Understanding Breast Cancer -- the Basics
What Causes Breast Cancer? continued...
Because of these risks, prevention strategies and screening guidelines for those with the BRCA genes are more aggressive. There are other genes that have been identified as increasing the risk of breast cancer, including the PTEN gene, the ATM gene, the TP53 gene, and the CHEK2 gene. However, these genes carry a lower risk for breast cancer development than the BRCA genes.
Generally, women over 50 are more likely to get breast cancer than younger women, and African-American women are more likely than Caucasians to get breast cancer before menopause.
A link between breast cancer and hormones is clear. Researchers think that the greater a woman's exposure to the hormone estrogen, the more susceptible she is to breast cancer. Estrogen tells cells to divide; the more the cells divide, the more likely they are to be abnormal in some way, potentially becoming cancerous.
A woman's exposure to estrogen and progesterone rises and falls during her lifetime. This is influenced by the age she starts menstruating (menarche) and stops menstruating (menopause), the average length of her menstrual cycle, and her age at first childbirth. A woman's risk for breast cancer is increased if she starts menstruating before age 12 (less than 2 times the risk), has her first child after 30, stops menstruating after 55, or does not breast feed. Current information about the effect of birth control pills and breast cancer risk is mixed. Some studies have found that the hormones in birth control pills probably do not increase breast cancer risk or protect against breast cancer. However other studies suggest that the risk of breast cancer is increased in women who have taken birth control pills recently, regardless of how long she has taken them.
Some studies suggest that the use of hormone replacement therapy with combined estrogen and progesterone containing compounds increases the risk of developing breast cancers. They also show, after a 7 year follow up, that the use of estrogens alone does not increase or decrease the risk of breast cancer development. Their use may, though, increase the risk of clotting.