While our understanding of what initiates and promotes the development of breast cancer in any given woman is imperfectly understood, we do recognize broad categories of circumstances that elevate a woman’s risk.
The strongest risk factor for developing breast cancer is having had it once before. In addition, women who have had benign biopsies showing either “atypical hyperplasia” or “lobular carcinoma in situ” (LCIS) are at significant risk for developing malignant disease in the future.
Women with a first degree relative (mother or sister) with breast cancer are at increased risk for developing the disease themselves. This risk is magnified if their family member’s disease was diagnosed before the age of 50. Having a more distant relative, like a grandmother, cousin, or aunt, from either the father’s or the mother’s side, elevates the risk as well, but not to the same extent.
We know of two genes, BRCA 1 and BRCA 2, which participate in the development of both breast and ovarian cancer. Women who have mutations or changes in these genes have an up to 85% chance of developing breast cancer in their lifetime along with an increased risk of ovarian cancer as well. These women generally develop their cancer at a younger age (40s or younger), and the disease may be in both breasts. When one of these genetic mutation runs in a family, multiple family members on either the mother’s or the father’s side may have breast or ovarian cancer, as well as a number of other types of cancers. Any woman who fits this profile should consider consultation with a genetics specialist to more accurately assess her risk for carrying these genetic mutations.
Most breast cancers are promoted by exposure to estrogen and progesterone, two hormones made naturally by the ovaries as soon as a woman starts menstruating. The ovaries stop making these hormones at menopause and their production is altered during pregnancy. As a result, women who begin menstruating early, enter menopause late, and either delay childbearing beyond the age of 30 or forgo it altogether, are exposed to high levels of these hormones which increases their risk for developing breast cancer.
Hormone replacement therapy after menopause can also increase a woman’s risk. A recent large scale study of women taking combination estrogen and progesterone after menopause showed an increased incidence of breast cancer as well as heart disease and stroke. While the numbers of these events were modest, the fact that they occurred warrants careful consideration of the risks and benefits of hormonal replacement therapy. Women on this type of hormone replacement should have a discussion with their physician regarding the relative risks and benefits particular to their situation.
Exposure to radiation of the chest, such as that delivered in the treatment of some lymphomas, may lead to breast cancer later in life. Alcohol consumption even in moderate amounts has also been related to an elevated risk, but this effect is eliminated if those whose diets include adequate folate, a B vitamin found naturally in whole grains and vegetables as well as in most multi vitamin supplements.