WASHINGTON, Sept. 28 (UPI) -- A 21-gene test can accurately predict whether women with breast cancer can be treated without chemotherapy, according to a large, long-term study.
The test, called the OncotypeDX, examines the expression of 21 genes in tumor biopsies. Based on the results of the test, researchers were able to correctly predict whether endocrine therapy or endocrine therapy with chemotherapy is best for individual patients.
Researchers said the study, published in the New England Journal of Medicine, is significant because of a lack of good options to help doctors select the safest, most effective course of treatment.
"This should provide a lot of reassurance to women and their physicians," said Dr. Kathy Albain, an oncologist at Loyola University Medical Center, in a press release. "In women whose breast cancer scored low on the multigene test, there was outstanding survival with endocrine therapy alone. The test provides us with greater certainty of who can safely avoid chemotherapy."
Related
Researchers enrolled 10,253 women with hormone-receptor positive breast cancer that had not spread to their lymph nodes. All of the women's tumors had features suggesting chemotherapy should be used in treatment, as well as an endocrine therapy such as tamoxifen.
Tumors tested using the OncotypeDX are assigned a score of 0 to 100, which is based on the chances for cancer to either recur or spread. A score of 0 to 10 on the test indicates a very low chance of the cancer coming back after treatment.
Of the more women participating in the study, 15.9 percent of the women, or 1,626, had tumors with a score between 0 and 10. These women were prescribed tamoxifen and no chemotherapy.
Five years after treatment, researchers found a 98 percent survival rate and less than a 2 percent chance that cancer had spread to nearby or distant cites in the body.
Researchers said that an additional 68 percent of women in the study had a score between 11 and 25. These women were randomly assigned to receive either endocrine treatment or endocrine treatment with chemotherapy. Follow-ups with these study participants are still ongoing to gauge the rates of cancer recurrence.
In an editorial published in the New England Journal of Medicine alongside the study, Dr. Clifford Hudis raises concerns about the cost of the test -- it runs more than $4,000, although it is covered by Medicare and many other insurers -- and patients whose tumors fall in the mid-range between 11 and 25.
"This multigene assay is unlikely to be the only test that can provide a prediction of chemotherapy benefit," Hudis wrote. "A less expensive and broadly distributed test would be valuable globally. For now, however, this assay is the most rigorously tested option and provides proof of the principle that we can develop reproducible predictive tests to select patients who should not receive chemotherapy. In that regard, it is one more step toward precision."
