DescriptionAn in-depth report on the causes, diagnosis, treatment, and prevention of breast cancer.
Alternative NamesMammograms; Mastectomy
A number of studies have suggested that regular exercise, particularly if it is vigorous, offers some modest protection against breast cancer by modulating estrogen. (Exercise may also be helpful for women with early stage breast cancer by improving physical function and blunting some of the negative effects of treatments, notably fatigue.)
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 other studies, in fact, monounsaturated fats (found in olive, peanut, and canola oils) may even be protective. Of some note, a 2003 study reported that young girls who modestly lowered their fat intake also changed their balance of estrogen and other sex hormones to one that theoretically could protect them against breast cancer.
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 the following:
Estrogen-like compounds (called phytoestrogens) require a special discussion. Such compounds are found in soybeans, black cohosh (an herb), whole wheat, berries, and flaxseed. Results are mixed.
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.
A 1999 study also 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.
A number of studies have now reported a higher risk for breast cancer with alcohol consumption. A well-conducted 2003 analysis of many of these studies suggested that for every daily drink there was a 7.1% increase in breast cancer. By age 80, women who consumed two drinks a day, have a 10% risk for developing breast cancer. The experts in the study suggested that based on these findings about 4% of breast cancer cases in developed nations may be attributed to alcohol. (Women who drink and who take hormone replacement therapy compound this risk.) Some research indicates that alcohol in such amounts increases levels of growth factors that can stimulate breast cancer cells. It should be noted, that 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. (Folic acid may help reduce the risk for breast cancer among women who regularly drink alcohol. More research is needed.)
Several studies have reported that breast feeding is associated with a lower risk for cancer in premenopausal women, and two 1999 studies suggest that some protective effect from breast feeding may last beyond menopause. Some 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 (although this is an area subject to change as more information becomes available):
Exercising and eating healthily is the first essential rule.
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 (antiestrogens) in others. Tamoxifen, the most studied of these, is currently used treat breast cancer and is the only drug to date approved for prevention. In spite of some negative European studies, most evidence now strongly suggests that it reduces the risk for estrogen-receptor positive cancers by nearly half 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. (It has no protective effects against estrogen-receptor negative cancers.)
Raloxifene, another SERM, is also proving to be protective against breast cancer and osteoporosis and has a lower risk than tamoxifen of causing uterine cancer. As with tamoxifen, it increases the risk for blood clots and hot flashes. A major comparison study is underway to compare raloxifene with tamoxifen.
Unfortunately, it is not clear how long SERMs should be taken or if even they actually save lives. Research is needed to resolve these issues. Although tamoxifen protects postmenopausal women from osteoporosis, it poses a risk for serious adverse effects, notably blood clots and uterine cancer. This makes it a better choice for younger women who have a lower risk for these complications than older women. None of these agents is recommended for any woman who is not at high risk for breast cancer or its recurrence. Meanwhile, high-risk women should discuss all the risks and benefits of SERMs with their physician.
Investigative Agents. The following investigative agents are showing promise, but should not be used for breast cancer protection except in clinical trials:
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 the BRCA genetic mutations. In one study, only three women who chose mastectomies developed breast cancer, whereas 40 would ordinarily have been expected to develop the disease. Shutting down estrogen production with preventive oophorectomy (ovary removal) is proving to be an effective alternative in reducing the risk of breast cancer in women in the BRCA genes.
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 physician, including oophorectomy and close monitoring. The use of other options such as tamoxifen is described below.