Smaller radiation fields can spare brain when treating tumors
Patients with aggressive brain tumors can be effectively treated with smaller radiation fields to spare the rest of the brain and preserve cognition.
A patient's cognition is related to how much normal brain tissue is irradiated. Focusing radiation on smaller areas of the brain may help maintain cognition and does not seem to lead to an increased likelihood of the tumor recurring. Overall, while long-term survival rates for patients with glioblastoma multiforme (GBM) have not improved much with treatment advances, the ability to treat with smaller radiation fields preserves cognition and provides the possibility of better quality of life.
Although other similar studies have been done, this one is the largest to compare smaller radiation margins to larger ones to document differences in patterns of failure for patients. This retrospective study reviewed records for 161 patients treated at Wake Forest Baptist Medical Center in Winston-Salem, North Carolina, over the past 10 years.
“We decided a few years ago that it would be worthwhile to look at whether using these tighter margins would affect the tumors coming back outside of the radiation field, or tell us if we are barely missing,” said Michael D. Chan, MD, of Wake Forest. “We are the first to show definitively that people with smaller margins don't do any worse than those with larger margins.”
Chan explained that in the 1990s, Wake Forest Baptist's Edward G. Shaw, MD, professor of radiation oncology, was part of a group that pioneered using smaller margins because it was less toxic. Smaller radiation margins around the tumor do not seem to lead to an increase in the tumor returning just outside of the radiation field, Chan said. A smaller radiation field, combined with modern treatment techniques, like newer chemotherapy agents and radiation technologies, provides physicians with more options.
“Treatments have gotten better over time and people with GBM may live longer than they had in the past. Our study found that the margins did not affect where the GBM came back or how long it took it to come back, and it did not affect the overall survival,” Chan said. “This could potentially be practice changing.”
These research findings were published by American Journal of Clinical Oncology (2012; doi:10.1097/COC.0b013e318271ae03).