Researchers examine whether cognitive impairment caused by chemotherapy drugs in breast cancer patients is a long-term issue.
Breast cancer patients frequently report feelings of mental fogginess and lingering cognitive impairments following treatment, commonly referred to as chemobrain.
In a study published in Behavioral Brain Research, researchers identified these same long-lasting impairments in mice treated with a breast cancer regimen. Although prior studies examined these effects in humans and animals, most of the studies do not assess long-term effects.
“Quality of life after chemotherapy is critically important, and chemobrain is significant in these survivors,” said researcher William Helferich.
The scientists set out to study the long-term effects of chemobrain on mice.
“The question is, after they completely recover from the acute assault of chemotherapy, many months or years later, do they still have cognitive impairments?” asked researcher Justin Rhodes.
For the study, the researchers used female mice that mimicked post-menopausal women, since they are the group most affected by breast cancer.
“We wanted a model that represents the human population so we have the best chance of having results that translate to humans,” Rhodes said.
First, researchers wanted to confirm that chemobrain was in fact long-lasting. To do this, they assessed the long-term effects of chemotherapy on learning and memory, as well as the formation of new neurons in the hippocampus.
To test the learning and memory of the mice, researchers used the Morris Water Maze, which trains mice to find a hidden platform in a maze. The results showed that the mice receiving the chemotherapy regimen took longer to find the platform, and were slower to learn the task compared with the control group.
Furthermore, the chemotherapy group had 26% fewer surviving hippocampal neurons born during the chemotherapy regimen, and generated 14% fewer hippocampal neurons in the 3 months that followed therapy. Authors noted that 3 months for a mouse is equivalent to about 10 years for humans.
The findings show long-term detriments to both the brain and behavior of the mice treated with chemotherapy.
“We need to have good animal models of these long-term cognitive problems following chemotherapy to understand what is going on and how to treat it,” said lead study author Catarina Rendeiro.
Although there are drugs that can be developed to address cognitive impairments, the side effects and negative interactions with the chemotherapy drugs could result in patients suffering even more. Instead, researchers hope to find a nonpharmaceutical intervention that mitigates chemobrain.
“A dietary intervention that could improve cognitive function after chemotherapy could benefit a lot of cancer patients,” Rendeiro said.
Researchers wanted to test the efficacy of an omega-3 fatty acid-enhanced diet in reversing these cognitive impairments, but unfortunately, the diet did not demonstrate any beneficial effects. Despite this, researchers expect the model will prove to be useful for examining alternative lifestyle interventions to help improve individuals affected by this phenomenon.