Effects of tamoxifen and exemestane on cognitive function in postmenopausal patients with breast cancer

Cognitive effects of tamoxifen have been described. We augment data from a previous short-term (ST) follow-up study with long-term (LT) data to evaluate ST and LT cognitive effects of tamoxifen followed by exemestane and exemestane in breast cancer patients.

Patients from the Tamoxifen and Exemestane Adjuvant Multinational trial received 5 years exemestane (exemestane group, n = 114) or 2.5 years tamoxifen followed by 2.5 years exemestane (sequential group, n = 92). Neuropsychological performance was assessed pre-endocrine therapy, after 1 year (ST follow-up) and at 5 years (LT follow-up). A control group of healthy participants (n = 120) were assessed with parallel intervals. With random effects modeling we evaluated cognitive changes from baseline to ST and LT follow-up. Statistical tests were 2-sided.

After controlling for age, intelligence quotient, attrition, menopausal symptoms, anxiety and/or depression, and/or fatigue, the sequential group showed ST and LT decline compared with control participants on verbal memory (effect size [ES] = 0.26, P = .01; ES = 0.34, P = .003) and executive function (ES = 0.27, P = .007; ES = 0.38, P = .002). Compared with the exemestane group, the sequential group demonstrated ST decline on information processing speed (ES = 0.33, P = .01) and executive function (ES = 0.32, P = .01) and LT decline on verbal memory (ES = 0.33, P = .02). The exemestane group showed no cognitive decline compared with control participants.

Cognitive adverse effects of tamoxifen alone and after switching to exemestane were observed, suggestive of a carryover effect of tamoxifen. Our results underline the need for well-controlled, prospective trials studying cognitive effects of endocrine therapy.