Newer Targeted Medication for Metastasized Cancer

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ECCO-ESMO: Radium-223 Improves Prostate Cancer Survival

By Charles Bankhead, Staff Writer, MedPage Today
Published: September 23, 2011
Reviewed by Dori F. Zaleznik, MD; Associate Clinical Professor of Medicine, Harvard Medical School, Boston.

STOCKHOLM -- Men with metastatic, castration-resistant prostate cancer lived significantly longer when treated with a first-in-class alpha pharmaceutical that targets bone metastases, data from a large phase III trial showed.

Treatment with radium-223 chloride (Alpharadin) was associated with a 30% reduction in the odds of dying during follow-up. The difference was associated with a three-month increase in median overall survival, when the trial ended prematurely at the recommendation of the monitoring committee.

Patients treated with the investigational agent also had fewer skeletal-related events (SREs), and the drug was well tolerated, investigators reported here at the European Multidisciplinary Cancer Congress, formerly known as the Congress of the European Cancer Organizations and Congress of the European Society for Medical Oncology (ECCO-ESMO).

Action Points
>Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
>Explain that use of radium-223, which selectively targets bone metastases with high-energy, short-range alpha particles, increased overall survival in men with castration-resistant prostate cancer metastatic to bone in a phase III trial halted early due to these results.
>Note that the treatment was not associated with immunosuppression or other reported adverse effects.

"This is the first drug targeted to bone metastases in prostate cancer to improve survival," Chris Parker, MD, of the Royal Marsden Hospital in London, said during an ECCO-ESMO press briefing. "There are other bone drugs used in prostate cancer, but they help to minimize symptoms; they don't improve survival.
"In my opinion, radium-223 is likely to become a new standard of treatment for advanced prostate cancer."
Two key contributors to the program here seconded Parker's optimism regarding future use of radium-223.
"This is really practice changing, and after regulatory approval, I think this is going to be a major player in advanced prostate cancer," said Jean-Charles Soria, MD, of Institut Gustave Roussy in Villejuif, France, and co-chair of the meeting's scientific program.
"I agree completely. This is a very important finding, certainly practice changing, and very likely to become a standard of care, at a different speed in different countries, but all over the world," said ECCO president Michael Baumann, MD, of the University of Hamburg in Germany.
Radium-223 selectively targets bone metastases with high-energy, short-range alpha particles. The radiopharmaceutical has an affinity for bone similar to that of calcium, in particular, homing in on areas of new bone formation.
"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 Parker. "We can be sure that the damage is being done where it should be, to the metastasis, and very limited elsewhere."
Advanced prostate cancer offered a logical patient population for evaluating the radium-223, as about 90% of patients with advanced disease develop bone metastases. In many cases, bone is the only site of metastatic spread.
Parker presented results from a randomized trial involving 922 men with advanced prostate cancer, a majority of whom had already received docetaxel. The remaining patients either were ineligible for docetaxel or had refused the therapy. All of the patients had at least two bone metastases documented by scintigraphy, and none had visceral metastases.
Investigators randomized the patients 2:1 to radium-223 or placebo, in addition to standard care. Each patient randomized to the alpha pharmaceutical received six injections, one every four weeks. The primary endpoint was overall survival.
A planned interim analysis occurred after 314 deaths. At that point, the data revealed a hazard ratio of 0.695 in favor of the radium-223 arm (P=0.00185).
Median overall survival was 14.0 months in the study arm and 11.2 months in the placebo arm.
Parker emphasized the favorable safety profile demonstrated by radium-223 in the trial. Hematologic toxicity consisted of neutropenia in 4% of patients (2% grade 3-4) and thrombocytopenia in 8% (4% grade 3-4).
The most common nonhematologic toxicities were bone pain (43 with radium-223 versus 58% in the placebo group), diarrhea (22% versus 13%), nausea (34% versus 32%), vomiting (17% versus 13%), and constipation (18% in both groups).
Grade 3-4 bone pain affected 18% of the radium-223 group and 23% of the placebo arm. Other grade 3-4 toxicities were uncommon.
Parker predicted that the favorable results will lead to clinical evaluation of radium-223 in other cancers that frequently metastasize to bone.
"We believe that our trial may have paved the way for improvements in survival for very many cancer patients," he said.

The authors reported no relevant disclosures.