Breast cancer is the most common cancer in women in the US, except for skin cancer, accounting for 30% of all new female cancers each year. Of the women diagnosed with early-stage breast cancer, 30% will go on to develop Stage IV, or metastatic breast cancer. One tool that may help doctors and patients understand the risk of developing cancer is genetic testing. Another tool is biomarker testing, which may help inform clinical decisions.
For people who have been diagnosed with breast cancer, whether early stage or metastatic (cancer that has spread to other parts of the body), knowing their biomarker status is an important first step in determining a treatment plan. Biomarkers are like the “molecular fingerprint” of the tumor, and understanding which biomarkers are present in a breast tumor can help doctors understand how likely it is that the tumor will grow and spread. With biomarker testing, the patient’s tumor can be better understood, which in turn can help the patient’s oncologist and their care team determine which treatment options are the most appropriate.
Genetic testing – which is done with a simple blood or saliva sample – examines a person’s genes to determine their lifetime risk of developing certain cancers. A genetic mutation can be hereditary (passed down from a parent) or acquired (developed later in life through certain risk factors). Certain mutations in the BRCA1 and BRCA2 genes have been found to impact a person’s chances of developing breast and other cancers. Everyone has both the BRCA1 and BRCA2 genes, which are responsible for suppressing tumor growth. When these genes are mutated, their normal function may be altered and tumors are more likely to grow, leading to an increased risk of cancer. It’s estimated that 55-65% of women with the BRCA1 mutation will develop breast cancer before age 70, and approximately 45% of women with a BRCA2 mutation will develop breast cancer by age 70.
In breast cancer, a gene called Human Epidermal Growth Factor Receptor 2, or HER2, is a biomarker that is amplified in approximately 15% of breast cancers. When there are too many HER2 proteins present on the tumor cell, the cancer is considered to be HER2-positive, and this is associated with a more aggressive form of the disease. Additionally, when some HER2 proteins but not as many as in HER2- positive tumors are present on the tumor cell to be diagnosed as HER2-positive, the cancer is considered to have low HER2 expression. Approximately half of all patients with breast cancer have tumors that are considered HER2-low, and this is a new way of understanding and characterizing breast cancer.
In 2022, the US is expected to see an estimated 339,250 new cases of breast cancer and 43,250 breast cancer deaths. The good news is that there are more therapies available to help treat these different types of breast cancer. At AstraZeneca, we remain committed to continuing to develop new and innovative treatment options in the fight against breast cancer.
To learn more, talk to a doctor to better understand genetic and biomarker testing.
Additional Resources
To learn more about breast cancer or to access helpful resources, visit: YOUR Cancer (YourCancer.org): Breast Cancer Resources
Beyond Pink (LifeBeyondPink.com): Understanding Biomarker & Genetic Testing