What is Genomic Testing?

Genomic testing looks at the particular mutations that occur in cancerous tissue. This is different than genetic testing, which can identify certain mutations that someone may be born with that may increase their risk of developing cancer. Genomic testing is done on a sample of a tumor and can be helpful in determining the risk of recurrence (cancer coming back) or which treatments might be most effective.¹

Types of genomic tests for advanced breast cancer

There are several genomic tests currently available for breast cancer, including^1-3:

• Breast Cancer Index^SM, which evaluates 7 genes to predict the risk of recurrence 5-10 years after initial diagnosis in estrogen receptor-positive breast cancer that has not yet spread to the lymph nodes
• BreastOncPx™, which looks at 14 genes to predict the risk of distant metastasis (spread to other parts of the body) 10 years after initial diagnosis in estrogen receptor-positive breast cancer that has not yet spread to the lymph nodes
• EndoPredict®, which examines 12 genes to predict the risk of distant metastasis within 10 years of diagnosis in breast cancer that is early-stage (involving 0-3 lymph nodes), estrogen receptor positive, and HER2 negative
• Genomic Grade Index, which analyzes 97 genes and assigns cancers as high or low grade (which can impact prognosis), as well as indicating which tumors might be more sensitive to chemotherapy
• MammaPrint®, which assesses 70 genes and calculates a risk of recurrence score and may be used to make treatment decisions on early-stage breast cancer
• Mammostrat®, which analyzes 5 genes to calculate a risk of recurrence score (if chemotherapy treatment is omitted) and may someday be used to make treatment decisions on early-stage, hormone-receptor-positive breast cancer
• Oncotype DX®, which evaluates 21 genes and estimates the risk of recurrence in early-stage, hormone-receptor-positive breast cancer, as well as whether the individual would likely benefit from chemotherapy following surgery
• Prosigna® Breast Cancer Prognostic Gene Signature Assay, which examines 58 genes and calculates a risk of recurrence score

How does genomic information impact treatment?

Some genomic tests can help guide treatment decisions. The Breast Cancer Index test can help predict the benefit of certain breast cancer patients receiving an additional 5 years of hormonal therapy, and the Oncotype DX can help determine which patients will likely benefit from chemotherapy following surgery, as well as which patients will likely not get additional benefit from chemotherapy.⁴

Other important information about an individual’s breast cancer that can help guide treatment decisions include the individual’s age and general health, the grade and tumor size of the breast cancer, and if it is positive or negative for particular receptors, such as⁴:

• Estrogen (ER+/-)
• Progesterone (PR+/-)
• Human epidermal growth factor receptor 2 (HER2+/-)

Who should have genomic testing?

Currently, there aren’t guidelines on who should receive genomic testing. All breast cancer tumors are routinely tested for hormone receptors (ER and PR) and HER2.⁵ Additional testing depends on the doctor and the healthcare facility.

How is genomic testing be used in metastatic breast cancer?

Several of the genomic tests used in breast cancer mentioned above may potentially be helpful for guiding treatment decisions or predicting recurrence for women with early-stage breast cancer. Genomic testing may also potentially be used to guide treatment in metastatic breast cancer.⁵

Researchers are continuing to study which genetic mutations are predictive of the benefit of certain treatments. Currently, the ability to test for certain mutations is ahead of clinical use. While the tests can tell which mutations a tumor has, researchers do not yet always know which treatments will work best for a particular mutation.^5,6