About 5 to 10% of breast cancer cases are linked to inherited gene mutations, which is why doctors recommend all women complete a risk assessment by age 25 to determine if they should get further genetic testing for cancer-linked BRCA mutations.
But women who got their genetic test results a while ago — before 2013 — may find it missed mutations we can easily test for now.
In fact, a recent study found than one in six women (17.3%) who tested negative for dangerous mutations in the early days of testing actually did have a dangerous variant when they retested an average of five years later.
“There are probably thousands of individuals out there who need to be retested,” Dr. Sofia Merajver, a breast cancer researcher, told the Washington Post.
Why was testing less accurate before?
You’ve probably heard of BRCA1 and BRCA2 — when these genes mutate, they carry the highest risk of breast cancer. When cancer does develop in people with mutations on these genes, it’s often more aggressive.
These genes were identified back in the 90s by Myriad Genetics, and for 15 years, the company held exclusive rights to screen and test for BRCA1 and BRCA2 mutations. Tests usually looked for one or the other, or both, excluding many other genes we now know hold risk.
In 2013, the Supreme Court ruled that human genes couldn’t be patented, opening the door easier testing that looked at both BRCA genes as well as mutations on up to 50 cancer-related genes in one test.
After 2013, costs also dropped from around $4,000 to less than $400. As a result, testing among both men and women steadily increased over the next decade.
As research has expanded, we now know about at least 11 more genes linked to increased risk of breast cancer outside of BRCA1 and BRCA2.
But that’s not an exhaustive list: Dozens of other genes are being investigated to see if they increase a person’s risk of breast cancer.
“It’s very worthwhile for someone to get retested because if you’ve only been tested for BRCA1 and 2, you only have part of the story,” Dr. Versha Pleasant, a breast cancer researcher, told the Washington Post.
Should you get tested for genetic breast cancer risk?
In the study that showed more than one in six women got a false negative on breast cancer genetic testing, most only returned to get retested after a family member was diagnosed.
Having a first degree relative (parent, sibling, or child) with breast cancer almost doubles a woman’s risk of developing it themselves.
Family history is one of the most important factors in a standard risk assessment assessing whether you should get genetic testing done. Ideally, it should be done with a doctor as DIY risk assessments
Genetic testing especially important for those who’ve already been diagnosed with cancer, as genetic mutations could change treatment plans.
For example, after a test shows a high-risk inherited gene mutation, a doctor may recommend a mastectomy (removal of all breast tissue) rather than a lumpectomy (removal of the tumor only, preserving the breast) to drop risk of cancer returning to the single digits.
Also, medications may work well for a certain mutation but not another. Genetic testing can point doctors to what treatment will work best.
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