Some women with early stage breast cancer may no longer need to have chemotherapy to increase their chance of survival.

Researchers looked at a group of more than 10,000 women who had particular features about their tumours.

The cancer was at an early stage and had not spread to the lymph nodes.

It was hormone receptor-positive and wasn't the kind of tumour that responds to the drug Herceptin.

Doctors already use a genetic test called which Oncotype DX or 21-gene assay to see whether women with breast cancer are likely to benefit from chemotherapy.

A high score means chemotherapy could be useful, and a low score less so.

But this trial looked at the women in the middle of the group, where the benefits of chemotherapy were uncertain.

Dr Joseph A Sparano, from the Albert Einstein Cancer Centre said the trial aimed to provide an answer for those women.

"The results of our trial suggest that the 21-gene-assay may identify up to 85 per cent of women with early breast cancer who can be spared adjuvant chemotherapy, especially those who are older than 50 years of age," the authors said.

Findings affect 'significant number of women'
Associate Professor Darren Saunders from the School of Medical Sciences at the University of New South Wales said the findings will affect a "significant number" of women.

"It will spare many of them from the side effects of chemotherapy," he said.

Some benefit for chemotherapy was found in women aged younger than 50.

The results have been published in the New England Journal of Medicine.