Mammogram FAQs: Part 4, Breast Cancer

What are the factors that place a woman at increased risk of breast cancer?
The risk of breast cancer increases gradually as a woman gets older. However, the risk of developing breast cancer is not the same for all women. Research has shown that the following factors increase a woman’s chance of developing this disease:

• Personal history of breast cancer – Women who have had breast cancer are more likely to develop breast cancer again.
• Family history – A woman’s chance of developing breast cancer increases if her mother, sister, and/or daughter have a history of breast cancer (especially if they were diagnosed before age 50).
• Certain breast changes on biopsy – Having a diagnosis of atypical hyperplasia (a non-cancerous condition in which cells have abnormal features and are increased in number) or lobular carcinoma in situ (LCIS) (abnormal cells found in the lobules of the breast) increases a woman’s risk of breast cancer. Women who have had two or more breast biopsies for other benign conditions also have an increased chance of developing breast cancer. This increase is due to the condition that led to the biopsy, and not the biopsy itself.
• Genetic alterations – Specific alterations in certain genes (BRCA1, BRCA2, and others) increase the risk of breast cancer. These alterations are rare; they are estimated to account for no more than 10 percent of all breast cancers.

• Reproductive and menstrual history – Evidence indicates that:

• - The older a woman is when she has her first child, the greater her chance of developing breast cancer.
• - Women who started menstruating at an early age (age 11 or younger), experienced menopause late (after age 55), or never had children are also at an increased risk of developing breast cancer.
• - Women who take hormone replacement therapy for a long time also appear to have an increased chance of developing breast cancer.

• Breast density – Breasts appear dense on a mammogram if they contain many glands and ligaments (called dense tissue), and do not have much fatty tissue. Because breast cancers nearly always develop in the dense tissue of the breast (not in the fatty tissue), older women who have mostly dense tissue on a mammogram are at an increased risk of breast cancer. Abnormalities in dense breasts can be more difficult to detect on a mammogram.
• Radiation therapy (“x-ray therapy”) – Women who had radiation therapy to the chest (including the breasts) before age 30 are at an increased risk of developing breast cancer throughout their lives. This includes women treated for Hodgkin’s disease. Studies show that the younger a woman was when she received her treatment, the higher her risk of developing breast cancer later in life.
• Diet and lifestyle factors – Diet is thought to play a role in breast cancer risk, although researchers have not yet identified specific dietary factors that affect risk. Differences in diet may explain the lower risk of breast cancer among Asian women compared with American women. Studies have found that obesity and weight gain in postmenopausal women increase breast cancer risk. A number of studies suggest that moderate alcohol consumption may also increase a woman’s chance of developing breast cancer.

What happens if mammography leads to the detection of ductal carcinoma in situ (DCIS)?
Over the past 30 years, improvements in mammography have resulted in an ability to detect a higher number of tissue abnormalities called DCIS. DCIS contains abnormal cells that are confined to the milk ducts of the breast. The cells have not invaded the surrounding breast tissue. Eighty percent of cases of DCIS are found by mammography because DCIS usually does not cause a lump that can be felt. Some of these cases later become invasive cancers.

Today, it is not possible to predict which cases of DCIS will progress to invasive cancer. Therefore, DCIS is usually removed surgically. Until recently, DCIS was often treated with mastectomy, but breast-conserving surgery is now an option for many women with DCIS. Radiation therapy, with or without tamoxifen, may also be an option. Women who have been diagnosed with DCIS should talk with their doctor to make an informed decision about treatment.

What are the chances a woman in the United States might get breast cancer?
Age is the most important risk factor for breast cancer. The older a woman is, the greater her chance of developing breast cancer. A woman’s chance of being diagnosed with breast cancer is:

• from age 20 to age 30. . . 1 out of 2,000
• from age 30 to age 40. . . 1 out of 250
• from age 40 to age 50. . . 1 out of 67
• from age 50 to age 60. . . 1 out of 35
• from age 60 to age 70. . . 1 out of 28
• Ever . . . . . . . . . . . . . . . . 1 out of 8

Most breast cancers occur in women over the age of 50; the number of cases is especially high for women over age 60. Breast cancer is relatively uncommon in women under age 40.