The term “chemo brain” was coined to describe mild cognitive problems in cancer patients attributed to chemotherapy. Although minor chemotherapy-induced memory and cognitive impairments have been described previously, a case-cohort study suggests that these effects can persist more than 20 years posttherapy.
The authors state that chemo brain effects are subtle compared with women who never had chemotherapy, but it’s possible that these effects place people at greater risk for cognitive decline associated with aging.
A partial explanation for chemo brain may be that chemotherapy penetrates the blood-brain barrier, killing healthy brain cells, or that chemotherapy affects the immune system or is proinflammatory.
The study, published online in February in the Journal of Clinical Oncology (Koppelmans V, Breteler MM, Boogerd W, et al) included 196 breast cancer survivors treated with adjuvant CMF (cyclophosphamide, methotrexate, and fluorouracil) who were tested with a series of cognitive and memory tests. Ages were from 50 to 80 years, the mean number of chemotherapy cycles was 6, and the mean interval since chemotherapy was 21 years. Scores on speed processing, word, memory, and general cognitive functioning tests were compared with scores of a population-based sample of 1509 women who did not undergo cancer treatment and were participants in a larger long-term study.
Women treated with chemotherapy scored significantly lower on tests of immediate and delayed verbal memory, processing speed, executive function, and psychomotor speed than the reference group and similarly on the other 10 tests included in the study. The intergroup differences were small. On word learning tests, women who had chemotherapy had an average score of 24.3 of 45 compared with a score of 25.5 in the control group.
Senior author Sanne Schagen, MD, Netherlands Cancer Institute, Amsterdam, the Netherlands, said that these differences might or might not be apparent, depending on the specific tasks involved in people’s daily lives. Someone in a demanding job might notice these changes in cognition, but someone who is not working and has a more relaxed lifestyle may not.
One limitation of this study is that CMF is an older chemotherapy regimen no longer considered a standard of care. However, Dr Schagen noted that more modern drugs would probably cause the same effects.
Other limitations include the inability to prove cause and effect between chemotherapy and cognitive changes, which may be an effect of breast cancer itself. Also, baseline mental function was not assessed prior to chemotherapy.
The study does not imply that women with breast cancer should not undergo chemotherapy. Rather, the implication is that patients and physicians should be aware of the potential cognitive effects of chemotherapy and seek help if these problems interfere with daily function.
The effects documented in this study do not appear to be serious cognitive impairment or even mild cognitive impairment, but patients are scoring slightly lower on tests of memory and thinking, explained neuropsychologist Barbara Collins, PhD, Ottawa Hospital, Ontario, Canada, who was not involved in this study.