A new drug for advanced prostate cancer patients has proved so effective that researchers stopped the clinical trial early to give all patients a chance to receive the life-extending medication, according to a UCSF-led study released Saturday.
The hormone treatment, Johnson & Johnson’s Zytiga, when added to a standard steroid therapy doubled the time it takes for the disease to progress in patients treated with the standard therapy alone, said the lead researcher, Dr. Charles Ryan, associate professor of clinical medicine at the UCSF Helen Diller Family Comprehensive Cancer Center.
The U.S. Food and Drug Administration last year approved Zytiga, also known as abiraterone, for use in men whose prostate cancer had spread to other parts of their body and had already been treated with chemotherapy. The FDA will have to approve it for patients who have not had chemotherapy before it can be marketed for broader use.
This trial focused on patients whose cancer had metastasized, may have been treated with other hormone therapies but had not yet gone through chemotherapy. The interim results are to be presented Saturday at the American Society of Clinical Oncology’s annual meeting in Chicago.
"If the FDA looks favorably upon the data … it will really change the standard of care in advanced prostate cancer away from chemotherapy toward a well-tolerated, oral therapy," Ryan said from Chicago. "It opens up the possibility of this life-prolonging therapy being given to a larger population of patients."
A treatable disease
Prostate cancer, the second most common form of cancer in males after only lung cancer, is diagnosed in about 200,000 men in the United States each year. And while it is generally treatable, the disease kills nearly 30,000 men a year.
Because their disease is often slow-growing, about a third of patients diagnosed with prostate cancer won’t be treated. Another third will undergo successful treatment, which could include surgery, various hormone therapies or chemotherapy.
Still, a third of patients will have recurrent or aggressive disease that may have been caught too late. Ryan said men tend to die when the cancer spreads outside the prostate, mostly to bone, and the patient becomes resistant to hormonal therapy. The cancer cells rely on testosterone to exist, so typically doctors treat patients with testosterone-blocking hormone therapy.
But patients become resistant when the cancer cells develop the ability to make their own hormone and learn to survive even in the face of the testosterone-blocking drugs, giving the disease the ability to progress, Ryan said.
Zytiga is the first FDA-approved drug that can go inside the cancer cell and block it from making its own testosterone.
The trial involved 1,088 men who were being treated by 151 cancer centers in 12 countries. Each was given a low dose of the steroid prednisone, which works to combat the cancer, but some received Zytiga while others were given a placebo.
All participants receiving the placebo drug were allowed in March to start taking Zytiga. Not only did they notice a slowdown in the progression of the disease, but patients also reported reduced pain and went longer before having to resort to chemotherapy.
If the FDA extends Zytiga’s approval to include patients who have not yet gone through chemotherapy, more health insurers will cover the drug. The final results of the trial are expected next year.