But that data was based on older chemotherapy and hormone therapies, and it was not clear how well it applied to modern treatments.
The findings, published Sunday in the New England Journal of Medicine, showed that 70 percent of women diagnosed with the common cancer that has not spread to the lymph nodes can forgo chemotherapy without risking their chance of recurrence or ability to be cured, said Loyola Medicine oncologist Dr. Kathy Albain, a co-author of the study and a member of the clinical trial's steering committee.
One more thing the new findings show?
The TAILORx trial used the Oncotype DX test, now available on the NHS, which allows doctors to predict the likelihood of the breast cancer coming back.
The confusion comes from a genetic test called Oncotype DX that rates the likelihood of breast cancer recurrence on a 100-point scale. "Most women in this situation don't need treatment beyond surgery and hormone therapy", he said, and "the rest of them are receiving chemotherapy unnecessarily". "The trial was created to address this question, and provides a very definitive answer".
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A high recurrence score, above 25, means chemo is advised to ward off a recurrence while a low score, below 10, means it is not.
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About 17 percent of the women tested had high-risk scores and were advised to have chemotherapy.
In a separate analysis, hormonal therapy alone did seem very effective in deterring the spread of cancer for women with an Oncotype score of 10 or below. "To have your health professional tell you don't need chemo, there's one side glad you don't have to have it and the other wondering are we really taking care of my breast cancer", said Garner. "But we need to be precise on when to use it and who to recommend it to". This therapy has allegedly been an essential treatment for many women as it lowers the risk of cancer recurrence, new tumors from appearing, and even death from the disease.
However, an exploratory analysis suggested, however, that some women with midrange scores might still benefit from the addition of chemotherapy, Sparano said. 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.
Because of her work as a nurse, she was familiar with chemotherapy's sometimes harsh effects.
"When someone had an intermediate score, it was hard to decide whether or not to proceed with chemotherapy", Bernik said.
But before this study came out, many people in this group were prescribed chemotherapy because doctors had, based on the best information available, assumed it would help them.
Dr Steven Rosenberg, who led the trial by the US National Cancer Institute, said.
It was first issued in 1998 and has been reissued multiple times since, and has raised more than $86 million for breast cancer research.