"While this practice has contributed to declining rates in breast cancer mortality, "...the majority of patients may receive chemotherapy unnecessarily".
Dr. Otis Brawley, chief medical and scientific officer for the American Cancer Society said that he was "delighted" by the study and anxious about unnecessary cancer treatment and the side effects that come from chemotherapy.
According to researchers from the U.S., early breast cancers can be successfully treated with a new form of immune therapy instead of traditional chemotherapy. Along with hair loss, nausea and vomiting, chemo can leave a woman with a depressed immune system, said Dr. Jennifer Litton, an oncologist and an associate professor at the University of Texas MD Anderson Cancer Center. Following this "recalibration" of the genetic test, the researchers estimated that chemotherapy was not justified in 70% of cases of breast cancer.
A sample of the tumour is tested after surgery for 21 genetic markers, which indicate if it could grow and spread.
The test randomized women with intermediate risk, about 67 percent.
The study is limited in some ways.
Thousands of women now have that option thanks to a recent study revealing chemo isn't the only way to go.
After nine years, 94 percent of both groups were still alive, and about 84 percent were alive without signs of cancer, so adding chemo made no difference.
It took about eight weeks to craft the therapy for the breast cancer patient.
"You have to balance risk versus benefit and if you can spare people the negative side effects that chemo brings along with the cost, that's big" ABC News' Chief Medical Editor Dr. Jennifer Ashton said on "Good Morning America". She also watched her brother and sister - who died of thyroid cancer and leukemia, respectively - suffer through chemotherapy treatments.
The TAILORx study, led by the Montefiore Medical Centre in NY, found women older than 50 with this form of breast cancer and a score of up to 25 did not need chemotherapy. Women with an RS of 10 or lower (1619, 17%) were in the ET arm and those with a RS of 26 or higher (1389, 14%) were in the CET arm.
Those who score 26 or higher on the scale do benefit and now receive chemotherapy.
James Doroshow, director of the division of cancer treatment and diagnosis at the National Cancer Institute, which was the primary sponsor of the study, predicted that the trial would lead to changes in treatment "for a large number of potential patients".
"I have definitely hit the jackpot", said Perkins, a retired engineer from Port St. Lucie, Fla.
In a media release, Genomic Health, who makes the Oncotype DX Breast Recurrence Score test, said it provided funding for collection of follow-up information from the treating sites, but was not involved in the planning and execution of the study.
"This is a hugely exciting first in the treatment of advanced breast cancer". Doctors then drain the defective white blood cells and inject the patient with the new super clones.
"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", he said.