• Highlights
• Introduction
• Risk Factors
• Prevention and Lifestyle Factors
• Symptoms
• Diagnosis
• Prognosis
• Treatment
• Surgery
• Radiation
• Medications
• Chemotherapy
• Hormone Therapy
• Resources
• References

Breast cancer

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of breast cancer.

Alternative Names

Mammograms; Mastectomy

Prevention and Lifestyle Factors

Exercise

Several studies suggest that regular exercise, particularly vigorous exercise, may offer some modest protection against breast cancer. Exercise can help reduce body fat, which in turn lowers levels of cancer-promoting hormones such as estrogen. Exercise can also help women who have been diagnosed with breast cancer. Studies indicate that both aerobic and weight training exercises benefit the body and the mind, and improve quality of life for breast cancer survivors. Even moderate exercise can help improve survival. A 2005 study in the Journal of the American Medical Association reported survival benefits for women diagnosed with breast cancer who walked 3 – 5 hours per week at an average pace.

Dietary Factors

Much research has targeted the role of diet in breast cancer, either as a risk factor or as a factor for patients already diagnosed with cancer.

Fats. Although some studies have found an association between high-fat intake and breast cancer, the most recent data suggest that fat from any source (vegetable oils or animal products) plays an insignificant role in increasing the risk for breast cancer. According to some studies, monounsaturated fats (found in olive, peanut, and canola oils) may even be protective.

Vitamins and Chemicals in Fruits and Vegetables. Many fresh fruits and vegetables contain chemicals that may be cancer fighters. Experts are investigating whether any specific vitamins, nutrients, or teams of them may be specifically valuable. Examples include:

• Isothiocyanates stimulate enzymes that convert estrogen to a more benign form and may block steroid hormones that promote breast and prostate cancers. They are found in broccoli, cabbage, Brussels sprouts, cauliflower, collards, kale, kohlrabi, mustard greens, rutabaga, turnips, and bok choy.

• Polyphenols, found in apples, onions, and green tea, may be beneficial, although this is controversial. (Chemicals in green tea in particular have been studied for cancer-fighting effects in breast cancer.)
• Lycopene, found in tomatoes may have cancer-fighting properties.

• There is some evidence that foods containing folate (folic acid) may be protective. It is found in avocado, bananas, orange juice, asparagus, fruits, green leafy vegetables, dried beans and peas, and yeast. It is also added to commercial grain products.

• Low levels of vitamin D may increase breast cancer risk, especially in older women. Vitamin D is activated by sunlight and obtained from fortified milk.

• Foods high in vitamin C have also been associated with a lower risk (although there is not evidence of protection from any vitamin supplements, including C or E).

Dairy Products and Other Protein Foods. Studies suggest that dairy products may also play a protective role in premenopausal women. If this is eventually verified, it is not clear if protection comes from calcium and vitamin D in these foods or if there are others factors involved. Women who increase their intake should choose low- or no-fat dairy products.

One study reported that women with breast cancer who had a high intake of protein from both poultry and dairy products had a better outlook than those with a lower intake of these foods. In this study, red meat appeared to have no effect one way or the other. Other studies, however, have found a higher risk of breast cancer in women who consume higher quantities of flame-broiled meats, particularly women who are sensitive to chemicals released during the process. Fish may offer some protection.

Iron. Animal studies have linked a higher incidence of breast cancer with iron-rich diets, and in humans, high iron stores have been associated with a higher risk for breast cancer. Estrogen appears to increase iron levels in cells, and iron produces oxidants (damaging particles) that are associated with cancer. More research is needed to confirm these findings, however.

Soy and Phytoestrogens Phytoestrogens are estrogen-like substances found in plant products. These include soybeans, black cohosh (an herb), whole wheat, berries, and flaxseed. In general, the evidence on their effects on breast cancer is unclear. Most research has focused on soy. In general, Asian women have a lower incidence of reproductive and breast cancers as well as a higher intake of soy. For example, a 2000 Asian study reported an association between high levels of soy compounds in the urine and a significantly lower risk for breast cancer. A 2001 study in China reported that high soy intake during adolescence was associated with a lower risk for breast cancer later on. The effects of phytoestrogens, however, in all cases are far from settled. Of concern are studies that report breast cell proliferation with low levels of genistein (one of the important isoflavones compounds in soy). In one study, the compound actually reversed the protective properties of tamoxifen, a drug used to prevent breast cancer in high-risk women. In general, women at risk for breast cancer, especially women who take hormone replacement therapy, should avoid consuming large amounts of plant products with high levels of phytoestrogens until more is known about their effects.

Avoiding Alcohol

Several studies have reported a higher risk for breast cancer in women who consume alcohol. A well-conducted 2003 analysis of many of these studies suggested that for every daily drink there was a 7% increase in breast cancer. By age 80, women who consumed two drinks a day had a 10% increased risk for developing breast cancer. Based on these findings, researchers suggested that about 4% of breast cancer cases in developed nations may be attributed to alcohol. (Women who drink and who take hormone replacement therapy have an even greater risk.) Some research indicates that alcohol in such amounts increases levels of growth factors that can stimulate breast cancer cells. However, light to moderate drinking has benefits for the heart that most likely outweigh the cancer risk in most women who have no other risk factors for breast cancer or alcohol abuse.

Breastfeeding

Several studies have reported that breastfeeding is associated with a lower risk for cancer in premenopausal women. Some studies also suggest that some protective effect from breastfeeding may last beyond menopause. Studies also indicate that the longer the mother breastfeeds, the better. In fact, some experts believe the high rates of breast cancer in developed countries may be partly due to a lack of or shorter duration of breastfeeding.

Specific Preventive Measures for High-Risk Women

Lifestyle Factors. Premenopausal women at elevated risk, usually because of family history, should take as many preventive measures as possible, starting at an early age. The following life-style choices may be beneficial:

• Exercising and eating healthily is the first essential rule.
• High-risk premenopausal women may choose alternatives to oral contraceptives and, if feasible, consider having children early in their life.
• High-risk postmenopausal women may want to forego hormone replacement therapy.
• Any woman at high risk for breast cancer might consider avoiding alcohol or drinking it sparingly.

In spite of some rumors published in the popular press, antiperspirants or use of deodorants after shaving have not been linked with any higher risk for breast cancer.

Tamoxifen and Other SERMs. Drugs known as selective estrogen-receptor modulators (SERMs) act like estrogen in some tissues but behave like estrogen blockers (anti-estrogens) in others. Tamoxifen (Nolvadex) is the most studied of these drugs. It is currently used to treat breast cancer and is the only drug to date approved for prevention. Evidence strongly suggests that it halves the risk for estrogen receptor-positive cancers in high-risk women, including those with BRCA2 mutations (although possibly not BRCA1). It also helps prevent recurrence in women who have been treated for breast cancers. However, it has no protective effects against estrogen receptor-negative cancers.

Raloxifene (Evista), another SERM, also protects against breast cancer and osteoporosis and has a lower risk than tamoxifen of causing uterine cancer. Results from a major comparison trial, Study of Tamoxifen and Raloxifene (STAR), were published in 2006. This study enrolled nearly 20,000 postmenopausal women at high risk for breast cancer. The data indicated that raloxifene worked as well as tamoxifen in reducing the risk of invasive breast cancer, and had a lower risk of causing blood clots. Side effects varied between the two drugs. Tamoxifen caused problems with gynecological symptoms, hot flashes, leg cramps, and bladder control. Women who received raloxifene tended to experience more musculoskeletal problems, sexual dysfunction, and weight gain.

Although the STAR study suggested that raloxifene is less likely to cause blood clots than tamoxifen, a 2006 study in the New England Journal of Medicine indicated that raloxifene carries its own risks for blood clots and fatal strokes. The researchers suggested that raloxifene may not be a safe choice for women at high risk of heart disease.

Tamoxifen and raloxifene are not recommended as prevention for women at low risk for breast cancer or its recurrence. Women at high risk for breast cancer should discuss with their doctors the risks and benefits of SERMs.

Investigational Drugs. The following investigative drugs are showing promise for prevention:

• Aromatase inhibitors are proving to be effective treatments for hormone-receptor positive breast cancer. Like tamoxifen, they are also being investigated for protection in high-risk women.
• Retinoids. Analogues of vitamin A called retinoids are being studied for protection against breast cancer. One retinoid, fenretinide, appears to offer some protection against a second breast cancer in previously diagnosed, premenopausal women (but not in postmenopausal women).

Prophylactic Mastectomies and Oophorectomies. Studies suggest that preventive breast removal (called prophylactic mastectomy) reduces the risk of breast cancer by about 90% in women who harbor BRCA genetic mutations. Shutting down estrogen production with preventive oophorectomy (ovary removal) is also proving to be an effective alternative in reducing the risk of breast cancer in women with BRCA1 gene mutations, and possibly BRCA2.

Still, the decision is not easy. Having the genes does not mean that cancer will always occur, meaning that mastectomy might not be necessary in all such women. Furthermore, even after mastectomy, some precancerous cells may persist that can activate the disease later on. Nevertheless, in one 2000 study, 70% of women were satisfied with their decision to have prophylactic breast removal. Women should discuss all options with their doctors, including oophorectomy and close monitoring.

Oophorectomy causes immediate menopause. Women who have a “surgical menopause” often experience more severe symptoms of hot flashes, sleep disturbances, and vaginal dryness than women who have a natural menopause. Hormone replacement therapy (HRT) is sometimes prescribed to help ease these menopausal symptoms. However, long-term use of HRT is a risk factor for breast cancer. A 2005 study suggested that short-term (less than 3 years) HRT is safe for women who have had preventive oophorectomy and will not increase their risk of developing breast cancer.

• Review Date: 4/3/2007
• Reviewed By: Editorial Team: Greg Juhn, M.T.P.W., David R. Eltz, Kelli A. Stacy. Previously reviewed by Harvey Simon, M.D., Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital (10/2/2006).

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