Most women with the most common form of early-stage breast cancer can safely skip chemotherapy without hurting their chances of beating the disease.

Doctors at the Montefiore Medical Centre in New York have used genetic testing to gauge each patient's risk.

Their 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 US and many more elsewhere the ordeal and expense involved.

Cancer care has been evolving in favour of gene-targeting therapies, hormone blockers and immune system treatments.

When chemo is used now, it's sometimes for shorter periods or lower doses than it once was.