The average woman in the US today has a 12.6 percent chance (or about one chance in eight) of developing breast cancer sometime during her lifetime. Her risk at any one age, however, is far lower. In addition to heredity, there are several other risk factors for breast cancer:
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Gender
Breast cancer is much more common in women than in men. Only about 1 percent of breast cancer cases occur in men.
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Age
The chance of developing breast cancer increases with age. Eighty percent of all breast cancers are found in women over the age of 50.
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Personal Medical History
A woman who has had cancer in one breast is more likely to develop it in the other.
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Menstrual History
A woman who began having menstrual periods early (before age 12) or went through menopause late (after age 50) has a higher than average risk of breast cancer. This may be related to the overall amount of estrogen the breast is exposed to over a lifetime.
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Reproductive History
Women who had their first child after the age of 30 or who never had children are at increased risk for the disease. This may be due to protective changes in breast tissue that occur with full-term pregnancy.
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Benign Breast Disease
Some types of noncancerous breast conditions may be an indication of an increased risk for breast cancer -- including atypical hyperplasia, in which abnormal cells are overproduced, and lobular carcinoma in situ, in which atypical cells are overproduced in the lobules. A history of breast cysts or fibrocystic changes does not increase the risk of breast cancer.
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Estrogen Replacement Therapy
Taking replacement hormones after menopause begins seems to raise the risk of disease very slightly, but the added risk disappears about five years after stopping the hormones.
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Oral Contraceptives
Taking the birth control pill also raises the risk of breast cancer very slightly, but the increased risk disappears about ten years after a woman stops taking the pill.
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Alcohol
A growing body of research shows that higher alcohol intake -- even the equivalent of one drink per day for women -- may be associated with an increased risk of breast cancer.
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Weight
Obesity leads to a higher risk of breast cancer in postmenopausal women, perhaps because fat cells produce excess estrogen. One study found that the risk of breast cancer was 40 percent higher in women who gained 44 to 55 pounds after the age of 18.
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Diet
The findings of some studies suggest an association between adequate vitamin D status and reduced cancer risk. However, more research is needed to clarify the nature of this relationship. A large study called WINS found that women who followed a low-fat diet had a lower risk of breast cancer recurrence. Women with estrogen-receptor-negative cancers received the most benefit from a low-fat diet. For now, doctors recommend following a healthful diet: a variety of vegetables and fruits, whole grains, and lean proteins; limited alcoholic beverages; and appropriate total calories to achieve and maintain a healthy weight. If you have questions or would like individual guidance, speak with a registered dietitian.
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Exercise
Engaging in regular exercise is also a key component of good health. It helps to achieve and maintain a ideal body weight and is likely to reduce breast cancer risk
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Radiation Exposure
Exposure to radiation, particularly during the first two or three decades of life, has been associated with an increased risk of breast cancer. (Exposure to low-dose mammography radiation in women over 40, however, poses little risk.)
