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Breast Cancer. 2005;12(4):279-87.

Mild cognitive impairment after adjuvant chemotherapy in breast cancer patients--evaluation of appropriate research design and methodology to measure symptoms.

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Department of Epidemiology, National Institute of Public Health, Wako-shi, Saitama 351-0197, Japan.


The development of new chemotherapeutic agents and regimens has contributed to reduced risk of cancer recurrence and prolonged patient survival. However, mild cognitive impairment (MCI), also known as ''chemofog'' or ''chemobrain'' following adjuvant chemotherapy for breast cancer has been reported since the late 1980s. Unfortunately, little is known about it's mechanism, type, severity, and episode length. This article reviewed related studies on the subject, and found that chemotherapy-induced MCI appears to occur in 10-40% of patients, and memory loss and lack of concentration are the most frequent symptoms. The symptoms are apparently transient, but take at least several years to disappear. Reviewed studies show a lack of clear understanding of what causes MCI directly. There is also a lack of consistency in symptom measurement. We point to the need to conduct well-designed studies which begin with a proper hypothesis. Future research needs to be randomized and longitudinal with a base measurement point before the chemotherapy cycle starts. Future studies must adopt an effective and sensitive method to measure MCI. The latest imaging technique, positron emission tomography (PET) may be a powerful tool. Also, all confounding factors, such as age, education, intelligence quotient (IQ), fatigue and depression, hormonal therapy and other treatments should be controlled within the study design. It is hoped that the results of such future studies will allow medical professionals to contemplate effective prevention, treatment and rehabilitation for MCI.

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