At least 20,000 women a year will be spared unnecessary breast cancer surgery thanks to a new procedure that will save the NHS millions of pounds each year.

Every breast cancer unit in the UK is to be taught the technique after an extensive trial showed it significantly improved breast cancer sufferers' quality of life by minimising pain, swelling and numbness after operations. It also reduced their stay in hospital by three days, a saving of some £24m a year.

The treatment, sentinel node biopsy, is practised in the US and is being pioneered in Britain by Robert Mansel, professor of surgery at Cardiff University, whose research is published today in the Journal of the National Cancer Institute.

The technique involves surgeons removing only one lymph node - the lead or sentinel node - from the armpit of a breast cancer sufferer, rather than the 20-30 nodes removed as standard practice.

Lymph nodes are removed as a precaution against cancer spread, but in 75% of screen-detected cancers there is no need to remove any more than the sentinel node, which acts as a filter for cancer cells.

In the only study of its kind, Prof Mansel taught breast surgeons at 13 units in the UK to carry out the procedure. In the randomised trial, the removal of the sentinel node was carried out on 515 patients, compared with 516 treated conventionally. Their arm function, swelling, overall quality of life and resumption of normal activities were compared at various stages.

Prof Mansel found that 92% of women undergoing the procedure had resumed normal activities after three months, compared with 86% operated on conventionally, and only 18% of women undergoing the procedure felt numbness after one month, compared with 62%. In addition they stayed in hospital for just one night compared with four. The results were so stark that the trial was ended early, on the grounds it was unethical to deny women in the control group the new treatment.