According to the results of a study published in Lancet Oncology, injection of the radioactive substance radium-223 produced relatively few side effects and improved a measure of bone turnover in men with hormone refractory prostate cancer and bone metastases.
Bone is one of the most common locations in the body to which cancer metastasizes, or spreads. The major cancer types that tend to metastasize to bone include multiple myeloma, breast, prostate, lung, kidney, and thyroid cancers. Bone metastases cause damage that may make the bone more susceptible to complications such as pain and fractures.
The goal of treatment for bone metastases is to relieve pain and reduce the risk of fracture. Treatment may consist of surgery, radiation therapy, pain medications, and/or bisphosphonate drugs.
One type of radiation therapy is called radiopharmaceutical therapy. This approach involves the injection of a radioactive substance, such as strontium-89 or samarium-153, into a vein. The substance is attracted to areas of bone that contain cancer. Providing radiation directly to the bone in this way destroys active cancer cells in the bone and can relieve symptoms. Common side effects of strontium-89 and samarium-153, however, include low levels of platelets and white blood cells.
Radium-223 is a type of radiopharmaceutical therapy that may produce fewer side effects. To explore radium-223 in the treatment of men with hormone refractory prostate cancer and bone metastases, researchers conducted a Phase II clinical trial among 64 patients. Study participants were treated with either radium-223 or a placebo for 12 weeks.
- Treatment with radium-223 reduced levels of bone-alkaline phosphatase (a marker of bone turnover).
- There was a suggestion that radium-223 decreased the risk of skeletal-related events such as increasing pain or fracture.
- Median overall survival was 65 weeks in patients treated with radium-223 and 46 weeks in patients treated with placebo.
- Radium-223 did not appear to increase the risk of blood-related adverse effects compared to placebo.
The researchers concluded that radium-223 was well tolerated and produced promising effects on bone, and that larger studies of this agent are warranted.
Reference: Nilsson S, Franzén L, Parker C et al. Bone-targeted radium-223 in symptomatic, hormone-refractory prostate cancer: a randomized, multicentre, placebo-controlled Phase II study. Lancet Oncology. 2007;8:587-94.