Commenting on the study by Deprez et al, Patricia Ganz, MD, noted the importance of the finding for clinicians.

“This study tells us that self-reported complaints mapped onto the neuropsychologic tasks; this has not been shown very often,” said Dr. Ganz, who is Director of the Division of Cancer Prevention and Control Research at the University of California, Los Angeles, Jonsson Comprehensive Cancer Center.

“It’s one of the first studies to show that what patients are saying is backed up by test abnormalities,” she said. “It shows we have to believe the patient.”

Evolving Acceptance of Chemobrain as ’Real’

In an editorial accompanying the study, Dr. Ganz traces three stages in the evolution of our understanding of cognitive impairment following chemotherapy. Early on, few patients reported problems and doctors tended to dismiss any possibility that such problems were caused by chemotherapy, believing that the drugs couldn’t cross the blood-brain barrier. As chemotherapy regimens became more intensive and complaints multiplied, the phenomenon that women were calling chemobrain was often attributed to depression. More recently, advancements in neuroimaging, greater understanding of the immune system, and other factors have led to wider acceptance of chemobrain as “real,” and the mechanisms are being actively investigated.

Research on the topic has expanded, with a number of studies showing changes in the brain and decreases in cognitive function following treatment. But researchers have had trouble correlating these changes with patient reports of problems. This study, however, used an established self-reporting instrument, the Cognitive Failures Questionnaire, and focused on specific problems within the questionnaire, such as word and name finding, rather than looking at the total score. By doing so, the researchers were able to associate specific self-reported complaints to a decrease in the neuropsychologic test results for the same kind of cognitive function.

Mechanisms Remain Unclear

The study supports the idea that in studying chemobrain and other cancer survivor issues, “it’s important to ask specific questions about quality of life, like depression, concentration, memory,” Dr. Ganz said. “If you just ask about global quality of life, you don’t get to the problem.”

While this and other studies provide evidence that chemotherapy can impair cognitive functioning, at least temporarily, the mechanisms involved are still unclear. Some evidence suggests that the immune system and/or host factors, such as particular single nucleotide polymorphisms (SNPs), may be involved in making some individuals more susceptible to the problem. ■

Disclosure: Dr. Ganz reported no potential conflicts of interest.