FDA OKs Vaccine Therapy for Prostate Cancer

The Food and Drug Administration approved the first therapeutic vaccine for prostate cancer today, after a three years of evaluations with the vaccine's manufacturers and researchers.

Earlier clinical trials of the vaccine, called Provenge, showed that the therapy could extend life by four to five months in men with advanced prostate cancer. But in 2007, the FDA asked for more research since studies curiously showed that Provenge seemed to extend life without slowing the progression of cancer.

"This is real big step," said Dr. David Penson, a researcher on the original Provenge studies and a professor of urologic surgery at Vanderbilt University in Nashville, Tenn. "You're using your body's own immune system to fight the cancer. In the future we hope it will make treatment more effective with few side effects."

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An estimated 220,000 men were diagnosed with prostate cancer in 2007 in the United States, according to the National Cancer Institute. About 28,000 men died from the disease that year.

Rather than obliterate new cells in the body as chemotherapy does, Provenge works by boosting the patient's own immune system.

Provenge Takes Intriguing Approach to Cancer

"It's not a miracle, but it's amazing that the immune system can still wake up even when a man has prostate cancer throughout his body," said Dr. Jonathan Simons, president and CEO of the Prostate Cancer Foundation.

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"In 1993 if you told someone that you could wake up the immune system to fight prostate cancer, they would have laughed you out of the room," said Simons.

About 18 years ago, Simons said scientists discovered that cells in our immune system called dendritic cells act as detectives that hunt down and identify potential invaders like cancer. The dendritic cells then "awake" or activate other cells in the immune system such at T-cells or B-cells to seek and destroy the cancer invaders.

Simons said it wasn't until 2000 that researchers believed the immune system of a person with severe prostate cancer could "wake up" and start to recognize the cancer as a disease.

Provenge works unlike other vaccines in which a standard dose is manufactured and distributed to doctors.

Men who are candidates for the vaccine must give a blood samples. The white blood cells are isolated, shipped to a specialized lab, and treated in a way that "trains" the white blood cells to recognize and attack cancer.

Small Steps Towards Extending Lives

Penson said a study of 500 men with metastasized, hormone-resistant prostate cancer confirmed the earlier finding that Provenge extends life by an average of four months. Men at that stage of prostate cancer usually have only one treatment option left -- a drug called Docetaxel, which has a "fair number" of side effects compared to Provenge.

"It has a survival benefit over placebo from three to four months," said Penson. "You know people look at me and say you know three to four months you're not curing anybody... but for someone who'd have 18 more months to live, you get 20 percent more life."

Considering how few treatment options are available for men at that time, some doctors worried whether there would be enough access to Provenge in future months. At the same time, others worried that more men would want Provenge than would be eligible for treatment.

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