This year, 275,000 women will be diagnosed with breast cancer. If detected early, it can be treated effectively with surgery, chemotherapy, radiation, and hormones. By evaluating the risk factors below, a woman and her physician can determine if she is at high risk for developing breast cancer. Women at high risk should be screened more often and may need medications like tamoxifen or surgery to prevent breast cancer.
Old Age
An age over 50 years is the most significant risk factor for breast cancer. Every woman should do self breast-exams and should have an annual mammogram beginning at age 40.
Family History and Genetic Mutations
5 to 10% of breast cancer is "familial" or hereditary. This means that the sisters, daughters, and granddaughters of a woman with breast cancer are more likely to develop breast cancer at an early age.
The two most common genetic mutations associated with breast cancer are mutations in the BRCA1 and BRCA2 genes. These genes, discovered in the mid-1990s, normally help to prevent breast cancer and ovarian cancer. However, when there is a genetic mutation, a woman has up to a 70-90% chance of developing breast cancer by age 70. These mutations also increase a woman's chance of developing breast cancer.
So, when two or more women in the same family develop breast cancer, especially before age 50, a physician may test for the BRCA1 and BRCA2 mutations. A woman who has a BRCA1 or BRCA2 mutation should do self breast exams every month, should get a mammogram every 6-12 months, and should see a physician regularly. Medications such as tamoxifen may reduce these women's chances of developing breast cancer.
Estrogen
Exposure to estrogen can increase a woman's risk of developing breast cancer.
Oral contraceptive pills: These "birth control pills" are generally very safe. Studies have shown that they slightly increase a woman's risk of breast cancer but decrease her risk of ovarian and colon cancer. Birth control pills also increase a woman's risk of coronary artery disease (heart disease) and blood clots. They should not be used by women who smoke or have a history of deep venous thrombosis (DVT, leg clots) or pulmonary emboli (PE, clots in the lungs). Overall, birth control pills are safe and are effective in preventing pregnancy.
Hormone Replacement Therapy: After menopause, some women take estrogen and progesterone pills to prevent hot flashes, vaginal dryness, and osteoporosis. Around 2002, these hormone pills were shown to increase a woman's risk of developing breast cancer by 1.6-2.5 times. These pills are still generally safe, but women taking them should do breast exams and receive mammograms regularly.
Radiation
Women who received radiation therapy for a cancer (lymphoma, etc.) of the chest, especially at a young age, are much more likely to develop breast cancer. Receiving radiation during early pregnancy can also increase the chance that the fetus will be small or have mental retardation.
History of Breast Cancer
A woman who had breast cancer in one breast has a 0.5-1% chance per year of developing breast cancer in the opposite breast. Medications like tamoxifen and regular mammograms can prevent the recurrence of breast cancer in the opposite breast.
Other Risk Factors
Alcoholism, a high-fat diet, obesity, low folate in the diet, and smoking all increase a woman's chance of developing breast cancer.
Summary
An age over 50, relatives with breast cancer, genetic mutations (BRCA1 and BRCA2) in the family, increased exposure to estrogen (hormone replacement), exposure to radiation in the chest, and a personal history of breast cancer are the main 6 risk factors for developing breast cancer.
References
American Cancer Society: provides more detail about risk factors
