A new prospective study has reported that chemotherapy for breast cancer results in measurable reductions in brain gray matter, translating into cognitive decline (commonly referred to as "chemo brain"). The study was designed to measure changes in gray matter in women before and after breast cancer treatment. Changes in gray matter have previously been reported after cancer treatment in magnetic resonance imaging (MRI) studies of breast cancer patient brains. This is the first prospective MRI study of women undergoing treatment for breast cancer (with and without chemotherapy) compared to healthy controls. Participants included 17 breast cancer patients treated with chemotherapy and 12 breast cancer patients not treated with chemotherapy, as well as 18 matched cancer-free women (the controls). MRI scans were performed at baseline (after breast cancer surgery but before radiation, chemotherapy, or anti-estrogen treatment), one month after completion of chemotherapy, and one year later. Voxel-based morphometry, a technique designed to compare brain volume, was used to evaluate gray matter density differences between the three study groups and over time. At baseline, there were no gray matter differences between the cancer patients and the cancer-free controls.

One month after chemotherapy, the chemotherapy group was found to have lower gray matter density in bilateral frontal, temporal, and cerebellar regions and in the right thalamus compared to baseline. Recovery was observed one year later in some brain regions, however some persistent reductions were also found. No significant changes were observed among the breast cancer patients who did not receive chemotherapy or the cancer-free controls. Further analysis demonstrated that these findings were not attributable to the recency of cancer surgery, cancer stage, psychiatric symptoms, psychotropic medication use, or the use of anti-estrogen treatments. The authors conclude that the gray matter alterations found in the study appear to be related primarily to chemotherapy, rather than individual patient factors, the cancer disease process, or the effects of other types of cancer treatments such as anti-estrogen therapy.