Breast Cancer Risk Factors
Any woman may develop breast cancer. However, the following risk factors may increase the likelihood of developing the disease.
Risk factors that cannot be changed:
- gender - breast cancer occurs nearly 100 times more often in women than in men
- age - two out of three women with invasive cancer are diagnosed after age 55
- race/ethnicity - Caucasian women develop breast cancer slightly more often than African-American women. However, African-American women tend to die of breast cancer more often. This may be partly due to the fact that African-American women often develop a more aggressive type of tumor, although why this happens is not known. The risk for developing breast cancer and dying from it is lower in Hispanic, Native American and Asian women.
- personal history of breast cancer
- previous therapeutic breast irradiation, such as for Hodgkins Disease in the past. Often, such radiation was given more than 15 years in the past. Such patients may benefit from increased screening, such as annual breast MRI.
- family history and genetic factors - having a close relative, such as a mother or sister, with breast or ovarian cancer increases the risk. Such hereditary risk may be due to mutations in genes such as BRCA1, BRCA2, p53 and others yet to be defined. Blood tests now exist for some of these risk markers and can be performed at Stanford.
- previous breast biopsy in which the tissue showed atypical hyperplasia
- menstrual periods that began early in life (before age 12)
- menopause that began later in life (after age 55)
- dense breast tissue - as defined on a mammogram. Older women with dense breast tissue are at increased risk. The cause of the increased risk is not well understood.
- Diethylstilbestrol (DES) exposure - women who took DES while pregnant (to lower the chance of miscarriage) are at higher risk. The possible effect on their daughters is under study.
The most frequently cited lifestyle-related risk factors:
- not having children, or having your first child after age 30
- recent use (within 10 years) of oral contraceptives
- physical inactivity
- alcohol use (more than one drink per day)
- long-term, post-menopausal use of combined estrogen and progestin (HRT)
- weight gain and obesity, especially after menopause
- environmental risk factors - exposure to pesticides, or other chemicals, is currently being examined as a possible risk factor.
Risk factors for male breast cancer may include:
- age
- radiation exposure
- estrogen treatment
- diseases associated with hyperestrogenism, such as cirrhosis or Klinefelter's syndrome
- heavy alcohol intake
- obesity
There are also familial tendencies for developing male breast cancer:
- increased incidence is seen in men who have a number of female relatives with breast cancer.
- increased risk of male breast cancer has been reported in families in which a BRCA2 (Breast Cancer 2) gene mutation has been identified. This gene is probably responsible for about 10 percent of breast cancers in men.
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