MONDAY, July 9 (HealthDay News) --The experimental drug abiraterone, which prevents testosterone production anywhere in the body, may reduce blood levels of the prostate cancer marker prostate-specific antigen (PSA) by half, new research shows.
The study also found that the drug can shrink tumors in men whose prostate cancer has continued to grow despite treatment.
The British findings were to be reported July 8 at the annual European Society for Medical Oncology meeting in Lugano, Switzerland.
Dr. Alison Reid, from The Institute of Cancer Research, and Dr. Gerhardt Attard, from The Institute and The Royal Marsden NHS Foundation Trust in London, reported on early results from two ongoing phase 2 trials of abiraterone in men with advanced prostate cancer.
Both trials have seen PSA levels reduced by 50 percent. PSA levels are a measure of a protein produced by cells in the prostate. Unusually high levels of the antigen indicate a growth in the prostate.
The men, all of whom had already been surgically or medically castrated to prevent testosterone production in the testes, were given 1,000 milligrams of abiraterone daily. The first study treated men who had not previously received chemotherapy.
Of the 34 men treated, 22 have seen their PSA levels drop at least 50 percent after two months. Tumors shrank in some of the patients, the researchers said.
In the second British study, researchers gave abiraterone to 28 men whose cancer was growing despite treatment with the standard chemotherapy drug docetaxel. Ten of these men have seen PSA declines of more than 50 percent that lasted at least three months. There have been no major side effects noted in the studies to date.
Male hormones primarily are produced in the testes but also in adrenal glands and other locations in the body. These hormones support prostate cancer growth, so a first step in treatment is to use medicine or surgery to prevent the testes from making hormones. However, this approach does not prevent other parts of the body from making male hormones. Abiraterone, which has to complete a phase 3 clinical trial before being ready for public sale, targets an enzyme which is necessary to the production of male hormones throughout the body.
Prostate cancer, one of the most commonly diagnosed cancers in the United States, was diagnosed in almost 186,000 American men in 2003, the most recent year for which data is available. That year, almost 30,000 men died from the disease.