Xtandi Now Indicated for the Treatment of Metastatic Castration-Sensitive Prostate Cancer

On December 16, 2019, the FDA approved a new indication for enzalutamide (Xtandi; Pfizer, Astellas) for the treatment of patients with metastatic castration-sensitive prostate cancer. Enzalutamide was previously approved for the treatment of patients with nonmetastatic and metastatic castration-resistant prostate cancer.

This latest approval of enzalutamide was based on results of the ARCHES study, a double-blind, randomized, multinational, phase 3 clinical trial of patients with metastatic castration-sensitive prostate cancer treated at sites in the United States, Canada, Europe, South America, and the Asia-Pacific region.

A total of 1150 patients were randomized in a 1:1 ratio to receive 160 mg of enzalutamide daily or placebo. Patients continued on a luteinizing hormone–releasing hormone agonist or antagonist or had a history of bilateral orchiectomy.

The main efficacy outcome measure in the trial was radiographic progression-free survival (PFS), defined as the time from randomization to radiographic disease progression at any time or death within 24 weeks after treatment discontinuation. Radiographic disease progression was defined by identification of ≥2 new bone lesions on a bone scan with confirmation (Prostate Cancer Working Group 2 criteria) and/or progression in soft-­tissue disease.

Treatment with enzalutamide significantly reduced the risk for radiographic progression or death compared with placebo (hazard ratio, 0.39; 95% confidence interval, 0.3-0.5; P <.0001). Overall survival data were not mature at the time of radiographic PFS analysis.

“Men with metastatic castration-sensitive prostate cancer face complex treatment decisions, and it is critical for physicians and patients to have as much information as possible when deciding on all of the options available,” said lead investigator Andrew J. Armstrong, MD, MSc, Professor, Medicine, Surgery, Pharmacology, and Cancer Biology; and Director, Research, Duke Cancer Institute’s Center for Prostate and Urologic Cancers, Durham, NC, in a press release. “The research supporting the FDA approval and updated treatment guidelines provide physicians and patients with compelling evidence to consider enzalutamide as a treatment option for men with this disease,” he added.

The most common adverse reactions (≥5%) that occurred more frequently in the enzalutamide arm compared with the placebo arm were hot flushes (27% vs 22%, respectively), asthenic conditions (24% vs 20%, respectively), hypertension (8% vs 5.6%, respectively), fractures (6.5% vs 4.2%, respectively), and musculoskeletal pain (6.3% vs 4%, respectively).

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