Tackling ‘chemo brain’ after cancer

Short attention span, memory loss common after difficult treatment

Medicine has come a long way in treating cancer: The survival rate has more than doubled over the past 65 years to 60 per cent.

Since more people are likely to recover from cancer, we need to turn our attention to improving the quality of life for people after treatment has run its course. As many as 70 per cent of cancer survivors who receive chemotherapy experience memory loss, difficulty focusing and mental confusion, a condition that has come to be known as “chemo brain” or “chemo fog.” These symptoms affect the lives of cancer survivors and may impact their abil- ity to live well after their treatment.

The medical community is divided on whether the condition does indeed stem from chemotherapy or from the psychological challenges of coping with a life-threatening disease and difficult treatment.

Through animal studies, we’ve discovered the condition’s name is misleading and the problem may be more complicated than originally thought. Chemo brain is not just the result of chemotherapy. Our research indicates it is from the combined effects of tumour growth and anti-cancer drugs. Both cause three separate, but related, brain changes:

1. As the tumour develops, the body’s immune system responds by releasing cytokines to inhibit the cancer’s development. Researchers discovered that the body’s reaction causes inflammation in the brain’s nervous system, which impacts its function.

2. Chemotherapy was found to limit the production of new brain cells in regions responsible for memory function, which leads to a loss of memory.

3. The combination of tumour growth and chemotherapy led to shrinkage in brain regions that are important for learning and memory.

While cancer survivors tend to experience mild to moderate cognitive impairment, this is enough to affect their quality of life and should be a cause for concern. Fortunately, treatment programs are being developed to reverse the impact of cancer and chemotherapy on their memory and thinking skills.

Scientists have discovered that physical exercise and an active lifestyle leads to the growth of new brain cells in the memory centre of the brain. Studies have shown that exercise also delays the onset of dementia and slows brain health declines that naturally come with aging.

There is also evidence that being socially active and keeping the brain stimulated and challenged are known to delay the onset of dementia. The same advice could be applied to managing chemo brain. When physical activity is combined with a stimulating environment, one of our studies found there were reduced cognitive side effects from the chemotherapy and less changes to the brain on mice.

Another one of our studies found the use of a cognition-enhancing drug, donepezil, used to help treat people with early Alzheimer’s disease, minimized the impact of chemo- therapy on cognitive ability in mice.

Chemo brain should not stop cancer survivors from resuming their daily activities. Cancer survivors who are experiencing any of the following problems should notify their family doctor:

Memory lapses for information that is typically easy to remember (e.g. phone numbers that you frequently call or your typical route from home to work) Short attention span Taking longer than normal to complete everyday tasks Difficulty learning new skills Unusual disorganization

Gordon Winocur is a professor of psychiatry and psychology, and senior scientist at Baycrest Health Sciences. Doctors’ Notes is a weekly column by members of the U of T Faculty of Medicine. Email doctorsnotes@thestar.ca.