Physical Activity, Sedentary Time, and Intrinsic Subtypes of Breast Cancer Public

Abstract

Previous epidemiologic studies have accumulated evidence that physical activity is associated with reductions in breast cancer risk. Given the heterogeneous nature of breast cancer, is it possible that associations with physical activity may vary by molecular subtype. The relation between sedentary sitting time and breast cancer subtypes is also unclear. Nine-hundred breast cancer cases with molecular data between 1992 and 2011 were identified among 71,057 women in the American Cancer Society Prevention Study II Nutrition Cohort. Joint Cox regression was used to estimate multivariable-adjusted relative risks (RR) of breast cancer subtypes in relation to total recreational physical activity and sedentary sitting time. While the observed associations were not statistically significant (p>0.05), the strongest associations were observed among women with basal-like breast cancer. The most active women (>17.5 MET-hours/week) had a 31% reduction in risk of breast cancer when compared to the least active women [>0-8.75 MET-hours/week; 95% confidence interval (CI), 0.39-1.20; Ptrend=0.14]. Additionally, women who reported sitting at least 3 hours per week experienced 32% increased risk of basal-like breast cancer than the less sedentary (<3 hours per week; 95% CI, 0.83-2.19). Given the poorer prognosis associated with basal-like tumors, the evidence of a modest association between basal-like breast cancer, physical activity and sedentary time may be of public health interest, especially among premenopausal African-American women who are more susceptible to basal-like breast cancer.

Table of Contents

Table of Contents

CHAPTER I: BACKGROUND/LITERATURE REVIEW... 1

1.1 Incidence of Breast Cancer 1

1.2 Intrinsic Subtypes of Breast Cancer 1

1.3 Risk Factors of Breast Cancer

1.3.1 Reproductive factors. 2

1.3.2 Hormonal factors. 3

1.3.3 Anthropometric factors. 4

1.3.4 Physical activity. 5

1.3.5 Sitting Time. 6

1.4 Physical Activity and Breast Cancer: Mechanisms. 7

1.4.1 Sex hormones. 7

1.4.2 Adipokines. 8

1.4.3 Insulin resistance. 9

1.4.4 Other mechanisms: immune functioning, oxidative stress, and epigenetics. 10

1.5 Physical Activity and Intrinsic Subtypes of Breast Cancer 11

1.6 Classification of Intrinsic Subtypes of Breast Cancer 13

1.7 Significance of thesis. 13

1.8 Aims of thesis. 14

CHAPTER II: PHYSICAL ACTIVITY, SEDENTARY TIME, AND INTRINSIC SUBTYPES OF BREAST CANCER.. 15

2.1 Abstract 15

2.2 Introduction. 16

2.3 Methods. 17

2.4 Results. 22

2.5 Discussion. 24

2.6 REFERENCES. 32

2.7 TABLES. 39

CHAPTER III: SUMMARY, PUBLIC HEALTH IMPLICATIONS, POSSIBLE FUTURE DIRECTIONS. 46

4 Appendices. 49

4.1 Appendix A.. 49

4.2 Appendix B.. 50

4.3 Appendix C.. 51

4.4 Appendix D.. 52

About this Master's Thesis

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School	Rollins School of Public Health
Department	Epidemiology
Degree	MPH
Submission	Master's Thesis
Language	English
Research Field	Health Sciences, Public Health Health Sciences, Epidemiology
Mot-clé	Physical Activity Breast Cancer
Committee Chair / Thesis Advisor	McCullough, Lauren, Emory University
Committee Members	Gaudet, Mia, American Cancer Society
Partnering Agencies	National or regional non-profit organization (e.g., American Cancer Society)

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