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ASCO GU 2024: Suspending Enzalutamide Monotherapy in High-Risk, Biochemically Recurrent Prostate Cancer

By: Jenna Carter, PhD
Posted: Monday, January 29, 2024

Findings from the EMBARK trial revealed that patients with metastasis-free, high-risk, biochemically recurrent prostate cancer showed clinical improvements after treatment with enzalutamide plus leuprolide acetate and enzalutamide monotherapy. Neal D. Shore, MD, FACS, of the Carolina Urologic Research Center, Myrtle Beach, South Carolina, and colleagues also reported that treatment was suspended in a subset of patients based on serum prostate-specific antigen (PSA) response; those who did not meet suspension criteria continued treatment. These study findings were presented at the 2024 American Society of Clinical Oncology (ASCO) Genitourinary (GU) Cancers Symposium (Abstract 15).

Patients with high-risk, biochemically recurrent prostate cancer were randomly assigned (1:1) to enzalutamide monotherapy (160 mg/d, open-label) or leuprolide acetate alone (22.5 mg every 12 weeks). Treatment was suspended at week 37 for patients who attained a PSA level less than 0.2 ng/mL at week 36. Treatment was, however, restarted when PSA levels reached at least 2 ng/mL (or 5 ng/mL for patients who had or did not have primary radical prostatectomy). The primary study outcome was metastasis-free survival, and the secondary outcome was the proportion of patients with undetectable PSA levels 2 years after treatment suspension.

Findings revealed that in those who suspended treatment, the 3-year metastasis-free survival rate was 88.1% (95% confidence interval [CI] = 83.8%–91.4%) with enzalutamide monotherapy and 90.0% (CI = 85.3%–93.2%) with leuprolide acetate alone; however, there was no difference between groups (hazard ratio [HR] = 0.840, 95% CI = 0.575–1.226; P = .3659). In the group that did not suspend treatment, the 3-year metastasis-free survival rates were 88.5% (CI = 68.5%–96.2%) and 66.9% (CI = 55.4%–76.1%), respectively; however, metastasis-free survival was longer with enzalutamide monotherapy vs leuprolide alone (HR = 0.340, 95% CI = 0.118–0.985; P = .0378). Based on these findings, the authors concluded that the treatment effect on metastasis-free survival was similar in both groups after treatment suspension.

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