Breast cancer can develop at any age, but the risk of developing it increases as women get older. The majority of cases develop for reasons we do not yet understand. 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
- With an inherited mutation in breast cancer genes, usually either BRCA1 or BRCA2. About 5% to 10% of breast cancers are related to these mutations. BRCA1 and BRCA2 are two tumor suppressor genes that help prevent cancer by producing proteins that suppress abnormal cell growth. Mutations in these genes can affect their normal function, potentially allowing uncontrolled cell growth and increasing the risk of cancer. Women with inherited BRCA1 or BRCA2 mutations have up to an 85% lifetime risk of developing breast cancer.
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. Family history (genetics) and exposure to estrogen are among the most important factors in breast cancer risk. Women should work with their healthcare provider 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 drugs tamoxifen or raloxifene 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 health practitioner can help assess the risks and benefits of such treatment.
For those women who have a gene mutation such as BRCA1 and BRCA2 that is 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 up to 97%. Other women elect to have a prophylactic mastectomy on their cancer-free breast after developing cancer in the other breast. A health practitioner can help advise and work with a woman who is considering prophylactic mastectomy.