Friday, May 25, 2018
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FDA OKs prostate cancer vaccine

WASHINGTON - The Food and Drug Administration yesterday approved the first treatment that uses a so-called cancer vaccine, a drug that trains the body's own immune system to fight the disease.

The drug, Provenge, developed by the Dendreon Corp., was approved to treat advanced prostate cancer. In clinical trials it extended the lives of patients about four months compared with a placebo.

Getting the immune system to attack cancer has tantalized scientists for decades because it promises to have fewer side effects than the harsh chemotherapy now used. But until now, the approach has yielded little but disappointment.

"The big story here is that this is the first proof of principle and proof that immunotherapy works in general in cancer, which I think is a huge observation," said Dr. Philip Kantoff, chief of solid tumor oncology at the Dana-Farber Cancer Institute in Boston and the lead investigator in Dendreon's largest clinical trial for the drug.

Provenge is not a preventive vaccine like those for measles, hepatitis, or even the new ones for cervical cancer, which prevent a viral infection that causes the cancer. Rather, it is a so-called therapeutic vaccine, used after prostate cancer has already been diagnosed.

Provenge has become a cause celebre among some patients. When the FDA declined to approve the drug three years ago, some prostate cancer patients and investors protested.

"I think it's fair to say that people are waiting for it," said Jan Manarite, who runs the telephone help line in Florida for the Prostate Cancer Research Institute, a patient advocacy group.

Some patients may be disappointed, however, because the company said it could produce enough vaccine to supply only 2,000 patients in the next year. Dendreon said Provenge would be available at first only in 50 centers that participated in the clinical trials. But manufacturing capacity will be expanded greatly in the coming year.

Provenge is personalized for each patient. The patient's white blood cells, which make up the immune system, are collected through a process often used for blood donations. The cells are then exposed to a protein often found on prostate tumors, combined with an immune system booster. The treated cells are then infused back into the patient three times over the course of a month.

A full treatment will cost $93,000. Dendreon officials defended that price, saying it was in line with those of other cancer drugs in terms of cost per extra month of life provided by the drug.

Men with prostate cancer typically have either radiation treatment or surgery to remove the prostate gland, followed by drugs that reduce the levels of the hormone testosterone, which fuels prostate tumors. Provenge was approved for men whose cancer has spread in the body and for whom the hormone-deprivation drugs no longer work but who still have minimal symptoms, or none at all.

The only approved treatment for these men before yesterday was the chemotherapy drug Taxotere, also known as docetaxel, which in clinical trials extended lives by about two or three months.

In the largest clinical trial of Provenge, involving 512 men, those who got Provenge had a median survival of 25.8 months after treatment, while those who got a placebo lived a median of 21.7 months. The main side effects were fever, chills, fatigue, and pain.

Doctors expect that Provenge might be used before Taxotere because it has fewer side effects. Many patients do not start on chemotherapy until their symptoms, mainly bone pain, have become obvious.

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