When doctors administer radiation therapy to lung cancer patients, they face a dynamic obstacle: The tumors are in constant motion.
Historically, radiologists have addressed this problem by targeting a wide margin around the outer boundaries of a tumor. This compensates for any chest movement caused by the patient’s breathing and heartbeat. And while it also ensures that a tumor will receive the prescribed dose of radiation regardless of its position, one consequence is that a large amount of healthy tissue can be damaged in the process.
But a new robotic method for tracking tumors, developed by medical physicists at Thomas Jefferson University and Jefferson’s Kimmel Cancer Center, offers unprecedented accuracy for radiation delivery during treatment.
A study evaluating the new method, led by Ivan Buzurovic, Ph.D., researcher in Jefferson’s Department of Radiation Oncology, and Yan Yu, Ph.D., Professor, Vice Chair and Director of Medical Physics at Thomas Jefferson University, was published in the November issue of Medical Physics.
Increased Doses of Radiation Improve Survival
Not only does the new method spare healthy tissue from unnecessary radiation exposure, but it also allows doctors to provide higher doses of radiation which have been shown to notably improve the survival of lung cancer patients in clinical studies.
A 2012 review of six clinical trials evaluating combination radiation therapy and chemotherapy concluded that higher doses of radiation improve local cancer control and survival for patients with non-small cell lung cancer. Despite this evidence, doctors typically avoid higher doses of radiation because they increase harmful side effects and put critical organs of the chest at risk.
These complications can be bypassed, however, with improved tumor tracking techniques that decrease the area targeted with radiation. Jefferson researchers accomplished this goal, and even found a way to incorporate the new technology into existing radiotherapy treatment couches, such as the HexaPOD robotic couch and the ELEKTA Precise Table.
“We’ve shown here that our system can better predict and continuously track moving tumors during radiotherapy, preventing unnecessary amounts of radiation from being administered to unnecessary areas,” said Dr. Buzurovic. “Just as important, we’ve successfully modified existing technology to integrate with the system to perform the tracking delivery, meaning no additional robotic systems are needed.”
A Safer, More Effective Approach
After proving the effectiveness of the new tumor tracking technique with computer simulations last year, the Jefferson researchers have now shown that the same results can be achieved feasibly in a clinical setting.
The new robotic control system, programmed with an algorithm developed by the researchers, automatically adjusts to keep the tumor’s position stationary during treatment. The system continually tracks the location of tumors in three-dimensional space and compensates for chest movement and system errors in real time.
Study results show that when activated, the tracking system can reduce the size of the radiation target by 20 to 30 percent for medium-sized tumors, and by more than 50 percent for smaller tumors.
“With this new technique, it shrinks the margin, and radiation oncologists would be able to administer more radiation and faster to the tumor than conventional methods,” said Adam P. Dicker, M.D., Ph.D., Professor and Chairman of the Department of Radiation Oncology at Jefferson University.
“And a higher, more targeted dose means a better cure in lung cancer.”