Harvard Reports on Cancer Prevention
Volume I: Human Causes of Cancer
Cancer Causes & Control:
An International Journal of Studies of Cancer in Human Populations
Official Journal of the International Association of Cancer Registries
Volume 7 Supplement November 1996 ISSN 0957-5243

Introduction

Harvard's Center for Cancer Prevention has been established on the premise that prevention offers the best hope for significantly reducing the suffering and death caused by cancer. This hope can be realized only if the public is adequately informed about what places people at risk of cancer, what measures they can take as individuals to reduce that risk, and what social policies can be implemented to reduce cancer risk for the population as a whole.

The Harvard Report on Cancer Prevention is designed to meet this educational need by providing a comprehensive overview of what we know about cancer risk in the United States and the preventive measures that people can take. The Report, written by Harvard-affiliated researchers and reviewed by other highly regarded investigators across the US, is intended to serve as a resource on cancer prevention for the scientific and medical communities, policy makers, news media, and general public.

Volume 1, Causes of Human Cancer, summarizes what we know from epidemiologic research on what does (and does not) cause cancer in the US. Each chapter covers recent investigations on several potential sources of risk (e.g., smoking, diet, occupational exposure, environmental pollutants). One of the most important conclusions to be drawn from this review is that cancer is indeed a preventable illness. Nearly two-thirds of cancer deaths in the US can be linked to tobacco use, diet, and lack of exercise.

Volume 2, Prevention of Human Cancer, which is planned for release in 1997, will summarize research on cancer screening, prevention programs, public education campaigns, and social policy measures for preventing cancer. Working in schools, health clinics, and workplaces as well as through the mass media and in the political arena, social scientists and health educators are designing innovative and effective health promotion programs to help people quit smoking, eat healthier, exercise more, and have regular screenings for cancer.

In subsequent years, the Center will publish updates of the Report so that readers can be kept abreast of developments in this fast-breaking field of inquiry.

Volume I: Causes of Human Cancer

Purpose
The public is saturated with news reports about studies that purport to show that cancer is associated with a variety of behaviors, foods, consumer goods, and environmental factors. Often this information is not placed into any understandable context about the degree of risk involved. As a result, the public can become overly concerned about minimal risks while losing sight of major cancer risk factors that can be controlled or modified, in particular, tobacco use, diet, exercise, and sun exposure.

Public confusion about cancer prevention is made worse by news coverage that indiscriminately reports even preliminary research findings. Truly, the public's perception of what they should do to maintain their good health changes moment to moment, depending on the latest headline. Recent reports have suggested that many Americans, frustrated by the cacophony of contradictory advice, are tuning out even accurate information.

In response, epidemiologists and other researchers have an obligation to take stock of what the research shows, sort through the sometimes conflicting findings, and then develop consensus recommendations to guide future research, health education programs, and policy development. Causes of Human Cancer is designed to meet this need.

We have prepared this report with both scientific and lay audiences in mind. The heart of each chapter is a brief review of the research literature on the impact of various exposures on a variety of cancers. Each chapter concludes with a consensus statement that represents the Harvard Center for Cancer Prevention's best scientific judgment about what the research tells us at this time.

At the same time, in order to meet the needs of policy makers, the news media, and the general public, we have deliberately avoided using technical language whenever possible. Our goal, then, is to offer research summaries that have scientific integrity, yet are simple enough to understand, memorable, and capable of motivating public action when that is appropriate. Each chapter includes a sidebar with recommendations based on the research evidence.

Contents
Causes of Human Cancer is organized by type of risk exposure rather than by cancer site (e.g., lung, colon, stomach). Focusing on risk exposures has the advantage of pointing the way to those factors that should be the focus of intensive public education and policy development efforts. Each chapter deals with a different risk exposure:

The final chapter provides a summary of the report's major conclusions. Attention is given both to protective factors that reduce cancer risk and harmful factors that increase risk. A table is presented that can be used for easy reference.

Given the nature of the research, use of some technical terms is unavoidable. Lay readers can refer to a glossary of terms in the appendix. It includes a mix of cancer related technical terms (e.g., sarcoma, carcinoma, and lymphoma) and epidemiologic technical terms (e.g., incidence, prevalence, confounder) that appear through out the volume.

Acknowledgments—We are grateful to our Harvard colleagues who contributed to this report. It is their participation that makes this report a unique contribution to the field of cancer prevention.

We are also grateful to Vincent L. Gregory Jr., who serves as chair of the advisory board for the Harvard Center for Cancer Prevention, for his leadership and inspiration; to Bryn Austin for her editorial assistance; and to Pamela Peirez and Alix Smullin for providing administrative and logistical support.

We also thank the following experts for serving as reviewers:

Development of the Harvard Report on Cancer Prevention was supported by the generous contributions of Margorie G. and Vincent L. Gregory Jr.

Editors