Breast cancer can develop at any age, but the risk of developing it increases as women get older. While 5% to 10% of breast cancers are related to an inherited defect in one of two breast cancer genes (BRCA1 or BRCA2), the majority of cases develop for reasons we do not yet understand. As a general rule, some of those at higher risk of developing breast cancer include women:
- With close relatives (mother, sister, aunt) who have had the disease
- Who have had a cancer in the other breast
- Who have not had children
- Who had their first child after the age of 30
A healthy lifestyle that includes regular exercise, maintaining a healthy body weight, and avoiding alcohol may help to minimize the risk of developing breast cancer. Research studies continue to identify factors that are associated with an increased or decreased risk of developing the disease, but there is no single set of actions that will cause or prevent breast cancer. The most important factors in breast cancer risk are family history (genetics) and exposure to estrogen. Women should work with their doctor to determine their personal risk factors and how to best address them. For example, a woman may choose to avoid long-term use of hormone replacement therapy (HRT).
Women who are at high risk of developing breast cancer may be able to take the drug tamoxifen to reduce their risk. However, tamoxifen can increase the risk of developing blood clots, endometrial (uterine) cancer, and possibly cardiovascular disease, so the decision to take the medication needs to be weighed carefully. A doctor can help assess the risks and benefits of such treatment.
For those women who have the gene mutation (BRCA1 and BRCA2) frequently associated with breast cancer, prophylactic mastectomy is an option. Women electing this option choose to have both breasts removed before developing cancer rather than run the high risk of developing the disease later in their lifetime. Studies have shown that such surgery can reduce the risk of developing breast cancer by approximately 90%. Other women elect to have a prophylactic mastectomy on their cancer-free breast after developing cancer in the other breast. A doctor can help advise and work with a woman who is considering prophylactic mastectomy.