The study is the largest ever done of breast cancer treatment, and the results are expected to spare up to 70,000 patients a year in the United States and many more elsewhere the ordeal and expense of these drugs.
For example, another study at the conference found that Merck's immunotherapy drug Keytruda worked better than chemo as initial treatment for most people with the most common type of lung cancer, and with far fewer side effects.
The study gave 10,273 patients a test called Oncotype DX, which uses a biopsy sample to measure the activity of genes involved in cell growth and response to hormone therapy, to estimate the risk that a cancer will recur.WHAT THE STUDY FOUNDAbout 17 percent of women had high-risk scores and were advised to have chemo. The 16 percent with low-risk scores now know they can skip chemo, based on earlier results from this study.
All had surgery and hormone therapy, and half also got chemo.
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.
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