Chemo Brain Caused by More Than Just Chemo

Most people who have gone through chemotherapy are familiar with the term ‘chemo brain.’

The idea is that the chemotherapeutic drugs, designed to attack and destroy the cancerous tumors, also have negative effects on the brain. The ability to think clearly declines. Learning new material becomes harder and remembering past memories becomes more difficult. Some people have also reported completely losing train of thought in the middle of a sentence.

Chemo brain can even impact your mood. Chemo brain, also called post-chemotherapy cognitive impairment, can present in many different forms.

But what if the culprit is not entirely the chemo drugs?

Dr. Gordon Winocur, from the Baycrest Centre for Geriatric Care in Toronto, Canada, used mice to examine chemo brain. And what they found was that some of the cognitive impairment and memory decline began even before chemotherapeutic drugs entered the picture.

Breast cancer and chemo brain

Approximately twenty five percent of all cancer survivors report the trouble thinking and remembering that heralds chemo brain, but that number is almost double for breast cancer survivors at forty-five percent.

Other reproductive cancers also have higher rates of chemo brain than non-reproductive cancers. For most people, it goes away shortly after chemotherapy has ended. For others, it lasts a lot longer, potentially up to four years.

Living that long with impaired thinking and memory can have a serious impact on a cancer survivor’s quality of life. As Dr. Winocur said, “...these side effects can lead to emotional and mental health issues that affect a person’s ability to function in society.”

“People are living longer thanks to more effective chemotherapy and cancer treatments,” said Dr. Winocur. This longer lifespan is a good thing, but chemo brain can take the joy out of surviving.

Something had to be done to reduce the harm caused by chemo brain, and Dr. Winocur took up the job. It was while he was investigating the mechanisms behind this chemo brain when he realized that the cognitive decline started prior to the drugs. Obviously, this avenue needed to be researched.

Of Mice and Memory

Dr. Gordon Winocur’s team included Hal Berman, Mary Nguyen, Malcolm A. Binns, Mark Henkelman, Matthijs van Eade, Micheline Piquette-Miller, Melanie J. Sekeres, J. Martin Wojtowicz, Johnson, Yu, Haibo Zhang, and Ian F. Tannock.

Their work was published as Neurobiological Mechanisms of Chemotherapy-induced Cognitive Impairment in a Transgenic Model of Breast Cancer in the scientific journal Neuroscience.

The transgenic part of the title refers to the fact that they used mice, specifically FVB/N-Tg (MMTV-neu) 202 Mul/J mice, that had been genetically modified to develop breast cancer at a high rate. Often, cancer and tumors are different between species, but this type of mouse cancer is similar to human breast cancer.

One half of the mice used had breast cancer while the other half did not. The second half without brain cancer was used as the control group.

All of the mice were tested for their ability to learn and recall information. Brain scans and tissue samples were taken as well, to measure neurogenesis, brain volume, and inflammation caused by cytokines.

Then they gave three weekly injections to some of the mice--both experimental and control groups--with chemotherapeutic drugs, specifically methotrexate and 5-fluorouracil. The other mice received a saline solution injection, of the same amount of liquid, instead.

Read on to learn more about the results of this study and what they could signify for the future of chemotherapy.