71.3%, 74.6%, and 67.6%, respectively).

Blinded, independent central review revealed that in patients who received prior radiotherapy, MFS for enzalutamide plus leuprolide acetate and for enzalutamide monotherapy were superior to placebo plus leuprolide acetate.

Additionally, Dr. Sridharan and colleagues noted that in patients without prior radiotherapy, MFS for enzalutamide plus leuprolide acetate was superior to placebo plus leuprolide acetate, though no difference was observed between the enzalutamide monotherapy and placebo plus leuprolide acetate cohorts. “The number of MFS events was too low to draw any conclusions” in the no-prior-radiotherapy group, they added.

“If approved, enzalutamide combination therapy may represent a new standard of care for patients with high-risk biochemical recurrence and prior radiotherapy,” researchers concluded.