A Cutting Edge Alternative to Cutting

By Tiffany Sharples

Correction Appended: January 23, 2008

The CyberKnife system from Accuray Inc. allows doctors to treat tumors using a noninvasive, outpatient procedure that helps patients avoid the side effects of surgery, chemotherapy or other forms of radiation. It uses software and robotics to home in on cancerous tissue and deliver large doses of radiation while sparing surrounding healthy tissue.

Since CyberKnife was first approved in 1999 for tumor treatment, it has been used in some 40,000 cases, and demand is growing. "We're getting a lot of patients who are self-referring for treatment," says Dr. Euan Thomson, Accuray's CEO. "They're finding out about it through friends who have had treatment, and friends of friends, and they're turning up at their physicians specifically requesting CyberKnife." More than 100 hospitals worldwide have this $4 million robotic radiotherapy system; two-thirds of them are in the U.S. Accuray's order backlog has reached $600 million.

In Florida, prostate-cancer specialist Dr. Jay Friedland uses the system at Naples Radiation Oncology, where he has treated 243 patients since the end of 2004. Only two had the cancer recur, an outstanding result. "The beauty of this is that it's five treatments in five days," says Friedland. Other radiation therapies require as many as 45 treatments over nine weeks.

The software can target tumors accurately within 0.5 mm, preserving more healthy tissue than other techniques, with fewer side effects. The precision stems from software that incorporates two perspectives of the tumor and combines them, much the way human eyes work binocularly. It then guides the robot to fire the radiation beam on target.

CyberKnife has its limitations. It cannot be used to treat blood-borne cancers, and because it is a local therapy, it cannot be used alone to treat metastatic disease--when the cancer has spread to involve not only the original area, but other organs or tissues as well. It can, however, be combined with other systemic treatments, such as chemotherapy, to treat metastatic disease, and has often been used to treat solid metastatic tumors most commonly found in the lungs, liver, spine and brain. And the technology is continually evolving. The company's Synchrony program allows doctors to irradiate lung tumors by synchronizing the robotic arm with the rise and fall of a patient's breathing. Says Thomson: "Our dream is that we'll make radiosurgery an option for every cancer patient."

The original version of this article inaccurately stated that Accuray's CyberKnife system, which noninvasively delivers radiation to cancerous tissue, "can't be used when the disease has metastasized or to treat very large tumors." Since CyberKnife is a local therapy, it cannot be used alone to treat metastatic cancer, but in fact it can be combined with other systemic treatments, such as chemotherapy, to treat metastatic disease. And CyberKnife has proved useful for treating large tumors.