(Associated Press) -- For the first time, an experimental drug has extended the lives of men with advanced prostate cancer who are no longer responding to other treatments and are out of options for fighting the disease, a company-led study found.

The benefit was modest -- an extra 10 weeks -- but cancer specialists were excited because no chemotherapy until now has been shown to boost survival in such men. And like any new drug tested on worst-case patients, there are hopes it will do better when tested in men who aren't as sick.

The drug is cabazitaxel, made by the French company Sanofi-Aventis SA. The federal Food and Drug Administration has said it will give it a quick review, which means it could be on the market soon.

In the study, the drug reduced the risk of dying during roughly one year of treatment by 30 percent, compared to another chemotherapy medicine that eases symptoms but does not prolong life, said Dr. Oliver Sartor of New Orleans' Tulane University.

He led the study and gave results in a telephone news conference Wednesday. They will be presented Friday at a meeting of the American Society of Clinical Oncology and several other groups. The study was sponsored by Sanofi, and most of the researchers work or consult for the firm.

Sanofi would not give a price estimate for the drug, which it plans to name Jevtana. Its potential market is around 15,000 to 20,000 men in the United States each year, Sartor said.

Prostate cancer is usually treated with surgery, radiation or medicine that blocks testosterone, a hormone that helps the cancer grow. When those fail, or if the cancer has spread so much that surgery won't help, the only approved treatment is docetaxel, sold as Taxotere by Sanofi.

"It eventually will fail in all men -- Taxotere doesn't cure people," Sartor said.

Cabazitaxel (kuh-BAH-zuh-TAX-uhl) is a chemical cousin of Taxotere designed to evade the mechanism that cancer cells use to resist chemo.

The study involved 755 men from several dozen countries. All were given prednisone, which eases pain and improves appetite. They also were given either periodic infusions of cabazitaxel or mitoxantrone, a chemotherapy sold as Novantrone by Melville, N.Y.-based OSI Pharmaceuticals.

Men in the cabazitaxel group lived a little more than 15 months on average, versus less than 13 months for those given the other drug.

"This is impressive," said Dr. Nicholas Vogelzang, a cancer specialist at US Oncology Research, a large private practice cancer speciality group in Las Vegas. He had no role in the study but helped review it for the oncology society.

Chemo has been a last-resort treatment for prostate cancer, but "now that there is something that works, the therapy might be given earlier and the survival advantage might be greater," he said.

One drawback: serious side effects were more common with cabazitaxel -- 57 percent suffered them versus 39 percent for the other drug. Most common were severely low white blood cell counts, diarrhea, nausea and fatigue.

The news comes on the same day that the American Cancer Society revised its prostate cancer screening guidelines to emphasize the potential risks of annual testing and digital rectal exams. These can lead to unnecessary biopsies and treatments that do more harm than good, says the society, which recommends that men talk with their doctors about whether screening is wise.

Besides the experimental chemo drug, another potential treatment is on the horizon for advanced prostate cancer: Dendreon Corp.'s Provenge vaccine, which trains the immune system to fight tumors. It's called a vaccine even though it treats disease rather than prevents it.

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