#1 Hereditary (genetic) breast cancer is not common
The true cause of breast and ovarian cancer is not known, as it is usually a combination of our lifestyle, genes, and the environment we live in. But, most women who have breast or ovarian cancer do not have a family history or a known gene mutation.
There are many genes that can affect breast cancer development, but most inherited cases involve mutations in two genes: BRCA1 (BReast CAncer gene one) and BRCA2 (BReast CAncer gene two).
It is estimated that less than 1% of the general population has a mutation in the BRCA1 or BRCA2 genes, and up to 10% of women and 20% of men diagnosed with breast cancer have a mutation in one of these genes.
Occurrence is higher in individuals of Ashkenazi Jewish descent, who have a 1 in 40 chance of having a BRCA mutation.
Risk of hereditary breast and ovarian cancer is low! Less than 1% of general population has a mutiation in the BRCA1 or BRCA2 genes.
#2 Breast cancer genes produce tumor-suppressing proteins
BRCA1 and BRCA2 genes provide instructions for making a protein that acts as a tumor suppressor and helps to prevent cells from growing and dividing too rapidly or in an uncontrolled way. BRCA1 and BRCA2 proteins are involved in repairing damaged DNA.
Most BRCA1 and BRCA2 gene mutations produce less or nonfunctional proteins and as a result, less of this protein is available to help repair damaged DNA or fix mutations that occur in other genes. As these defects accumulate, they can trigger cells to grow and divide uncontrollably to form a tumor.
#3 There are more than 1,800 mutations in the BRCA1 and BRCA2 genes
There’s not one mutation of a single gene, but thousands and new mutations still get discovered. The DNA sequence of a gene can be altered in different ways, which is why mutations have different effects on health, depending on where they occur and how (or if) they alter the function of essential proteins.
It’s important to know that not all mutations are pathogenic, meaning they don’t always increase your susceptibility or predisposition for a disease. Some pathogens are more common in certain geographic areas or for people of certain descent (like people with Ashkenazi Jewish ancestry).
Not all genetic mutations increase susceptibility or predisposition for a disease.
#4 Are you at higher risk for BRCA gene mutations?
Some people have a higher risk of a BRCA gene mutation than others. You may be at increased risk for a BRCA1 or BRCA2 mutation if your family history includes:
- Several relatives with breast cancer.
- Any relatives with ovarian cancer.
- Relatives who got breast cancer before age 50.
- A relative with cancer in both breasts.
- A relative who had both breast and ovarian cancers.
- A male relative with breast cancer.
- Ashkenazi Jewish ancestry (Central or Eastern European) and any relative with breast or ovarian cancer.
- A relative with a known BRCA gene mutation.
You may have a higher risk for a mutation if you’ve had:
- Breast cancer before age 50.
- Triple-negative breast cancer.
- Male breast cancer.
- Breast cancer more than once.
- Ovarian cancer, fallopian tube cancer, or primary peritoneal (lining of the abdomen) cancer at any age.
- Both breast and ovarian cancers.
- Breast cancer or ovarian cancer at any age and you are of Ashkenazi Jewish ancestry (Central or Eastern European).
- Breast cancer and you have a family member with breast or ovarian cancer.
These factors are also considered when deciding on genetic counseling. In Slovenia, you can’t get genetic testing for BRCA if you don’t meet one of these criteria (although, the age limit is 45, not 50).
Also worth mentioning. It’s best to test the person who has (or had) cancer, before testing their healthy relatives.
If you’ve had breast cancer before the age of 50 or have relatives who did, you are at greater risk for a BRCA mutation.
#5 BRCA gene mutation carriers have a high risk of breast cancer
The risk of breast cancer is getting higher as we get older. We don’t have the same risk at the age of 30 as we do at the age of 80, but the risk is always higher for women with gene mutations. Women who have the BRCA1 gene mutation have a 60–90% risk of breast cancer in their lifetimes and women with BRCA2 gene mutation have a 45–85% lifetime risk.
In comparison, the average woman only has around a 10% chance of getting breast cancer by the age of 75. Women with one or two close relatives affected with breast cancer have a lifetime risk of 17–30%, depending on the specific family history. Even if women with breast cancer have tested negative for gene mutations, the risk is still higher for their close female relatives.
Women without a genetic mutation only have up to a 10% chance of getting breast cancer by the age of 75.
#6 BRCA mutation means an increased risk of developing breast cancer at a young age
Carriers of the BRCA1 mutation have a greater risk of developing breast cancer before they reach 40 years, compared to carriers of the BRCA2 mutation. Over the age of 55 women who carry the BRCA2 mutation remain at higher risk of developing breast cancer and women carrying the BRCA1 mutation have a lesser risk.
#7 BRCA also increases a chance of ovarian cancer
Chances of developing ovarian cancer in their lifetimes are much higher for women with BRCA1 mutations (35-60%) than with BRCA2 (12-25%).
Ordinary women without gene mutations only have a 1.6% chance of the disease.
Women with BRCA1 mutation have up to 90 % chance of getting breast cancer and up to 60% chance of ovarian cancer.
#8 BRCA1 mutation carriers have higher chances for more aggressive breast cancer
60% to 80% of women with the BRCA1 mutation have triple-negative breast cancer. Triple-negative means that the three most common types of receptors known to fuel most breast cancer growth (estrogen, progesterone, and the HER-2/neu gene) are not present in the cancer tumor.
It’s considered to be more aggressive and has a poorer prognosis than other types of breast cancer, mainly because there are fewer targeted medicines for treating triple-negative breast cancer.
It seems to be more common among younger women. Because it’s also more common in women with BRCA1 gene mutation, experts recommend that patients with triple-negative breast cancer younger than 60 get genetic counseling.
#9 You can inherit BRCA gene mutation from either parent
It is a myth you can only inherit the BRCA gene mutation from your mom! Men and women both have BRCA genes and every person inherits one copy of a gene from each parent. This means that either mother or father can pass on the gene mutation to their children, regardless of the child’s sex.
BRCA mutations are inherited in an autosomal dominant pattern. They don’t skip a generation and one copy of the altered gene is enough to increase a person’s chance of developing cancer.
You can inherit get BRCA gene mutation from your mother or your father.
#10 Surgery is not the only option for BRCA carriers
Having a bilateral mastectomy and having your ovaries and/or fallopian tubes removed is not the only option. If you have a BRCA gene mutation, you can opt for regular screenings (MR or mammography) and other preventative measures (like having certain cancer markers checked) until you’re ready for operation. This probably depends on the country you’re living in and your health insurance, but there are always options. The options available to you should be presented to you during your genetic counseling.
But sadly the best preventative measure against breast cancer is a mastectomy, and even that doesn’t completely eliminate risk, it only reduces it.
Because they can’t remove every single cell of breast tissue, there is still a 2-5 % risk of breast cancer after a mastectomy.
Salpingo-Oophorectomy is the best way to reduce risk for ovarian cancer.
#11 Not everyone with the mutation will get the disease
It is important to know that with inherited BRCA mutation you only inherit an increased likelihood of developing cancer, not the disease itself. Around 20-30% of people with BRCA gene mutations never get breast or ovarian cancer.
If you’re considering irreversible preventative measures, this is one of the things you need to keep in mind.
Sources:
https://ghr.nlm.nih.gov/condition/breast-cancer
https://ghr.nlm.nih.gov/gene/BRCA1
https://ghr.nlm.nih.gov/gene/BRCA2
https://bmccancer.biomedcentral.com/articles/10.1186/1471-2407-8-155
https://www.cancer.net/cancer-types/hereditary-breast-and-ovarian-cancer
https://www.mariekeating.ie/cancer-information/brca/managing-risk-breast-cancer/
