Patients with brain metastases who experience cognitive side effects after radiation therapy appear to eventually regain cognitive function, according to a presentation delivered on 29 September at the American Society for Radiation Oncology (ASTRO) meeting in Washington, DC.
This recovery was more likely for people treated with targeted radiation techniques rather than standard whole-brain treatment, wrote a team led by Dr. Hua-Ren Ryan Cherng of the University of Maryland Medical Center in Baltimore.
"Our research finds that the cognitive side effects of radiation treatment for people with brain metastases appear to be fully reversible, and patients appear to be able to sustain that recovery over the long-term," Cherng said in a statement released by the society.
Brain metastases tend to be treated by either whole-brain radiation therapy (WBRT) or a "conformal" protocol that targets radiation dose to the tumor site, the group noted. Common types of conformal radiation are stereotactic radiosurgery (SRS) -- which imparts fewer but higher doses of radiation per treatment to the tumor site -- and hippocampal avoidance WBRT, which limits delivery of radiation to the parts of the brain that have been shown to manifest neurocognitive side effects following treatment, it explained. But how patients treated with targeted radiation are affected long-term has not been determined.
"There's been a focus in the last decade on approaches to decrease or delay the cognitive side effects of cranial irradiation," Cherng said. "We had a lot of data looking at the onset of cognitive changes, but not much data and no randomized trials looking at how these patients fare down the road after developing cognitive side effects."
Cognitive side effects from radiation therapy can include decreased executive function, learning ability, and memory, the authors wrote. They explored whether brain cancer patients who experience these side effects eventually recover their cognitive health via a study that included data from 288 patients with long-term cognitive testing data; the group compared whole-brain radiation therapy with different types of targeted radiation treatment. Patients underwent a series of cognitive tests before radiation therapy and six and 12 months after the loss of cognitive function.
The investigators found the following:
- Six months after the first signs of cognitive deterioration, 38% of patients experienced full cognitive recovery; this increased to 42% of patients at one-year follow-up.
- Six months after treatment, 73% of patients showed improvement on one or more cognitive tests; this increased to 76% at 12-month follow-up.
- Full cognitive recovery was higher among patients who received stereotactic radiosurgery compared with those who underwent whole-brain radiation therapy (hazard ratio, or HR, of 2.68, with 1 as reference) and among patients who underwent stereotactic radiosurgery alone compared with stereotactic radiosurgery with whole-brain radiation therapy (HR, 2.35).
The study results could help clinicians paint a more accurate picture for their patients of the likelihood of improvement of cognitive side effects after radiation therapy, according to Cherng.
"These data show that what sounds good in theory is being borne out with more conformal types of radiation therapy," he said. "Not only do these [targeted] techniques potentially help delay the onset of cognitive changes, but, downstream from treatment, [they yield] a higher prevalence of cognitive recovery."
