New Science

Chemo-Brain Confirmed in Long-Term Mouse Study

It is well known that chemotherapy comes with a long list of side effects; nausea, fatigue, muscle pain and sores in the mouth and throat to name a few. These are often necessary evils and most patients would agree that they are worth suffering through in order to treat their cancer.

According to Cancer Research UK, however, between 17 and 50% of patients undergoing chemotherapy for breast cancer may suffer from a so-called ‘chemo-brain’, cognitive impairment characterised by confusion, memory loss, poor concentration and general ‘mental fogginess’. It is a very under-researched phenomenon, but new evidence from the University of Illinois may support these complaints.

The research team, led by Dr. Catarina Rendeiro, bred mice to mimic the biological markers of post-menopausal women, who are most at risk of developing breast cancer. Half the mice were given chemotherapy and all were subsequently tested on a well-researched cognitive task, the Morris Water Maze. The maze is a navigation task in which the mice are placed into a pool and required to find a hidden platform. It consists of a training phase and a testing phase to demonstrate learning and memory skills.

memory-water-maze-setup

Dr Rendeiro found that the mice who received chemotherapy performed worse than their control counterparts on two measures; time taken to learn the task during the training phase, and time taken to find the platform during the testing phase.

The mice also underwent neurological testing over a three month period (the life-span equivalent of approximately 10 human years) to assess whether chemotherapy has any lasting effects on structures within the brain. Over time the brain naturally
produces new neurons in the hippocampus, an area responsible for memory. It is, in fact, the only area of the brain where neurogenesis occurs in adulthood. Compared
with the control group, mice who were given chemotherapy showed 26% greater neuronal death within the hippocampus

hippocampus-inline
The Hippocampus

during treatment, and they also generated 14% fewer neurons over the 3 months following treatment cessation.

In an attempt to reverse the effects of chemotherapy the researchers provided the mice with a diet rich in Omega-3 fatty acids, which have previously been shown to prevent cognitive decline (e.g. Denis et al, 2013). Unfortunately there were no significant improvements in the identified cognitive impairments.

This research raises a number of questions, both about the nature of our cancer treatments and what we can do to prevent these side-effects. It also asks deeper questions of what we are willing to sacrifice for our own survival.

Chemo-brain is an understudied and little-known phenomenon yet it may affect thousands of individuals. Who may be at risk is not clear-cut; although women with breast cancer were the first to report cognitive symptoms, signs of chemo-brain have also been identified in prostate cancer survivors (Cancer Research UK). Furthermore, the little treatment available is not well-tested.

In 2006 the International Cognition and Cancer Task Force (ICCTF) was set up to help fund and guide research into chemo-brain. For instance, a study by Oana Lindner was conducted with younger adults, an age group who had until then been relatively ignored by chemo-brain research. The results of the study are awaiting publication.

Despite the use of animal models, and the fact that no treatment for chemo-brain was identified, Dr Rendeiro’s study does add to the literature on this phenomenon. This in turn can provided a basis for further research.

To find out more about the project, take a look at the original journal article published in Behavioural Brain Research.

 

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