The CyberKnife, a precision radiotherapy system previously used only to treat cancer in the head and neck areas, has recently been approved by the Food and Drug Administration (FDA) for use anywhere in the body, say officials of the company that makes the device.

"With this system, we can now treat many patients with tumors that previously were untreatable, who might earlier have had no other options than to go into hospice or 'comfort care'," says Steven Chang, MD, assistant professor of neurosurgery at the Stanford University School of Medicine.

The broader approval adds an option for other patients as well, notes Chang.

The CyberKnife is a new twist on the technique of stereotactic radiosurgery. The technology has been in use in the US in other forms for more than 30 years, almost exclusively on brain or head and neck tumors.

In stereotactic radiosurgery, tightly-focused, high-intensity radiation beams are fired into a tumor from several different directions. In most such systems, a metal frame is fixed to the patient's head with screws or pins to immobilize the head during radiation. This minimizes the chance that a patient's movement will cause destruction of nearby normal tissue.

But until the recent broadened FDA approval of the CyberKnife, stereotactic radiosurgery was not widely used outside the head and neck area because other areas were more difficult to immobilize than the head and neck.

With the introduction of the CyberKnife system, a patient does not have to be immobilized to provide a stationary target.

Instead, when it is used to treat tumors outside the head, doctors inject small gold pellets into the tumor as markers and use CT scans or MRI to map the location of the tumor in relation to the markers.

Then, as a mobile robotic arm moves around the patient firing bursts of high-intensity radiation into the tumor from different positions, two X-ray cameras trained on the markers relay any marker movement to image tracking software that keeps the radiation focused on the tumor.

The usefulness of the CyberKnife in treating brain tumors led to FDA approval for its limited use at several cancer centers on tumors in other parts of the body, says Chang, who treated spinal tumors with the tool at Stanford.

The data from the treatments at those centers led to the FDA approval for use anywhere in the body where radiation is effective, he notes.

A neurosurgery expert agrees with Chang that the CyberKnife's wider-use approval holds promise.

"By delivering the tremendous power of radiation that's more focused, we hope to provide a better alternative than either conventional radiation therapy or conventional surgery for patients with tumors in the lung, the liver, the spine, and elsewhere," says Douglas Kondziolka, MD, professor of neurosurgery and radiation oncology at the University of Pittsburgh.

But Kondziolka says large numbers of patients have not yet been treated with the CyberKnife for tumors below the head and neck area, so it is not yet known whether it is better than conventional radiotherapy for those tumors.

"There is a huge population of cancer patients who are being very well treated with existing devices, and they shouldn't be panicking, thinking, 'I need to get to a facility with a CyberKnife,' because that's just not true," adds Kondziolka.

"For many patients, this would be the best treatment, and for others, I might choose a different procedure," says Chang. "What's important is that it increases the effective options for doctors and patients, and that's always a good thing."