Genetic Testing - Black TNBC Sanctuary

There are two types of genetic tests commonly performed on patients with TNBC: germline testing and biomarker testing.

1. Germline Testing

Everyone inherits genes from their biological/birth mother and father. Imagine round beads that, when strung together, make a necklace. The round beads are your genes; the necklace is your unique DNA. When a gene has a mutation, the necklace changes. There are different types of mutations—for instance, a bead may be added or removed from the necklace or a bead may be the wrong shape.

There are certain genetic mutations that can, if you have them in your DNA (on your necklace), increase your risk of developing cancer. You can find out if you have any of these specific genetic mutations through germline testing—a type of genetic testing. Germline testing is recommended for anyone diagnosed with TNBC.

Genes that, when mutated, increase the risk for TNBC include BRCA1, BRCA2, BARD1, PALB2, RAD51D, BRIP1, RAD51C, and TP53.

If you never received germline testing/genetic testing when you were first diagnosed, you can still get tested! And if you were tested before 2014 or were only tested for a handful of genes and want to know the benefits of additional testing, you should talk to your doctor or a genetic counselor. Scientists are discovering new genetic components to breast cancer all the time, so the germline tests performed today are able to test for more genetic mutations than they did ten years ago.

A note: Genetics are one risk factor, but for Black families, family health history is as significant as a genetic mutation. Talk to your family members about anyone who was diagnosed with breast cancer or prostate cancer and make sure you share this information with your doctor.

Anyone who is considering genetic testing should meet with a genetic counselor who can help assess the need for testing. If testing is recommended, genetic counselors can also help explain the process and what the results mean.

2. Biomarker Testing

Biomarker testing looks for mutations that are unique to the cancer itself. These mutations are only found in the tumor. They are not inherited, so there is no risk that other family members also have them. Identifying these mutations can help doctors decide on the best course of treatment and may make you eligible for certain targeted therapies.

Triple negative breast cancers may be tested for the following biomarkers:

BRCA1 and BRCA2: In addition to being inherited, mutations in BRCA1 and BRCA2 can also arise in tumor tissue itself. Patients with BRCA1 or BRCA2 tumor mutations may be eligible for a type of medicine called PARP inhibitors (see the targeted therapy section for more details).
PD-L1: Tumors with PD-L1 can turn off immune cells that come to attack the cancer. For this reason, some TNBCs with PD-L1 are eligible for treatment with immunotherapy (see the immunotherapy section for more details).
MSI-H/dMMR/TMB-H: Certain genetic features—including high microsatellite instability (MSI-H), DNA mismatch repair deficiency (dMMR), and high tumor mutation burden (TMB-H)—can make a tumor more likely to respond to immunotherapy. Drugs that boost the immune system may be given to these patients (see the immunotherapy section for more details).
NTRK fusion: Sometimes, part of the NTRK gene gets fused to another gene, which can promote tumor growth. Patients with NTRK fusion-positive TNBC may be eligible for an NTRK inhibitor.
FGFR fusion: Similar to NTRK, one of the three genes in the FGFR family can get fused to another gene and promote cancer growth. Patients with FGFR fusion-positive TNBC may be given an FGFR inhibitor.