ASCO: Radium-223 Helps in Hormone-Refractory Prostate Cancer

CHICAGO, June 4 -- Radium-223, an investigational bone-seeking radioisotope, appeared to slow progression of skeletal metastases in hormone-refractory prostate cancer, researchers reported here.

In a phase II study of 64 men, bone-alkaline phosphatase -- a marker for progression of hormone-refractory prostate cancer -- decreased by a median of 65.6% after four radium-223 treatments, said yvind S. Bruland, M.D., Ph.D., of the Norwegian Radium Hospital Trust in Oslo, Norway. This compared with a 9.3% increase in a placebo group (P

Dr. Bruland said the four injections of radium-223 were so well tolerated that his group is considering a study using a six-injection protocol.

Unlike other radioisotopes, radium-223 had little to no myelotoxic effect. He said this was not surprising since radium-223 was specifically chosen because it emits alpha radiation, which has higher energy and travels less distance than beta radiation.

"So it doesn't get into the bone marrow but has a significant effect on bone metastases," he said.

There was no significant difference in time to first skeletal-related event -- 14 weeks in the radium group and 11 weeks in the placebo group.

Dr. Bruland said, however, that the study has a number of limitations including its small sample size and the fact that all patients also received external-beam radiation.

Moreover, he noted that when the study was started docetaxel (Taxotere) was not really the standard of care in Scandinavia so radium-223 has not been evaluated in the setting of current standard treatment.