Expect Questions About Genetic Testing for Breast Cancer

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A STUDY finding that pathogenic variants in 5 genes are associated with a high risk of triple-negative breast cancer and a 20% lifetime risk for overall breast cancer1 may increase interest in genetic testing. “This is the first study to establish which genes are associated with high lifetime risks for triple-negative breast cancer,”2 according to Fergus J. Couch, PhD, a geneticist in the Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, and the study’s corresponding author.

The study looked at multigene panel testing for 10,901 patients diagnosed with triple-negative breast cancer and found that 12% had pathogenic variants in 1 of 5 genes—BARD1, BRCA1, BRCA2, PALB2, and RAD51D. “The results suggest that all triple-negative breast cancer patients should undergo multigene panel testing, regardless of age at diagnosis or family history of cancer, for improved cancer risk assessment and because of the ongoing development of targeted therapeutic approaches for triple-negative breast cancer patients with mutations in predisposition genes,” the authors concluded.

Many at Elevated Risk

FOR MANY patients, when geneticists or clinicians look at “family history, age at diagnosis, prior biopsies, what we are finding is that a lot of people have an elevated risk, over 20% chance of having a mutation. That would qualify them for genetic testing under the current guidelines,” Dr. Couch told The ASCO Post.

However, “anybody who really wants testing can probably find a way to get the test,” Dr. Couch said. “A lot of people are getting tested, even though they don’t necessarily strictly qualify. As a result of that, we are finding a lot of mutations, which hopefully is a value to them going forward,” he said. “There are a lot of mutations out there, and we have no way of identifying those people ahead of time without testing.”

DISCLOSURE: Dr. Couch is a consultant/advisor to AstraZeneca, has received research funding from GRAIL, and has an unspecified relationship with Ambry Genetics.


1. Shimelis H, LaDuca H, Hu C, et al: Triple-negative breast cancer risk genes identified by multigene hereditary cancer panel testing. J Natl Cancer Inst August 7, 2018 (early release online).

2. Dangor J: Mayo-led research team identifies genes that increase risk for triple-negative breast cancer. Mayo Clinic News Network, August 7, 2018. Available at Accessed September 6, 2018.

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