CyberKnife radiation for cancer of prostate in use too fast for some
Posted on Monday, December 1, 2008
WASHINGTON — When Georgetown University Hospital bought a new high-tech system in 2001 to treat patients with radiation, doctors at first used the computerized, robotic device only for brain and spinal tumors that would be difficult if not impossible to fight any other way.
But Georgetown, along with Virginia Hospital Center and others around the country, is now aggressively marketing the $ 4 million machine, known as the CyberKnife, for early prostate cancer, one of the most common cancers. That trend has sparked an intense debate about whether it represents an important advancement or the latest example of an expensive and potentially profitable new technology proliferating too soon.
While its advocates say the CyberKnife offers prostate cancer patients a safe and effective — and much more convenient — alternative to traditional radiation treatment, many experts fear that it could leave many men unnecessarily vulnerable to recurrences or potentially serious complications.
“This is really pushing the envelope,” said Anthony Zietman, president-elect of the American Society for Therapeutic Radiology and Oncology. “It might be as good and more convenient. It may be better and more convenient. But it could turn out to be a disaster. No one knows.”
Proponents argue that enough evidence has accumulated to make them confident that the approach is at least as good as standard therapies and that it can prevent unnecessary deaths by making treatment less daunting. Because CyberKnife can more precisely target tumors with higher doses of radiation, it could prove even safer and more effective, they say.
“I’m very excited about this,” said Sean Collins, a Georgetown radiation oncologist. “I think it’s an important addition to the treatment of prostate cancer. We’ll definitely save more lives.”
Some critics worry, however, that the push to expand the use of the CyberKnife may be motivated in part by financial incentives: The manufacturer wants to sell more machines, hospitals and private practices want to recover the cost of the systems, and urologists can receive a Medicare payment of about $ 1, 200 for each patient who opts for the therapy.
“Unfortunately, it often comes down to the money,” said Louis Potters, who chairs the society’s Health Policy Council. Potters said that because prostate cancer is so common it could easily become a ready source for revenue opportunities.
The debate illustrates the issues that can arise when costly new medical technologies arrive before researchers have thoroughly evaluated their risks and benefits.
“You have a lot of factors that converge to make something take off,” said Diane Robertson, of the ECRI Institute, an independent, nonprofit organization that evaluates medical technologies. “If you have a promising technology coupled with favorable reimbursement coupled with hospitals’ need to be competitive, that’s enough to give something a push.”
Prostate cancer strikes more than 186, 000 American men each year and kills more than 28, 000, making it the second-most common cancer after skin cancer and the second leading cancer killer after lung cancer among men.
Because the tumors often grow slowly, many men can choose to have doctors closely monitor them. For those who decide to treat the cancer, the most common approaches are surgery to remove the prostate or various forms of radiation, including radioactive “seeds” that are implanted in the gland or “external beam” radiation that subjects the tumor to relatively low doses spread over about 40 fifteen-minute sessions. All the treatments can produce complications, including incontinence, bleeding, problems urinating and impotence. CyberKnife enables men to complete treatment in just four or five sessions by much more accurately delivering about quadruple the usual dose of radiation each time.
Doctors inject four tiny gold cylinders into the prostate to create a precise target. The patient lies on his back for each one-hour session as a robotic arm swivels around to shoot dozens of beams from multiple angles. “You are able to give very high doses and sculpt those doses to the tumor,” said Omar Dawood, of Accuray Inc. in Sunnyvale, Calif., which has installed more than 90 systems in the United States as doctors have started using the machine for other cancers. “It could revolutionize the way prostate cancer is treated.”
Dawood said that more than 2, 000 prostate cancer patients have been treated, and that the approach seems to work as well as standard treatment with about the same, or perhaps even fewer, short-term side effects. At least one study that followed patients for several years indicates that it continues to be safe and effective, and the company is sponsoring two studies at multiple sites nationwide.
“We’ve been getting very good outcomes,” said Collins, the Georgetown oncologist. “Prostate cancer is a real killer, and people are not getting treated because it’s inconvenient for them. This offers them a much more convenient option.”
At the Virginia Hospital Center, the CyberKnife is quickly becoming the most popular option.
“About half of our patients are CyberKnife now,” said Timothy Jamieson, medical director of radiation oncology.
While there is a biological reason to think that fewer but higher doses of radiation may work well for prostate cancer, skeptics said the studies done so far have been too small and followed patients for too short a time.
“We just don’t have the data to support treating prostate cancer with five days of radiation,” said Kevin Camphausen, of the National Cancer Institute, noting that prostate cancer can recur many years or even decades later. And high-intensity radiation, even though it is more precisely focused, might still damage the rectum, bladder and urethra, potentially causing complications years later.
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