Objective: The primary purpose of this study was to evaluate the cognitive effects of adjuvant hormonal therapies in breast cancer patients.

Participants and methods: Post-menopausal breast cancer patients scheduled to receive tamoxifen (n=31) or anastrozole (n=14) completed neuropsychological testing around the time of commencement of treatment (T1), and again 5-6 months later (T2). A sample of healthy female volunteers (n=28) was tested at comparable intervals. A standardized regression-based approach was used to assess cognitive change. This method uses test/retest scores of the healthy control group to generate an equation that predicts T2 scores from T1 scores. The difference between the predicted and obtained T2 scores divided by the standard error of the estimate produces a deviation score that reflects the discrepancy from the T1-T2 difference scores that would be expected on the basis of practice and error alone.

Results: Analysis of individual deviation scores revealed that both the patients taking tamoxifen and those taking anastrozole were more likely than healthy controls to show reliable cognitive decline from T1 to T2 (39, 64, and 7%, respectively). Processing speed and verbal memory were the cognitive domains most affected.

Conclusion: These data suggest that hormonal therapies exert a subtle negative influence on cognition in breast cancer patients. Further analyses indicated that this effect was not fully accounted for by demographic factors or fatigue. Methodological limitations of the current study are addressed, along with recommendations for future studies in this area.