Mapping radiation therapy: Brain models could help preserve function after treatment

The creation of a model of radiation-induced cognitive decline appears to be feasible and may guide radiation oncologists who treat brain tumors in preserving brain function while still eradicating cancer, according to research published in the February issue of Journal of Neurology.

Ann M. Peiffer, PhD, and colleagues from the Wake Forest School of Medicine in Winston-Salem, N.C., looked at how radiation treatment to different brain areas impacts function to help protect cognition for patients during and after radiation therapy.

“Our results suggest that a sufficient amount of radiation to the primary motor regions or to temporal cortex can lead to worsening of global cognition,” they wrote. “The damage to these two regions may or may not occur by the same mechanism (e.g., vascular injury, demyelination). However, the fact that damage to these sites leads to injury implies that selective avoidance of such structures may preserve function.”

The researchers’ creation of a “toxicity map” is the first attempt to relate treatment dose to brain function, as opposed to brain tissue death. This is important because cognitive and functional problems can occur following doses much lower than those needed to kill tissue, according to the authors.

Findings were based on data from larger clinical trials at Wake Forest Baptist. In one study, 57 brain cancer survivors completed cognitive testing following radiation treatment, and these scores provided the performance data for the toxicity map. These scores were then matched with the patients’ radiation dose levels and MRIs taken prior to treatment.

“Regions that predicted global cognitive outcomes at doses <60 Gy included the corpus callosum, left frontal white matter, right temporal lobe, bilateral hippocampi, subventricular zone and cerebellum,” wrote Peiffer and colleagues.

The basis of the authors’ conclusions is neuroanatomical target theory, which suggests selective damage to various targets in the brain can affect different cognitive abilities depending on which structures are involved. They noted that the total amount of radiation received by the brain as a whole was not predictive of cognitive outcomes in their study.

Peiffer and colleagues suggested a prospective trial with nonvariable follow-up times would be needed to validate their data and refine the model.