A new kind of radiation therapy is targeting cancer the same way a Global Positioning System, or GPS, pinpoints the location of your car. The Calypso 4D Localization System is now being offered to prostate cancer patients at The Nebraska Medical Center, one of only five medical centers worldwide to attain the Calypso technology.
“I am extremely excited to be able to offer men radiation therapy using Calypso. Out of all the radiation targeting therapies used to treat cancer today, the Calypso system is the most advanced and the most accurate,” said Charles Enke, M.D., chairman of the Department of Radiation Oncology at the University of Nebraska Medical Center.
The Nebraska Medical Center was one of five institutions to participate in the pivotal trial that led the Food and Drug Administration to approve Calypso for use in prostate cancer patients last fall. Dr. Enke led the study in Omaha.
“Calypso appears to hold great promise for improving the technical accuracy of radiation therapy, so it stands to reason it could also improve the odds for prostate cancer cure rates,” Dr. Enke said.
Though most cases of prostate cancer are diagnosed when the cancer is still confined to the prostate, when cure rates are highest, this cancer is still expected to take the lives of 27,000 men in 2007.
“I was 250 miles away, driving an eighteen wheeler, when I got a call on my cell phone. It was my urologist; he told me I had prostate cancer,” said Ron Jorgensen of Omaha.
It was late 2005. Jorgensen, 66 years old, was stunned by the news. “My heart just dropped. As soon as I was finished talking to my doctor, I called my wife and said, ‘Boy, what’s my life going to be like now?’ But during my first appointment with Dr. Enke, we talked for an hour and 45 minutes. He never left the room. He told me about Calypso, and I decided to join the study they were doing at The Nebraska Medical Center.”
Jorgensen was one of five patients enrolled in the Omaha portion of the pre-FDA study.
Dr. Enke, who has treated more than 2,100 prostate cancer patients, is a leading authority on radiation therapy for prostate cancer, and said Calypso appears to hold several unique advantages.
“I’ve worked with numerous radiation targeting therapies, but Calypso is the only system that works like a global positioning system. It allows the physician to pinpoint the tumor location with greater accuracy, while the treatment is being delivered. That’s what I would want if I were the patient.”
Dr. Enke said Calypso is also the only system that doesn’t require human interpretation to pinpoint the tumor target. Instead, tiny electromagnetic sensors about the size of a grain of rice are implanted in the patient’s prostate before treatment. Then, during the entire treatment, the sensors continuously transmit information back to Calypso, 10 times per second, regarding the position and motion of the prostate.
“We knew the prostate moved during radiation treatment, but we were surprised to learn from the pre-FDA approval study just how much, and how often it moves,” Dr. Enke said.
To account for that motion, physicians traditionally use larger margins around the treatment borders, but that means more radiation exposure to healthy tissue, which can cause unpleasant side effects.
Calypso’s ability to target the tumor more accurately during treatment translates into fewer side effects.
Ron Jorgensen had 45 radiation treatments using Calypso, and suffered no side effects. “The advantage with Calypso is that radiation goes right to the cancerous area,” he said. “You know how thin a dime is, if the transponder was off just a little bit, the amount of three dimes stacked on top of each other, it would send out an alert, and the radiation treatment would stop until the target was back in range.”
Here’s how it works: when Calypso detects transponder motion, or the tumor target becomes improperly aligned with the radiation beam, it sends out an alert.
Dr. Enke says this is called the action threshold. It allows the clinician to retarget the radiation beam at any time during treatment.
“We set an action threshold for the system to alert us when it detected prostate motion of three millimeters or greater. These are much tighter tolerances than normally used. We wanted to know if it was clinically practical, and we proved it was—you can incorporate these tight tolerances into daily practice.”
These tight tolerances mean doctors can target the malignancy with higher doses of radiation which is why Calypso appears to offer a better chance for a cancer cure. Dr. Enke points out that it also provides the ability to decrease the treatment margin around the prostate thereby decreasing the dose to surrounding normal structures.
Dr. Enke plans to use Calypso as the standard targeting system for all men receiving outpatient prostate radiation treatment, and he anticipates using Calypso for many other types of cancer over time.