The American Cancer Society defines a risk factor as anything that increases a person's chance of getting a disease such as cancer. According to ACS, different cancers have different risk factors. For example, unprotected exposure to strong sunlight is a risk factor for skin cancer, and smoking is a risk factor for lung cancer.
However, having a risk factor, or even several, does not mean that you will get the disease. Some women who have one or more breast cancer risk factors never develop the disease, while most women with breast cancer have no apparent risk factors. Even when a woman with breast cancer has a risk factor, there is no way to prove that it actually caused her cancer.
There are different kinds of risk factors. Some factors, like a person's age or race, can't be changed. Others are linked to cancer-causing factors in the environment. Still others are related to personal choices such as smoking, drinking and diet. Some factors influence risk more than others, and your risk for breast cancer can change over time. Getting older, a new breast biopsy result or a new diagnosis of breast cancer in your family could change your risk. The American Cancer Society has detailed the following information about breast cancer:
Risk Factors That Can Not be Changed
Gender: Simply being a woman is the main risk factor for developing breast cancer. Because women have many more breast cells than men do and perhaps because their breast cells are constantly exposed to the growth-promoting effects of female hormones, breast cancer is much more common in women. Men can develop breast cancer, but this disease is about 100 times more common among women than men.
Aging: Your risk of developing breast cancer increases as you get older. About 18% of breast cancer diagnoses are among women in their forties, while about 77% of women with breast cancer are older than 50 when they are diagnosed.
Genetic risk factors: Recent studies have shown that about 10% of breast cancer cases are hereditary as a result of gene changes (mutations). The most common gene changes are those of the BRCA1 and BRCA2 genes. Normally, these genes help to prevent cancer by making proteins that keep cells from growing abnormally. However, if you have inherited the changed gene from either parent, you are at increased risk for breast cancer.
See the section Do We Know What Causes Breast Cancer? for more information about genes and DNA. Women with an inherited BRCA1 or BRCA2 mutation have a 50% to 85% chance of developing breast cancer during their lifetime. Women with these inherited mutations also have an increased risk for developing ovarian cancer.
Other genes have been discovered that might also lead to inherited breast cancers. One of these is the ATM gene. ATM stands for ataxia-telangiectasia mutation. The gene is responsible for repairing damaged DNA. Certain families with a high rate of breast cancer have been found to have mutations of this gene. Another gene, the CHEK-2 gene, also increases breast cancer risk when it is mutated. Very recently, scientists have also found increased breast cancer risk associated with changes in genes linked to the BRCA genes. This may affect their ability to function.
Inherited mutations of the p53 tumor suppressor gene can also increase your risk of developing breast cancer, as well as leukemia, brain tumors and/or sarcomas (cancer of bones or connective tissue). The Li-Fraumeni syndrome, named after the two researchers who described this inherited cancer syndrome, is a rare cause of breast cancer.
If you are considering genetic testing, it's strongly recommend that you talk to a genetic counselor, nurse or doctor qualified to interpret and explain these tests before being tested. It is very important to understand and carefully weigh the benefits and risks of genetic testing before these tests are done. Testing is expensive and is not covered by some health plans. There is concern that people with abnormal genetic test results will not be able to get life insurance or that coverage may only be available at a much higher cost. For more information, see our position statement on genetic testing.
Family history of breast cancer: Breast cancer risk is higher among women whose close blood relatives have this disease. Your risk of developing breast cancer is increased if:
Having one first-degree relative (mother, sister, or daughter) with breast cancer approximately doubles a woman's risk, and having two first-degree relatives increases her risk five-fold. Although the exact risk is not known, women with a family history of breast cancer in a father or brother also have an increased risk of breast cancer.
Personal history of breast cancer: A woman with cancer in one breast has a three - to four-fold increased risk of developing a new cancer in the other breast or in another part of the same breast. This is different from a recurrence (return) of the first cancer.
Race: White women are slightly more likely to develop breast cancer than are African-American women. But African-American women are more likely to die of this cancer because their cancers are often diagnosed later and at an advanced stage when they are harder to treat and cure. There is also some question about whether African-American women have more aggressive tumors. Asian, Hispanic and Native American women have a lower risk of developing breast cancer.
Previous breast biopsy: Women whose earlier breast biopsies detected proliferative breast disease without atypia or usual hyperplasia have a slightly higher risk of breast cancer (one and one-half to two times greater than other women). Having a previous biopsy result of atypical hyperplasia increases a woman's breast cancer risk by four to five times. Having a biopsy specimen diagnosed as fibrocystic changes without proliferative breast disease does not affect breast cancer risk.
Previous breast irradiation: Women who as children or young adults have had radiation therapy to the chest area as treatment for another cancer (such as Hodgkin's disease or non-Hodgkin's lymphoma) have a significantly increased risk for breast cancer.
Menstrual periods: Women who started menstruating at an early age (before age 12) or who went through menopause at a late age (after age 50) have a slightly higher risk of breast cancer.
Symptoms, Abnormalities and Changes
Early breast cancer usually does not cause pain. In fact, when breast cancer first develops, there may be no symptoms at all. If you have any concerns or find even a small change, call your doctor. Some symptoms that may indicate breast cancer include, but are not limited to:
Sources: American Cancer Society and The National Cancer Institute.
Mammogram: a specialized x-ray of the breast to help detect breast cancers which cannot be felt by a health care professional:
Clinical Breast Exam (CBE): an examination of the breast by a health care professional.
Breast Awareness and Self-Examination (BSE): a method of checking one’s own breast for lumps or suspicious changes.
Sources: American Cancer Society and The National Cancer Institute
Lifestyle-Related Factors and Breast Cancer Risk
Not having children: Women who have had no children or who had their first child after age 30 have a slightly higher breast cancer risk.
Oral contraceptive use: It is still not clear what part oral contraceptives (birth control pills) might play in breast cancer risk. Studies have found that women now using oral contraceptives have a slightly greater risk of breast cancer than women not using them. Women who stopped using oral contraceptives more than 10 years ago do not appear to have any increased breast cancer risk. When considering using oral contraceptives, women should discuss their other risk factors for breast cancer with their healthcare team.
Estrogen replacement therapy: Most studies suggest that long-term use (five years or more) of estrogen replacement therapy (HRT) after menopause may slightly increase your risk of breast cancer. If you still have your uterus (womb), doctors generally prescribe estrogen and progesterone. Estrogen is prescribed to prevent menopausal symptoms and osteoporosis. ERT clearly reduces the risk of heart attacks and bone fractures. It, however, can increase the risk of developing cancer of the uterus. Progesterone helps prevent cancer of the uterus.
If you no longer have your uterus, then only estrogen is prescribed. Several studies have found that the increased risk of breast cancer related to combined HRT is mostly due to the progesterone. Estrogen alone does not appear to increase the risk as much.
The risk of HRT applies only to current and recent users, and a woman's breast cancer risk appears to return to that of the general population within five years of stopping HRT.
The decision to use hormone replacement therapy after menopause should be made by the woman and her doctor after weighing the possible risks and benefits. Factors to consider include your other risk factors for breast cancer, osteoporosis (thinning and weakening of bones), and the severity of menopausal symptoms. HRT increases the risk of blood clots and strokes. It reduces the risk of bone fractures and colon cancer.
Breast feeding: Some studies suggest that breast feeding may slightly lower breast cancer risk, especially if breast feeding is continued for one and one-half to two years. Other studies found no impact on breast cancer risk.
The explanation of this may be that both pregnancy and active breast feeding reduce a woman's total number of lifetime menstrual cycles. This may be similar to the reduction of risk due to late menarche (start of menstrual periods)or early menopause, which also decrease the total number of menstrual cycles. The study concluded that having more children and breast feeding longer could reduce the risk of breast cancer by half.
Alcohol: Use of alcohol is clearly linked to a slightly increased risk of developing breast cancer. Compared with nondrinkers, women who consume one alcoholic drink a day have a very small increase in risk, and those who have two to five drinks daily have about one time the risk of women who drink no alcohol. Alcohol is also known to increase the risk of developing cancers of the mouth, throat and esophagus. It's recommended that you limit your consumption of alcohol, if you drink at all.
Obesity and high-fat diets: Obesity (being overweight) is associated with an increased risk of developing breast cancer, especially for women after menopause (which usually occurs at age 50). Although your ovaries produce most of your estrogen, fat tissue can change some other hormones into estrogen. Having more fat tissue can increase your estrogen levels and increase your likelihood of developing breast cancer.
The connection between weight and breast cancer risk is complex, however. For example, risk appears to be increased for women who gained weight as an adult but is not increased among those who have been overweight since childhood. Also, excess fat in the waist area affects risk more than the same amount of fat in the hips and thighs. Researchers believe that fat cells in various parts of the body have subtle differences in their metabolism that may explain this observation.
Studies of fat in the diet and breast cancer risk have often given conflicting results. Most studies found that breast cancer is less common in countries where the typical diet is low in total fat, low in polyunsaturated fat and low in saturated fat.
On the other hand, many studies of women in the United States have not found breast cancer risk to be related to dietary fat intake. Researchers are still not sure how to explain this apparent disagreement. Many scientists note that studies comparing diet and breast cancer risk in different countries are complicated by other differences (such as activity level, intake of other nutrients, genetic factors) that might also alter breast cancer risk.
More research is needed to better understand the effect of the types of fat eaten and body weight on breast cancer risk. But, these factors have been shown to influence the risk of developing several other types of cancer, and intake of certain types of fat is clearly related to heart disease risk. We recommend you maintain a healthy weight and limit your intake of red meats, especially those high in fat or processed.
Physical activity: Exercise and cancer is a relatively new area of research. Recent studies show that strenuous exercise in your youth might provide lifelong protection against breast cancer and that even moderate to strenuous physical activity as an adult can lower breast cancer risk. More research is being done to confirm these findings.
Environmental pollution: A great deal of research has been reported and more is being done to understand environmental influences on breast cancer risk. The goal is to determine their possible relationships to breast cancer.
Currently, research does not show a clear link between breast cancer risk and exposure to environmental pollutants, such as the pesticide DDE (chemically related to DDT), and PCBs (polychlorinated biphenyls).
Factors with Uncertain, Controversial or Unproven Effect on Breast Cancer Risk
Antiperspirants: Internet rumors have suggested that chemicals in underarm antiperspirants are absorbed through the skin, interfere with lymph circulation, and cause toxins to build up in the breast and eventually lead to breast cancer. There is no experimental or epidemiological evidence to support this rumor. Chemicals in products such as antiperspirants are tested thoroughly to ensure their safety. The claims about toxin buildup are not supported by the scientific basis of carcinogenesis (cancer formation).
Underwire bras: Internet e-mail rumors and at least one book have suggested that bras cause breast cancer by obstructing lymph flow. There is no scientific or clinical basis for that claim.
Smoking: While no studies have yet linked cigarette smoking to breast cancer, smoking affects overall health and increases the risk for many other cancers, as well as heart disease.
Induced abortion: Several studies have provided very strong data that induced abortions have no overall effect on the risk of breast cancer. Also, there is no evidence of a direct relationship between breast cancer and spontaneous abortion (miscarriage) in most of the studies that have been published. This, however, is still controversial, with some doctors believing that abortion does increase the risk of breast cancer.
Breast implants: Several studies have found that breast implants do not increase breast cancer risk although silicone breast implants can cause scar tissue to form in the breast. Implants do make it harder to see breast tissue on standard mammograms, but additional x-ray pictures called implant displacement views can be used to completely examine the breast tissue.
Night work: A few recent studies have suggested that women who work at night, for example, nurses on a night shift, have an increased risk of developing breast cancer. However, this increased risk has not yet been proven, and when further studies are conducted, this factor may be found to be unimportant.
Support & Information for Breast Cancer patients and their loved ones:
The Susan G. Komen Breast Cancer Foundation
National Breast Cancer Foundation
The Breast Cancer Site
The National Alliance of Breast Cancer Organizations
Breast Cancer. Org
Mothers Supporting Daughters with Breast Cancer (MSDBC)
Avon Breast Care Fund
Breast Cancer Resource Committee
Cosmetic Executive Women Foundation
The Iris Cantor Center for Breast Imaging at UCLA's Jonsson Cancer Center
The Avon Foundation