SUMMARY REPORT

Review of Lifestyle and Environmental
Risk Factors for Breast Cancer

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Report of the Working Group on Primary Prevention of Breast Cancer

Canadian Breast Cancer Initiative

SUMMARY REPORT: Review of Lifestyle and Environmental Risk Factors for Breast Cancer (375 KB) in PDF Format

CONTENTS

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Introduction

Summary of Literature Reviews (by topic)

Chapter 1:	Review of Diet and Breast Cancer
Chapter 2:	The Association Between Breast Cancer and Alcohol Consumption
Chapter 3:	Review of Anthropometric Factors and Breast Cancer
Chapter 4:	Review of Physical Activity and Breast Cancer
Chapter 5:	The Association Between Breast Cancer and Active Smoking and Exposure to Environmental Tobacco Smoke
Chapter 6:	Literature Review of Associations Between Breast Cancer and Occupational Exposures
Chapter 7:	The Association Between Breast Cancer and Exposure to Extremely Low Frequency Electromagnetic Fields
Chapter 8:	Organochlorines: A Meta-analysis
Chapter 9:	Emerging Hypotheses and Methodological Approaches in Breast Cancer Etiology
Chapter 10:	Review of the Mechanism of Action of Some Etiologic Risk Factors for Breast Cancer
Chapter 11:	Breast Cancer Etiology and Prevention from an Evolutionary Perspective

Conclusion and Recommendations for Future Research

References

Appendix: Recommendations (by topic)

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INTRODUCTION

Anastasia Chyz, MA, Janet Faith, MSc, Christine Friedenreich, PhD, Mark Goldberg, PhD, Sarah Lenz, MSc

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This report summarizes 11 literature reviews completed by members of the Canadian Breast Cancer Initiative Working Group on Primary Prevention of Breast Cancer. These reviews were prepared in response to concern about the possible association between breast cancer and potentially modifiable risk factors such as diet and exposure to specific chemicals. Members of the Working Group reviewed the scientific literature and outlined their findings and recommendations in Review of Lifestyle and Environmental Risk Factors for Breast Cancer. The literature reviews were written in order to

• summarize the scientific evidence for the associations between selected modifiable risk factors and breast cancer
• identify gaps in current understanding regarding these relationships
• highlight the biological mechanisms that might be operative if these associations are indeed causal
• provide recommendations for future epidemiological and related interdisciplinary research.

Each author or group of authors focused on one of the following topics:

• Diet
• Alcohol consumption
• Anthropometric factors
• Physical activity
• Active smoking and exposure to environmental tobacco smoke
• Occupational exposures
• Electromagnetic field exposure
• Organochlorines
• Emerging hypotheses and methodological approaches
• Biological mechanisms for breast cancer
• Evolutionary etiology of breast cancer

This introductory section describes the work of the Canadian Breast Cancer Initiative and the Working Group; it also provides an overview of breast cancer in Canada and the world. The body of the Summary Report contains a summary of each literature review completed, and the concluding section describes the Working Group's recommendations, which are listed with each summary and in the Appendix.

The Canadian Breast Cancer Initiative

Breast cancer is the most frequently diagnosed cancer among Canadian women. Early in the year 2000, estimates suggested that there would be 19 200 new cases and 5500 deaths from this disease.¹ Recognizing that breast cancer is an important health issue in need of a nationwide initiative, Health Canada established the Canadian Breast Cancer Initiative (CBCI) in 1993. The activities and programs of the CBCI are designed to

• reduce the incidence of breast cancer
• reduce mortality from breast cancer
• improve the quality of life of those affected by breast cancer.

Phase I

The need for a federal initiative in the area of breast cancer was brought to the forefront in 1992 with the publication of "Breast Cancer: Unanswered Questions," a report from the Standing Committee on Health and Welfare, Social Affairs, Seniors, and the Status of Women. The federal government responded to this report by launching Phase I (1993-1998) of the CBCI with a $25-million, 5-year commitment to support breast cancer research and other related activities. The government contributed $10 million to the Canadian Breast Cancer Research Initiative (CBCRI) and dedicated the remaining $15 million to the development and enhancement of program activities for clinical practice guidelines, breast cancer screening, information exchange pilot projects, and professional education.

Phase II

In 1998, the federal government recognized the need to continue building on the important work accomplished in the breast cancer programs and research of Phase I, and renewed its commitment to the CBCI for Phase II (1998-2003) with stable, ongoing funding of $7 million per year. In addition, the Medical Research Council, now the Canadian Institutes of Health Research (CIHR), agreed to contribute $2 million per year to the Canadian Breast Cancer Research Initiative over the same period.

The renewed CBCI represents a collaborative effort involving federal, provincial, and territorial governments, professional associations, non-governmental organizations, academic institutions, and community groups. Phase II involves an expansion of research and programs that will build on the products, services, and outcomes of Phase I, while incorporating the capacity to address gaps in knowledge and emerging issues related to breast cancer. During Phase II, the CBCI will focus on the following areas:

• Research on breast cancer
• Prevention, early detection, and screening
• Surveillance and monitoring
• Enhancement of high-quality approaches to diagnosis, treatment, and care
• Community capacity building
• Evaluation and coordination.

The Primary Prevention Working Group

In 2000 the CBCI established a Working Group on Primary Prevention of Breast Cancer to advise on the priority areas for research and prevention initiatives. In order to fulfill its mandate, the Working Group conducted a series of literature reviews on the association between breast cancer and factors possibly implicated in the etiology of the disease. Given that there are many possible risk factors that could be considered when dealing with primary prevention of breast cancer, the group decided to limit the scope of its work by focusing on modifiable risk factors, such as cigarette smoking, alcohol consumption, and occupational exposures. Much research has already been done on non-modifiable risk factors, such as menstrual history. Furthermore, when developing public health recommendations and population interventions, it is more appropriate to focus on behaviours and risk factors that individuals may be able to modify or that regulatory agencies may be able to control in some way (e.g., eliminating the use of carcinogenic chemicals in the workplace).

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Note: An examination of the literature on chemoprevention of breast cancer was considered beyond the scope of the Working Group's mandate. Instead, the CBCI's Steering Committee on Clinical Practice Guidelines for the Care and Treatment of Breast Cancer and the Canadian Task Force on Preventive Health Care have undertaken an extensive review of the literature on chemoprevention, and jointly developed a clinical practice guideline on this topic. The guideline presents evidence and recommendations regarding the benefits and risks of chemoprevention of breast cancer with the estrogen modulators tamoxifen and raloxifene.²

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Joint CBCI/CBCRI workshop on the primary prevention of breast cancer

The literature reviews that this report summarizes were prepared as background for a workshop on the primary prevention of breast cancer. The epidemiological evidence collected in Review of Lifestyle and Environmental Risk Factors for Breast Cancer will be the basis for discussion when a panel of invited scientists joins the Working Group members in delineating future steps for research in primary prevention of breast cancer.

This workshop will be held in Quebec City on May 3, 2001, before the second CBCRI Reasons for Hope scientific research conference. The CBCI and the CBCRI have convened this meeting with the following goal and objectives in mind:

Goal

To identify gaps in knowledge and research needs for breast cancer in women that will inform primary prevention research (excluding research about chemoprevention)

Objectives

• To evaluate scientific data regarding the etiology of breast cancer
• To provide recommendations for future research on modifiable risk factors with particular emphasis on lifestyle and environmental risk factors and the underlying biological mechanisms involved in the etiology of breast cancer

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Members of the Working Group on Primary Prevention of Breast Cancer: Christine Friedenreich, PhD (Chair); Kristan J. Aronson, PhD; Karen DeKoning; Mark Goldberg, PhD; Ruth Heisey, MD; Valerie Hepburn; Rosemonde Mandeville, MD, PhD; Carolyn Pim, MD; Katherine Wynne-Edwards, PhD

Health Canada Participants: Anastasia Chyz, Dr. Rosemarie Ramsingh, Carol Silcoff

Authors of the document summarized in this report, Review of Lifestyle and Environmental Risk Factors for Breast Cancer: Kristan J. Aronson, PhD; Sally Campbell, MSc; Janet Faith, MSc; Christine Friedenreich, PhD; Mark Goldberg, PhD; Maria-Graciela Hollm, BSc; France Labrèche, PhD; Sarah Lenz, MSc; Rosemonde Mandeville, MD, PhD; Marie-France Valois, MSc; Christy G. Woolcott, MSc; Katherine Wynne-Edwards, PhD

Editor of the Summary Report: Barbara Tomlin, West Coast Editorial Associates

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SUMMARY REPORT: Review of Lifestyle and Environmental Risk Factors for Breast Cancer

(375 KB) in PDF Format