Chemo Brain, or Loss of Mental Sharpness, Found to Have Biological Basis

2011-11-23 08:59

Although up to 75% of cancer survivors experience altered mental function following treatment – often called “chemo brain” or “chemo fog”, doctors often believed that these effects were psychological, a form of depression. However, a new study, published in the Archives of Neurology, has Stanford Cancer Center researchers providing biological evidence that the effects are real, particularly for women who have undergone chemotherapy.

Cancer patients who complain of loss of mental sharpness are actually complaining about loss of prefrontal-executive function, the type of mental activity that includes the ability to selectively pay attention, work with information, and choose the appropriate response in a situation.

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Shelli R. Kesler and colleagues scanned the prefrontal cortex of the brains of 25 breast cancer patients who had been treated with chemo, 19 breast cancer patients who had not had chemotherapy, and 18 healthy women. The researchers used functional magnetic resonance imaging (fMRI) while the women completed a brainteaser in which they tried to discern a pattern in a series of cards printed with geometric shapes. This test measures cognitive flexibility, or the ability to identify the best solution to a problem by testing several possibilities. The women also completed questionnaires to assess their own cognitive abilities.

Overall, both groups of breast-cancer patients showed less activity in the regions of the brain involved in executive function tasks than did the control group of health women. The chemotherapy-treated ladies displayed the least activity of any group in the parts of the brain associated with cognitive flexibility. These women made the most mistakes on the task on average, and took the most time to complete it.

Although it doesn’t happen to every patient, previous research has found that about three-fourths of cancer survivors do experience an altered mental function that can last for five years or longer, said Kesler. And despite the common name of “chemo brain,” the effect does also occur in patients who have not undergone chemotherapy. For example, more than half of the women in both breast-cancer groups took tamoxifen, an estrogen-blocking drug that has also been linked to cognitive impairment. Radiation therapy and anesthesia during surgery can also affect the brain.

Finally, cancer itself could be the harmful factor. "When you get a disease like cancer, it activates your immune system," Kesler says. "Sometimes you can have increased inflammation for a really long period of time, and inflammation can affect the brain."

The researchers are conducting further trials to investigate “chemo brain” and what other factors may be in play, such as age (older survivors tended to have less brain activity than their younger counterparts) and pre-cancer mental function (amount of brain activity tended to increase with the women’s level of education.) Kesler’s team is also developing strategies to help patients adapt to changes in mental function through a trial of a cognitive rehabilitation program which they developed.

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