Risk Factors for Breast Cancer
- Age: Risk increases with age. Seventy-seven percent of women with breast cancer are older than 50 years at diagnosis; women aged 20 to 29 years represent less than 0.4% of the total.
- Genetics: Around 5% to 10% of breast cancers result from inherited mutations. Sixty to seventy percent of women with mutations of BRCA1 and BRCA2 genes will develop a breast cancer by age 70 years. Also mutations of the p53 gene increase the risk. In addition, some families without gene mutations have multiple family members in multiple generations with breast cancer. Women from such families are at an increased risk for developing breast cancer.
- Family history: Women who have a first-degree relative (sister, mother, or daughter) with breast cancer double the risk, and those who have two affected relatives multiply the risk three times.
- Medical history: A previous breast cancer increases risk (3 to 4 times) of developing a cancer in the same breast or in the opposite side.
- Fibrocystic breast disease does not increase the risk, but a type of microscopic change known as atypical hyperplasia of the breast tissue does confer an 3 to 5 fold increased risk.
- Previous therapeutic irradiations always cause a meaningful increase in risk.
- Menstrual cycles: Early onset of menstruation (before age 12 years) or late menopause (older than 55 years) or both slightly increases risk.
- Pregnancies: No pregnancy, or first pregnancy after age 30 years, adds a low amount of risk.
- Hormone therapy (HT) for menopause: Combination hormone therapy with estrogen and progesterone increases the risk of breast cancer, but the risk is canceled five years after stopping the therapy. HT with estrogen alone does not appear to increase risk, although this type of therapy has other health risks.
- Oral contraceptive use may slightly increase breast cancer risk, but this risk decreases over time when the pill is stopped. There does not appear to be an increase in risk after 10 years of stopping oral contraceptive pills.
- Breastfeeding: According to some studies, breastfeeding for 1 1/2-2 years reduces risk.
- Alcohol: High consumption of alcoholic beverages increases risk.
- Smoking: There is some evidence that smoking may increase risk.
- Obesity: Being overweight increases risk.
- Physical activity: Movement and daily activity reduce risk and are therefore useful.
Medically reviewed by Steven Nelson, MD; Board Certified Obstetrics and Gynecology
Medscape.com. Mammogram Guidelines.
MedscapeReference.com. Mammography in Breast Cancer.
Medically Reviewed by a Doctor on 12/24/2014
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