If you’re an older woman with breast cancer, we have some good news…and some not-so-good news. The largest US study looking at the question of brain function following treatment for breast cancer contains a bit of both.

Background: Because aging adults often worry about their memory and cognitive abilities, researchers from Georgetown University Medical Center wanted to investigate how breast cancer and its treatment may affect brain function in older patients.

Study details: To analyze this question, researchers compared 344 women who had been newly diagnosed with nonmetastatic breast cancer (cancer that has not spread beyond the breast) with 347 women without cancer. The women in both groups were age 60 and older and similar in their education levels, lifestyles and other factors.

When the research began—and before the women with breast cancer started their treatment—both groups of women took a series of 13 neuropsychological tests that assessed their attention, thinking, learning and memory skills. At that time, none of the study participants had cognitive problems or dementia. The women with cancer then received treatment with chemotherapy with or without hormonal therapy. All the women then took the same series of tests one year and two years later.

Good news: The study found that most older women treated for breast cancer do not experience any cancer-related cognitive difficulties, including having trouble remembering or taking longer to complete everyday tasks, within the first two years of diagnosis and treatment.

However: For a small subset of women—those who have one or two copies of the APOE4 gene, which has been found to significantly increase risk of developing Alzheimer’s disease—a steady decline in cognitive function occurred after chemotherapy compared with patients without the APOE4 gene and noncancer study participants.

“It is not that the chemotherapy causes Alzheimer’s disease, but that these patients may be at risk for both cancer-related cognitive problems and Alzheimer’s—perhaps through a process of accelerated aging or other shared disease processes,” explained Jeanne Mandelblatt, MD, MPH, lead author of the study and professor of oncology at Georgetown Lombardi Comprehensive Cancer Center.

Bottom Line: Most older women with breast cancer do not have to worry about the cognitive effects of treatment. But women who are APOE4-positive do appear to be more vulnerable to such adverse effects. If these preliminary results are replicated and confirmed by other trials, testing for the APOE4 gene may become part of breast cancer care to ensure that each woman receives the safest and most effective treatment.

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