(LifeWire) - The causes of breast cancer are complex, but certain factors -- lifestyle, hormonal and genetic -- are known to play key roles in breast cancer development and so guide the main breast cancer prevention strategies. Some steps you can take yourself, while other steps (generally limited to women at very high risk) may be provided or prescribed through your physician.
Lower Your Risk
Many lifestyle factors influence whether a woman will develop breast cancer. Here are some ways to shift the odds in your favor:
Regular exercise. The American Cancer Society recommends 45 to 60 minutes of exercise at least five days a week to lower breast cancer risk. Harvard Medical School and Harvard School of Public Health researchers found that women who got about three to four hours of running (or 13 hours of walking) per week, from age 12 to 22, were 23% less likely to develop breast cancer later in life.
A healthy weight. Maintaining a healthy weight is important for good health - and breast cancer prevention. A long-term Harvard study of 49,514 women found that women who gained 55 or more pounds after age 18 had a risk for breast cancer about 1.5 times that of women who maintained a healthy weight. On the other hand, women who lost 22 pounds after menopause lowered their risk of developing breast cancer by 57%.
A low-fat diet. The National Cancer Institute (NCI) views the evidence for low-fat diets as insufficient, but they may help reduce risk, particularly in postmenopausal women.
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High-risk women, including breast cancer survivors, may benefit from including soy products, such as tofu, in a balanced diet low in saturated fats and rich in fruits. Phytoestrogen supplements, though, are not recommended. A NCI-sponsored clinical trial of genistein, an isoflavone in soy, may give more definitive answers for high-risk women. Further research is needed to establish the benefits of soy, if any, for older women.
Flaxseed and some other high-fiber foods contain lignans, a subclass of phytoestrogen, but research on lignans remains inconclusive, though animal studies suggest that a lignan-rich diet could reduce breast cancer risk.
Bearing children and breastfeeding. Having children reduces breast cancer risk, but the impact depends on the woman's age at childbirth, with little or no benefit for women more than age 35. Breastfeeding for at least 12 months has a minor beneficial effect, reducing breast cancer risk by 4.3%.
Risks to Consider
Hormone Replacement Therapy (HRT). In 2002, the Women's Health Initiative, a large study of HRT, reported that Estrogen plus progesterone supplements increased breast cancer risk by 24%. Thereafter, the number of women using combined HRT dropped precipitously, and the United States experienced a one-time sharp decline in the number of newly diagnosed breast cancer cases.
Alcoholic beverages. Breast cancer risk varies with the average number of drinks per day; each additional drink in the per-day average adds roughly 7% to a woman's risk.
Environmental pollutants. A number of environmental pollutants or toxins may play a role in breast cancer, including Polychlorinated Biphenyls (PCBs), Polycyclic Aromatic Hydrocarbons (PAHs) and organic solvents. Further research is clearly needed in this area. The Susan G. Komen for the Cure Breast Cancer Foundation and the Silent Spring Institute offer a database of environmental pollutants that have been linked to an increased risk of developing breast cancer.
Preventive Medical Therapies
Prescription medications or surgical procedures to prevent breast cancer are generally only available to women who are at a very high hereditary risk or have already had the disease (as a means to prevent recurrence).
Endocrine therapy. These medications limit the availability of estrogen and are only effective against estrogen receptor-positive breast cancer. They include Selective Estrogen Receptor Modifiers (SERMs). The best-known endocrine therapy drug is Nolvadex (tamoxifen), a SERM. Novadex has been shown to reduce breast cancer risk by about 50% - but its side effects can include menopause-like hot flashes and night sweats.
Retinoids. These synthetic drugs resemble vitamin A. Though they have not won FDA approval for breast cancer prevention, recent research suggests their use in breast cancer prevention may be promising. Increasing dietary Vitamin A may also have preventive benefits.
Prophylactic surgery. Women at very high genetic risk may undergo surgery to remove their breasts (prophylactic mastectomy) - reducing breast cancer risk by 90% - or their ovaries (prophylactic oophorectomy) - reducing risk by about 50%. But such drastic measures should only be undertaken after careful counseling.
Sources:
"Breast Cancer Prevention PDQ" Cancer.gov. 5 May 2008. 4 Jun. 4, 2008.
"Detailed Guide: Breast Cancer Can Breast Cancer Be Prevented." Cancer.org. 13 Sep. 2007. American Cancer Society. 26 May 2008.
Duffy, C., et. al.. "Implications of Phytoestrogen Intake for Breast Cancer." CA: A Cancer Journal for Clinicians. 57(2007): 260-277.
Eliassen, A., et. al.. "Adult Weight Change and Risk of Postmenopausal Breast Cancer." Journal of the American Medical Association. 296(2006): 193-201.
"Environment and Breast Cancer: Science Review." Silent Spring Institute. 26 May 2008.
"Lifestyle vs. Breast Cancer The Role of Food, Fitness, and Weight in Your Risk of Breast Cancer." American Cancer Society. 10 Dec. 2006. American Cancer Society. 26 May 2008.
Maruti, Sonia S., Walter C. Willett, Diane Feskanich, Bernard Rosner, and Graham A. Colditz. "A Prospective Study of Age-Specific Physical Activity and Premenopausal Breast Cancer." J Natl Cancer Inst. 21 May 2008. 100(10):728-37. (subscription)
"NIOSH Safety and Health Topic: Organic Solvents." CDC.gov. National Institute for Occupational Safety and Health. 26 May 2008.
"ToxFAQs for Polychlorinated Biphenyls (PCBs)." ToxFAQs. 11 Sep. 2007. Agency for Toxic Substances and Disease Registry. 26 May 2008.
"ToxFAQs for Polycyclic Aromatic Hydrocarbons (PAHs)." ToxFAQs. 11 Sep. 2007. Agency for Toxic Substances and Disease Registry. 26 May 2008 .
Zanardi, S, et. al.. "Clinical Trials with Retinoids for Breast Cancer Chemoprevention." Endocrine-Related Cancer.13 (2006): 51-68.
