Association of Endocrine Therapy and Dementia in Women with Breast Cancer

Abstract

Purpose

Prior studies have reported differing results regarding the association between endocrine therapy (ET) in the treatment of breast cancer and dementia risk. However, existing findings may be limited by common sources of bias and confounding. Here we investigate the association of ET utilized in the definitive setting to treat non-metastatic breast cancer with dementia risk accounting for multiple potential sources of bias and confounding.

Patients and Methods

We conducted a retrospective study in SEER-Medicare of women aged ≥ 66 years with non-metastatic breast cancer. We examined the risk of all-cause dementia among ET users versus non-ET users using multivariable regression models, accounting for the competing risk of death, and using a start of the follow-up period as 12-months following breast cancer diagnosis for both groups to avoid immortal time bias.

Results

Among 25,777 individuals there were 2,869 incident dementia cases. We found a statistically significantly decreased risk of any dementia among ET users in unadjusted and adjusted models that completely attenuated when accounting for the competing risk of death (hazard ratio, 0.98; 95% confidence interval, 0.90–1.07).

Conclusion

When accounting for common sources of bias and confounding we did not find evidence to support an association between ET in the definitive treatment of non-metastatic breast cancer and dementia risk. These results suggest that ET may not be associated with dementia risk.

Keywords:

• breast cancer
• endocrine therapy
• dementia
• aromatase inhibitors
• selective estrogen receptor modulators

Acknowledgments

The research was supported, in part, by National Institutes of Health CCSG P30 CA016672. Dr. Nead and Dr. Wehner are Cancer Prevention Research Institute of Texas (CPRIT) Scholars in Cancer Research. Dr. Nead is supported by CPRIT RR190077. Dr. Wehner is supported by CPRIT FP9178. Dr. Giordano is supported by CPRIT RP160674 and Komen SAC150061. The funding organizations had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication. Dr. Nead had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Dr. Niu conducted and is responsible for the data analysis.

Disclosure

The authors report no conflicts of interest in this work.