1. Who develops breast cancer?

Breast cancer is the most frequently diagnosed non-skin cancer in American women. An estimated 213,000 American women will be diagnosed with breast cancer in 2006. The risk of breast cancer increases as women get older. Over the years, researchers have identified certain characteristics, usually called risk factors, which influence a woman's chance of getting the disease. Still, many women who develop breast cancer have no known risk factors other than growing older, and many women with known risk factors do not develop breast cancer.

2. What is the Breast Cancer Risk Assessment Tool?

The Breast Cancer Risk Assessment Tool is a computer program that was developed by scientists at the National Cancer Institute and the National Surgical Adjuvant Breast and Bowel Project (NSABP) to assist health care providers in discussing breast cancer risk with their female patients. The tool allows a health professional to project a woman's individual estimate of breast cancer risk over a 5-year period of time and over her lifetime and compares the woman's risk calculation with the average risk for a woman of the same age. The Breast Cancer Risk Assessment Tool can be found at: http://www.cancer.gov/bcrisktool.

3. What are the risk factors used to estimate breast cancer risk in the Breast Cancer Risk Assessment Tool?

The risk factors included in the tool are:

• Personal history of breast abnormalities. Two breast tissue abnormalities—ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS)—are associated with increased risk for developing invasive breast cancer.
• Age. The risk of developing breast cancer increases with age. The majority of breast cancer cases occur in women older than age 50.
• Age at menarche (first menstrual period). Women who had their first menstrual period before age 12 have a slightly increased risk of breast cancer.
• Age at first live birth. Risk depends on age at first live birth and family history of breast cancer, as shown in the following table of relative risks.

  Relative Risk of Developing Breast Cancer*

  Age at first live birth	# of affected relatives
  	0	1	2 or more
  20 or younger	1	2.6	6.8
  20–24	1.2	2.7	5.8
  25–29 or no child	1.5	2.8	4.9
  30 or older	1.9	2.8	4.2

For women with 0 or 1 affected relative, risks increase with age at first live birth. For women with 2 or more first degree relatives, risks decrease with age at first live birth.

* Adapted from Table 1, Gail MH, Brinton LA, Byar DP, Corle DK, Green SB, Shairer C, Mulvihill JJ: Projecting individualized probabilities of developing breast cancer for white females who are being examined annually. J Natl Cancer Inst 81(24):1879–86, 1989. [PubMed Abstract]

• Breast cancer among first-degree relatives (sisters, mother, daughters). Having one or more first-degree blood relatives who have been diagnosed with breast cancer increases a woman's chances of developing the disease.
• Breast biopsies. Women who have had breast biopsies have an increased risk of breast cancer, especially if the biopsy showed a change in breast tissue, known as atypical hyperplasia. These women are at increased risk because of whatever prompted the biopsies, not because of the biopsies themselves
• Race. White women have greater risk of developing breast cancer than Black women (although Black women diagnosed with breast cancer are more likely to die of the disease).

4. Why are some other risk factors left out of the Tool?

Other risk factors for breast cancer have been identified or proposed but are not included in the Breast Cancer Risk Assessment Tool for several reasons: because evidence that these factors contribute to breast cancer risk is not conclusive, because researchers cannot determine whether these factors add useful information to factors already in the model, or because data on other risk factors was not available in the research data used to develop the model. Such risk factors include: age at menopause, use of birth control pills, high body mass index, a high-fat diet, alcohol, radiation exposure, and environmental pollutants. Recently published research indicates that breast tissue density, measured from mammograms, can add useful information, but risk models with breast tissue density measurement still need to be validated with additional independent studies. Research also indicates that other risk factors, such as use of hormone therapy, might improve the tool.

5. Is the Breast Cancer Risk Assessment Tool useful for all women?

The Breast Cancer Risk Assessment Tool was developed for women in the United States population age 35 years or older. It should not be used for women with a previous diagnosis of breast cancer, women exposed to breast radiation for treatment of Hodgkin lymphoma, or women who reside in, or recently migrated from, regions with low breast cancer risk, such as rural China or Japan. More accurate methods to project risk may be available for women with certain rare identified mutations, such as alterations in the breast cancer susceptibility genes BRCA1 and BRCA2. The Breast Cancer Risk Assessment Tool was developed and has been validated in populations consisting mainly of non-Hispanic white women. More research is needed to validate or refine the model for other racial and ethnic groups.

6. What are some of the latest research findings on breast cancer risk?

Two studies in the September 6, 2006, issue of the Journal of the National Cancer Institute identified breast density as an important risk factor.* In one, a study of 11,638 women diagnosed with breast cancer, researchers identified different sets of risk factors in pre- and post-menopausal women. For pre-menopausal women, the risk factors included age, breast density, family history of breast cancer, and prior cancer diagnosis. For post-menopausal women, the risk factors included ethnicity, body mass index, age at natural menopause, use of hormone therapy, and a prior false-positive mammogram, in addition to all the risk factors for pre-menopausal women. The two separate models in this study for predicting breast cancer in pre- and post-menopausal women may be particularly helpful in identifying women at high risk for breast cancer.

The other study adds breast density and weight to the Gail model, a model that is the basis for the Breast Cancer Risk Assessment Tool (see Question 2). As before, the new model can be used to project risk over 5, 10, 20 and 30 year intervals. The new model predicted higher risks than the previous model in women with high breast density, and previous analyses indicated that the new model had modestly higher accuracy. Independent validation studies are needed before this model should be used for counseling, and before making a permanent change to the Breast Cancer Risk Assessment Tool.


7. Are there ways to decrease the chance of developing breast cancer?

Launched in April 1992, the Breast Cancer Prevention Trial (BCPT) was designed to see whether the drug tamoxifen could prevent breast cancer in women with an increased risk. Data reported in 1998 showed that both pre- and post-menopausal women taking tamoxifen had 49 percent fewer diagnosed cases of breast cancer. These results were also the first clear indication that a chemopreventive agent could be effective in preventing cancer in a high-risk population. For women over 50, tamoxifen was associated with serious side effects, such as endometrial cancer and blood clots. (http://www.cancer.gov/cancertopics/factsheet/Prevention/breast-cancer)

Starting in 1999, post-menopausal women ages 35 or older at increased risk for breast cancer participated in the Study of Tamoxifen and Raloxifene (STAR). The study compared tamoxifen with raloxifene, an osteoporosis drug. The initial results of the trial were announced on April 17, 2006 (see http://www.cancer.gov/newscenter/pressreleases/STARresultsApr172006), and showed that the drug raloxifene works as well as tamoxifen in reducing breast cancer risk for post-menopausal women at increased risk of the disease. In STAR, both drugs reduced the risk of developing invasive breast cancer by about 50 percent. In addition, within the study, women who were prospectively and randomly assigned to take raloxifene daily, and who were followed for an average of about four years, had 36 percent fewer uterine cancers and 29 percent fewer blood clots than the women who were assigned to take tamoxifen. Uterine cancers, especially endometrial cancers, are a rare but serious side effect of tamoxifen. Both tamoxifen and raloxifene are known to increase a woman’s risk of blood clots. Data from STAR continue to be analyzed. (http://www.cancer.gov/cancertopics/factsheet/STARresultsQandA)


8. How did BCPT and STAR use the Breast Cancer Risk Assessment Tool to add to our knowledge of breast cancer risk?

Both breast cancer prevention studies, BCPT and STAR, explored ways of reducing the risk of developing breast cancer; their findings have increased our knowledge of risk. Both trials involved women who have not had breast cancer, but were at high risk of developing it. BCPT used the Breast Cancer Risk Assessment Tool to determine eligible participants by projecting each woman's individualized estimate of breast cancer risk. The projections were accurate; thus the BCPT results validated the Breast Cancer Risk Assessment Tool. STAR researchers used the Breast Cancer Risk Assessment Tool for determining eligibility for enrollment. All STAR participants had to have an increased risk of breast cancer equivalent to or greater than that of an average 60- to 64-year-old woman.

9. What else can a woman do about breast cancer?

NCI recommends that women in their 40s and older get screening mammograms every one to two years. Women who are at higher than average risk of breast cancer should talk with their health care providers about whether to have mammograms before age 40 and how often to have them. Women also can take an active part in the early detection of breast cancer by having regular clinical breast exams (breast exams performed by health professionals).

Advances in screening have provided new tools for detection. In September of 2005, preliminary results from a large clinical trial of digital vs. film mammography found no difference in detecting breast cancer for the general populations of women in the trial. However, the Digital Mammographic Imaging Screening Trial (DMIST) found that women with dense breasts, who are pre- or perimenopausal (women who had a last menstrual period within 12 months of their mammograms), or who are younger than age 50, may benefit from having a digital rather than a regular film mammogram. More information about DMIST can be found at http://www.cancer.gov/newscenter/pressreleases/DMISTQandA.

# # #

* Barlow WE, White E, Ballard-Barbash R, Vacek P, Titus-Ernstoff L, Carney PA, Tice JA, Buist, DSM, Geller BM, Rosenberg R, Yankaskas BC, Kerlikowske K. Prospective Breast Cancer Risk Prediction Model for Women Undergoing Screening Mammography. Journal of the National Cancer Institute September 6, 2006; 17:Vol. 98.

Chen J, Pee D, Ayyagari R, Graubard B, Schairer C, Byrne C, Benichou J, Gail, MH. Projecting Absolute Invasive Breast Cancer Risk in White Women With Model That Includes Mammographic Density. Journal of the National Cancer Institute September 6, 2006; 17:Vol. 98.

# # #

• National Cancer Institute Fact Sheet 4.18, Breast Cancer Prevention Studies ¹
  (http://www.cancer.gov/cancertopics/factsheet/Prevention/breast-cancer)
• Breast Cancer Home Page ²
  (http://www.cancer.gov/cancertopics/types/breast)
• Prevention, Genetics, Causes Home Page ³
  (http://www.cancer.gov/cancertopics/prevention-genetics-causes)
• What You Need To Know About™ Breast Cancer ⁴
  (http://www.cancer.gov/cancertopics/wyntk/breast)

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Glossary Terms

Not normal. An abnormal lesion or growth may be cancer, premalignant (likely to become cancer), or benign (not cancer).

A chemical substance found in beer, wine, and liquor. Alcohol is also found in some medicines, mouthwashes, essential oils (scented liquid taken from plants), and household products.

In healthcare, a process used to learn about a patient’s condition. This may include a complete medical history, medical tests, a physical exam, a test of learning skills, tests to find out if the patient is able to carry out the tasks of daily living, a mental health evaluation, and a review of social support and community resources available to the patient.

A benign (not cancer) condition in which cells look abnormal under a microscope and are increased in number.

The removal of cells or tissues for examination by a pathologist. The pathologist may study the tissue under a microscope or perform other tests on the cells or tissue. There are many different types of biopsy procedures. The most common types include: (1) incisional biopsy, in which only a sample of tissue is removed; (2) excisional biopsy, in which an entire lump or suspicious area is removed; and (3) needle biopsy, in which a sample of tissue or fluid is removed with a needle. When a wide needle is used, the procedure is called a core biopsy. When a thin needle is used, the procedure is called a fine-needle aspiration biopsy.

A measure that relates body weight to height. BMI is sometimes used to measure total body fat and whether a person is a healthy weight. Excess body fat is linked to an increased risk of some diseases including heart disease and some cancers. Also called BMI.

The long, tube-shaped organ in the abdomen that completes the process of digestion. The bowel has two parts, the small bowel and the large bowel. Also called intestine.

A gene on chromosome 17 that normally helps to suppress cell growth. A person who inherits certain mutations (changes) in a BRCA1 gene has a higher risk of getting breast, ovarian, prostate, and other types of cancer.

A gene on chromosome 13 that normally helps to suppress cell growth. A person who inherits certain mutations (changes) in a BRCA2 gene has a higher risk of getting breast, ovarian, prostate, and other types of cancer.

Cancer that forms in tissues of the breast, usually the ducts (tubes that carry milk to the nipple) and lobules (glands that make milk). It occurs in both men and women, although male breast cancer is rare.

Describes the relative amount of different tissues present in the breast. A dense breast has less fat than glandular and connective tissue. Mammogram films of breasts with higher density are harder to read and interpret than those of less dense breasts.

The use of drugs, vitamins, or other agents to try to reduce the risk of, or delay the development or recurrence of, cancer.

A physical exam of the breast performed by a health care provider to check for lumps or other changes. Also called CBE.

A type of research study that tests how well new medical approaches work in people. These studies test new methods of screening, prevention, diagnosis, or treatment of a disease. Also called clinical study.

The process by which a professional counselor helps a person cope with mental or emotional distress, and understand and solve personal problems.

A noninvasive condition in which abnormal cells are found in the lining of a breast duct. The abnormal cells have not spread outside the duct to other tissues in the breast. In some cases, DCIS may become invasive cancer and spread to other tissues, although it is not known at this time how to predict which lesions will become invasive. Also called ductal carcinoma in situ and intraductal carcinoma.

The process of identifying a disease, such as cancer, from its signs and symptoms.

The things a person eats and drinks.

Any substance, other than food, that is used to prevent, diagnose, treat or relieve symptoms of a disease or abnormal condition. Also refers to a substance that alters mood or body function, or that can be habit-forming or addictive, especially a narcotic.

A noninvasive condition in which abnormal cells are found in the lining of a breast duct. The abnormal cells have not spread outside the duct to other tissues in the breast. In some cases, ductal carcinoma in situ may become invasive cancer and spread to other tissues, although it is not known at this time how to predict which lesions will become invasive. Also called DCIS and intraductal carcinoma.

Cancer that forms in the tissue lining the uterus (the small, hollow, pear-shaped organ in a woman's pelvis in which a fetus develops). Most endometrial cancers are adenocarcinomas (cancers that begin in cells that make and release mucus and other fluids).

A record of the relationships among family members along with their medical histories. This includes current and past illnesses. A family history may show a pattern of certain diseases in a family. Also called family medical history.

A computer program that uses personal and family medical history information to estimate a woman’s chance of developing breast cancer. Also called Gail risk model.

The functional and physical unit of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.

A cancer of the immune system that is marked by the presence of a type of cell called the Reed-Sternberg cell. The two major types of Hodgkin lymphoma are classical Hodgkin lymphoma and nodular lymphocyte-predominant Hodgkin lymphoma. Symptoms include the painless enlargement of lymph nodes, spleen, or other immune tissue. Other symptoms include fever, weight loss, fatigue, or night sweats. Also called Hodgkin disease.

Treatment that adds, blocks, or removes hormones. For certain conditions (such as diabetes or menopause), hormones are given to adjust low hormone levels. To slow or stop the growth of certain cancers (such as prostate and breast cancer), synthetic hormones or other drugs may be given to block the body’s natural hormones. Sometimes surgery is needed to remove the gland that makes a certain hormone. Also called endocrine therapy, hormonal therapy, and hormone treatment.

In medicine, a process that makes pictures of areas inside the body. Imaging uses methods such as x-rays (high-energy radiation), ultrasound (high-energy sound waves), and radio waves.

Cancer that has spread from where it started in the breast into surrounding, healthy tissue. Most invasive breast cancers start in the ducts (tubes that carry milk from the lobules to the nipple). Invasive breast cancer can spread to other parts of the body through the blood and lymph systems. Also called infiltrating breast cancer.

A condition in which abnormal cells are found in the lobules of the breast. LCIS seldom becomes invasive cancer; however, having it in one breast increases the risk of developing breast cancer in either breast. Also called lobular carcinoma in situ.

A condition in which abnormal cells are found in the lobules of the breast. Lobular carcinoma in situ seldom becomes invasive cancer; however, having it in one breast increases the risk of developing breast cancer in either breast. Also called LCIS.

An x-ray of the breast.

The time of life when a woman’s ovaries stop producing hormones and menstrual periods stop. Natural menopause usually occurs around age 50. A woman is said to be in menopause when she hasn’t had a period for 12 months in a row. Symptoms of menopause include hot flashes, mood swings, night sweats, vaginal dryness, trouble concentrating, and infertility.

The periodic discharge of blood and tissue from the uterus. From puberty until menopause, menstruation occurs about every 28 days, but does not occur during pregnancy.

Any change in the DNA of a cell. Mutations may be caused by mistakes during cell division, or they may be caused by exposure to DNA-damaging agents in the environment. Mutations can be harmful, beneficial, or have no effect. If they occur in cells that make eggs or sperm, they can be inherited; if mutations occur in other types of cells, they are not inherited. Certain mutations may lead to cancer or other diseases.

The National Cancer Institute, part of the National Institutes of Health of the United States Department of Health and Human Services, is the Federal Government's principal agency for cancer research. The National Cancer Institute conducts, coordinates, and funds cancer research, training, health information dissemination, and other programs with respect to the cause, diagnosis, prevention, and treatment of cancer. Access the National Cancer Institute Web site at http://www.cancer.gov. Also called NCI.

A condition marked by an abnormally high, unhealthy amount of body fat.

A condition that is marked by a decrease in bone mass and density, causing bones to become fragile.

Describes the time in a woman’s life when menstrual periods become irregular as she approaches menopause. This is usually three to five years before menopause and is often marked by many of the symptoms of menopause, including hot flashes, mood swings, night sweats, vaginal dryness, trouble concentrating, and infertility.

A collection of information about a person’s health. It may include information about allergies, illnesses and surgeries, and dates and results of physical exams, tests, screenings, and immunizations. It may also include information about medicines taken and about diet and exercise. Also called personal health record and personal medical history.

Energy released in the form of particle or electromagnetic waves. Common sources of radiation include radon gas, cosmic rays from outer space, medical x-rays, and energy given off by a radioisotope (unstable form of a chemical element that releases radiation as it breaks down and becomes more stable).

The active ingredient in a drug used to reduce the risk of invasive breast cancer in postmenopausal women who are at high risk of the disease or who have osteoporosis. It is also used to prevent and treat osteoporosis in postmenopausal women. It is also being studied in the prevention of breast cancer in certain premenopausal women and in the prevention and treatment of other conditions. Raloxifene blocks the effects of the hormone estrogen in the breast and increases the amount of calcium in bone. It is a type of selective estrogen receptor modulator (SERM).

A measure of the risk of a certain event happening in one group compared to the risk of the same event happening in another group. In cancer research, relative risk is used in prospective (forward looking) studies, such as cohort studies and clinical trials. A relative risk of one means there is no difference between two groups in terms of their risk of cancer, based on whether or not they were exposed to a certain substance or factor, or how they responded to two treatments being compared. A relative risk of greater than one or of less than one usually means that being exposed to a certain substance or factor either increases (relative risk greater than one) or decreases (relative risk less than one) the risk of cancer, or that the treatments being compared do not have the same effects. Also called risk ratio.

Something that increases the chance of developing a disease. Some examples of risk factors for cancer are age, a family history of certain cancers, use of tobacco products, being exposed to radiation or certain chemicals, infection with certain viruses or bacteria, and certain genetic changes.

A person who has studied science, especially one who is active in a particular field of investigation.

Checking for disease when there are no symptoms. Since screening may find diseases at an early stage, there may be a better chance of curing the disease. Examples of cancer screening tests are the mammogram (breast), colonoscopy (colon), Pap smear (cervix), and PSA blood level and digital rectal exam (prostate). Screening can also include checking for a person’s risk of developing an inherited disease by doing a genetic test.

A problem that occurs when treatment affects healthy tissues or organs. Some common side effects of cancer treatment are fatigue, pain, nausea, vomiting, decreased blood cell counts, hair loss, and mouth sores.

Cancer that forms in tissues of the skin. There are several types of skin cancer. Skin cancer that forms in melanocytes (skin cells that make pigment) is called melanoma. Skin cancer that forms in basal cells (small, round cells in the base of the outer layer of skin) is called basal cell carcinoma. Skin cancer that forms in squamous cells (flat cells that form the surface of the skin) is called squamous cell carcinoma. Skin cancer that forms in neuroendocrine cells (cells that release hormones in response to signals from the nervous system) is called neuroendocrine carcinoma of the skin. Most skin cancers form in older people on parts of the body exposed to the sun or in people who have weakened immune systems.

A procedure to remove or repair a part of the body or to find out whether disease is present. An operation.

A drug used to treat certain types of breast cancer in women and men. It is also used to prevent breast cancer in women who have had ductal carcinoma in situ (abnormal cells in the ducts of the breast) and in women who are at a high risk of developing breast cancer. Tamoxifen is also being studied in the treatment of other types of cancer. It blocks the effects of the hormone estrogen in the breast. Tamoxifen is a type of antiestrogen. Also called tamoxifen citrate.

A group or layer of cells that work together to perform a specific function.

Cancer that forms in tissues of the uterus (the small, hollow, pear-shaped organ in a woman's pelvis in which a fetus develops). Two types of uterine cancer are endometrial cancer (cancer that begins in cells lining the uterus) and uterine sarcoma (a rare cancer that begins in muscle or other tissues in the uterus).