Dr Alistair Ring, consultant medical oncologist at the Royal Marsden NHS Hospital in London, said: "I think this is a fundamental change in the way we treat women with early-stage breast cancer and will lead to a considerable number of women no longer needing to have chemotherapy".
Over the years, the Cancer Institute has used its $59.8 million in proceeds for studies trying to improve early detection and to determine which cancers are most unsafe and need heaviest treatment and which are less so.
In addition to having their tumors removed, the women in the study underwent a genetic test called Oncotype DX, manufactured by California-based Genomic Health.
The New England Journal of Medicine published a study on Sunday that examined a popular genetic test that estimated cancer risk based on nearly two dozen genes linked with the recurrence of breast cancer, according to CNN.
There was some benefit from the chemotherapy for a small subgroup - women with a score of 16 to 25 who were age 50 or younger, Sparano's team said.
To find the answer, researchers randomly assigned more than 6,700 women with intermediate scores - 11 to 25 - to two groups.
About 17 percent of women had high-risk scores and were advised to have chemo. They benefit just as much from chemotherapy, which many don't tolerate well and can have long-term consequences, as they do from hormone treatments, which have many fewer side effects.
What will she tell women who under prior guidelines received chemo and all its side effects and didn't need it after all? Instead, doctors say the only treatment necessary is surgery and hormone therapy.
After nine years, the cancer-free rates were 83.3 percent for the hormone-therapy-only group and 84.3 percent for the hormone-therapy-plus-chemotherapy group.
"It also helps identify those women with this disease who really do benefit from the chemotherapy", he said. These women should discuss chemotherapy with their doctors, the researchers said. But until this new research, patients and doctors didn't have all of the information they needed to recommend treatment based on a patient's particular results.
Findings of the past have indicated that women who met these criteria and scored below ten on the index test could safely skip chemotherapy without raising their rate of recurrence, however, those above 25 would nearly always be advised to use chemotherapy as a necessary treatment to lower risk of recurrence.
"We are now at the cusp of a major revolution in finally realising the elusive goal of being able to target the plethora of mutations in cancer through immunotherapy", Radvanyi said.
Immunotherapies, such as adoptive cell transfer, are playing an increasingly prominent role in the treatment, however now only about 20 per cent of patients respond.
Dr. Laszlo Radvanyi of the Ontario Institute for Cancer Research in Toronto described it as "an unprecedented response in such advanced breast cancer".
How does the study fit into the debate over "de-escalating" treatment of early-stage breast cancer?
"We went rafting down the Grand Canyon", said Perkins, who has two sons and two stepsons with her husband.
"They were sick all the time", she said.