For orthopaedic researcher Joyce Keyak, Ph.D., finding ways to battle breast cancer is a personal as well as a professional mission. Her cousin died from the disease several years ago. Dr. Keyak still remembers the incredible pain her cousin experienced when the cancer spread to her spine. A new study released by Dr. Keyak and her colleagues at the University of California, Irvine, shows patients whose breast cancer metastasizes to their spines may have a better option than the usual treatment, which can include up to 10 sessions of radiation therapy. The study looked at alternative — injecting radioactive bone cement into the vertebral body — with promising results.

The UCI researchers collaborated with a colleague from St. Jude Heritage Medical Group in Fullerton, Calif., to investigate this technique. Dr. Keyak is presenting the team’s findings in the paper “Feasibility of Using Radioactive Bone Cement to Treat Vertebral Metastases” during the 55th Annual Meeting of the Orthopaedic Research Society, Feb. 22–25, 2009, in Las Vegas.

“With further development, this technology may yield a clinically feasible procedure that would eliminate the need for 10 radiation therapy sessions, making it more convenient for the patient,” says Dr. Keyak, an associate professor in UCI’s department of orthopaedic surgery. “This procedure would also deliver a higher dose to the bone metastases and a lower dose to the spinal cord and other normal tissues than conventional external beam radiation therapy, potentially improving the clinical outcome,” she explains.

“The negligible dose to the spinal cord would also make it possible to treat recurrent spinal tumors in patients who have already received the maximum allowable radiation dose to the spinal cord.”

According to the American Cancer Society, almost 185,000 people in the United States — mainly women — were diagnosed with invasive breast cancer in 2008. In addition, a study published in the journal Spine showed that, of those patients whose breast cancer metastasizes, almost 75 percent develop spine tumors.
Spinal metastases can cause pain and vertebral collapse. And, due to the proximity of the spinal cord and nerves, those tumors can lead to serious neurological complications. Conventional treatment often occurs in two phases:

1. A surgical procedure (vertebroplasty or kyphoplasty) in which bone cement is injected into the body to stabilize the bone
2. Subsequent external beam radiation therapy (or EBRT) to control tumor growth

The effectiveness of EBRT for spinal metastases is limited because the spinal cord restricts the dose of radiation that can be safely delivered. In addition, EBRT is typically provided in multiple sessions to reduce toxicity to the spinal cord, making treatment inconvenient for the patient.

The therapy investigated by Dr. Keyak and her colleagues would combine the two treatment phases into one procedure by mixing a radioactive compound with the injected cement. A single procedure using this radioactive bone cement would provide structural reinforcement to the bone while simultaneously irradiating the tumor from within (i.e., vertebral brachytherapy). Results of the study showed that a therapeutic dose of radiation would reach the intended bone without undue risk to tissue beyond a certain range (such as the spinal cord).

Once the results are validated, subsequent studies will look at the following:
• Refining the choice of radioisotope(s), amount of activity and geographic distribution of the cement
• Sensitivity of the radiation dose distribution to variations in bone size, density and tumor type; differences in bone cement formulations; and other factors associated with a potential clinical application

Source: American Academy of Orthopaedic Surgeons (AAOS)