FDA OKs Vaccine Therapy for Prostate Cancer

Vaccine called Provenge works by revamping immune system to recognize cancer.

April 29, 2010— -- 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."

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.

"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.

"I think that many men will be eager to try this agent for their prostate cancer, but it's important to note that the pivotal clinical trials enrolled men with metastatic, castrate-resistant disease, not for earlier stages of disease," said Dr. Charles G. Drake, associate professor of Oncology, Immunology and Urology at Johns Hopkins Sidney Kimmel Comprehensive Cancer Center in Baltimore.

Barri Winiarski, a spokeswoman for Dendreon Corp., the company that makes Provenge, said the company would be able to treat 2,000 patients within the first 12 months. The company's single manufacturing facility for Provenge would be running by early 2011 and two more sites in California and Georgia would be open by mid-2011.

Critics and supporters of Provenge have said there are still questions about the results of the trials and how a cancer treatment could improve survival without actually shrinking cancer tumors.

"One vexing question remains about why Provenge would increase survival without improving progression-free survival, two factors that until now have always gone together," said Dr. Otis Brawley, chief medical officer for the American Cancer Society said in a statement.

" But even those who do not know why this could be have come around to agree this approach works and will soon be using it on patients who fit the criteria," he said.

Several more months of life might not be considered a "home run," but the method of treatment and the small step in a new direction has prostate cancer advocates and other cancer researchers excited.

"All of us want to see home runs, but the reality is we don't have something like that," said Dr. Nina Bhardwaj, director of the Tumor Vaccine Program at New York University Langone Medical Center in New York City. "Even in cancer when new chemo drugs are coming out if you can improve survival by four to six months, it's a big step."

"This represents a small but significant improvement and supports approaches that use of cell-based vaccines to treat cancer," said Bhardwaj.

However, as Bhardwaj predicted, cell-based vaccines like Provenge will be expensive. Patients have to pay for the expensive process of extracting the blood, the processing of the blood and the transport of all the samples.

"Being individualized therapy like that makes it expensive -- just like the bone marrow transplant," said Bhardwaj.

A spokeswoman from Dendreon Corp. said the company "has not yet set the price, however we expect it will be similar to other novel biologics that prolong survival."

Other "novel biologics" run from $50,000-$100,000 for a course of treatment.

However experts still see Provenge as a door to more research for various forms of cancer.

"We can now look forward to additional studies of this approach in breast cancer and melanoma, and eventually in other diseases," said Brawley. "Many experts feel the real impact of this immunotherapy approach may be more significant for cancer overall than for prostate cancer alone."

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