Vanderbilt-Ingram Cancer Center’s new Trilogy diagnostic imaging system gives radiation oncologists a highly accurate new weapon in the fight against cancer.
photo by Dana Johnson
New system boosts radiation oncology efforts
Vanderbilt-Ingram Cancer Center has acquired new technology that will allow radiation oncologists to treat a wider variety of patients with pinpoint accuracy.
VICC is only the second center in the world to begin using the new system, which received clearance by the U.S. Food and Drug Administration earlier this year. The system is called Trilogy because it offers three advances:
• real-time imaging with X-ray or CT scan to guide conventional treatment;
• stereotactic radiosurgery and radiotherapy (previously limited primarily to brain tumors) to treat cancers throughout the body;
• “gating,” which coordinates delivery of radiation with respiration or other natural movement of the body.
“On-board, real-time imaging allows us to treat our patients with unprecedented precision, so virtually every patient could benefit,” said Dennis Hallahan, M.D., professor and chairman of Radiation Oncology and professor of Biomedical Engineering.
“We're particularly excited about the ability to offer stereotactic radiosurgery to patients with extracranial tumors. We'll be able to continue to use stereotactic treatment for our brain tumor patients but without the heavy metal head frame that we've used to pinpoint the target. We'll be able to offer this promising approach to patients whose tumors are in non-rigid areas of the body, like the lung or liver.”
VICC began using the Trilogy system in October and is currently treating as many as 10 patients per day, Hallahan said.
The heart of the technology is a linear accelerator with a multi-leaf collimator, dozens of metal fingers controlled by computer that move in and out throughout the treatment to sculpt the radiation beam so that more radiation hits the tumor, but nearby healthy structures are more effectively protected.
What makes the Trilogy system different is the on-board imaging systems that will permit fine-tuning at the time of treatment to accommodate subtle changes in patient positioning or movement of tumor tissue due to digestion, respiration and other processes that result in organ shifting.
“With real-time tumor tracking, we can escalate radiation doses for faster relief of symptoms and greater potential for cure of inoperable pancreas, prostate and lung cancer,” said Anthony Cmelak, M.D., associate professor of Radiation Oncology.
Stereotactic radiosurgery and radiotherapy deliver very high doses of radiation to a tiny focal point over a short period of time.
Because of the precision — the Trilogy system can deliver the beam with 1-millimeter accuracy — radiation oncologists can push the dose of radiation much higher than would be possible otherwise, Hallahan said.
VICC will begin offering extracranial stereotactic radiosurgery and radiotherapy in early 2005, after delivery of additional software.
At that time, Hallahan and his colleagues will begin a multi-center clinical trial, involving about a half dozen centers expected to acquire Trilogy in the coming months, to study whether this approach can improve treatment of early stage lung cancer patients who could not undergo surgery, for instance, because of other illness.
“Researchers at Indiana University have demonstrated in a small group of patients that they could achieve 100 percent control of lung cancers by giving massive doses of radiation once a week for three weeks,” Hallahan said.
“Essentially, this approach ablates the tumor with radiation. This study is designed to confirm those results in a larger group of patients at multiple centers.”
Another important group of patients who will benefit greatly from the availability of stereotactic radiosurgery are breast cancer patients who develop tiny metastases in bone, brain or eyes, Hallahan said.
“These are women who are now able to live with their breast cancer as a chronic disease, but many of them develop these localized metastases,” he said. “By treating these individual spots with tremendous precision, we can continue to retreat as new spots develop. Previously, we've been limited by an organ's tolerance for additional radiation.”
VICC will also begin offering “gating,” which is still considered investigational, early in 2005. Special sensors detect when the target has moved out of the radiation beam frame and the system shuts off the beam.
“In essence, it allows us to hit a moving target,” Hallahan said. “It will be particularly useful in treating lung tumors because of respiration and coughing during treatment.
For instance, the average person inhales about 15 times in a minute; the beam would go off during those inhalations and come back on during the exhale.”
The FDA gave clearance to the Trilogy system, made by Palo Alto, Calif.-based Varian Medical Systems, in January. Emory University Medical Center in Atlanta was the first to use the system earlier in October.