Breast cancer can arise from environmental factors and inherited genetic predispositions. Understanding the role of genetics involves more than a simple count of genes. Scientific discoveries continually expand our knowledge, revealing a spectrum of genetic influences rather than a fixed number of breast cancer genes.
Genes with High Breast Cancer Risk
Certain genes significantly increase an individual’s risk of developing breast cancer when mutated. BRCA1 and BRCA2 are the most prominent. These genes normally function in DNA repair pathways, helping to fix damaged DNA and maintain genomic stability within cells. When a person inherits a mutation in BRCA1 or BRCA2, this critical DNA repair mechanism is impaired, allowing errors to accumulate that can lead to uncontrolled cell growth and cancer.
For individuals with a BRCA1 mutation, the lifetime breast cancer risk can range from 45% to 85%, and for BRCA2 mutation carriers, this risk is 40% to 85%. Other genes also confer a high risk, though they are less common. For instance, PALB2 mutations can lead to a lifetime breast cancer risk of 30% to 60%. Similarly, a mutation in TP53, a tumor suppressor gene, is associated with Li-Fraumeni syndrome, which significantly increases breast cancer risk, often at a young age.
Genes with Moderate and Emerging Risk
Beyond high-risk genes, a broader array contributes to breast cancer risk to a lesser degree. These moderate-risk genes lead to an elevated risk not as profound as BRCA1 or BRCA2 mutations. For example, CHEK2 mutations, involved in cell cycle arrest and DNA repair, can increase breast cancer risk by two to four times the general population risk. ATM gene mutations, also playing a role in DNA damage response, are associated with a two to three-fold increased risk.
Another example is CDH1, primarily known for its association with hereditary diffuse gastric cancer, but also linked to an increased risk of lobular breast cancer. Research continually identifies new genes and refines our understanding of existing ones.
Genetic Testing for Breast Cancer Risk
Genetic testing identifies inherited mutations in genes associated with an increased risk of breast cancer. This testing typically involves a blood or saliva sample, analyzed to sequence specific genes. Individuals with a strong personal or family history of breast cancer, especially at young ages, or those with certain cancer types, are often candidates. A positive result indicates a specific gene mutation, while a negative result means no known mutation was found.
Sometimes, results may show a “variant of uncertain significance” (VUS), meaning a genetic change was found but its impact on cancer risk is unclear. Genetic counselors play a crucial role, helping individuals understand their family history and test results. They provide guidance on appropriate tests, interpret complex findings, and discuss the impact on medical management and family members. This support ensures informed decisions about genetic health.
Personalized Care Based on Genetics
Knowing one’s genetic predisposition enables healthcare providers to tailor screening and prevention strategies. For individuals with high-risk gene mutations, personalized screening often includes earlier mammograms and the addition of breast MRI scans, sometimes starting as early as age 25. These enhanced surveillance methods aim to detect cancer at its earliest, most treatable stages. Preventive strategies like chemoprevention, involving medications such as tamoxifen, can also reduce breast cancer risk.
Some individuals may choose prophylactic surgeries, such as a preventive mastectomy or oophorectomy, to significantly lower their risk of developing breast or ovarian cancer. This highly personal decision is made in consultation with healthcare providers. If breast cancer develops, genetic information can also influence treatment decisions, as certain mutations may suggest different therapeutic approaches. This personalized approach empowers individuals and their healthcare teams to proactively manage breast cancer risk and treatment.