investments would facilitate sustained coordination across research and regulatory agencies with the objective of reducing or eliminating harmful environmental exposures and modifying social and lifestyle factors implicated in breast cancer. Transform How Research Is Conducted The Committee recommends investigation into compelling scientific themes using a transdisciplinary approach. Studies of breast cancer over time have revealed a complex disease. Researchers have distinguished several subtypes of breast cancer, each with potentially different causes and contributing factors that could require different approaches for research and for prevention.4 By engaging investigators from many disciplines, including epidemiology, basic/ mechanistic science, toxicology, social science, and computer and information science, new ways of thinking about breast cancer prevention can be developed. Investing in the development of tools to facilitate knowledge management and integration also is essential for success. Committee Recommendations • Prioritize prevention. • Transform how research is conducted. • Intensify the study of chemical and physical factors. • Plan strategically across federal agencies. • Engage public stakeholders. • Train transdisciplinary researchers. • Translate and communicate science to society. By urgently pursuing research, research translation, and communication on the role of the environment in breast cancer, we have the potential to prevent a substantial number of new cases of this disease in the 21st century. Prioritize Prevention The Committee recommends a national breast cancer prevention strategy to prioritize and increase federal government investments in breast cancer prevention. Historically, investments in breast cancer research have focused primarily on diagnosis and cure. Comparatively speaking, there are remarkably few examples of advances in the area of breast cancer prevention, and finding ways to identify and What is the environment? For this report, the environment includes: • Lifestyle and behavioral factors, such as alcohol intake and physical activity. • Chemical agents that people are exposed to through pesticides, industrial pollutants, consumer products, and medications. • Physical agents, such as radiation from medical and other environmental sources and other nonchemical substances. • Social and cultural influences, such as family, community, psychosocial/social, and societal factors that may influence breast cancer risk. 1-3 Breast Cancer and the Environment: Prioritizing Prevention 1 Intensify the Study of Chemical and Physical Factors The Committee recommends research on the effects of chemical and physical factors that potentially influence the risk of developing and likelihood of surviving breast cancer. Past studies have identified contributors to breast cancer risk, including: (1) increased age; (2) family history of breast cancer; (3) certain rare genetic variants, including BRCA 1 and 2; (4) alcohol consumption; (5) a sedentary lifestyle; (6) benign breast disease; (7) high breast density; (8) radiation exposure; (9) a number of reproductive characteristics, including early age at menarche; (10) hormonal influences; and (11) high body mass index for risk of postmenopausal breast cancer. These recognized risk factors have not been examined in interaction with physical and chemical exposures, and most have not been examined by breast cancer subtype. In addition to these established risk contributors, several other risk factors have been identified with some evidence linking them to breast cancer. The Committee recommends making research efforts to close the knowledge gap about these potential risk factors a priority. Characterizing the myriad of exposures in our environment is another important challenge. Certain chemicals—for example, endocrine disruptors and physical agents such as low-dose radiation—require further research that employs the animal-human paradigm. This paradigm integrates animal and human research to accelerate progress in understanding breast cancer. Filling knowledge gaps regarding how environmental exposures affect the mammary gland in animals and the breast in humans requires a comprehensive approach that includes in vivo, in vitro, and human studies. Improved understanding of the molecular and clinical features of the different subtypes of breast cancer, the availability of high-throughput testing methods, and the integration of different types of chemical testing have created opportunities to make Factors such as lifestyle, social context, economic determinants, and disproportionate environmental exposures must be examined, particularly in minority and underprivileged populations. In addition, studies must examine how exposures and risk profiles differ among racial and ethnic groups, particularly groups that are insufficiently studied. Targeted research can improve understanding of the specific environmental risks for breast cancer in underserved populations. This research can in turn form the basis for new, comprehensive policies to reduce the broad spectrum of exposures that increase risk, ameliorate environmental disparities, and promote behaviors that can reduce breast cancer risk. The complexity of breast cancer necessitates increased investment in research to explore