In the fight against cancer, radiation therapy has long been one of the primary tools used to eradicate tumors. The difficulty lies in sparing healthy tissue near the tumor site. Physicians have been developing increasingly targeted methods for irradiating cancerous cells while avoiding healthy adjacent cells, and Siteman Cancer Center is now using the most advanced method available.
“Although research for development of MRI-guided radiation therapy has been ongoing for years, the MRI-guided radiation therapy system implemented at Washington University is the first of its kind, and represents the first time this technology has been translated successfully for clinical practice,” says Dr. Jeffrey Olsen, a radiation oncologist at Siteman.
Olsen is referring to a new technique that allows physicians to see the tumor via magnetic resonance imaging (MRI) throughout the radiation treatment process. Instead of targeting the beam and hoping the patient remains perfectly still during treatment, the new method gives physicians an ongoing view so they can immediately adjust for even the tiniest motions, keeping the radiation beam trained only on the tumor.
“The amount of movement during a treatment varies considerably depending on the specific disease site that is being treated. Abdominal and lung tumors, for example, move a great deal due to breathing motion, up to several centimeters,” Olsen says.
Prior to the new technology, physicians administering radiation therapy could increase the overall volume of irradiated tissue in order to account for these small movements or turn the beam on and off throughout the procedure to account for breathing or other small motions. “Since technology has not previously existed to visualize the actual tumor motion during treatment, we have relied on surrogates of breathing motion, such as movement of the abdominal wall, rather than actual tumor visualization,” Olsen says. “For certain treatments, such as radiation for brain or bone tumors, the degree of motion is much less, with uncertainty on the order of a few millimeters.”
Siteman Cancer Center began using the technology, produced by ViewRay Inc., earlier this year. The technology is so new that clinical trials of its efficacy have yet to be published, although most patients receiving the MRI-guided radiation are enrolled in trials that will track treatment outcomes.
“As research into MRI-guided radiation therapy continues, we should expect significant advancement of this technology,” Olsen says. “Current research efforts are ongoing to allow adaptation of a patient's treatment plan based on findings observed on MRI. This would potentially allow re-planning on a routine basis to account for day-to-day variability in patient anatomy. It may become possible to increase the radiation tumor dose, or to reduce the radiation dose to normal tissues in near real-time based on MRI.”
Dr. Timothy Eberlein, Siteman Cancer Center director, said in a news release that offering this innovative technology reflects the cancer center’s goal of advancing patient care through clinical research and physician expertise. “We are constantly working to provide the best care possible,” he said. “We do this in many ways, including using innovative technologies that offer better, less toxic treatment options to our patients.”