A genomic test (also called a genomic assay) analyzes the activity of a group of genes linked to the risk of a particular disease. The tests are done on blood or tissue samples. For example, a genomic test may help figure out if a woman diagnosed with early-stage, hormone-receptor-positive breast cancer has a high, medium, or low risk of recurrence (the cancer coming back), as well as if she’s likely to benefit from chemotherapy to reduce that risk.
A study suggests that an experimental genomic test on a group of 58 genes from early-stage, hormone-receptor-positive breast cancer can estimate whether a woman is at higher or lower risk of having the cancer come back somewhere else in the body more than 5 years after diagnosis.
The study was presented at the 2013 IMPAKT Breast Cancer Conference in Belgium on May 2, 2013. Read the abstract of “Predicting risk for late metastasis: The PAM50 risk of recurrence (ROR) score after 5 years of endocrine therapy in postmenopausal women with HR+ early breast cancer: A study on 1,478 patients from the ABCSG-8 trial."
The ABCSG-8 trial was a large study comparing two hormonal therapy regimens: 5 years of tamoxifen versus 2 years of tamoxifen followed by 3 years of Arimidex (chemical name: anastrozole) to treat early-stage, hormone-receptor-positive breast cancer.
Tamoxifen is a SERM (selective estrogen receptor modulator). SERMs block the action of estrogen in breast and certain other cells by sitting in the cells’ estrogen receptors. SERMs don’t affect all estrogen receptors the same way because they’re selective (as the name says). In bone cells, SERMs interact with the receptors the way estrogen does and strengthen bones. In breast cells, SERMs block the receptors’ interaction with estrogen and limit cell growth.
Arimidex is an aromatase inhibitor. Aromatase inhibitors stop the production of estrogen in postmenopausal women. Aromatase inhibitors work by blocking the enzyme aromatase, which turns androgen hormones into small amounts of estrogen in the body. This means that less estrogen is available to stimulate the growth of hormone-receptor-positive breast cancer cells.
In this study, the researchers used an experimental genomic test, called PAM50, to analyze the cancers from 1,478 women in the ABCSG-8 trial.
The PAM50 test looks at the activity levels of 58 genes in hormone-receptor-positive breast cancer. Based on these activity levels, test results are reported as a risk of recurrence score that classifies women as having either high or low risk of breast cancer coming back somewhere in the body away from the breast more than 5 years after diagnosis. Doctors call this “late metastatic recurrence.”
After about 11 years of follow up, the researchers found that the PAM50 test was very good at estimating which women were at high risk of late metastatic recurrence and which women were at low risk:
- only 1.3% of the women classified as low-risk had a late metastatic recurrence between 5 and 10 years after diagnosis
- 8.5% of women classified as high-risk had a late metastatic recurrence between 5 and 10 years after diagnosis
The PAM50 test can be used to analyze both cancers that have spread to the lymph nodes (node positive) and cancers that haven’t (node negative).
Knowing whether a woman has a high or low risk of the cancer coming back in a part of the body away from the breast more than 5 years after diagnosis can help doctors decide how long hormonal therapy medicine should be taken. Research has shown that taking tamoxifen for 10 years instead of 5 years can better lower the risk of recurrence and improve overall survival for some women. If doctors knew that a woman had a low risk of late metastatic recurrence, they could spare her the extra 5 years of hormonal therapy treatment. At the same time, women at high risk would benefit from the extra 5 years of treatment.
While the results of this study are promising, the PAM50 test, made by NanoString, isn’t yet available in the United States or approved by the U.S. Food and Drug Administration. The test has received the CE mark, which means it can be sold in European Union countries, as well as Iceland, Liechtenstein, and Norway.
When making treatment decisions, you and your doctor will consider a number of factors, including:
- your age
- your menopausal status
- the size of the cancer
- hormone receptor protein levels
- cancer grade
Armed with the best information possible, you and your doctor can decide on a treatment plan that makes the most sense for your unique situation.