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


Talk with almost any breast cancer survivor, and they're likely to bring up the topic of "chemobrain," that fuzzy, murky state that patients blame for impaired memory.

Talk with almost any breast cancer survivor, and they’re likely to bring up the topic of “chemobrain,” that fuzzy, murky state that patients blame for impaired memory. When you first began hearing patients complain about chemobrain you may have wondered whether it truly existed. As time has passed, you may now be wondering why science hasn’t found a solution.

This column, the first of three, will focus on the basics of chemobrain: the type of complaints reported by patients, timeframe and prevalence, and other factors which may impair memory. Future posts will concentrate on the evolving science behind chemobrain, as well as providing strategies for coping with cognitive deficits due to chemobrain.

What Types of Complaints Are Reported?

In a review of both cross-sectional and prospective longitudinal studies documenting cognitive decline after chemotherapy, the most common complaints concerned learning and memory, processing speed, verbal and spatial abilities, and executive function (planning and decision-making).1 Interestingly, about half of the studies reviewed documented cognitive decline even before the initiation of chemotherapy. Cognitive impairment due to chemotherapy can significantly impair patients’ quality of life.2 A recent review of 17 qualitative studies focusing on patients’ experience of chemobrain3 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.

Does Everyone Get Chemobrain? How Long Does It Last?

There is a broad range of estimates of the prevalence and duration of chemobrain, due in part to timing of assessment and degree of impairment. A recent meta-analysis4 demonstrated that about 16% to 75% of breast cancer patients had moderate to severe impairment. As 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.5 Older patients with lower cognitive reserve at baseline are most likely to have higher levels of impairment.6

Patients Go Through A Lot During Treatment. Aren’t There Factors Other Than Chemotherapy That Can Impair Memory?

Absolutely. Memory is a complex process. At the most basic level, memory involves three processes: encoding, storage, and retrieval. These processes require filtering out extraneous stimuli, paying sustained attention to stimuli, and shifting from one stimulus to another. The speed at which an individual processes information is important because slower processing speed raises the chance that the process of creating a memory may be interrupted. Motivation also plays a part because motivation provides the drive to continue to focus on one thing, or to work at trying to retrieve a memory.

Fatigue, distress, and insomnia may also impact the ability to remember. Fatigue, an almost universal symptom during and shortly after cancer treatment, may impair memory by decreasing attention, processing speed, and motivation.

Approximately 30% of cancer patients experience depression, anxiety, or distress during treatment,6 and depressed individuals score lower than non-depressed individuals on neuropsychological tests in attention, sustained attention, processing speed, recall, fluency, and speed of retrieval. In addition, about 30% to 60% of cancer patients report having insomnia,7 which may cause poor concentration and memory.


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  • Wefel JS, Schagen SB. Chemotherapy-related cognitive dysfunction. Curr Neurol Neurosci Rep. 2012;12:267-275.
  • Ahles TA, Saykin A. Cognitive effects of standard-dose chemotherapy in patients with cancer. Cancer Invest. 2001;19:812-820.
  • Myers JS. Cancer- and chemotherapy-related cognitive changes: The patient experience. Sem Oncol Nursing. 2013;29:300-307.
  • Jim HSL, Phillips KM, Chait S, et al. Meta-analysis of cognitive functioning in breast cancer survivors previously treated with standard-dose chemotherapy. J Clin Oncol . 2012;30:3578-3587.
  • Koppelmans V, Breteler MMB, Boogerd W, et al: Neuropsychological performance in survivors of breast cancer more than 20 years after adjuvant chemotherapy. J Clin Oncol. 2012;30:1-7.
  • Ahles TA, Saykin AJ, McDonald BC, et al. Longitudinal assessment of cognitive changes associated with adjuvant treatment for breast cancer: Impact of age and cognitive reserve. J Clin Oncol. 2010;28:4434-4440.
  • Zabora J, Brintzenhofeszoc K, Curbow B, et al. The prevalence of distress by cancer site. Psycho-Oncol. 2001;10:19-28.
  • Garland SN, Johnson JA, Savard J, et al. Sleeping well with cancer: a systematic review of cognitive behavioral therapy for insomnia in cancer patients. Neuropsych Disease Treatment. 2014;10:1113-1124.

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