What to Know About Home Genetic Tests for Breast Cancer Risk
By: Holly Pederson, MD • Posted on September 12, 2018
The field of genetics, genomics and risk assessment for cancers have exploded. You may have seen advertisements about home DNA testing to assess your risk for disease. And perhaps family or friends have even been tested by 23 and Me and/or Ancestry.com.
The U.S. Food and Drug Administration has given a company the go ahead to offer consumers a home DNA test to assess for genetic mutations that are linked to a higher risk of breast and/or ovarian cancer.
Is using the test a good way to determine your risk?
While the self-test is easy to complete, and you can do it conveniently from your home, its usefulness is unfortunately, limited.
How at-home testing works
The home DNA test requires no prescription, can be ordered online and requires submitting a saliva sample.
A lab analyzes DNA from cells in your saliva to look for three pathogenic variants, i.e. mutations, in the BRCA gene: two in BRCA1 and one in BRCA2.
These produce a much higher risk for breast and/or ovarian cancer than is seen in the general population. The mutations can also cause prostate or breast cancer in men.
Two major limitations of the at home test
1. If you’re not of Ashkenazi Jewish ancestry, the test won’t help you.
There are at least 1,000 known BRCA mutations — probably many more — and this test only accounts for the three most common mutations seen in the Jewish population.
The three BRCA1/BRCA2 mutations — known as Ashkenazi founder mutations — typically do NOT occur in other populations.
2. If you are of Ashkenazi Jewish ancestry, the test will NOT screen for everything.
When you’re of Ashkenazi descent, your chance of having a BRCA1 or BRCA2 gene mutation is much higher at 1 in 40, compared to 1 in 400 to 500 for the general population.
The home DNA test is a pretty good screen for most Jewish people, but it may not go far enough as it screens for the BRCA1 and BRCA2 mutations that account for 80 to 90 percent of the cancer-causing mutations seen in the Jewish community.
It does not evaluate other high-risk genes, including other BRCA genes and nearly a dozen more genes that have been identified as breast cancer risk genes
Additionally, families may share other less significant genes or environmental exposures that contribute to risk, even when a specific gene mutation is not identified. Only 10-15% of breast cancer is truly hereditary.
So it is important to realize even IF your home DNA test is negative, you may still benefit from additional genetic testing, and even if negative, breast MRI screening and/or preventive medication.
Genetic counseling: The key to understanding your risk
I recommend working with a genetic counselor regardless of ancestry if you have the following:
- A strong personal or family history of breast cancer.
- Any personal or family history of ovarian cancer, male breast cancer or pancreatic cancer.
The genetic counselor can help you understand which test is best, anticipate possible results, discuss risk reduction strategies and interpret test results.
Having a gene mutation doesn’t mean you’ll get cancer; it only means your risk of cancer is elevated.
Options for managing your risk
- Being watched more carefully by doctors
- Considering medication to reduce your risk
- Pursuing risk-reducing surgeries
Finding out you carry a gene mutation that puts you at higher risk for breast and ovarian cancer can be overwhelming. It's important to have a relationship with an expert physician and health team beforehand that you can turn to afterward — especially if the news is disconcerting.
Importantly, if the testing is NEGATIVE, you may STILL be at increased risk for cancer. Genetic counselors can help estimate this risk and suggest risk reducing strategies and referrals. The lack of having a back-up heath care team to address concerns and questions with is one definitive disadvantage to processing direct-to-consumer testing results.
Lifestyle choices that can reduce breast cancer risk in everyone
- Limiting alcohol consumption to 7 drinks a week or less
- Limiting the duration of combined hormone therapy after menopause
- Achieving and maintaining ideal body weight
About ¼ of all ovarian cancer is hereditary. Taking hormonal contraceptives can reduce ovarian cancer risk by 50%. New guidelines recommend starting colon cancer screening at age 45 as opposed to age 50.
Who should get full genetic testing after counseling?
There are several known hereditary cancer syndromes and a lot of overlap. Commonly, gene PANEL testing is performed, looking for mutations in a number of cancer related genes. Nearly all of these mutations WILL NOT be assessed for in a home DNA test.
For example, Lynch syndrome is a common hereditary syndrome caused by mutations in one of a group of mismatch repair genes (MLH1, MSH2, MSH6, PMS2 or EPCAM). Lynch syndrome markedly increases the risk for:
- colon cancer
- endometrial cancer
- ovarian cancer
- other cancers
Red flags for this condition are a personal or family history of colon or endometrial cancer under the age of 50.
Know Your Family History
Pay attention to cancers diagnosed at a young age, rare cancers (for example, ovarian and pancreatic cancer) and multiple cancers. These are red flags for hereditary risk.
Guidelines to evaluate risk for hereditary breast/ovarian cancer include:
- Breast cancer diagnosed at or under age 50
- Ovarian cancer at ANY AGE
- “Triple Negative” breast cancer (estrogen, progesterone and her2neu NEGATIVE)
- Male breast cancer at any age
- Pancreatic cancer at any age
- Metastatic prostate cancer
- Ashkenazi Jewish decent with breast, ovarian and/or pancreatic cancer
- Known gene mutation in blood relative
- Family History: unaffected patient who has a 1st or a 2nd degree relative that meets the above criteria
If you have a mutation and/or at high risk, do NOT despair as there are several options to reduce risk and increase surveillance.
If you have had a negative/normal home DNA test it does not mean you are totally in the clear.
And even if you have no family history of cancer or have an unknown family history, you still need regular cancer screenings appropriate to age.
Be Strong. Be Healthy. Be in Charge!
-Holly J. Pederson, MD
Medical Breast Specialist
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