About 70% of women with the most common form of early stage breast cancer can be spared the “agony of chemotherapy”, researchers say.

It follows trials of a genetic test that analyses the danger of a tumour.

Cancer doctors said the findings would change practice in UK clinics on Monday, and meant women in this group could be treated safely with just surgery and hormone therapy.

Charities said the news, affecting 3,000 UK women a year, was “wonderful”.

Chemotherapy is often used after surgery to reduce the chance of breast cancer spreading or coming back.

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It saves lives, but side-effects of the toxic drugs range from vomiting, fatigue and infertility to permanent nerve pain.

In rare cases it can lead to heart failure and leukaemia.

This trial of 10,273 women analysed cancers using a genetic test that is already widely available, including on the NHS.