Breast cancer is one of the most common public-health problems, with an estimated worldwide incidence of 39 per 100,000 individuals annually.1 In 2011, it was predicted that over 230,000 women would be diagnosed with breast cancer, and close to 40,000 would die of this disease.2 As more breast cancer survivors are living longer post-treatment, there is a serious need to understand the long-term outcomes of adjuvant therapies, as well as the cancer itself. Bone-marrow suppression, malnutrition, and infection/fever are the most commonly associated adverse effects experienced with chemotherapy.3 The incidence of neurotoxicity, although less well known, is often associated with peripheral neuropathy and encephalopathy, which fall under the traditional definition of neurotoxicity. 4
Many women experience chemotherapy-induced cognitive changes in memory, attention, psychomotor speed, and executive functioning. Some refer to this as “chemo brain” or “chemo fog,” a mental haziness that occurs during and shortly after chemotherapy.5,6 Several neuropsychological trials have confirmed these chemotherapy-induced cognitive changes.7–10 The question remains as to whether or not these changes are associated with abnormal brain function. Deprez and colleagues were able to demonstrate a change in cognitive functioning and cerebral white-matter integrity in 34 young, premenopausal women with early-stage breast cancer receiving chemotherapy.11 These women did not perform well on attention, psychomotor, speed, and memory tests as compared to their performance before the start of chemotherapy, and compared to healthy controls and women that did not receive chemotherapy. Chemotherapy-treated women had significant decreases in fractional anisotropy in frontal, parietal, and occipital white matter, whereas both control groups stayed the same.
Breast cancer survivors are increasingly concerned about developing these possible cognitive sequelae, as growing numbers of cancer survivors plan to return to their educational, financial, and familial lives, which rely heavily on their cognitive abilities. There is a growing demand to better understand the impact of chemotherapy and breast cancer on the brain and cognitive functioning.