Memantine Protects Cognitive Function After Whole Brain Irradiation

[Hopeful]

IMNG Medical Media. 2012 Oct 30, N Osterweil

BOSTON (IMNG) - Memantine, a drug normally prescribed for slowing cognitive decline in Alzheimer's disease, can help to preserve cognitive function in cancer patients who have undergone whole brain irradiation, a study showed.

In a phase III trial, patients with brain metastases were randomly assigned to take 20 mg memantine (Namenda) or placebo daily for 24 weeks after whole brain radiation therapy (WBRT). The memantine cohort had a 17% relative reduction in cognitive decline compared with patients who got a placebo, Dr. Nadia N. Laack reported at the annual meeting of the American Society for Radiation Oncology.

The finding teetered on the edge of statistical significance (P = .059), however, because only one-third of patients (32%) completed the 24 weeks of drug therapy, due to death (survival was poorer than expected), disease progression, or noncompliance, said Dr. Laack. a radiation oncologist at the Mayo Clinic in Rochester, Minn.

"Overall, we feel that the weight of evidence supports our conclusion that memantine helps to preserve cognitive function after whole brain radiotherapy in patients with brain metastases," Dr. Laack said at a briefing prior to presenting the data at a plenary session.

WBRT is associated with cognitive impairment in a majority of patients who receive it, Dr. Laack said, noting that at 4 months post radiation, 60% of patients will have declines in one or more cognitive domains.

Because the mechanism of decline is similar to that seen with Alzheimer's and vascular dementias, and because memantine has been shown to modestly improve mild to moderate cognition in both dementia types, Dr. Laack and his colleagues hypothesized that it might protect brains exposed to therapeutic doses of radiation.

A total of 508 patients were tested at baseline and at 8, 16, 24, and 52 weeks after radiation with 37.5 Gy in 15 fractions. They were evaluated with MRI and cognitive assessment; domains of memory, processing speed, executive function, global function, self-reported cognitive function, and quality of life were evaluated. Median overall follow-up was 12.4 months.

There were no differences between the treatment groups in overall survival at a median of 6 months or in progression-free survival at 5 months.

Among 149 patients available for analysis at 24 weeks, patients who took memantine had a significantly longer time to memory decline than did those on placebo (P = .02), and had a trend toward less decline in the primary end point, the Hopkins Verbal Learning Test-Revised delayed recall instrument (median decline of 0 standard deviation, vs. -2 standard deviations for patients on placebo).

For the secondary objective of cognitive function decline/failure, defined as a change greater than reversible cognitive impairment or 2 standard deviations decline from baseline on any domain of brain function, the hazard ratio for memantine at 24 weeks was 0.784 (P = .01), indicating a significant reduction in the incidence of cognitive dysfunction.

"Although memantine was discontinued at 6 months, the effect on cognitive function was maintained for the duration of the trial, suggesting that memantine may be preventing radiation injury rather than simply treating cognitive dysfunction," Dr. Laack said.

The trial was sponsored by grants from the National Cancer Institute and Forest Pharmaceuticals. Dr. Laack reported no relevant financial disclosures.

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