Dr. Joseph Sparano of Montefiore Medical Center in NY, lead author of the study says that the impact of this test could spare thousands of women from chemotherapy and for them surgery and hormone therapy could be sufficient.
The two most recent studies it is funding look at tomosynthesis - a newer breast imaging technique - versus standard-of-care 3D mammograms, and research on whether weight loss impacts breast cancer treatment and outcomes.
Very high scores are at increased risk of the cancer spreading, and those patients have benefited a lot by chemotherapy.
The study was funded in part by the proceeds from sales of the breast cancer postage stamp.
Dr Steven Rosenberg, who led the trial by the US National Cancer Institute, said.
"This is another significant step towards personalised breast cancer treatment and we hope these practice-changing findings will help refine our use of chemotherapy on the NHS".
Patients scoring 26 or higher on the scale do benefit and receive chemotherapy. Women with low risk scores - those below 10 - don't need chemotherapy after surgery, and instead can be treated with hormone therapy, previous studies have found.
What will she tell women who under prior guidelines received chemo and all its side effects and didn't need it after all? Now they can have confidence in those decisions, experts said.
"Moving forward, when women are making this decision, this study will help us put it into perspective and give them better advice next week than we were able to give them last week", Jennifer Litton, an associate professor and oncologist at MD Anderson Cancer Center in Houston, Texas, explained to USA Today.
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"We have been waiting for these results for years", said Allison Kurian, an oncologist at Stanford University who wasn't involved in the trial.
"Most women diagnosed with breast cancer are over 50, but younger women can also get breast cancer", says the NHS on its website.
The researchers were specifically interested in women who scored 10 to 25 on the test - scores that fall in the range of a medium risk of the cancer returning after surgery.
More than 20,000 women in the United Kingdom are diagnosed with hormone-receptor positive, HER2-negative, node-negative breast cancer annually. Another, more sinister, aspect to these headlines is the potential to fuel myths and conspiracy theories about the effectiveness of chemotherapy.
"The uncertainty is over", she said.
The Oncotype DX genetic test has been available on the NHS since 2013, but the National Institute for Health and Care Excellence (Nice) is now updating its guidance on whether it should be recommended for use.
A promising experimental treatment has left a Florida woman's advanced breast cancer in remission.
"Oncologists have been getting much smarter about dialing back treatment so that it doesn't do more harm than good", said Steven Katz, a University of MI researcher who examines medical decision-making.
Women at low risk could skip chemo. Others want chemo for even the smallest chance of benefit.
It provides important information on a safe way to cut back treatment, an issue that has prompted vigorous debate not only for breast cancer but also for other malignancies.