Association of Endocrine Therapy and Dementia in Women with Breast Cancer

Abstract

Mikayla R Thompson,1 Jiangong Niu,2 Xiudong Lei,2 Malgorzata Nowakowska,3 Mackenzie R Wehner,2,4 Sharon H Giordano,2,5 Kevin T Nead6,7 1Department of Epidemiology and Environmental Health, University at Buffalo School of Public Health and Health Professions, Buffalo, NY, USA; 2Department of Health Services Research, University of Texas MD Anderson Cancer Center, Houston, TX, USA; 3Department of Medicine, Baylor College of Medicine, Houston, TX, USA; 4Department of Dermatology, University of Texas MD Anderson Cancer Center, Houston, TX, USA; 5Department of Breast Medical Oncology, University of Texas MD Anderson Cancer Center, Houston, TX, USA; 6Department of Epidemiology, University of Texas MD Anderson Cancer Center, Houston, TX, USA; 7Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX, USACorrespondence: Kevin T Nead Tel [phone]Email [email protected]: 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

Keywords

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