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Hi-Tech Tool Offers Breakthrough Cancer Treatment

It's designed to minimize radiation exposure to healthy tissue

SATURDAY, Jan. 24, 2004 (HealthDayNews) -- Cruise-missile technology has joined the battle against cancer.

CyberKnife is a device that delivers highly concentrated doses of radiation, beamed from the end of a flexible robotic arm, to precisely target tumors.

It lets physicians painlessly treat cancers of the brain, neck and spine -- even some that have been deemed inoperable -- without making a single incision.

The tool's pinpoint accuracy -- within a millimeter -- allows the maximum amount of radiation to target tumors, while minimizing exposure to healthy tissue, doctors familiar with CyberKnife say. But it's too soon to predict the instrument's potential impact on survival rates, some physicians add.

Dr. Mark J. Brenner uses CyberKnife at Sinai Hospital in Baltimore, where he is chief of radiation oncology.

"What this enables us to do is key in on the tumor with very, very precise margins. This is what radiation oncology has been aiming for all along," Brenner says. "This is the ultimate local therapy -- surgery without the scalpel."

CyberKnife, he says, provides an alternative to surgery as well as traditional radiation therapy and significantly reduces the amount of treatment time. Instead of taking weeks, a patient typically can be treated with the tool in a matter of days, Brenner says.

"It's just so different for me. In this field, you're sort of used to delaying gratification, not seeing immediate results, and I suddenly have something where I can see amazing results almost immediately," says Brenner, medical director of Sinai's CyberKnife Center. "It's a real joy. It's like medicine in the ideal."

Insurance companies also have embraced CyberKnife, which is cheaper than comparable surgery, Brenner says.

Conventional radiation therapy irradiates the tumor and a large amount of surrounding healthy tissue. But CyberKnife is a form of "stereotactic radiosurgery," which uses multiple beams of radiation converging to focus precisely on their target.

Gamma Knife, the first radiosurgical device, directs high-intensity radiation into a small area in the brain. But when the Gamma Knife is used, to keep the head immobile, the patient must wear a painful external metal frame attached to the skull by screws.

Unlike the Gamma Knife, the CyberKnife -- with its flexible, multi-jointed robotic arm -- can be used to treat tumors of the brain, neck and spine, and no rigid immobilization device is required. CyberKnife also provides continual monitoring of the target and compensates for slight patient movements using an image-guidance system.

CyberKnife's a marvel to watch in action, Brenner says. "It moves around very quietly doing this computer-controlled tai-chi," he says. "It looks like it's alive. It's elegant. It's so quiet, we tell patients to bring music."

CyberKnife was developed by Accuray Inc., a privately held, Sunnyvale, Calif., company, in conjunction with Stanford University. The device has treated more than 6,200 patients worldwide, the company says.

Each treatment, Accuray says, takes only a few hours and is normally done on an outpatient basis.

Dr. Thomas C. Gates, chairman of the Radiation Therapy Department at St. Mary Medical Center in Long Beach, Calif., says CyberKnife provides a means of doing radiosurgery beyond the brain.

"It's part of an ongoing evolution in radiation therapy in terms of being able to target the tumor more specifically than in the past and minimizing the dose to surrounding tissue," Gates says.

CyberKnife should permit higher doses of radiation by minimizing risk to non-tumorous tissue. But, Gates adds, "How much difference this is going to make in terms of cancer survival is not clear at this time."

"We're pretty good at controlling local [tumors]. The major problem with cancer is systemic disease," such as cancers that spread to the lymph nodes or through the bloodstream, he says.

Gates also says long-term effects of higher doses of radiation on healthy tissue are unclear. For instance, radiation exposure can be extremely dangerous, even fatal, in part of the lung, he says.

And even with the more precise targeting of radiation, Gates says, slight body movements such as those caused by a heartbeat or breathing can expose healthy tissue to radiation.

More information

For more on CyberKnife, visit the CyberKnife Society. Check with the National Cancer Institute to learn more about radiation therapy.

SOURCES: Mark J. Brenner, M.D., chief, radiation oncology, Sinai Hospital, Baltimore; Thomas C. Gates, M.D., chairman, Radiation Therapy Department, St. Mary Medical Center, Long Beach, Calif.
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