Lifting the fog on ‘chemo-brain’

Cancer patients have long claimed that chemotherapy was affecting the way they think. It was like they were in a fog, not thinking clearly—an unproven condition dubbed chemo-fog.

Chemo-fog was coined by patients to explain the changes they noticed in their mental clarity after starting chemotherapy—absentmindedness, difficulty concentrating or multi-tasking, a general lack of clarity in thinking. 

The anecdotal evidence from patient reports needed science to prove or disprove the phenomena. The Ottawa Hospital took the lead, being one of the first in the world to do a pre/post study of the effects of chemotherapy on the brain. Since then, it has become a huge area of research for different kinds of cancer treatment. Fifteen years ago, a cancer patient suffering from chemo-fog was referred to neuropsychologist Dr. Barbara Collins of The Ottawa Hospital. Dr. Collins had never heard the term and at the time there was very little research on the subject.

“The establishment didn’t believe that there was any kind of brain fog,” said Dr. Collins. “It believed the brain-blood barrier—a membrane that separates the circulating blood from the brain—kept chemotherapy drugs out of the brain. Any cognitive changes patients experienced were blamed on stress, depression or other factors.”

MRIDr. Collins and her colleagues designed a clinical trial to look at patients before, during, and after chemotherapy. They enrolled 120 people in the study (60 breast cancer patients, and 60 non-cancer patients) and over 15 months the group did a number of cognitive tests. Twenty of these women participated in magnetic resonance imaging (MRI) studies where brain activity was observed while they responded to cognitive questions.

Dr. Collins and her research team could clearly see a decline in the women’s cognitive abilities over the course of their chemotherapy treatment. Chemo-fog was real and they had the science to prove it.

“In the women who received chemotherapy, you could see differences in the patterns of brain activation in the MRI even when they performed perfectly normally on the test,” said Dr. Collins. “In simplistic terms, the brain is working harder. Now, we know that some of these chemicals do get into the brain. And as a result of studies like this one, championed at The Ottawa Hospital, chemo-fog is now taken more seriously.”