Image-guided adapted radiation therapy (IGART)

Fine-tuning precision: radiation oncology’s quest for the holy grail

An estimated 60 percent of cancer patients receive radiation therapy as part of their treatment. Many patients are benefiting from research and technologies that enable radiation to be delivered in less time with more effectiveness and precision than ever before.

At VCU Massey Comprehensive Cancer Center, radiation oncology researchers are spearheading a $10.7-million National Cancer Institute Project Program Grant to develop even better ways to target tumors through radiation while avoiding “collateral damage” to healthy tissue.

“Anyone can acquire treatment technology, but knowing how to maximize its potential by layering on advances in imaging science, biostatistics and biology is what will really improve cancer outcomes in patients,” said Jeffrey Williamson, Ph.D., principal investigator on the grant.

Image-Guided Adaptive Radiotherapy

Williamson and colleagues are parlaying their expertise into Image-Guided Adaptive Radiotherapy (IGART), which combines treatment planning imaging with treatment delivery systems to take radiation oncology into a new realm of precision.

“Human anatomy is dynamic and constantly changing, and organs shift and deform differently during each daily treatment,” Williamson explained. “We know that tumor shape and location in the patient’s body vary not only day to day, but in some cases second by second. By acquiring data on these motions and developing ‘four-dimensional’ models and predictions, we will be better able to predict where a tumor will be a second from now, rather than where it was a second ago, as we deliver radiation.”

In a treatment scenario, IGART’s imaging of the tumor will enable the radiation beam to adapt to even the most subtle changes of the tumor. A patient’s breathing, slight movements and bodily functions can cause such movements. By anticipating and adapting to these movements during the course of treatment, the outcome can be improved.

The project will enhance the safety and effectiveness of current treatments by incorporating quantitative and predictive image analysis into treatment planning. A key goal is to optimize on-board imaging, which is the main input data for IGART.

Conventional plans typically use 8- to 20-millimeter margins that allow normal tissue damage. “We might be able to reduce that margin by as much as 80 percent, or 6 to 16 millimeters, by combining adaptive planning and 4-D modeling,” Dr. Williamson said.

One of the technologies being adopted for the project functions much like a GPS and will be implanted in tumors to provide real-time feedback to scientists. The information on tumor movement will be updated 10 times per second.

Clinical studies

Researchers will accrue patients with lung, cervical or prostate cancer to participate in the IGART project. They expect to enroll about 25 patients from each cancer type for the first two years of study.

Using state-of-the-art technologies that provide images to guide the delivery of radiation doses, researchers first will carefully examine the movement of tumors and then employ adaptation techniques based on the unique characteristics of those tumors.

“By updating the 4-D anatomy as patients are treated, we can adapt or modify the treatment daily or, if necessary, on a second-to-second basis to accommodate anatomical and biological changes,” Dr. Williamson said.

NCI Program Project Grants: Few and far between

About a dozen leading institutions in the U.S. hold NCI Program Project Grants for radiation oncology. Of these, only Massey and Massachusetts General Hospital have grants in both biology and physics within their radiation oncology programs. These grants tend to lead to proof-of-concepts and new standards of treatment for cancer treatment nationwide.

The other radiation oncology NCI Program Project Grant at Massey is titled “Genetic Modulation of Cellular Radiation Response,” which is now in its eighth year under the leadership of Kristoffer Valerie, Ph.D.

The IGART project will involve the contributions of dozens of researchers at VCU. In addition to Dr. Williamson, principal investigators include radiation oncology faculty members Jeffrey Siebers, Ph.D.; Martin Murphy, Ph.D.; Nesrin Dogan, Ph.D.; and Paul Keall, Ph.D., an adjunct professor at VCU who is also director of radiation oncology physics at Stanford University.