As an organization that promotes the importance of evidence-based medicine, the Susan G. Komen for the Cure is eager to see science yield more answers that will eventually lead to new ways to prevent breast cancer. We have made progress in the US in expanding life-saving access to breast cancer screening and treatment but not in substantially reducing incidence. Many of the identified risk factors, including family history of the disease, age at menarche and menopause, parity, breast density, and age at a first full-term pregnancy, cannot be readily modified. Pursuing new evidence of risk factors that can be changed is a crucial priority if we are to achieve our vision of a world without breast cancer. The preliminary report this year that US breast cancer incidence declined by 7%—14,000 women—in 2003 and that the drop may be due to reduced use of hormone replacement therapy1 reinforces our commitment to studies of other exogenous chemicals, behaviors that affect hormones, and other factors with the potential to significantly affect risk for many thousands of women.
To advance that goal, in 2004, Komen commissioned the Environmental Factors and Breast Cancer Science Review with Massachusetts-based Silent Spring Institute and their collaborating partners at Harvard University, Roswell Park Cancer Institute, and the University of Southern California to collect and assess existing published scientific reports on possible links between specific environmental factors and breast cancer. In its first year the review targeted epidemiologic studies on environmental pollutants, dietary factors, body size, physical activity, and interactions of these factors with various genetic polymorphisms, and the group reviewed toxicology studies to identify chemicals that cause mammary tumors in animals. Reviews are currently under way on additional topic areas: the toxicology of endocrine disruptors, perinatal and early life exposures, nonhormonal pharmaceuticals, tobacco smoke, occupational exposures, light at night, and psychological stress. Topics were chosen to reflect areas of active research with particular promise for identifying new opportunities for prevention.
The chief goal of the Silent Spring Institute study was to evaluate published research to determine what is known and what is not known about the possible link between environmental factors and the incidence of breast cancer. Breast cancer is an extremely complex disease, caused by the interaction of multiple factors, including exposure to carcinogens, genetics, various aspects of lifestyle, and income disparities, among many others. These factors, coupled with the timing, dose, and duration of harmful exposures, further complicate our understanding of and ability to study an individual's risk for developing breast cancer. Understanding the weight of evidence in this multifaceted area of science can guide public information, public health policy, and future research.
The outcomes of the Silent Spring Institute study are of particular value to the scientific research and public policy communities. The study provides:
The most comprehensive, searchable database of potential mammary carcinogens, based on animal studies, including a list of 216 carcinogens and more detailed information on 97 with the most widespread exposure.
A searchable database containing summaries and critical reviews of significant existing and ongoing epidemiologic research regarding possible links between breast cancer and diet, physical activity, body size, environmental pollutants, and gene-environment interactions with these factors. The critical review articles that integrate and evaluate the results contained in the databases are included in this special issue, and the databases are accessible online at www.komen.org/environment and www.silentspring.org/sciencereview
The study results are especially useful in pointing out where there is consensus within the scientific community on the relationship between environmental factors and breast cancer and where additional research or improved research methods are required. As an advocacy organization, Komen has identified several core messages from the science that will inform our work. The results provide consistent evidence to reinforce the importance of physical activity and its potential to lower a woman's risk of developing breast cancer. Conversely, although alcohol consumption increases breast cancer risk, studies of other aspects of diet do not currently support clear recommendations related to breast cancer risk reduction. For environmental pollutants, toxicologic studies raise concerns about a large number of chemicals for which exposure is common; the epidemiologic evidence is beginning to catch up, although this area has received relatively little attention and gaps in our knowledge remain.
The results underscore the need for further research on the relation between dietary factors, environmental pollutants, and breast cancer risk. As a direct follow-up to the review, Komen announced a new “Focused Areas of Study” program that will support at least $5 million in grants to develop new environmental research methods. In addition, Komen continues to fund environmental projects as part of its investigator-initiated grants program, and Komen also supports and champions agencies such as the National Cancer Institute (NCI), the Environmental Protection Agency (EPA), and the National Institute of Environmental Health Sciences (NIEHS) that continue to investigate the impact of the environment on breast cancer incidence.
The review articles contained in this issue and the databases will prove helpful beyond Komen to public policymakers, researchers, advocacy groups, and granting organizations in developing funding strategies and setting research and public policy priorities by providing an evidence-based foundation for decision-making while science continues to unfold. Further, the process of commissioning an assessment of the primary scientific literature and making the review transparent and accessible in online databases is a model that may be helpful to other patient advocate groups.