SOME women with early stage breast cancer may not need chemotherapy after surgery.
The breakthrough means fewer women with breast cancer who would currently be given chemotherapy can be spared from the toxic treatment without harming their chance of survival, according to a major international study.
Researchers looked at over 10,000 women, aged 18 to 75, with a common form of breast cancer (hormone-receptor positive HER2 negative breast cancer) with early stage tumours that had not spread to the lymph nodes.
Until now, women with this diagnosis have faced uncertainty about whether to add chemotherapy to hormone therapy.
A widely-used genetic test is already used on tumours to see if women will benefit from chemotherapy. This is called the Oncotype DX or 21-gene assay.
Previous studies have shown that patients with a low score on the gene marker test (under 10) did not need chemotherapy, while it was recommended for women with high scores (above 25).
But there was no conclusive research on whether patients with mid-score (11 to 25) would benefit from the treatment.
The new research shows that of the female patients in the mid tier, around 70 per cent could be spared chemotherapy.
And while some benefit for chemotherapy was found in women younger than 50, the study said the for women aged 50 to 75 with the mid-range gene score there was no significant difference between the chemotherapy and no chemotherapy groups.
Study co-author Dr Kathy Albain said the study will have a huge impact on doctors and patients.
"We knew we were over-treating a lot of women with chemotherapy, in our gut. We can escalate toxic treatments and do that with certainty," Dr Albain said.
University of New South Wales associate professor Darren Saunders, writing in The Conversation, said the findings will affect a "significant number" of women.
"This has the potential to spare thousands of women from the awful side effects of chemotherapy, including nausea, hair loss and heart and nerve damage," he said.
But he warned that we must be "crystal clear" that it applies to a very specific subset of women.
"Patients should not make any changes to their treatment based off this study, and should always consult their doctors," he said.
The results of the study - the largest breast cancer treatment trial conducted - have been published in the New England Journal of Medicine.
