Breast Cancer Risk and Prevention

Breast cancer is a major health concern for women. As with any common and potentially serious disease, it is important to know what your risks are, and how to eliminate or minimize them. The earlier breast cancer is detected, the better chance you have of a cure.

The two most important things you need to know about breast cancer are your risk factors and which screening procedures you should have.

A risk factor is anything that increases the chance of getting cancer. There are two types of risk factors: genetic and nongenetic. A genetic factor is inherited from your parents and cannot be changed. A nongenetic, or environmental, factor is something in your environment, which often can be changed. Nongenetic factors may include diet, exercise, or exposure to various substances.

As with many cancers, breast cancer has both genetic and nongenetic risk factors.

Genetic Factors

If you have a family history (mother, sister, aunt, grandmother, or cousin) of breast cancer, you are at increased risk for developing the disease. Most hereditary breast cancers occur in women with genetic abnormalities known as BRCA1 or BRCA2 genes.

Women with the BRCA1 gene have an 85 percent risk of developing breast cancer, a 60 percent risk of developing ovarian cancer by age 70, and an increased risk of colon cancer. Those with the BRCA2 gene are also at an increased risk of developing breast and ovarian cancers, although their risk is lower than those with the BRCA1 gene. Genetic abnormalities cause only about 5 percent to 10 percent of breast cancers.

If you have had breast cancer previously, you are at an increased risk of a recurrence. This is also true if you have had ovarian cancer or endometrial cancer.

Women with female fraternal (two egg) twins seem to have more than twice the risk of developing postmenopausal breast cancer as women who do not have a twin. The risk for women with a male twin was also elevated, although the risk for identical (one egg) twins was no higher than the risk for women without a twin.

Nongenetic Factors

There are several nongenetic risk factors that have been associated with an increase in the risk of  breast cancer:

• Early age at first menstrual cycle and a late age at menopause; the risk increases with a higher number of menstrual cycles
• Late age at the birth of the first child
• Hormone replacement therapy
• Oral contraceptives
• A high-fat diet
• Obesity
  

Prevention

In most cases, the cause of breast cancer is unknown. It is therefore difficult to know what measures you should take to reduce the risks. However, some aspects of Western lifestyle are known to increase the overall risk for cancer. Changing these aspects of your life will reduce your risk of getting many kinds of cancer. It is very likely that breast cancer will be among them.

• Diet - There is an enormous amount of information available about diet. Unfortunately, much of it is confusing and contradictory. However, some common behaviors related to diet are clearly and strongly linked to cancer risk.
  

  Excess body fat greatly increases the risk for many types of cancer. A high-calorie diet usually results in a high body mass index. It makes no difference whether the calories come from fats or carbohydrates. The best way to prevent excess body fat is to reduce the number of calories you consume. Regular exercise can help you to maintain your weight once you have reduced it.

  Diets that are high in fat, red meat, or dairy products increase cancer risk. One way to reduce this risk is to replace red meat with chicken, fish, nuts, and legumes.

  High fruit and vegetable consumption is known to reduce the risk for several cancers.

  Fruits and vegetables contain large amounts of antioxidants, which are known to protect against cancer. Carotenoids, folic acid, vitamin C, flavonoids, phytoestrogens, and isothiocyanates are all antioxidants.

• Exercise - Women who are active throughout their lives have a lower risk of developing breast cancer. The Shanghai Breast Cancer Study found that women who exercise during adolescence and adulthood have the most significant reduction in breast cancer risk.
• Hormone replacement - Hormone replacement therapy (HRT) with estrogens or progestins or both appears to somewhat increase the risk of breast cancer in postmenopausal women. However, if you are using or considering HRT, you should weigh the risk against the beneficial effects of hormone replacement.
  
  Fortunately, breast cancers developing in women on hormone replacement tend to be slow growing, thus allowing them to be detected early when they are highly curable.
• Oral contraceptives - Oral contraceptives are associated with an increased risk of breast cancer and a decreased risk of ovarian cancer. As with HRT, you should weigh the risks and benefits carefully.
• Breast-feeding - In a study conducted in China, researchers found that women who breast-fed had a reduced breast cancer risk. In this study, women who breast-fed a child for more than 2 years had a 54 percent reduced risk of developing breast cancer compared with those who breast-fed for 6 months or less. Women who had a lifetime duration of lactation anywhere from 73 to 108 months had an even lower risk. The risk was further decreased for women who breast-fed for 109 or more months of their lives.
  

Prevention for Women at High Risk

Women with a family history of breast cancer and women who carry the BRCA1 and BRCA2 genes are at an increased risk of developing breast cancer and may choose to take more aggressive preventive measures, such as the use of antiestrogen therapy, prophylactic (preventive) bilateral mastectomy (removal of both breasts), and/or prophylactic oophorectomy (removal of the ovaries).

• Chemoprevention - Tamoxifen is a chemopreventive drug that blocks estrogen from entering the cells. Tamoxifen and other antiestrogens are commonly used in the treatment of breast cancer. They are also helpful in the prevention of cancer in women at high risk.
  

  Tamoxifen is effective against the type of disease known as estrogen receptor-positive breast cancer. It prevents the growth of breast cancer cells. Someone who is at high risk for developing breast cancer can use tamoxifen to help prevent the cancer from occurring. Tamoxifen may help women who carry the BRCA2 mutation, but does not seem to benefit women with BRCA1.

  Cancer of the uterus is a possible complication of antiestrogen therapy, but is not common. Since the majority of uterine cancers will be detected at an early stage when they are highly curable, the overall benefit of antiestrogen treatment in breast cancer patients probably outweighs the risk of uterine cancer. Anyone who has a uterus and is receiving antiestrogen therapy should undergo regular gynecologic examinations. This may be a slightly different issue for women with a diagnosis of breast cancer compared with those who are not taking the drug for prevention.

  A new class of antiestrogens—called selective estrogen receptor modulators (SERM)—is believed to have positive effects on bones as well as antiestrogen effects on breast cancer. SERMs do not increase the risk of uterine cancer.

  Evista^® (raloxifene) is a SERM that has been approved by the U.S. Food and Drug Administration for the treatment of osteoporosis in postmenopausal women. Raloxifene reduces breast cancer risk in postmenopausal women with osteoporosis. It is especially beneficial to those with high lifetime estrogen exposure.

  A large clinical trial comparing raloxifene to tamoxifen published in 2006 found that raloxifene was as effective as tamoxifen in reducing the risk of invasive breast cancer, yet it has a lower risk of blood clots and cataracts.

• Bilateral prophylactic mastectomy (preventive removal of both breasts) - Women who have a family history of breast cancer and women who carry the BRCA1 and BRCA2 genes may reduce their risk of developing breast cancer by 90 percent by undergoing bilateral prophylactic mastectomy. Prophylactic mastectomy is a drastic measure. Although it greatly reduces the risk of breast cancer, it may increase stress related to self-esteem, sexuality, and femininity. If you are considering this procedure, you should weigh the benefits against the consequences. These include the irreversibility of the procedure, the psychological impact, the possibility that you may still get cancer, and potential problems with implants and reconstructive surgery.
• Prophylactic oophorectomy (preventive removal of the ovaries) - The BRCA1 and BRCA2 genes increase the risk of both breast and ovarian cancer. The ovaries produce estrogen, which is linked to the development of both cancers. Because of this, some women who are at a high risk for developing either cancer will choose to have the ovaries removed.

  If you are considering this approach, you need to weigh the benefits against the consequences. These include sterility and the potential that cancer could still develop. In addition, removal of both ovaries before menopause can introduce the issue of hormone replacement therapy. This also carries risks.

Screening and Early Detection

"Screening" means the regular use of examinations or tests in people who are at high risk for cancer, but do not have any cancer symptoms. If you have certain risk factors, then you may be at high risk for a particular type of cancer. Screening will help to ensure that you discover any cancer at the earliest possible time. In most cases, this will greatly increase your chances of a cure.

Starting at age 40, you should undergo a routine mammography screening for breast cancer. If you are at high risk, you should begin screening with an MRI and screening mammogram every year at age 30.

• Annual physical examination/breast self-examination (BSE) - An annual gynecologic examination is an important screening procedure for many types of cancer. The annual examination includes a physical examination of the breasts. During the procedure, a physician manually examines the breasts to feel for any lumps or irregularities. Your physician can teach you how to perform a BSE. You should do the BSE every month. This will give you a greater chance of finding any lump early in its development.

For more information on BSE, see Breast Self-Examination.

• Mammography - Beginning at 40, women should have a yearly mammogram. This is an x-ray image of the breast that can reveal abnormalities and help to detect cancer early. Women with a high risk of developing breast cancer should begin having mammograms and MRIs annually at age 30. Mammography at 6-month intervals is advised for younger women at high risk of developing breast cancer. These women tend to develop more rapidly growing cancers. Increasing surveillance in women with a family history of breast cancer increases the chance that cancer is found at an early stage. To make sure you get the best possible mammogram, make sure the center where you receive the mammogram carries the U.S. Food and Drug Administration certification. For more information, please see Frequently Asked Questions about Mammography.
• Predictive genetic testing - Most breast cancers are not the result of known inherited mutations, so not all women benefit from genetic testing. However, women who may be at high risk may benefit from having a genetic test. An accurate genetic test can reveal a genetic mutation, such as BRCA1 or BRCA2, but cannot guarantee that cancer will or will not develop. A positive genetic test gives you the option of taking preventive measures.
  

Strategies to Improve Screening and Early Detection

Several new methods for the screening of breast cancer are being studied in clinical trials. Despite progress in this area, it is still important to continue to use the standard screening procedures. You may wish to consider participation in clinical trials that will help to determine the effectiveness of these new techniques.

• Ductal lavage - Ductal lavage is a safe and simple procedure that has proven successful in detecting cancerous or precancerous cells in fluid extracted from a woman's milk duct. During the procedure, a small, flexible needle is inserted about a half an inch into the milk duct and a salt water stream washes cells out of the ducts.
  

  These cells are then examined under a microscope to check for any abnormalities.

  Because most breast cancers begin in the breast milk ducts, ductal lavage can detect cancers that are not yet seen on mammography. This test does not replace mammography, but may be used in addition. To date this test is not viewed as a screening procedure.

• Fiberoptic ductoscopy - Fiberoptic ductoscopy (FDS) is a new technique that builds on ductal lavage and allows physicians to directly view the inside of a milk duct. During this procedure, a small, flexible tube containing a video camera is inserted into the milk duct, creating a live picture of the inside lining of the duct.

  This allows the physician to see the lining of the milk duct and identify any abnormalities. As in ductal lavage, a water stream washes cells out of the duct for examination under a microscope. This procedure could eventually become an additional screening procedure, especially for women who are experiencing nipple discharge.

• Computer-aided diagnosis (CAD) or digital mammography - CAD is a procedure used to review mammogram results. It can help to find abnormalities overlooked by radiologists. It uses a laser scanner to convert mammography film into digital data. The computer then identifies suspicious areas. A radiologist can use both the mammogram and the computer output to make a diagnosis. The CAD system acts as a second opinion to the mammogram.
  
• Tumor biomarkers - These are chemicals produced by cancer cells. If they are found in nipple fluid, a tumor may be present. However, the test is not yet reliable enough on its own for early breast cancer detection.
• Improvements in genetics - Although the breast cancer susceptibility genes BRCA1 and BRCA2 are similar, it has been discovered that the cancers they produce associated with these mutations may be different. Usually, BRCA2 mutations lead to estrogen receptor-positive breast cancer. BRCA1 mutations lead to estrogen receptor-negative breast cancer. This knowledge could lead to individualized treatment for different types of breast cancer that used to be treated as the same.