"Now with these genomic tests, we are finding that we have multiple types of breast cancer, perhaps several dozen", said Brawley, "and we are being able to tailor our therapies to the type of breast cancer every woman has".
About 17 percent of women had high-risk scores and were advised to have chemo.
This was particularly the case for women aged over 50.
The landmark study showed that genetic testing can reveal which women with early-stage breast cancer need chemo and which do not. The challenge so far in cancer immunotherapy is it tends to work spectacularly for some patients, but the majority do not benefit.
The National Institute for Health and Care Excellence (NICE) guidelines on the use of this test are now being reviewed, so new guidance will be available soon on this topic.
It was sponsored by the National Cancer Institute (NCI) and led by the ECOG-ACRIN Cancer Research Group (ECOG-ACRIN). It was published in the peer-review New England Journal of Medicine and is free to read online.
Media coverage of the story was mixed.
The work "provides a major "proof-of-principle" step forward, in showing how the power of the immune system can be harnessed to attack even the most difficult-to-treat cancers", he said.
Countless breast cancer patients in the future will be spared millions of dollars of chemotherapy thanks in part to something that millions of Americans did that cost them just pennies: bought a postage stamp.
Tumours can have a genetic profile which can help healthcare teams identify whether or not a particular tumour may respond to a specific treatment.
They found these women may benefit from surgery and hormone therapy and may not have to go through chemotherapy treatments. Of those women, 6,711 had test scores between 11 and 25, which placed them in the intermediate risk group.
An RCT is an appropriate way of looking at this. The primary endpoint was invasive disease-free survival (iDFS), and the trial was created to show noninferiority for ET alone.
Patients were randomly assigned to receive hormone therapy or chemotherapy, followed by hormone therapy.
What did the research involve?
The 49-year-old patient with advanced breast cancer was given three months to live before enrolling into the trial.
Thirty percent of the women in the trial did have evidence of cancer hiding in their bodies.
All women underwent surgery to remove as much of their tumour as possible.
A group of 10,273 women with hormone-receptor-positive breast cancers were tested for 21 genes known to influence cancer return rates.
What were the basic results?
Until now, women have faced considerable uncertainty about whether to add chemo to hormone therapy after a diagnosis with hormone-receptor positive, HER-2 negative breast cancer when found at an early stage, before it has spread to the lymph nodes.
"The 9-year rate of distant recurrence in women with a recurrence score of 11 to 25 in our trial was approximately 5%, irrespective of chemotherapy use", the authors write.
How did the researchers interpret the results?
Compared to 52 women who only received an American Cancer Society pamphlet on chemotherapy, the 48 women in the texting group reported an overall lower level of distress and a higher quality of life during their therapy. Forty percent of women who were 50 years of age or younger had a recurrence score of 15 or lower. Similar tests including one called MammaPrint also are widely used. "But because this new approach to immunotherapy is dependent on mutations, not on cancer type, it is in a sense a blueprint we can use for the treatment of many types of cancer".
But there is a note of caution in interpreting the study's findings. Making sure that people around the country receive the same access to the best diagnostic and treatment approaches is another important consideration.