A study shows that the Mammostrat test can offer more information on the risk of early-stage hormone-receptor-positive breast cancer coming back (recurrence) and help postmenopausal women and their doctors make treatment decisions.
The study was published online on Oct. 8, 2012 by the Journal of Clinical Oncology. Read the abstract of “Mammostrat as an Immunohistochemical Multigene Assay for Prediction of Early Relapse Risk in the Tamoxifen Versus Exemestane Adjuvant Multicenter Trial Pathology Study.”
The Mammostrat test measures the levels of five genes in breast cancer cells. These genes can affect how the breast cancer will behave and respond to certain treatments. These measurements are used to calculate a risk index score. The higher the risk index, the more likely the cancer is to come back. Women are assigned to a risk category (high, moderate, or low) based on their risk index score. Women in the high risk category are more likely to benefit from chemotherapy in addition to hormonal therapy after surgery. Women in the low risk category may be able to avoid chemotherapy that probably won’t give them any additional benefits.
There are two other tests used to predict recurrence risk for early stage breast cancer: the Oncotype DX test and the MammaPrint test. These tests are called genomic assays because they analyze the activity of a group of genes rather than a single gene. While all three tests are somewhat similar, there are differences:
- The Oncotype DX test is used to estimate a woman’s risk of recurrence of early-stage, hormone-receptor-positive breast cancer, as well as how likely she is to benefit from chemotherapy after breast cancer surgery. The Oncotype DX test is also used to estimate a woman’s recurrence risk of DCIS (ductal carcinoma in situ) and/or the risk of a new invasive cancer developing in the same breast, as well as how likely she is to benefit from radiation therapy after DCIS surgery. The Oncotype DX test analyzes the activity of 21 genes and then calculates a recurrence score number between 0 and 100; the higher the score, the greater the risk of recurrence.
- The MammaPrint test is used to estimate a woman’s recurrence risk for early-stage breast cancer. The breast cancer can be hormone-receptor-positive or hormone-receptor-negative. The MammaPrint test analyzes 70 genes to see how active they are and then calculates either a high-risk or low-risk recurrence score. MammaPrint results can help a woman and her doctor make a more informed decision about whether to use chemotherapy to reduce recurrence risk.
In this study, researchers did Mammostrat tests on breast cancer tissue samples from more than 4,500 women who participated in the TEAM (Tamoxifen versus Exemestane Adjuvant Multicenter) trial. The TEAM trial was designed to see if 5 years of Aromasin (chemical name: exemestane) was better than 3 years of tamoxifen followed by 2 to 2.5 years of Aromasin to reduce the risk of recurrence in postmenopausal women diagnosed with early-stage, hormone-receptor-positive breast cancer. About 47% of the women had breast cancer cells in their lymph nodes and about 36% of the women got chemotherapy after breast cancer surgery.
The researchers then compared the Mammostrat risk index score for specific types of cancers to the women’s outcomes to see how accurate the risk index scores were.
Node-negative (no cancer cells were found in the lymph nodes) cancers that weren’t treated with chemotherapy after surgery: Women in this group who received a Mammostrat risk index score of moderate risk or high risk were 68% and 247% more likely to have a recurrence than women with low risk index scores.
All cancers not treated with chemotherapy: Women in this group who received a Mammostrat risk index score of high risk were 123% more likely to have a recurrence compared to women with low risk index scores.
All cancers in the study: Women who received moderate risk or high risk Mammostrat risk index scores had a 50% and a 91% increase in recurrence risk compared to women who received low risk index scores.
If you’re a postmenopausal woman diagnosed with early-stage, hormone-receptor-positive breast cancer, you and your doctor will consider a number of factors when deciding whether to add chemotherapy to your treatment plan, including:
- your age
- the size of the cancer
- cancer grade
- hormone receptor protein levels
- whether cancer cells were found in nearby lymph nodes
A test like the Mammostrat test may offer additional information that helps you and your doctor decide if chemotherapy makes sense for your unique situation.
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.