Hereditary Breast and Ovarian Cancer Facts
Posted on October 12 2018
As part of our weekly Breast Cancer Awareness series, every Friday for the month of October we're discussing different topics related to the disease and sharing information about aspects of breast cancer you might not be familiar with. This week, we're discussing the genetic basis of breast cancer. Although most often sporadic, with no known causes, a significant portion of breast cancers are part of a syndrome called Hereditary Breast and Ovarian Cancer. This indicates a higher risk of cancers passed down through a genetic line. We'll show you how this happens, and how you can investigate your family health history for signs of the syndrome, so that you can better protect and screen yourself for breast cancer.
Tumor Suppressor Genes: Most inherited breast cancers are caused by mutations, abnormal changes, in two particular genes, BRCA1 and BRCA2 (BReast CAncer genes 1 and 2), having been passed on from a parent. Everyone carries these two tumor suppressor genes, which repair cell damage and maintain proper growth of breast and ovarian cells. Every cell has two copies of every gene, one from each parent. A gene mutation only has to occur in one of these copies to be passed along, meaning that a child has a 50% chance of inheriting a mutated gene from a parent who has one.
Mutations in BRCA1 and 2 are rare; only 1% of the total population is estimated to have them. However, these genes account for 10 to 15% of all breast cancers. While most breast and ovarian cancers occur sporadically, without known cause, the possibility of carrying mutations in these genes should be regarded seriously.
Other Genes: Although tumor suppressor genes make up the bulk of inherited cancers, other genes may be responsible for other incidences, both inherited and sporadic. These include:
- Oncogenes: Normal genes, typically ones that promote cell growth, can become mutated and encourage growth of tumors. These mutations are not inherited.
- DNA Repair Genes: These repair mistakes made when DNA is copied in new cells, and can include tumor suppressor genes. If these genes are damaged, mistakes go uncorrected and mutations form, possibly leading to cancer.
Identifying Risk: The first step in understanding your inherited cancer risk level is a study of your family history. Increased incidence of cancer, particularly specific cancers on the same side of the family, may be an indication that genetic testing should be done. Consulting a genetic counselor can help you understand not only the results of genetic testing, but also the implications of your family history.
When possible, try to collect the following information about your family's cancer history:
- Cancer type(s)
- Age of diagnosis
- Lineage: cancer records on both your maternal and paternal family sides.
- Ethnicity: non-Hispanic white women have higher rates of breast cancer, but African-American women have higher incidence rates before age 40.
Previous genetic testing, if available.
- An abnormal breast cancer gene in your family.
A personal or family history of:
- Breast cancer diagnoses at age 50 or younger.
- Triple negative breast cancer.
- Male breast cancer.
- Ovarian cancer.
- A history of cancers on the same side of a family, especially in multiple generations.
- A second diagnosis of breast cancer in either breast.
- 1 or more blood relatives who meet any of the above criteria.
- 2 or more blood relatives with breast cancer diagnosed at age 50 or younger, or with ovarian cancer.
- Askenazi Jewish heritage on either side of your family.
This isn't quite a complete list, as family and personal health circumstances can vary greatly. Any family history of cancer should be looked at closely for unusually high incidence or recurrence, among other atypical occurrences. Knowing your family history is vital in protecting yourself.
Cancer Risks for Inherited Mutations
Women with mutations associated with hereditary breast cancer face many increased cancer risks compared to other women. These go beyond just breast cancer, and include other types such as ovarian cancer. Some of these risks include:
- Lifetime risk of breast cancer: 50% to 85%
- BRCA1: 55% to 65% by age 70.
- BRCA2: 45% by age 70.
- Breast cancer diagnosis before age 50: 30% to 50%
- Second breast cancer development: 40% to 60% (this risk rises 2% to 3% every year)
- Lifetime risk of ovarian cancer:
- BRCA1: 25% to 50%
- BRCA2: 15% to 30%
These risks don't just affect women, either. Men with inherited mutations also show increased risk for various cancers, especially compared to regular incidence rates for men. These risks include:
- Lifetime risk of breast cancer:
- BRCA1: 1% to 2%
- BRCA2: 6%
- Risk of prostate cancer:
Triple negative breast cancer: Not all breast cancers function or grow in the same way. A triple negative form of breast cancer has cells that test negative for the presence of receptors for the hormones estrogen or progesterone, or for the gene HER2. Estrogen and progesterone do not help these cancers grow; neither does the presence of too many HER2 receptors. This means that these cancers don't respond to hormonal therapies, or ones that target HER2 receptors. About 10% to 20% of breast cancers are triple negative. This type of breast cancer also can indicate the presence of specific mutations:
- 60% to 80% of breast cancers in women with a BRCA1 mutation are triple negative.
- 70% to 80% of breast cancers in women with a BRCA2 mutation are only negative for HER2 receptors.
Triple negative breast cancer has specific challenges in treatment, as do all breast cancers. Knowing about your family's cancer history and genetics can give you crucial information towards identifying cancer risks and treating cancers.
Keeping Yourself Safe
Finding out that you have a gene mutation or a family history of breast cancer can be distressing, but you can mitigate the risks of developing a cancer in numerous ways.
Lifestyle Changes: Adopting healthy practices in your lifestyle can reduce the risk of cancer for both those with inherited mutations and family histories, and even those without preexisting risks. Among these changes:
- Maintaining a healthy weight: Fat cells produce estrogen, so excess fat cells can increase the risk of hormone-receptor-positive breast cancer.
- Maintaining a healthy diet: The links between unhealthy food and breast cancer are still being explored, but being overweight has a confirmed link, as described above. In addition, a proper diet boosts immune function.
- Regular exercise: Staying active not only helps maintain a healthy weight, but also helps control blood sugar. This limits the amount of insulin growth factor (IGF) hormones, which stimulate breast cancer cell growth.
- Avoiding alcohol: Women who drink 3 alcoholic drinks per week have a 15% higher risk of breast cancer than women who don't. Drinking 3 to 5 drinks per week during adolescence increases the risk of developing benign chest lumps threefold.
- Avoiding smoking: Pre-menopausal women who smoke have a high risk of breast cancer. Smoking can also increase complications from breast cancer treatment.
Hormonal Therapy and Other Medications: Medications that lower the production of estrogen or block estrogen receptors reduce the risk of hormone-receptor-positive breast cancer. Additionally, birth control pills may lower the risk in women with abnormal BRCA1 and BRCA2 genes.
Protective Surgery: Prophylactic, or protective, surgery, involves removing most of the breast tissue to prevent cancer from forming in the future. It can also be used on other organs or glands in high-risk patients. This is an extremely aggressive prevention method, but it can reduce risk of breast cancer by up to 97%. Women with BRCA1 or BRCA2 mutations can also reduce cancer risk by 50% by removing their ovaries or Fallopian tubes before the onset of menopause.
More Frequent Screening: Screening options are various, and will depend on your personal and family history, plus any results from genetic testing. The risks accumulated during different ages of life will also factor into the frequency of testing. A healthcare professional and genetic counselor are invaluable guides to developing a useful and timely screening schedule. Screening plans may include:
- Monthly self-exams.
- Yearly breast exams by a doctor.
- Yearly digital mammograms starting at age 30.
- Yearly MRIs starting at age 30.
A thorough and well-structured screening plan can not only detect cancer early, potentially saving your life, but can also be a strong foundation for coping with the possibility of breast cancer. Learning about an inherited condition can cause anxiety, frustration, and grief. But regular screenings can help reduce these fears, and a close relationship with a doctor, genetic counselor, or other healthcare professional can be an immense source of comfort. The importance of being open about your fears with your doctor cannot be overstated. Managing these fears will help you better manage the risks of a genetic condition and give you a feeling of control over your own health.