By Rob Stein
Washington Post Staff Writer
Friday, April 30, 2010; A03
The first cancer treatment that harnesses the power of a patient's immune system to fight tumors won government approval Thursday, a step scientists and patient groups hailed as what could be the beginning of a new era in cancer therapies.
The Food and Drug Administration approved Provenge, sometimes called a "cancer vaccine" because it stimulates the immune systems of men with advanced prostate cancer to attack their malignancies.
While the benefit of the approach is modest -- extending the lives of patients by a few months -- it was welcomed by researchers and patient advocates who had fought for years for the approval.
"The availability of Provenge provides a new treatment option for men with advance prostate cancer, who currently have limited effective therapies available," said Karen Midthun, acting director of the FDA's Center for Biologics Evaluation and Research, in announcing the approval.
Researchers said they hoped it would be the first in a series of similar treatments for other cancers. Unlike a standard vaccine, which is given before a person gets sick to stimulate their immune system to fight off infections, Provenge is an example of "therapeutic vaccine," which is designed to attack cancer cells in a person's body. Similar vaccines are showing promise for a variety of other cancers, including breast cancer, lung cancer, melanoma and lymphoma.
"This is great news," said Philip Kantoff, an oncologist at the Dana-Farber Cancer Institute in Boston and a professor of medicine at the Harvard Medical School who helped study Provenge. "This is really a proof-of-principle that you can harness the immune system and fight cancer. This is something the world has been working on for decades."
Prostate cancer strikes 192,00 men in United States each year and kills about 27,000, making it the second most common type of cancer, after skin cancer. Currently, the only therapies are surgery, radiation, hormones and one chemotherapy drug called Taxotere, which has been shown to extend the lives of the most advanced patients by an average of two months.
To produce Provenge, doctors remove white blood cells from patients, expose the cells in the laboratory to a protein found on most prostate cancer cells and another substance, and infuse the cells back into the patient.
In a study involving 512 patients with advanced prostate cancer, Provenge increased overall survival by about four months, boosting median survival from 21.7 months to 25.8 months.
Dendreon, which developed the vaccine, has been trying for years to win FDA approval. Critics said the delay exemplified the need to pass legislation that would require the agency to make experimental treatments available sooner.
But an FDA spokeswoman defended the agency, saying the delay was necessary because of "deficiencies" in the Seattle company's initial application that "precluded" approval. More study was needed to prove the vaccine's effectiveness, she said.
"Without this information, FDA could not make an approval determination," FDA spokeswoman Shelly Burgess said in an e-mail.