A genomic test (also called a genomic assay) analyzes the activity of a group of genes linked to a specific cancer. The genomic test is used to predict how aggressive the cancer is and how it will respond to treatment.
Right now, three genomic tests -- Oncotype DX, MammaPrint, and Mammostrat -- can be used to help evaluate the risk of early-stage, hormone-receptor-positive breast cancer coming back (recurring). MammaPrint also may be used to evaluate early-stage, hormone-receptor-negative breast cancer. These tests can help a woman and her doctor figure out her individual risk of recurrence and if she's likely to benefit from chemotherapy AFTER surgery (adjuvant chemotherapy) to reduce the risk of the cancer coming back.
New research published in the Journal of the American Medical Association suggests that an experimental genomic test can help doctors figure out if invasive HER2-negative breast cancer will respond to chemotherapy BEFORE surgery (neoadjuvant chemotherapy).
Chemotherapy is sometimes given before surgery for early-stage and locally advanced breast cancer to weaken, shrink, or destroy cancer cells. The experimental genomic test also helped predict survival without the cancer coming back in a part of the body away from the breast.
Researchers used the genomic test on breast cancer tissue from 310 women diagnosed with stage II or stage III HER2-negative invasive breast cancer. All the women were treated with chemotherapy before surgery. The cancers also were tested for hormone receptor status. After surgery, women with hormone-receptor-positive breast cancer were treated with hormonal therapy. Like chemotherapy after surgery, hormonal therapy is given after surgery to reduce the risk of recurrence.
During surgery, the researchers evaluated the cancer tissue to see how well the cancer responded to the neoadjuvant chemotherapy (pathologic response). The researchers then monitored the women's health in the months and years after surgery, keeping track of women who were alive and did not have breast cancer come back in a part of the body away from the breast (distant relapse-free survival). The researchers then compared the treatment outcome prediction based on the genomic test results to the actual pathologic response found at surgery, as well as to how many women were alive 3 years after surgery without cancer coming back in a part of the body away from the breast.
The genomic test predicted that 28% of the women would respond to the chemotherapy given before surgery. At the time of surgery, 56% of those women had an excellent pathologic response to the chemotherapy before surgery and 92% of them were alive with no recurrence in a part of the body away from the breast 3 years after surgery.
The excellent pathologic response and survival rates among the women the genomic test predicted to respond to chemotherapy before surgery was better than what would be expected overall. These results suggest that the experimental genomic test successfully identified women who were more likely to have an excellent pathologic response to chemotherapy before surgery and who would have better distant relapse-free survival after surgery.
The experimental test predicted that 30% of women diagnosed with hormone-receptor-positive breast cancer would respond to treatment, which was slightly higher than the average. The test predicted that 26% of women with hormone-receptor-negative cancer would respond to treatment, which was slightly lower than the average. Three-year distant relapse-free survival was higher (97%) among women with hormone-receptor-positive cancer compared to women with hormone-receptor-negative cancer (83%).
The genomic test studied in this research is experimental. Much more work needs to be done to understand how it should be used to predict response to treatment before surgery and prognosis and how that information can best be used to guide treatment decisions.
Stay tuned to Breastcancer.org Research News to learn about new results that could some day lead to better ways to diagnose and treat breast cancer.
Editor's note: Since this research was published, new genomic tests have come to market. For the most up-to-date information, visit the Breastcancer.org Breast Cancer Tests page.