Results of a phase III clinical trial of the drug Enzalutamide, recently published in the New England Journal of Medicine, show the drug extends life by an average five months in the most advanced stages of prostate cancer.
"This is a major advance. Not only do we see more survival benefit than from traditional chemotherapy, but the side effects of Enzalutamide are much lower. It provides both more benefit and less harm—you get the quantification of more life, but also see quality of life improvements," said study co-author, Thomas Flaig, MD, medical director of the University of Colorado Cancer Center's clinical investigations shared resource.
The study, AFFIRM, followed 1,199 patients with prostate cancer who had progressed despite both hormonal and chemotherapy treatments, with two-thirds of patients receiving the drug Enzalutamide versus control. Median overall survival for patients in the treatment arm of the trial was 18.4 months compared to 13.6 months for patients in the placebo arm. In addition to prolonged survival, patients given Enzalutamide showed meaningful improvement in other measures including PSA blood levels, an increase from 3.0 months to 8.3 months in time until PSA progression, and an increase from 2.9 months to 8.3 months in overall progression-free survival.
The once-a-day oral drug works by blocking prostate cancer's ability to supply itself with androgens—hormones including testosterone that otherwise drive the cancer's growth. It does this by binding to cancer cells' androgen receptors, blocking their ability to grab androgen.
"Prostate cancer has traditionally been viewed as having two phases. First is the hormone-sensitive stage and second is the stage at which the disease is no longer dependent on hormones and we're forced to turn to more toxic chemotherapies,” explained Flaig. "This approach represents a much more potent and effective means of targeting the androgen receptor than possible with previously available agents. While this study examined the effect of adding Enzalutamide to standard androgen deprivation therapy, future studies could explore a single agent approach with this drug to treat prostate cancer.”