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Pages 1-24

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From page 1...
... "Environment" was broadly defined to encompass all factors that are not directly inherited through DNA, and a qualitative review examined current evidence on selected factors that illustrate various environmental agents and conditions that may be more amenable to modification. For some of these factors, epidemiologic studies consistently support associations with increased risk for breast cancer (e.g., ionizing radiation, combination hormone therapy, greater postmenopausal weight)
From page 2...
... Recommendations for research include applying a life course perspective and a transdisciplinary approach to studies of breast cancer, developing new and better tools for epidemiologic research and carcinogenicity testing of chemicals and other substances, developing effective preventive interventions, developing better approaches to modeling breast cancer risks, and improving communication about breast cancer risks to health care providers, policy makers, and the public. B reast cancer has long been the most common invasive noncutaneous cancer among women in the United States, accounting for an esti mated 230,480 new cases in 2011.1 After lung cancer, it is the second most common cause of women's cancer mortality, with about 39,520 deaths expected in 2011.
From page 3...
... REVIEWING EVIDENCE ON CERTAIN ENVIRONMENTAL FACTORS The committee explored the available evidence concerning breast cancer risks associated with a necessarily limited selection of specific factors that illustrate a variety of environmental agents and conditions (see Box S-2 and Chapter 3)
From page 4...
... Review the evidentiary standards for identifying and measuring cancer risk factors; 2. Review and assess the strength of the science base regarding the relationship between breast cancer and the environment; 3.
From page 5...
... ) Dioxins Shift work Metals • Aluminum • Arsenic • Cadmium • Iron • Lead • Mercury aThe committee reviewed a selected set of factors for illustration; the chemicals were not chosen to be representative of any class.
From page 6...
... Among the environmental factors reviewed, those most clearly associated with increased breast cancer risk in epidemiologic studies are use of combination hormone therapy products, current use of oral contraceptives, exposure to ionizing radiation, overweight and obesity among postmenopausal women, and alcohol consumption. Greater physical activity is associated with decreased risk.
From page 7...
... Tracing multiple and potentially interacting causes of breast cancer will be difficult. Some risk factors may have very weak effects or effects in only a small portion of the population, making their contribution to risk hard to detect.
From page 8...
... Gene–environment interactions for breast cancer risk have been shown in several epidemiologic studies for high alcohol intake combined with polymorphisms in enzymes involved in alcohol metabolism. For most chemicals, however, exposures are generally low, and efforts to study interactions between genetics and environmental factors are also hampered by lack of data on environmental exposures of interest in most datasets currently used for genomic studies.
From page 9...
... The breast undergoes substantial changes from the time it begins developing in the fetus through old age, especially in response to hormonal changes during puberty, pregnancy, lactation, and menopause. The timing of a variety of environmental exposures may be important in directly increasing or reducing breast cancer risks or in acting indirectly by influencing the developmental events.
From page 10...
... For a limited set of other risk factors, women have a greater opportunity to act in ways that may have the potential to reduce risk for breast cancer while carrying limited risks of increasing other adverse health outcomes (Table S-1)
From page 11...
... The committee urges efforts to better inform consumers and health professionals about the limits of FDA's role, to encourage manufacturers to identify hormonally active ingredients in cosmetics and dietary supplements, and to ensure that FDA has effective tools to identify contaminants or ingredients that are potential contributors to increased risk of breast cancer. Similarly for chemicals in consumer products, interested organizations can help inform the public about the current provisions for testing chemicals and encourage manufacturers to improve testing and make existing information on their products more readily available.
From page 12...
... Studies have not been done that provide evidence that a specific form of physical activity is optimal for reducing breast cancer risk. bThe committee's comments on other benefits or risks highlight major considerations, but they are not intended to be exhaustive.
From page 13...
... No known benefit of high alcohol consumption All ages No Likely to reduce risk for cardiovascular disease, diabetes May increase risk for injury Unclear No Likely to reduce risk for cardiovascular disease, diabetes, other cancers Varies No May reduce risk for other forms of cancer or other health problems May result in replacement with products that have health or other risks not yet identified High-risk women Yes Depending on the agent, increased risk of endometrial cancer, stroke, deep-vein thrombosis, among others dCombination hormone therapy with estrogen and progestin increases the risk of breast cancer, and the associated risk is reduced upon stopping therapy. Oral contraceptives are also associated with an increased risk of breast cancer while they are being used.
From page 14...
... Moreover, much of the evidence on breast cancer risk factors has come from studies of postmenopausal breast cancer in white women, and it has pointed to a greater potential to reduce risk for estrogen receptor–positive (ER+) cancers than other types.
From page 15...
... the biol ogy of breast development; the mechanisms of carcinogenesis early in life, including the role of the tissue microenvironment in tumor suppression and development, and differences that may be related to tumor type; differences in effects of exposures by tumor type; the potential contribution of timing of exposure to variation in risk; and analytical tools for investigating the potential for interactions among exposures and the impact of mixtures of environmental agents on biological processes. Other work to aid investigation of environmental influences on breast cancer risk includes • identifying cellular, biochemical, or molecular biomarkers of early events leading to breast cancer and validating their predictive value for future risk for breast cancer; • determining whether intermediate endpoints (e.g., indicators of breast development, peak height growth velocity)
From page 16...
... These studies should include collection of information on the prevalence of known breast cancer risk factors among the study population.
From page 17...
... Exposure assessment becomes particularly challenging over such extended intervals. Recommendation 4: Breast cancer and exposure assessment researchers and research funders should pursue research to improve methodologies for measuring, across the life course, personal exposure to and biologi cally effective doses of environmental factors that may alter risk for or susceptibility to breast cancer.
From page 18...
... For example, overweight and obesity are recognized as increasing risk for postmenopausal breast cancer, but the contribution of weight loss to reducing risk is much less clear. Recommendation 6: Breast cancer researchers and research funders should pursue prevention research in humans and animal models to develop strategies to alter modifiable risk factors, and to test the effec tiveness of these strategies in reducing breast cancer risk, including timing considerations and population subgroups likely to benefit most.
From page 19...
... Additional research is needed to identify other drugs that can reduce risk of all forms of breast cancer with minimal risk of other adverse health effects. Recommendation 7: Breast cancer researchers and research funders should pursue continued research into new breast cancer chemopreven tion agents that have minimal risk for other adverse health effects.
From page 20...
... The test development should also include exploring the predictive value of in vitro and in vivo experimental testing for site-specific cancer risks for humans.
From page 21...
... New Approaches to Testing Hormonally Active Candidate Pharmaceuticals Given the evidence for hormonal influences on the development of breast cancer, the committee is concerned that testing required to gain marketing approval for various hormonally active pharmaceuticals, including oral contraceptives and menopausal hormone therapies, does not adequately address the potential for increased risk for breast cancer. Recommendation 10: The pharmaceutical industry and other sponsors of research on new hormonally active pharmaceutical products should support the development and validation of better preclinical screening tests that can be used before such products are brought to market to help evaluate their potential for increasing the risk of breast cancer.
From page 22...
... Recommendation 12: Breast cancer researchers and research funders should pursue efforts to (1) develop statistical methodology for the estimation of risk of breast cancer for given sets of risk factors and that takes the life course perspective into account, (2)
From page 23...
... Familiar advice about healthful lifestyles appears relevant, but it remains difficult to discern what contribution a diverse array of other environmental factors may be making. Important targets for research are the biologic significance of life stages at which environmental risk factors are encountered, what steps may counter their effects, when preventive actions can be most effective, and whether opportunities for prevention can be found for the variety of forms of breast cancer.


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