Provenge provides a new treatment option for men with advanced prostate cancer, who currently have limited effective therapies available," Karen Midthun, acting head of the Food and Drug Administration's biologics center, said in a statement.

Unlike traditional vaccines that prevent a disease, Provenge treats prostate cancer by stimulating the body's own immune system to attack malignant cells. It is produced by taking cells from a patient's tumor and incorporating them into a vaccine that is injected back into the patient.

The field has been littered with failures. Dendreon is the first company to show a cancer vaccine can extend patient survival. In a late-stage study of 512 patients, men given Provenge lived an average of 4.1 months longer than those who got a placebo.

Common side effects were chills, fever and headache that lasted up to two days following infusion. This is seen as an advantage over the debilitating side effects typical of chemotherapy.

Most reactions were mild or moderate but one-quarter of patients reported a serious problem, the FDA said. Problems such as strokes were seen in 3.5 percent of Provenge patients compared with 2.6 percent in the placebo group.

Dendreon said Provenge would cost a total of $93,000 for the full treatment of three infusions.

Prostate cancer is the second most common cancer among U.S. men behind skin cancer and usually occurs in older men.

The FDA approved Provenge for hormone-resistant prostate cancer that has spread in the body but is causing no or minimal symptoms.

Dr. Len Lichtenfeld, deputy chief medical officer at the American Cancer Society, said Provenge would give a boost to future efforts to develop treatment vaccines for cancer.

"This is exciting because it does represent a proof of concept. (Provenge) does seem to prolong life in a very specific group of men," he said.

Other companies are exploring the field. GlaxoSmithKline (GSK.L) is studying a lung cancer vaccine while Bristol-Myers Squibb (BMY.N) is testing a melanoma vaccine.

Danish biotech Bavarian Nordic A/S (BAVA.CO) is about to start late-stage testing of a rival prostate cancer vaccine called Prostvac that does not need to be tailored to the individual patient.

By By Lisa Richwine Reuters