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Hereditary Breast Cancer

You are in control of you. Not genes, not your doctor, not fate, you.

Dr. Kristi Funk, Author Breasts: The Owner’s Manual

Hereditary Breast and Ovarian Cancer

According to the US Centers for Disease Control and Prevention, about 5% to 10% of breast and 10% to 15% of ovarian cancers are hereditary. Hereditary cancer means cancer runs in your family, and could be caused by a change in certain genes that you inherited from your mother or father.

Genes act as instructions and contain information to build and maintain cells in the body. Humans inherit one set of genes from their mother and one set of genes from their father. Genes are made up of DNA. DNA tells the body what traits will be passed on from parents to children, such as blood type, hair color, eye color, and risks of getting certain diseases.

BRCA Gene Mutations: Cancer Risk and Genetic Testing

What are BRCA1 and BRCA2?

Source: National Cancer Institute

BRCA1 (BReast CAncer gene 1) and BRCA2 (BReast CAncer gene 2) are genes that produce proteins that help repair damaged DNA. Everyone has two copies of each of these genes—one copy inherited from each parent. BRCA1 and BRCA2 are sometimes called tumor suppressor genes because when they have certain changes, called harmful (or pathogenic) variants (or mutations), cancer can develop.

People who inherit harmful variants in one of these genes have increased risks of several cancers—most notably breast and ovarian cancer, but also several additional types of cancer. People who have inherited a harmful variant in BRCA1 and BRCA2 also tend to develop cancer at younger ages than people who do not have such a variant. 

A harmful variant in BRCA1 or BRCA2 can be inherited from either parent. Each child of a parent who carries any mutation in one of these genes has a 50% chance (or 1 in 2 chance) of inheriting the mutation. Inherited mutations—also called germline mutations or variants—are present from birth in all cells in the body.  

What are the treatment implications of having a harmful BRCA1 or BRCA2 variant for patients who have already developed cancer?

Because the BRCA1 and BRCA2 genes are involved in DNA repair, tumors with alterations in either gene are particularly sensitive to anticancer agents that act by damaging DNA, such as cisplatin. 

A class of drugs called PARP inhibitors, which block the repair of DNA damage, have been found to arrest the growth of cancer cells that have harmful BRCA1 or BRCA2 variants. Four PARP inhibitors—olaparib [Lynparza], rucaparib [Rubraca], niraparib [Zejula], and talazoparib [Talzenna]—are approved by the FDA to treat certain cancers bearing harmful variants in BRCA1 or BRCA2.

Breast cancers with harmful BRCA1 variants are more likely to be “triple-negative cancers” (that is, the breast cancer cells do not have estrogen receptors, progesterone receptors, or large amounts of HER2/neu protein) than sporadic breast cancers or breast cancers with harmful BRCA2 variants. Triple-negative cancers are harder to treat and have a poorer prognosis than other types of breast cancers.

If someone has tumor genetic testing that reveals the presence of a harmful BRCA1 or BRCA2 variant in the tumor, they should consider having a germline genetic (blood) test to determine if the variant was inherited. Knowing if the variant was inherited is important for that individual to understand their risks to potentially develop other cancers in the future. It can also determine if other family members may be at risk of inheriting the harmful variant.

What can I do to stay healthy?

Genes load the gun but the environment pulls the trigger

Dr. Judith Stern, Distinguished Professor of Nutrition and Internal Medicine

This study says: there is emerging new evidence that adopting a healthy lifestyle may be particularly relevant for women with hereditary susceptibility to breast cancer. On the absolute risk scale, studies suggest that the presence of certain risk factors, such as excessive body weight, had a substantially higher impact on breast cancer risk if women had a hereditary predisposition to cancer. 

…the adoption of a healthy lifestyle will affect breast cancer risk to a considerably greater extent among women with a hereditary susceptibility to breast cancer compared to women without a family history of cancer. 

Conclusion: Building upon the growing evidence linking lifestyle factors to (BRCA-associated) breast cancer, we suggest that action should be taken to incorporate timely lifestyle recommendations into the daily practice of clinicians and genetic counselors. To begin with, maintaining a healthy weight, limiting alcohol consumption, smoking cessation, and being physically active on a regular basis is a message medical practitioners and patients can act upon until more precise recommendations can be made.

This study says only 5–10% of all cancer cases are due to genetic defects and that the remaining 90–95% are due to environment and lifestyle.

The major contributors to cancer deaths are:
Smoking 25-30%
Diet 30–35%
Infection 15–20%
Obesity 10–20%


Other factors account for 10-15% of cancer deaths:
Physical inactivity
Excess alcohol
Sun over-exposure
Environmental pollutants

Here is more information on cancer prevention

Breast Cancer

Updated 2024

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