Cognitive sequelae of endocrine therapy in women treated for breast cancer: a meta-analysis

Purpose Evidence suggests anti-estrogen endocrine therapy (ET) is associated with adverse cognitive effects; however, findings are based on small samples and vary in the cognitive abilities affected. We conducted a meta-analysis to quantitatively synthesize the evidence. Methods Electronic databases were searched in November 2016. Fourteen studies totaling 911 BC patients on aromatase inhibitors (AIs) or tamoxifen (TAM) and 911 controls (i.e., non-cancer controls and BC controls not using ET) were included. Neuropsychological tests were categorized into six domains. Effect sizes were computed to compare (1) ET patients versus controls and (2) TAM patients versus AI patients. Results In cross-sectional comparisons, ET patients performed worse than control groups on verbal learning/memory, visual learning/memory, frontal executive function, and processing speed, but did not differ on psychomotor efficiency or visuospatial function. Subgroup analyses revealed that verbal learning/memory was the only domain where ET patients performed worse than both non-cancer and BC controls. In other domains, ET patients and BC controls performed equivalently. Regarding change from pre-treatment performance, ET patients did not differ from controls on any domain. TAM and AI patients did not from one another differ overall; however, subgroup analyses indicated that TAM patients performed better than non-steroidal AI patients on several domains, but showed few performance differences relative to steroidal AI patients. Conclusions Verbal learning/memory was the only domain where ET patients performed worse than both non-cancer and BC controls, suggesting specific adverse effects on this domain. Additional studies assessing change from pre-treatment performance and differences between steroidal and non-steroidal AIs are warranted.