23andMe and breast cancer gene testing: What you should know

You may be familiar with 23andMe and other at-home genetic test services, which can trace ancestry to a specific group of people that lived over 1,000 years ago, build out your family tree and connect you to distant relatives.

But what many don't know is that the services can also provide a report on the types of diseases and conditions that individuals might be predisposed to, including Type 2 diabetes, Celiac disease, Parkinson's disease, late on-set Alzheimer's and the BRCA1 and BRCA2 mutations, amongst others.

23andMe DNA Test - Health + Ancestry Personal Genetic Service ($199, Amazon) 

What is BRCA? 

While the BRCA gene, known as the "breast cancer gene," is only found in 1 in 400 people and accounts for between 5 to 10 percent of breast cancer cases and 15 percent of ovarian cancer cases, it has received particular emphasis from physicians and patients as of late. Although not everyone who has the mutation will develop cancer, BRCA1 or BRCA2 increases a female's breast cancer risk from 12 percent (the general population's risk) to between 50 and 85 percent. Additionally, women who test positive have a 60 percent chance of developing ovarian cancer, while women and men both are also at increased risk for pancreatic cancer. Whether these patients have a family history of cancer or the mutations or not, the issue at large is that many don't know they are BRCA positive and consequently miss out on increased screenings and other preventative measures.

“Half of the people with a BRCA mutation have no known family history of the BRCA cancers,” said Lauren Corduck, founder of OneinForty, to the New York Times. “Physicians who are not offering testing to patients need to be educated and patients should be proactive on their own behalf.”

Given these consequences, new guidelines were issued by a health group in late August of this year to suggest the expansion of lifesaving BRCA testing to include more women: Now, testing is advised for women previously treated for breast, ovarian or tubal cancer and are deemed "cancer-free," or if their ancestry is prone to BRCA, such as those of Ashkenazi descent.

Limitations of at-home genetic testing for BRCA

Direct-to-consumer genetic testing like 23andMe's Genetic Health Risk Report, which is included in the company's Health and Ancestry Service, can help alert individuals to genetic variants like BRCA 1 or BRCA 2, which can be lifesaving if they don't know if they have a family history.

However, there are a number of limitations to the test in regards to BRCA diagnosis, which customers should be aware of -- the biggest, and most important factor, being that 23andMe only tests for three variants most commonly found in Ashkenazi Jews, and not the thousands of other variants.

"We are not testing for all BRCA variants. There are over 1,000 variants in the BRCA genes known to increase cancer risk," explained Stacey Detweiler, a Medical Affairs Associate from 23andMe, to AOL Lifestyle. "In addition, the report does not include variants in other genes that have also been associated with hereditary cancers."

"Due to this, and the fact that other non-genetic factors like lifestyle play a role in cancer risk, a negative result doesn’t mean forgoing recommended cancer screening. however the variants we are testing for carry significant risk," she continued, adding that individuals will need to undergo confirmatory testing with their physicians.

"For any customers who receive a positive result, we recommend that they speak with a healthcare provider to discuss confirmatory testing in a clinical setting," Detweiler concluded. 

Other lifestyle and genetic factors may play a part in increasing or decreasing the risk of developing or inheriting these conditions, but it's vital to note that there are certain markers, like other BRCA variants, that the report does not cover -- your genetic counselor or physician will be able to advise further.