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The association between endocrine therapy use and dementia among post-menopausal women treated for early-stage breast cancer in Ontario, Canada


Purpose — The association between endocrine therapy and risk of dementia remains uncertain. We investigated the association between adjuvant endocrine therapy for breast cancer and risk of developing dementia in a real-world, population-based study.

Methods — We used health administrative data collected from post-menopausal women (aged ≥66 years) who were diagnosed with breast cancer and started on adjuvant endocrine therapy from 2005 to 2012 with follow-up until 2017. Patients were classified by the use of either an aromatase inhibitor or tamoxifen and followed to estimate the unadjusted cumulative incidence of developing dementia. A multivariable Cox proportional hazards model was created adjusting for age, income quintile, medical co-morbidities, and duration of endocrine therapy.

Results — We identified 12,077 patients of whom 73% were treated with an aromatase inhibitor and 27% with tamoxifen. Our multivariable analysis showed a lower rate of dementia in patients treated with an aromatase inhibitor as compared to tamoxifen [Hazard ratio (HR) = 0.88, 95% confidence interval (CI): 0.78–0.98, p-value = .02) at a median follow-up of 5.9 years. The 5-year dementia rate among patient treated with either an aromatase inhibitor or tamoxifen was 7.4% and 9.2% respectively. Older age, previous history of ischemic heart disease, diabetes, hypertension and history of stroke were all significantly associated with the development of dementia.

Conclusion — Aromatase inhibitor therapy was associated with a decreased incidence of dementia as compared to treatment with tamoxifen among post-menopausal women with early stage breast cancer. Further prospective studies with longer-term follow-up investigating the neurocognitive effects of endocrine therapy are warranted.



Blanchette PS, Lam M, Le B, Richard L, Shariff SZ, Pritchard KI, Raphael J, Vandenberg T, Fernandes R, Desautels D, Chan KKW, Earle CC. J Geriatr Oncol. 2020; 11(7):1132-7. Epub 2020 Jun 28.

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