Pre-diagnostic Blood Selenium Status and Mortality Among Women with Breast Cancer Open Access

Abstract

Evidence from experimental studies support a possible association between higher selenium (Se) status and lower mortality risk among breast cancer survivors. However, human data are limited and mostly include dietary assessment of Se intake. Therefore, more studies are needed to understand this association especially in populations that may have low exposure to Se.

The associations of pre-diagnostic Se status [as measured by serum Se and selenoprotein P (SePP)] with overall and breast cancer-specific mortality were estimated using multivariable Cox proportional hazards regression among 2,205 breast cancer cases in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Potential effect modification by biologically plausible reproductive, lifestyle, and environmental factors was also investigated.

Over a mean follow-up period of 10.6 years (SD = 3.70), 496 deaths occurred of which 322 (64.9%) were due to breast cancer. Se was measured on average 4.48 years (SD = 2.71) and SePP was measured on average 4.75 years (SD = 2.64) before cancer diagnosis. None of the associations in the primary analysis were statistically significant. In stratified analyses, there was evidence of a potential effect modification by tumor stage, geographic region, body mass index, and smoking status. For breast cancer-specific mortality, the HRs per 1 SD increase in Se were 0.77 (95% CI: 0.61-0.96) for never smokers, 1.25 (95% CI: 0.97-1.60) for former smokers, and 1.32 (95% CI: 0.93-1.89) for current smokers (p interaction < 0.001). For overall mortality, the HRs per 1 SD increase in Se were 0.82 (95% CI: 0.68-0.98) for never smokers, 1.15 (95% CI: 0.93-1.42) for former smokers, and 0.91 (95% CI: 0.70-1.19) for current smokers (p interaction = 0.006).

Our results suggested that higher pre-diagnostic exposure to Se is not associated with lower risk for overall and breast cancer-specific mortality among breast cancer survivors. However, it is possible that this association is limited to never smokers and possibly other subgroups of breast cancer survivors.

Table of Contents

Introduction …………………………………………………………………...………….………1

Methods ……………………………………………………………………………….………….12

Results …………………………………………………………………………………..………..17

Discussion …………………………………………………………………………….….………20

Public Health Implications ……………………………………………………………..………24

References ……………………………………………………………………………….………26

Tables ………………………………….…………………………………………….…………..30

Appendix ………………………………………………………………………….………….….34

About this Master's Thesis

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School	Rollins School of Public Health
Department	Epidemiology
Subfield / Discipline	Epidemiology - MPH & MSPH
Degree	M.P.H.
Submission	Master's Thesis
Language	English
Research Field	Health Sciences, Epidemiology
Keyword	Breast Cancer Survival Selenium Overall Mortality Breast Cancer Specific Mortality
Committee Chair / Thesis Advisor	Roberd M. Bostick, Emory University
Committee Members	Veronika Fedirko, Emory University

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