Is Chemo the Cause of Mental Fog After Breast Cancer?

Nov. 14, 2011 -- The mental fog many breast cancer survivors complain of after treatment may be due to changes in their brains, whether or not they had chemotherapy, a study suggests.  

New research shows that even breast cancer survivors who have not received chemotherapy might experience the mental fog similar to what's commonly known as "chemo brain."

The study is published in the Archives of Neurology.

Many breast cancer survivors complain about the inability to think as clearly as they did before their cancer was diagnosed and treated. Often, their complaints are ignored.

Researchers found changes in breast cancer survivors' brains whether or not they'd received chemotherapy. The changes correlated with their complaints of not being able to think as clearly as they used to only in the women who'd had chemotherapy.

Comparing Brain Scans

The scientists scanned the brains of 25 women who'd received a variety of chemotherapy drugs for breast cancer, 19 breast cancer survivors who had not received chemotherapy, and 18 healthy women.

About half of people in each of the breast cancer groups were taking tamoxifen; all of them were disease-free and had no history of cancer recurrence at the time of the study. While their brains were being scanned, the women were asked to do a card-sorting task on a computer.

Compared to the women who'd never had breast cancer, the two groups of breast cancer patients demonstrated significantly reduced activation in a part of the brain called the prefrontal cortex, responsible for planning, reasoning, and problem-solving.

The women who'd received chemo showed the most reduced activation in that part of the brain. Whether the chemo itself or their more advanced disease at diagnosis was to blame for the findings in the chemotherapy group isn't clear, says researcher Shelli Kesler, PhD, an assistant professor of psychiatry and behavioral science at Stanford University.

On average, the women had completed their chemotherapy four years earlier, Kesler says. "This study is really interesting because it shows these problems are really long-term."

She theorizes that the changes found in the brains of survivors who had not received chemotherapy were due to inflammation caused by the disease itself or from radiation therapy or tamoxifen, which reduces a woman's amount of estrogen. The hormone has been linked to brain function and the ability to remember things.

More Research Needed

Laura Nikolaides, MS, a breast cancer survivor who directs research and quality care programs at the National Breast Cancer Coalition, called Kesler's study "very preliminary" and quite small.

"It's interesting but doesn't give us conclusive information," Nikolaides says. "We know that breast cancer treatment has significant side effects, but as far as [thinking], we don't know how much it lasts."

A more informative study would be one that follows women over time, she says. Kesler says she's seeking funding to conduct such research.

Breast cancer survivors had mixed feelings when she recently presented her findings to them, Kesler says.

"It is hard for them to hear this is probably a brain change," she says. However, "they were mostly very excited, because they've been dismissed, ignored. They're very happy to hear that somebody is paying attention to it."

Because many people have tended to write off the mental fog as a psychological rather than a physical problem, Kesler says, sufferers have been unable to get workplace accommodations or disability payments.