Chemobrain—It's Real, It's Complex, and the Science Is Still Evolving

Talk with almost any cancer survivor, and he or she is likely to bring up the topic of "chemobrain," that fuzzy, murky state that patients blame for impaired memory. A review of the research shows how we're focusing on the problem.
BY SUSAN KRIGEL, PHD
PUBLISHED: FEBRUARY 17, 2015
Talk with almost any cancer survivor, and he or she is likely to bring up the topic of “chemobrain,” that  that fuzzy, murky state that patients blame for impaired memory. When physicians first began hearing patients complain about chemobrain, they may have wondered whether it truly existed. As time has passed, they may now be wondering why science hasn’t found a solution.

A review of the research documenting cognitive decline after chemotherapy indicates that the most common complaints have concerned learning and memory, processing speed, verbal and spatial abilities and executive function (planning and decision-making).

Interestingly, about half of the studies reviewed documented cognitive decline even before the initiation of chemotherapy. Cognitive impairment due to chemotherapy can significantly impair a patient’s quality of life. A recent review of 17 qualitative studies focusing on patients’ experience of chemobrain documented that patients reported fearing that they “were going crazy,” or developing Alzheimer’s. Patients noted they had difficulty learning and had to work harder to accomplish tasks. As a result, they were less confident in work and social situations.

[Read "Finding Solutions for Chemobrain" from CURE's winter 2013 issue]

Estimates vary on the prevalence and duration of chemobrain, due in part to timing of assessment and degree of impairment. A recent meta-analysis demonstrated that about 16 percent to 75 percent of breast cancer patients had moderate to severe impairment. As may be expected, deficits are most evident during treatment, with most patients returning to baseline within a few months of completing chemotherapy. However, a subset of patients has been found to have ongoing deficits, even after 20 years. Older patients with lower cognitive reserve at baseline are most likely to have higher levels of impairment. Co-occuring factors may also contribute to chemobrain. Approximately 30 percent of cancer patients experience depression, anxiety or distress during treatment, and depressed individuals score lower than non-depressed individuals on neuropsychological tests in attention, sustained attention, processing speed, recall, fluency, and speed of retrieval.

Fatigue, an almost universal symptom during and shortly after cancer treatment, may impair memory by decreasing attention, processing speed, and motivation. In addition, about 30 percent to 60 percent of cancer patients report having insomnia, which may cause poor concentration and memory.

What Is the Evidence Behind Chemobrain?

Although cancer patients have been reporting symptoms of cognitive impairment for many years, the first scientific studies began appearing in the mid-1990s. Some of the first studies began exploring the impact of particular chemotherapy protocols on cognition.

But as studies progressed, it seemed that more questions arose than were being resolved. There were so many confounding factors, such as age, hormonal status, baseline cognitive performance, educational level, genetic predisposition, comorbidities that impact oxygenation, depression, anxiety, fatigue, pain, anemia, time since treatment and dietary factors. How would it be possible to control for all those factors?

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