What distinguishes the CyberKnife, Shankar said, is "its uncanny accuracy." Moreover, he said, "it's the only machine with a robotic arm, the only one that treats tumors in real time and the only one where the number of radiation beams you can direct (at a tumor) is unlimited." For Martin, compared with an actual surgery for her first lung cancer, which she describes as "the worst experience of my life," the CyberKnife treatments were uneventful and spanned only a few days."You lay there for two to three hours and that's it," she said. "This robot thing moves around you and then it's over." Before treatment, Shankar implanted gold seeds the size of rice at her tumor sites. The radiation machine then targeted the seeds, tracking Martin's movements and adjusting to her breathing pattern every few seconds, before delivering the prescribed radiation dose.

Some prefer 'tried and true'

The Cancer Care Centers of Brevard is the only oncology group in the county that has the CyberKnife, but other radiation oncologists locally questioned its superiority to their devices. "It has limited use," said Dr. Wasfi Makar, a cancer physician with the American Cancer Treatment Center in Rockledge. "It was designed to treat brain tumors that are difficult to get to without overdosing surrounding tissue." And for these cases, in tumors less than 2 centimeters in size, "it works well." But Makar said his issue with the technology is the lack of long-term clinical trials or research studies, demonstrating the technology works better than Varian's Trilogy, for example, which also can perform radiosurgery and is cheaper for treating many other cancers, such as prostate and lung. "I prefer the tried and true," he said.

Similarly, Dr. Cynthia Bryant, medical director of radiation oncology for the Space Coast Cancer Center, said the center's top-of-the-line Varian devices have the full capabilities of the CyberKnife. "There's nothing they can't do," she said. Plus, she said, total radiation exposure to the whole body is higher than with the Trilogy, even though radiation beams are targeted to specific sites. And she questioned whether the CyberKnife's accuracy is that much better.

At Stanford University Medical Center, where the CyberKnife was developed, the center treats about 500 cancer patients a year, mostly with brain or spinal tumors, according to Dr. Steven Chang, professor of neurosurgery and neurosurgeon at Stanford. "If I told you I had five different machines with different accuracy and different doses, which would you pick, the one that treats your cancer in three days or the one that takes several weeks?" Chang asked. "As a consumer, I would want to know which technology has the best chance of killing my tumor." The CyberKnife is the most accurate, he said, hitting tumors with a margin of error of less than 1 millimeter. In neurosurgery, Chang said, the CyberKnife is the standard of care today, while the Food and Drug Administration has approved its use in any cancer that conventional radiation also treats.

There are volume limits to its effectiveness, when tumor masses are too large, he said, but those limits are higher than most people think. Ultimately, asking any cancer doctor to say one machine is better than another, however, is like "asking a Toyota dealer what he thinks of Honda," Chang said. "It hurts their practice."

Up to patients to decide

Even Shankar acknowledges it's up to patients to decide if this is the right option for them. "It's a choice," he said.

As with any technology, the challenges include "giving a good dose" able to kill dividing cancer cells, he said, while making every effort to prevent radiation toxicity to surrounding tissues. Although clinical data to date with the CyberKnife still is limited, it's evolving, he said. "New technologies take time to show they're better." At least for one patient, Shankar would get no argument. Martin said the shorter treatment times allowed her to go back to work that much sooner, and she had few side effects, except being tired. And so far, as she approaches the third anniversary of completing treatment, she continues to be cancer-free. "It saved my life," she said, an infectious laugh testament to her innate optimism.

Although Martin admits that occasionally she gets down, especially when she sees young patients struggling against cancer, she refuses to allow the disease to define her. Instead, she uses her compassion and insight to help others, recently joining the Cancer Care Centers Foundation, talking to the newly diagnosed most every day. "I tell them, 'I understand how you feel because I've been there,' " she said.

Contact
Susan Jenks
321-242-3657
sjenks@floridatoday.com.