As I have discussed previously memory complaints are quite common. Many medical conditions and life events are associated with memory complaints or even measureable dysfunction in memory and other areas of cognition. We hear of breastfeeding fog, lupus fog, fibro fog, and then there is chemobrain.
What is chemobrain?
Patients undergoing chemotherapy for cancer often complain of mild problems with memory, attention and speed of thinking. This has been called chemobrain or chemotherapy-induced cognitive impairment. Contrary to what you might believe cognitive problems are not only noted by those who receive chemotherapy for brain cancer but among patients with a variety of cancers.
Chemobrain has been most studied in breast cancer. It has been found that 20 – 75% of women notice changes in cognition following chemotherapy for breast cancer. But does this necessarily mean that chemotherapy causes brain dysfunction which eventually leads to cognitive dysfunction?
Does chemotherapy cause chemobrain?
Patients who notice memory problems during chemotherapy may naturally be concerned about possible toxic effects on the brain. But there are other possible explanations of chemobrain than toxicity. Cognitive complaints might be due to anxiety, low mood, lack of sleep and fatigue associated with a serious and potentially lethal disease and difficult treatment. It has also been suggested that the cancer itself, rather than the therapy, might influence cognitive ability. There are other possible causes (e.g. hormonal imbalances in breast cancer). And, as always, there might be more than one reason for the observed complaints in a group of patients! We should not forget individual differences!
The notion that chemotherapy adversely affects the brain and cognition has also been challenged on the grounds that the studies documenting it have been flawed. For example, comparing the cognitive status of two groups of patients with the same type of cancer, with one group receiving chemotherapy and the other not, is important. It is also important to follow patients over time and take into account prior cognitive functioning. In a well conducted study where women with breast cancer were assessed prior to chemotherapy as well as after 6 and 18 months Jenkins and colleagues found that “a few women experienced objective measurable change in their concentration and memory following standard adjuvant therapy, but the majority were either unaffected or even improve over time” (p. 828).
Chemotherapy drugs are cytotoxic. They kill cancer cells but also healthy cells. Some anticancer drugs can enter the brain although they may not be directed at it. It is therefore not illogical to postulate that chemotherapy may cause damage to the brain. Studying rats is the ideal way to look at this. When studying rats we avoid the complications associated with cancer therapy in humans (e.g., depression, anxiety, different coping skills etc.). Nokia and her colleagues recently showed that chemotherapy interfered with learning in rats. Chemotherapy also reduced neurogenesis (i.e. the development of new cells) in the hippocampus which is critical for normal memory functioning.
An important area of research
Research in this area is obviously quite important and we have a lot to learn. We need more, and better, studies looking directly at brain structures in human chemotherapy survivors. The few studies that already have been conducted are not without limitations (e.g., few patients) but they show some specific structural brain changes following chemotherapy.
With an ever increasing number of cancer survivors it is important to investigate fully the possible side-effects of available treatments. Last but not least we need to focus on helping patients to maintain psychological health during cancer treatment as well as teach them how to deal with memory and attentional problems in daily life.
Jenkins, V. et al. (2006). A 3-year prospective study of the effects of adjuvant treatments on cognition in women with early stage breast cancer. British Journal of Cancer, 94, 828 – 834
Nokia, M. S., Anderson, M. L. And Shors, T. J. (2012). Chemotherapy disrupts learning, neurogenesis and theta activity in the adult brain. European Journal of Neuroscience, 36, 3521-3530.
Raffa. R. B. et al. (2006). Is ‘chemo-fog’/’chemo-brain´ caused by cancer chemotherapy? Journal of Clinical Pharmacy and Therapeutics, 31, 129-138.
Raffa, R. B. (2010). Is a picture worth a thousand (forgotten) words?: neuroimaging evidence for the cognitive deficits in ‘chemo-fog’/’chemo-brain´. Journal of Clinical Pharmacy and Therapeutics, 35, 1-9.
Wefel, J. S., Saleeba, A. K., Buzdar, A. U. og Meyers, C. A. (2010). Acute and late onset cognitive dysfunction associated with chemotherapy in women with breast cancer. Cancer, 116, 3348-3356.
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