The following factors may be associated with breast cancer risk in the general population. It is not yet known how these factors influence risk in carriers of BRCA1 or BRCA2 mutations. The risk for breast cancer increases with age. Eighty percent of cases occur in women older than age 50. Women who have already had breast or ovarian cancer may be at increased risk for developing additional cancers.
Estrogen stimulates the normal growth of breast tissue and is naturally produced by the body.
It is suspected that excess estrogen may contribute to breast cancer risk because of its natural role in stimulating breast cell growth. And women who have had their first menstrual period before age 12 or enter menopause after age 55 have a slightly increased risk of breast cancer as do women who have had their first child after age 30. Birth Control Pills. Most studies show a slight or no increase in breast cancer risk in women taking birth control pills, but a decreased risk for ovarian cancer. Some studies suggest that a woman who has taken birth control pills for more than 8 years, and began taking them at an early age or before her first pregnancy, has a small increase in her risk for breast cancer.