Chemotherapy and the brain: the reasons behind the mental fog

This review examined the cognitive difficulties experienced by breast cancer survivors following chemotherapy treatment.

Chemotherapy has been associated with cognitive (conscious mental activities such as thinking, reasoning, learning and remembering) impairments in breast cancer (BC) survivors up to two years following treatment. The most common problems are with memory and executive function, which refer to brain processes that help us achieve goals (such as attention, remembering details, and managing behavior). How chemotherapy leads to cognitive difficulty is not fully understood, but imaging studies (such as magnetic resonance imaging or MRI, which can image brain tissue using a magnetic field) show differences in the structure of the brain in patients following chemotherapy. Structural changes to the brain can change the way the brain functions, leading to cognitive difficulties. There is also the possibility that these structural changes could increase the risk of dementia (a group of symptoms affecting thinking and social abilities severely enough to interfere with daily functioning) in elderly patients. Rates of BC survival and dementia diagnosis in elderly patients are both increasing, therefore it is essential to understand how chemotherapy affects brain structure and functioning, as well as if it increases the risk of dementia.

This review evaluated fourteen studies that measured cognitive functioning in BC patients, 5 or more years following chemotherapy. The most common cognitive impairments found were related to attention and executive functioning, but other problems were also evident. For instance, 5 years following chemotherapy, BC survivors performed significantly worse on memory and motor skill tests than did BC survivors who did not receive chemotherapy. By 17 years following treatment, chemotherapy recipients had significant difficulties with tasks requiring attention and other processes associated with executive functioning.

While imaging studies found that patients had multiple changes to brain structure 10 years following chemotherapy, there is no long-term evidence of an increased risk for dementia.

This review concluded that chemotherapy for breast cancer can lead to cognitive difficulties in the years following treatment. Chemotherapy does not, however, lead to an increased risk of dementia.

Each of the studies reviewed here used different tasks to test cognitive function, and included patients with different types and stages of cancer. It may be that disease characteristics also contribute to cognitive difficulties, not just the effects of chemotherapy.

Talk to your physician about ways to improve your cognitive functions following chemotherapy.