Enzalutamide Can Improve Outcomes for Men with Metastatic Prostate Cancer

The oral androgen receptor Enzalutamide improves outcomes for men with metastatic hormone-sensitive prostate cancer (mHSPC), according to a study presented during the American Society of Clinical Oncology (ASCO) Annual Meeting and published in The New England Journal of Medicine.

Researchers of this open label, randomized, phase III trial arbitrarily assigned 1,125 men to receive either testosterone suppression plus either open enzalutamide or the standard nonsteroidal antiandrogen therapy. The average follow-up in this study was 34 months. Overall survival was established as the primary end point, while secondary end points, determined by the prostate-specific antigen (PSA) level, included progression-free survival, clinical-progression-free survival, as well as adverse events.

Results of the study showed that there were 102 deaths in the enzalutamide group and 143 deaths in the standard-care group (HR=0.67; 95% CI, 0.52 to 0.86; P=0.002). Kaplan–Meier estimates used in the study suggest overall survival at three years were 80% (based on 94 events) in the enzalutamide group juxtaposed to 72% (based on 130 events) in the standard-care group. Moreover, improved results with enzalutamide were also seen in PSA progression-free survival (174 and 333 events, respectively; HR=0.39; P<0.001) and in clinical progression-free survival (167 and 320 events, respectively; HR=0.40; P<0.001). However, treatment discontinuation due to adverse events was more prevalent in the enzalutamide group than in the standard-care group (33 events and 14 events, respectively). Furthermore, fatigue was more common in the enzalutamide group with seizures occurred in seven patients in the enzalutamide group (1%) compared to zero in the standard-care group.

An Alternative to Chemotherapy

“These findings are truly practice-informing, adding an effective drug option in treating mHSPC,” said study co-chair Sweeney who presented results during the ASCO plenary session. “Adding enzalutamide to testosterone suppression in men with mHSPC can give much better cancer control and much longer survival. This is true both for patients with high burden of disease, with multiple bone metastases or liver metastases, as well as men with a lower burden of disease. The new treatment option is especially relevant for men who cannot tolerate chemotherapy and have a lower burden of disease.”

“The benefits of enzalutamide had already been established for prostate cancers that are no longer responding to hormonal therapy,” said Ian D. Davis, MBBS, PhD, ANZUP chair and study co-chair. “The actual result in patients starting hormonal therapy, noting patients had a 60% improvement in the time it takes to detect the cancer growing again along with a 33% increase chance of survival, was far higher than we expected.”