Estimating Breast Cancer Risks - Q&A

Key Points

• The risk of breast cancer increases as women get older (See Question 1).
• Risk factors include personal history of breast abnormalities, current age, age at first menstrual period, age at first live birth, breast cancer history of close relatives, whether a woman has had a breast biopsy, obesity, physical inactivity, and race (See Question 3).
• The Breast Cancer Risk Assessment Tool (http://www.cancer.gov/bcrisktool) estimates a woman's risk of developing breast cancer for two time periods: over the next five years and over her lifetime (See Question 2).
• Recently published research shows that a woman's risk of developing breast cancer is also affected by breast density and whether she has used hormone therapy; including these additional risk factors in a breast cancer risk assessment tool might increase its accuracy, but researchers still need to validate these additional factors with data from independent studies (See Questions 4 and 6).

	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?
	Control your weight and exercise. Make healthy choices in the foods you eat and the kinds of drinks you have each day. Stay active. Learn more about keeping a healthy weight and ways to increase your physical activity. Know your family history of breast cancer. If you have a mother, sister, or daughter with breast cancer, ask your doctor what is your risk of getting breast cancer and how you can lower your risk. For more information, visit the Agency for Healthcare Research and Quality for information about medicines to prevent breast cancer and genetic testing for breast cancer. Find out the risks and benefits of hormone replacement therapy. Some women use hormone replacement therapy (HRT) to treat the symptoms of menopause. Ask your doctor about the risks and benefits of HRT and find out if hormone replacement therapy is right for you. To learn more about HRT, visit the Agency for Healthcare Research Quality and the National Cancer Institute (NCI)-Menopausal Hormone Use and Cancer: Questions and Answers. Limit the amount of alcohol you drink. For more information, see the Alcohol Chapter of the Dietary Guidelines for Americans 2005. Get screened for breast cancer regularly. By getting the necessary exams, you can increase your chances of finding out early on, if you have breast cancer. For more information about the kinds of tests used to screen for breast cancer, and to learn how you can be screened, see Screening.
	8. What screening options are available for detecting breast cancer?
	Breast cancer screening means checking a woman's breasts for cancer before there are signs or symptoms of the disease. Three main tests are used to screen the breasts for cancer. Talk to your doctor about which tests are right for you, and when you should have them. Mammogram. A mammogram is an X-ray of the breast. Mammograms are the best method to detect breast cancer early when it is easier to treat and before it is big enough to feel or cause symptoms. Having regular mammograms can lower the risk of dying from breast cancer. If you are age 40 years or older, be sure to have a screening mammogram every one to two years. Clinical breast exam. A clinical breast exam is an examination by a doctor or nurse, who uses his or her hands to feel for lumps or other changes. Breast self-exam. A breast self-exam is when you check your own breasts for lumps, changes in size or shape of the breast, or any other changes in the breasts or underarm (armpit). Which tests to choose: Having a clinical breast exam or a breast self-exam have not been found to decrease risk of dying from breast cancer.1 Keep in mind that, at this time, the best way to find breast cancer is with a mammogram. If you choose to have clinical breast exams and to perform breast self-exams, be sure you also get regular mammograms. For more information about cancer, please visit the NCI Web site at http://www.cancer.gov, or call NCI's Cancer Information Service at 1-800-4-CANCER (1-800-422-6237).