A London hospital halted trials on a radiopharmaceutical for prostate cancer, saying it was so effective it would have been morally wrong not to have extended the treatment to the other patients in the nearly 1,000-man study.

The drug, radium-223 chloride, was linked with a 30 percent reduction in mortality in men with metastatic, castration-resistant prostate cancer, compared with those taking a placebo, the doctors said this week at the 2011 European Multidisciplinary Cancer Congress in Stockholm.

Radium-223 Chloride, also called Alpharadin, blasts bone metastases with alpha radiation. Bone metastases are a common development of advanced prostate cancer.

And alpha radiation is more effective at knocking out tumors because only one alpha particle is needed to kill a cancer cell, and the particles have a short range -- only a few millionths of a meter -- so healthy tissue is spared, according to Dr. Chris Parker, the lead investigator and an oncologist with Royal Marsden Hospital, where the phase III trial was conducted.

"This is the first drug targeted to bone metastases in prostate cancer to improve survival," he told reporters at a press conference, according to MedPage Today. "There are other bone drugs used in prostate cancer, but they help to minimize symptoms; they don't improve survival."

The randomized trial involved 922 patients. Median survival for men taking radium-223 chloride was 14 months, compared with 11.2 months for those on placebo. Side effects were moderate and lower for patients taking the drug, according to the researchers, and included nausea, diarrhea, vomiting and constipation. Bone pain was somewhat milder for those taking radium-233 chloride.

Algeta, an Oslo-based cancer drug company, is co-developing radium-223 chloride with Bayer Pharma AG. Algeta said it plans on filing applications with U.S. and European regulators, based on this study, by the the middle of next year. If the drug's approved, it will be commercialized by Bayer, Algeta said.