Carol Gandy was not happy with the choices she was being offered. Three years after treatment for breast cancer, a new cancer had appeared in her liver. Surgery, she was told, was her only option. Then, a friend called her. "I've been up since 3 a.m. and I found a new radiation oncology machine at Stanford," she told Gandy.
Once she arrived, Gandy said, "They didn't waste any time at all. They went right along–and that's really something when you're scared. It really worked out great."
Gandy's cancer was treated without surgery, using highly focused and intensive radiation therapy known as Stereotactic Ablative Radiotherapy (SABR)–and she became the first person in the world to be treated by combining all the advanced features of the TrueBeam STX radiation treatment system:
- Volumetric modulated arc therapy (RapidArc) for intricate sculpting of the radiation dose
- Respiratory gating that virtually freezes tumor motion caused by breathing
- Flattening filter free (FFF) mode for ultra-fast treatment.
The Stanford Cancer Center was one of the first five treatment centers in the world to have the TrueBeam STX, and the Stanford team's use of all its advanced SABR technology makes Stanford's TrueBeam, known as LA-15, one of the fastest and most accurate radiation therapy machines in the world.
"The TrueBeam is the most advanced technology that's available for stereotactic ablative radiotherapy," 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 our patients more rapidly and effectively, and at the same time, more safely than ever before."
For Gandy, the TrueBeam STX was ideal, said Daniel T. Chang, MD, who treated Gandy. "Where her particular tumor sits is next to some very important structures we want to spare from radiation–the bowel and the stomach. We also want to minimize how much radiation the rest of her liver gets. TrueBeam has improved our capability to do that."
Her liver tumor was also a challenge because it does move up and down with every breath, Chang said, which means the TrueBeam STX's gating feature is perfect.
SABR, also known as radiosurgery or stereotactic body radiation therapy (SBRT), is 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 any incisions. The TrueBeam 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.
The TrueBeam is the newest model 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.
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, said Stanford radiation oncologist Albert Koong, MD, PhD. Certain liver and lung tumors would be included in that group. 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," Koong said. "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."
An important part of the new machine's radiation delivery precision is its built-in imaging capabilties. TrueBeam's on-board imaging system captures CT scans and fluoroscopy, or movie-like x-ray images to help physicians ensure that the patient's tumor and normal organs are positioned with millimeter accuracy, and that motion is properly controlled.
The respiratory gating feature is especially good for tumors in the chest and belly because it adjusts for movements in tumors, which are nudged in various directions with each breath. With respiratory gating, the TrueBeam sends out radiation only when the tumor is within the beam's line of delivery. In combination with the TrueBeam's on-board imaging, the effect is a much higher degree of protection for healthy tissue adjacent to the cancer.
The TrueBeam's capabilities mean physicians can have more confidence in the accuracy of treatment, said Stanford's Billy Loo, MD, PhD, Thoracic Radiation Oncology Program Leader. Shortening the amount of time a patient is in position for the radiation reduces the movement that can happen "if you're in a position that may be a little unnatural, like holding your arms over your head," he said.
Ultimately, more important than any specific technology is the expertise of the physicians and treatment team: Koong and Chang, who specialize in SABR for digestive tract tumors, and Loo and Maximilian Diehn, MD, PhD, who specialize in SABR for lung tumors. They are experts who have conducted landmark clinical trials and who provide education and training to physicians around the world. At Stanford, they have at their disposal an entire range of technologies including PET-CT and 4-D CT for the most accurate treatment planning, and CyberKnife, Trilogy, and TrueBeam STX treatment systems, each with its own strengths, so that the best treatment can be chosen for each individual patient.
Gandy was impressed with two things. Her Stanford physicians "were right to the point and told me exactly what they were going to do, step by step," she said. And once everything was set up, the treatment was quick, much quicker than the radiation she'd had elsewhere three years earlier. This time, "it took me longer to take my top off and put it back on than it did to do the radiation," she said.