Breast cancer is a prevalent disease affecting millions worldwide, with various contributing factors influencing its development. While many cases arise from acquired changes in breast cells during a person’s lifetime, approximately 5% to 10% are hereditary. These cases result from specific gene alterations passed down through generations. Understanding the role genetics plays in breast cancer is important for personalized risk assessment and management.
Key Genes Linked to Breast Cancer
Genes are segments of DNA that contain instructions for building and maintaining the body, including regulating cell growth and division. A “mutation” refers to a change in this genetic code, which can prevent a gene from functioning correctly. In breast cancer, mutations in certain genes can impair their normal processes, increasing susceptibility to the disease.
The most recognized genes associated with hereditary breast cancer are BRCA1 and BRCA2. These genes normally act as tumor suppressors, producing proteins that help repair damaged DNA and prevent uncontrolled cell growth. When a mutation occurs in BRCA1 or BRCA2, this DNA repair process is compromised, leading to an increased risk of cancer development. Women with a BRCA1 mutation have a 55-72% chance of developing breast cancer by age 70-80, while those with a BRCA2 mutation have about a 45-69% risk by the same age. These mutations also elevate the risk of other cancers, including ovarian cancer.
Beyond BRCA1 and BRCA2, other genes are linked to an increased, though often less pronounced, risk of breast cancer. These include PALB2, CHEK2, and ATM. For instance, women with an abnormal PALB2 gene may have a breast cancer risk 9.47 times higher than average, with a 35% risk by age 70. Mutations in these genes are rarer but contribute to hereditary breast cancer risk.
Genetic Testing and Counseling
Genetic testing for breast cancer involves analyzing a sample of blood or saliva to detect specific gene mutations. These tests look for changes in BRCA1 and BRCA2, and many use multi-gene panels to screen for mutations in several other genes. Results can take several weeks or months to become available.
Genetic testing is recommended for individuals with a strong family history of breast and ovarian cancers, or a personal history of breast cancer diagnosed at a younger age. Other criteria include triple-negative breast cancer diagnosed at any age, cancer in both breasts, male breast cancer, or a known BRCA mutation in a family member. Individuals of Ashkenazi or Eastern European Jewish ancestry with a moderate family history of breast and ovarian cancers may also consider testing.
Genetic counseling is part of this process, taking place both before and after testing. A genetic counselor is a healthcare professional with specialized training who helps individuals understand their cancer risk based on personal and family medical history. They explain the implications of genetic testing, assist in interpreting results, and discuss how these findings may affect family members. This guidance helps individuals make informed decisions about testing and health management.
Managing Inherited Breast Cancer Risk
For individuals identified with high-risk genetic mutations, various strategies exist to manage their increased susceptibility to breast cancer. These measures focus on prevention or early detection, rather than treating existing cancer. Decisions about these strategies are made in close consultation with healthcare providers.
Enhanced surveillance involves more frequent and specialized screenings. For instance, women with BRCA1 or BRCA2 mutations begin annual breast MRI screenings as early as age 25, alongside yearly mammograms starting around age 30. Clinical breast exams every 6 to 12 months, beginning at age 25, are part of this intensified monitoring. This approach aims to detect cancers at their earliest, most treatable stages.
Prophylactic surgery offers substantial risk reduction. Bilateral prophylactic mastectomy, the surgical removal of both breasts, can reduce breast cancer risk by approximately 90-95% in women with BRCA1 or BRCA2 mutations. While it does not eliminate all risk, it substantially lowers the chance of developing breast cancer. Prophylactic oophorectomy, the removal of the ovaries (and often fallopian tubes), is also recommended for women with BRCA1 or BRCA2 mutations by age 40, to reduce ovarian cancer risk and potentially lower breast cancer risk.
Chemoprevention involves taking medications to reduce cancer development risk. Tamoxifen and raloxifene are two such drugs, known as Selective Estrogen Receptor Modulators (SERMs), which block the effect of estrogen on breast tissue, as many breast cancers are estrogen-receptor positive. Tamoxifen can be used by both pre- and post-menopausal women, while raloxifene is for post-menopausal women. These medications, taken daily for five years, can reduce breast cancer risk by up to 30-40% in high-risk women.
Adopting healthy lifestyle choices also plays a role in risk management, even for those with inherited genetic risks. Maintaining a healthy weight, regular physical activity, and limiting alcohol consumption can contribute to a lower overall cancer risk. While these choices do not negate the impact of a genetic mutation, they can still improve an individual’s health outlook.