The study, published Sunday in the New England Journal of Medicine, enrolled 10,273 women with early-stage invasive breast cancer from the United States, Australia, Canada, Ireland, New Zealand and Peru. Women 50 or younger can avoid chemo if their scores are lower than 16, said lead author Joseph Sparano, associate director for clinical research at the Albert Einstein Cancer Center in NY.
Study author Dr Steven A Rosenberg from the National Cancer Institute said the research was "experimental right now".
"They really had to pass the hat around", said Dr Otis Brawley, chief medical officer of the American Cancer Society, who had no role in the study, but is familiar with its funding history.
How do doctors and patients know if a patient is high-risk?
According to researchers from the USA, early breast cancers can be successfully treated with a new form of immune therapy instead of traditional chemotherapy.
There were 1.7 million new breast cancer cases in 2012, according to the World Cancer Research Fund International, making it the most common form of cancer in women globally.
"Breast cancer is the most diagnosed cancer of women in Arkansas, one in eight".
Women at low risk could skip chemo. They also have a score between 11 and 25 on the Oncotype DX Breast Recurrence Score test. The test looks at 21 different genes known to play a role in the development of breast cancer. Now only about 60 percent of USA patients who could potentially benefit from it are taking the gene test, he says. The tumor is assigned a "recurrence score" from 0 to 100; the higher the score, the greater the chance the cancer will recur in distant organs and decrease survival.
"Those are the cancers that have likely already metastasized and a small amount could be hiding in a woman's lung, liver or bones", said Brawley. Should we not give them chemotherapy? These women should discuss chemotherapy with their doctors, the researchers said. They say the data "provide evidence that that adjuvant chemotherapy was not beneficial in these patients". The treatment can cause unpleasant side effects, some of which can put a woman's life at risk.
This study supports sparing thousands of women from the sometimes nasty side effects of chemotherapy, but we must be crystal clear that it applies to a very specific (and significant) subset of women. The 67 percent of women who were at intermediate risk all had surgery and hormone therapy. Indeed, a genetic test can be done at the time of the operation to predict the risk of recurrence. After nine years, 94% of both groups were still alive and about 84% were alive without signs of cancer, meaning the chemo made no difference.
Simon Vincent, director of research at Breast Cancer Now, added: "This is a remarkable and extremely promising result, but we need to see this effect repeated in other patients before giving hope of a new immunotherapy for incurable metastatic breast cancer". When chemo is used now, it's sometimes for shorter periods or lower doses than it once was.
Experts cautioned, however, that the findings may not apply to those who have larger tumors or those with cancer that has started to spread, or metastasize.
One of the tragic features of cancer is that to treat the disease, doctors sometimes have to make the body sicker through chemotherapy.
"Tumors grow more aggressively in premenopausal women, not just women under 50", Brawley said.
The type of hormone therapy administered was dependent upon whether women were premenopausal or postmenopausal-91% of postmenopausal women received an aromatase inhibitor-based regimen, whereas premenopausal women were most commonly prescribed either an endocrine therapy regimen comprising either tamoxifen alone or tamoxifen followed by an aromatase inhibitor (78%).