Jill Shelton, RN, BSN
As nurses, we are often in a unique position to detect subtle changes in our patients, ones that cannot be seen on a monitor or gleaned from an office visit. A slight change in behavior or mood can indicate a problem under the surface, and perhaps nowhere is this more applicable than in our ability to detect signals of chemotherapy-induced cognitive impairment (CICI), also known as “chemobrain.” We must diligently listen to our patients, validate their concerns, and provide strategies they can apply.
To be effective in this endeavor, nurses must stay current with the research and recommendations, with an eye toward understanding possible causes, treatment strategies, and most importantly, learning how we can best support these patients.
With symptoms such as short-term memory loss, difficulty multitasking, and impaired thinking, CICI can be accompanied by commonly associated conditions like fatigue, insomnia, and depression. The research shows that patient concerns most commonly involve learning and memory, processing speed, verbal and spatial abilities, and problems with executive function (eg, planning and decision making).1,2
A validated assessment tool for CICI has not yet been established. Neuroimaging has been used in the setting of studies or clinical trials but is not a cost-effective option.2
An MRI may reveal decreased integrity and volume of cerebral gray and white matter, as well as structural and functional changes that correlate with complaints of cognitive decline.1,3
Neuropsychological testing is time consuming for patients and requires special training to administer. Self-reporting of cognitive decline by patients, although difficult to quantify, still provides important data that indicate what the patient is experiencing and whether there has been improvement.2
Functional MRIs have been used to assess brain activity while performing tasks. Susan Krigel, PhD, a licensed clinical psychologist with the Midwest Cancer Alliance, described a 2007 study by Ferguson et al involving 60-year-old twins—one who had had chemotherapy and one who hadn’t—and each was asked to perform tasks during a functional MRI. For the woman who had chemotherapy, more parts of her brain were seen to be working at the same task, suggesting areas of hyperactivity that may demonstrate deficits.4
“There has also been some thought as time has gone on, that areas of hypoactivity are also indicative of problems,” Krigel explained. “Even at rest, there are differences in what the brain is doing … people who’ve had chemotherapy, whose brains are really active, they’re kind of ping-ponging around as if they have attention deficit disorder.”
Possible Causes of Chemobrain
Merriman et al proposed a model suggesting that the combination of cancer treatment and clinical factors results in changes to regulation of hormones, neurotransmitters, and cytokines. In combination with age and genetics, this leads to cognitive changes.5
Fardell et al proposed a model suggesting that “chemotherapy increases inflammation and oxidative stress and decreases brain vascularization, neurogenesis, growth factors, and catecholamines,” leading to impaired memory and learning.6
Arash and Myers note that variants of genes encoded with apolipoprotein E (APOE), which is involved in repairing the brain after injury, and catechol-O-methyltransferase (COMT), which participates in the breakdown of catecholamines, are associated with age-related decline. The “accelerated aging hypothesis” suggests that cancer treatment speeds up the aging process through multiple channels (ie, inflammation, DNA damage) and individual patients may be susceptible to a certain channel.2
While we know that certain chemotherapy drugs are especially neurotoxic, it can be difficult to differentiate them when multiple agents are used in combination, in addition to radiation or surgery.2
Systemic inflammation from chemotherapy and other treatments such as radiation, surgery, and biologic therapy is another possible cause. Studies show that circulating pro-inflammatory cytokines impair memory in animals and, when administered to the brain, increase use of neurotransmitters that are critical to sleep, memory, and mood.2