February 24, 2011
Cancer Goes Cutting Edge
by Kate Ferguson
Hi-tech tools usher in a new era of treatment for this old disease.
About 50 years ago, scientists were just beginning to lay the foundation for the GPS technology that helped put Oteilus Walters’s prostate cancer into remission. Today, the 75-year-old retired teacher couldn’t be more thankful for the space-based navigational satellite system that spawned the Calypso 4D Localization System, a.k.a. “GPS for the Body.”
Walters opted to try the treatment after his doctor told him about the device’s availability at the Hospital of the University of Pennsylvania. “It was the first time I’d heard of it,” he says. “After they described the procedure in general terms, it sounded like a very good way for me to go. I have nothing but praise for the treatment.”
The reason Walters chose the Calypso system is because he was concerned about possible damage from radiation treatment to the healthy tissue surrounding his enlarged prostate. (Because of breathing and normal movement in the intestines, prostate motion is unpredictable and variable and can cause the gland to become a moving target during radiation treatment. As a result, doctors expand the treatment area to ensure the prostate is irradiated. Often, this leads to damaged healthy tissue.)
But after doctors told Walters that the Calypso system’s GPS technology allowed for targeted applications of radiation therapy to the prostate, this helped alleviate his concerns. “What the Calypso technology does is help us to track where the prostate is located in real time, second by second while the patient is receiving radiation therapy each day,” says Neha Vapiwala, MD, an assistant professor and residency program director at the University of Pennsylvania Department of Radiation Oncology.
Typically, the Calypso treatment involves a one-time placement of three transponders, called “beacons” and smaller than a rice grain, into the prostate. Doctors implant the beacons into the prostate through the rectum using ultrasound guidance during an outpatient procedure prior to the patient starting radiation therapy.
These beacon transponders emit radiofrequency waves which allow doctors to accurately align the prostate before each treatment session. “There’s no actual direct side effect or down side to using this therapy to enhance the radiation delivery,” Vapiwala says.
The best prostate cancer candidates for Calypso treatment are patients who opt for radiation therapy. But patients who have pacemakers or cardiac defibrillators shouldn’t receive this treatment. “One would not want beacon signals to interfere in any way with pacemaker placement,” Vapiwala explains.
But in addition to these medical devices, patients who have a certain body shape and weight distribution may not be eligible to receive the treatment. “This is something that a doctor can help determine when he or she meets the patient,” Vapiwala says.
And although many may be unaware of this GPS application, the Calypso system is an FDA-approved procedure that’s a cool new tool doctors can use to enhance radiation therapy delivery. In addition, the treatment is generally covered as part of radiation therapy. But you’d want to be sure and check with your insurance company, Vapiwala suggests.
In general, doctors recommend prostate cancer radiation therapy with the Calypso system each day for five days a week over an eight- to nine-week period. Walters was pleasantly surprised with his Calypso experience. “I was in a radiation room by myself lying on my back on a bench-platform and the machine rotated around me,” he says. “I had a pillow under my head and it was very comfortable. They put something for me to rest my feet and legs in to minimize any movement and they asked me what kind of music I liked then played it. It was a very enjoyable experience.”
Walters says he experienced no side effects from the treatment, even though he was told he might feel a little tired. “But I went to the gym and would work out for a couple hours after that,” he says. “I didn’t feel any fatigue at all. It was completely painless.”
What was even better? Says Walters, “When the doctors told me that I had no indication of prostate cancer.”
Another FDA-approved tool in doctors’ treatment arsenal, the CyberKnife Robotic Radiosurgery System is the world’s first and only non-invasive alternative to surgery developed to treat both cancerous and non-cancerous tumors. The device delivers very high doses of radiation to patients from different angles using pencil-sized beams.
“What this allows doctors to do is deliver these beams extremely accurately and precisely to the patient to target tumors in the body,” explains Omar Dawood, MD, MPH, vice president of clinical development at the Sunnyvale, California-based company Accuray Incorporated, which developed the CyberKnife Robotic Radiosurgery System. “This means you’re able to spare normal tissue and deliver a more potent radiation dose all at once to a tumor.”
This method of radiation delivery to a cancerous tumor is very different from the one used in traditional radiation therapy, which usually treats a wider area and dramatically increases the risk of damage to normal tissue.
As with the Calypso system, the CyberKnife’s precision radiation delivery reduces the number of treatments the patient needs and also allows the radiation to follow the motion of tumors.
In addition, the CyberKnife system also offers very sick cancer patients a way to get radiation therapy without the drawbacks that accompany more invasive treatment methods. “We’re able to still treat the tumor, but without the incisions and risks that are typically associated with scalpel usage in an operating room,” Dawood says.
As far as CyberKnife side effects, that depends on the body part that’s being treated. For example, brain tumor patients may experience some nausea after treatment, or prostate cancer patients may notice slight urinary discomfort or urgency immediately after therapy. But typically patient risks are much less with CyberKnife. “There are certain risks that don’t exist or are much reduced as compared with taking a patient into the operating room,” Dawood explains.
But the best patient candidates for CyberKnife are those who don’t have widespread cancer. The system is typically used for patients with early-stage cancers or those in late-stage disease using other treatment methods.
Currently, CyberKnife system coverage depends on the treatment application. “There’s coverage of the procedure for most applications, but for newer treatment areas, such as prostate cancer, it’s covered in 36 states plus the District of Columbia,” Dawood says.
But as effective as targeted radiation therapies such as CyberKnife and Calypso can be, the technology has raised questions about the safety and possibility for serious problems these treatments pose. Last year, a New York Times story tackled the topic with a look at the help and harm radiation therapy offers.
“While this new technology allows doctors to more accurately attack tumors and
reduce certain mistakes, its complexity has created new avenues for error—
through software flaws, faulty programming, poor safety procedures or
inadequate staffing and training. When those errors occur, they can be crippling.”
Nevertheless, these targeted radiation therapies are being used to treat patients in leading cancer centers nationwide. “CyberKnife was approved since 2001 and over 100,000 patients treated,” Dawood says.
And since the FDA approved the Calypso System in 2006, doctors have treated more than 5,000 patients with radiation therapy using its GPS technology.
Unlike the targeted radiation therapies previously discussed, genotype testing—gene tests that tell the biology of a tumor—helps determine the most appropriate care for cancer patients.
Once patients are diagnosed with cancer, these gene tests are conducted to gather more definitive information about the tumor's biology and better predict how it will respond to treatment. Doctors use them to check for different genes in tumors that show a cancer’s cell formation, growth and its ability to spread. Doctors developed the tests when it became clear that breast cancer was not just one disease and treatment for it had to be individualized.
“The one-size-fits-all approach is not accurate or appropriate,” says Jessica Rhee, MD, MS, a breast cancer specialist from Hoag Hospital-affiliated Gynecologic Oncology Associates, in Newport Beach California. “We have found that there are certain genes that are important for breast cancer to continue to grow and divide and result in poor outcomes for breast cancer patients so molecular tests were developed to test whether a patient’s tumor has those specific genes that are more or less active.”
Initially, doctors developed gene tests for women with early-stage, hormone-sensitive breast cancer. These women usually don’t need chemotherapy and are the best candidates for genotype testing. “In the past, we had no good way of distinguishing which women with early-stage, hormone-sensitive breast cancer had a more aggressive type of cancer that would benefit from chemotherapy so we tended to overtreat breast cancer patients to try to save a few,” Rhee explains.
With genotype testing, doctors are able to determine a breast cancer patient’s chances of a good treatment outcome, and whether or not that person will benefit from chemo.
Currently, genotype testing is routinely available and the procedure is covered by Medicare and all insurance companies and health maintenance organizations. “It has become the standard of care and is actually in the guidelines for treating breast cancer patients,” Rhee says.
Doctors are also doing a similar kind of testing for early-stage colon cancer patients to determine whether they might benefit from chemotherapy. This is a way to spare people who wouldn’t benefit from chemo and use the treatment on those who need it, Rhee says.
But the most important thing is that these special gene tests go beyond standard cancer pathology testing. Genotype testing shows how aggressive the cancer is so doctors can prescribe more accurate and effective individualized patient treatments.
As Rhee sums up, “We’re moving more toward personalized medicine to tailor therapies to patients.”
Search: Oteilus Walters, Neha Vapiwala, MD, Jessica Rhee, MD, Omar Dawood, MD, Calypso System, GPS for the body, CyberKnife System, genotype testing, prostate cancer, breast cancer, radiation treatments, cancer treatments, personalized medicine
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