Advanced prostate cancer most commonly spreads or "metastasizes" to bone, interfering with bone strength and leading to pain, fractures, disability and death.

"This is really practice changing, and after regulatory approval, I think this is going to be a major player in advanced prostate cancer," Dr. Jean-Charles Soria of Institut Gustave Roussy in Villejuif, France, told MedPage Today.

The Alpharadin results were presented at the 2011 European Multidisciplinary Cancer Congress (EMCC) in Stockholm.

Bayer and Algeta conducted the phase III study enrolling 922 men with advanced prostate cancer. The men enrolled in the study had all either received docetaxel chemotherapy or were ineligible for the standard therapy. All the patients also had prostate cancer that had spread to bone. Patients were randomized to either injections of Alpharadin or a placebo.

The study was stopped early after an interim analysis concluded that Alpharadin decreased the risk of death by 30% compared to placebo. Median overall survival was 14 months for Alpharadin-treated patients compared to 11.2 months for patients in the placebo arm.

Alpharadin significantly delayed the time to first skeletal related events in patients by 5.2 months (13.6 months compared to 8.4 months) and also decreased reports of bone pain.

Commonly reported side effects of Alpharadin included nausea, diarrhea, constipation and vomiting -- all at rates similar to placebo. Rates of blood-related toxicity and infection were relatively low dueto the targeted nature of Alpharadin, researchers reported.

"It takes only a single alpha particle to kill a cell, and collateral damage is minimized because the particles have such a tiny range -- a few millionths of a meter," said Dr. Chris Parker of London's Royal Marsden Hospital during a media briefing at the EMCC conference, as reported by MedPage Today. "We can be sure that the damage is being done where it should be, to the metastasis, and very limited elsewhere."

Alpharadin's relatively few side effects may make it an ideal drug to be combined with other new prostate cancer therapies, including Johnson & Johnson's ( JNJ) Zytiga or Medivation's ( MDVN) still-experimental MDV-3100, researchers said.

Zytiga was recently approved as a treatment for advanced prostate cancer in patients who, like those in the Alpharadin study, were previously treated with chemotherapy. Medivation is expected to announce soon results from a phase III study in the same prostate cancer patient population.

Dendreon's ( DNDN) Provenge is used in patients with less advanced prostate cancer.

--Written by Adam Feuerstein in Boston.

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Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.

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