MONDAY, May 16 (HealthDay News) -- For men with advanced hormone-resistant prostate cancer who have also failed chemotherapy, the new drug Zytiga (abiraterone acetate) along with the steroid prednisone appears to increase survival modestly, a new study reports.

Based on data from the ongoing clinical trial, Zytiga was approved by the U.S. Food and Drug Administration in April. It works by inhibiting the production of the male hormone testosterone, which promotes the growth of cancer cells. In this regard, the drug mimics hormone therapy.

"Abiraterone prolonged overall survival in this patient population that had extremely limited therapeutic options after chemotherapy," lead researcher Dr. Fred Saad, chief of urology at Notre-Dame Hospital in Montreal, Canada, said during a Monday morning press conference.

Men taking the drug combination had an average survival of 14.8 months, compared with 10.9 months for men taking a placebo.

"Abiraterone represents a valuable treatment option for patients with metastatic, castration [hormone]-resistant prostate cancer who had been treated previously with chemotherapy, with very manageable treatment-related toxicity," Saad said.

The study findings were scheduled to be presented Monday at the American Urological Association's annual meeting, in Washington D.C. Because the study was presented at a meeting, the data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.

The study included 1,195 men with prostate cancer who did not respond to hormone therapy and had failed earlier chemotherapy. The researchers, from 147 hospitals across 13 countries, randomly assigned the men to take either Zytiga plus prednisone, or a placebo.

The drug combination was well tolerated and resulted in less fatigue, back pain and spinal compression among the men taking it, compared with the placebo, Saad said.

The most common side effects among those taking Zytiga and prednisone were lower levels of white blood cells, fluid retention, low potassium levels, abnormal liver function tests, high blood pressure and heart problems, the researchers noted.

A one-month supply of 120 pills of Zytiga costs $5,000, said Kelly McLaughlin, a spokeswoman for the maker of the drug, Centocor Ortho Biotech Inc., and sponsor of the study.

"This study tells us that there is a form of hormonal therapy, abiraterone, that works in people who had standard hormonal therapy and chemotherapy," said prostate cancer expert Dr. Anthony D'Amico, chief of genitourinary radiation oncology at Brigham and Women's Hospital in Boston.

"It will provide people with late-stage disease with an opportunity for an extended survival that they didn't have before. I can't say it's a home run because it's only a few months improvement," he added.

Very aggressive prostate cancer may be able to make its own testosterone, which the cancer cells need to grow. "Zytiga blocks that," D'Amico explained.

"This drug provides longer life and better quality of life to men with very advanced prostate cancer," D'Amico said. "There are studies now to see if this drug will improve cure rates in men with advanced, but not metastatic [cancer that has spread to other organs], prostate cancer," he added.

More information

For more on prostate cancer, visit the American Cancer Society.