STANFORD, Calif.— On Thursday, Sept. 16, the Stanford Cancer Center became the first treatment center on the West Coast and the fifth in the world to offer cancer patients the TrueBeam, a machine that represents an exponential leap forward in the speed, power and precision of radiation therapy.
The TrueBeam linear accelerator is capable of delivering radiation at a faster dose rate than most conventional linear accelerators. This advance translates into shorter treatment times for patients. The time for a typical radiation treatment could be cut in half with the TrueBeam. Other special features improve the accuracy of treatment so the overall duration of a course of treatment may also be shortened from several weeks to just a few days.
The TrueBeam can treat any cancer, but its special qualities may be of particular advantage with certain types of cancer. "People with pancreatic tumors have historically needed a five- to six-week course of treatment, but when you have a limited life expectancy, that amount of time may be too long," said Stanford radiation oncologist Albert Koong, MD. "Compressing treatment down to a week or less is a significant improvement. It also means we don't have to interrupt certain types of chemotherapy."
The TrueBeam's technology also enables more effective treatment of tumors in locations that were previously difficult to treat because of the sensitivity of the surrounding tissue to radiation. Koong said certain liver and lung tumors would be included in that group.
The new machine's radiation delivery precision is controlled to within less than a millimeter, as its advanced imaging checks accuracy every 10 milliseconds, continually monitoring more than 100,000 data points. TrueBeam's 4D imaging system captures views in 60 percent less time than in previous machines and reduces overall X-ray exposure for that imaging by one-quarter. The increased speed means less blurring in each image, which helps to more clearly define the edges of a tumor.
The TrueBeam system is especially good for tumors deep in the body because it adjusts for movements in tumors, which are nudged in various directions with each breath. In a technique called respiratory gating, the TrueBeam sends out radiation only when the tumor is within the beam's line of delivery. The platform couch which holds the patient also adjusts with the same sub-millimeter accuracy.
In combination with the TrueBeam's rapid, multi-dimensional imaging, the effect is a much higher degree of protection for healthy tissue adjacent to the cancer.
"This is the most advanced technology that's available for radiosurgery," said Richard T. Hoppe, MD, Stanford's Chair of Radiation Oncology. "When we combine this technology with our expert group of physicians who are developing cutting edge treatment programs, we can treat ourpatients more rapidly and effectively, and at the same time, more safely than ever before."
Radiosurgery or stereotactic radiotherapy are terms that include a type of cancer therapy in which very precisely focused beams of radiation target the tumor. The beams are as exact as a scalpel, but accomplish tumor destruction without conventional surgical tools. The TrueBeam, however, is so large it requires almost the same amount of space as an operating room. It stands 9 feet tall and 15 feet long, and including all its components, weighs more than 9 tons. Its curvilinear arm, called a gantry, rotates in a complete circle to enable treatment from any direction. The level of control is remarkable considering the weight of the gantry.
Just a decade ago, when Koong was a resident, "this kind of treatment wasn't possible," he said. "The whole field has evolved. Treatments have changed so much that now, if we think about early stage lung cancer, for instance, we might recommend this kind of radiation therapy instead of traditional surgery. Machines like the TrueBeam might one day replace or be considered the equivalent of surgery."
The TrueBeam was developed by Varian Medical Systems, a Palo Alto-based company that has built other advanced radiation delivery devices, including the Trilogy. The TrueBeam, however, is driven by a new form of medical linear accelerator, the mechanism that transforms electrons into photons by shooting them at a metal target at nearly the speed of light. The energy from that impact is measured in millions of volts.
When the photons, or X-rays, contact cancer cells, the result is meant to be so lethal that the cancer cells will lose their ability to reproduce and will then die.
Stanford received one of the first three TrueBeam machines Varian manufactured. The University of Zurich and Memorial Sloan-Kettering Cancer Center were the other two.
Stanford's role in the development of radiation delivery is particularly distinguished. In 1956, the Western Hemisphere's first medical linear accelerator was used to successfully treat a two-year-old with a malignant tumor of the eye. The device, designed by Stanford radiation oncologist Henry Kaplan, MD, and Edward Ginzton, electrical engineering and physics professor at Stanford, would become the essential platform for radiation therapy worldwide. More than half of all cancers are treated with radiation delivered with a linear accelerator.
by Sara Wykes