Hormone-depleting drug appears to have efficacy in localized high-risk prostate tumors

by Bruce Sylvester – Emerging uses of FDA Approved Drugs –

A hormone-depleting drug approved in 2011 for the treatment of metastatic prostate cancer appears to help eliminate or nearly eliminate tumors in patients with aggressive cancers that have not metastasized, researchers reported in May at the 2012 Annual Meeting of the American Society of Clinical Oncology (ASCO) in June.

In the phase 2 study, the investigators studied abiraterone acetate (Zytiga) in combination with prednisone and surgery in 58 men with high-risk prostate cancer isolated to the prostate gland. Subjects were treated with either 3 or 6 months of the 2-drug regimen followed by prostatectomy.

At the end of treatment, one-third of the participants had no or almost no tumor tissue left.

“Very high-risk cancers localised to the prostate are rarely cured by prostatectomy alone,” said lead author Mary-Ellen Taplin, MD, Dana-Farber Cancer Institute, Boston, Massachusetts. “Therapies that combine surgery with older androgen-inhibiting drugs have not historically improved outcomes. This unmet need has given rise to efforts to develop new drugs capable of more completely reducing androgen levels within the prostate tumours.”

The investigators used half the standard dose of prednisone given with abiraterone acetate, to reduce side effects associated with steroids while maintaining benefits of protecting against steroid imbalances associated with abiraterone. But, there were no increased side effects from abiraterone, and the the researchers concluded that the lower dose of prednisone (5mg daily) is adequate in most situations.

“Most of the patients in this study had large tumours, high grade prostate cancers, and were at high risk for cancer spread,” said Dr. Taplin. “We’re very encouraged by the results and have begun another phase 2 study investigating another novel androgen signaling inhibitor, MDV3100, in the neoadjuvant setting for high risk prostate cancer. We are also developing a clinical trial program investigating the addition of the investigational drug ARN509 to abiraterone.”
“To prove the overall benefit of intensive androgen deprivation treatment in conjunction with prostatectomy, a large randomised clinical trial will need to be done,”  he added