A breast cancer treatment which may cut the risk of the disease returning in some patients is to be launched in the UK this week.

Studies suggest that Arimidex may perform better, and with fewer side-effects, than the last decade's "wonder-drug", tamoxifen.

Many women who have a breast tumour have an operation to remove the growth, which may be followed by a course of chemotherapy or radiotherapy in an attempt to eradicate any remaining cells.

Tamoxifen is often given to women whose cancer cells were responsive to the female hormone oestrogen.

Essentially it stops the hormone having an effect on the cells, hampering the growth of the tumour.

Experts say it has contributed greatly to a decline in mortality from breast cancer over the past decade.

Arimidex uses the same principle, but blocks the production of oestrogen instead - and has been licensed for use in more advanced breast cancer since 1995.

However, its licence is now to be extended to cover many more women.

Good results

Research carried out at centres across the world revealed that women on Arimidex compared with tamoxifen had a 75% lower chance of cancer recurring in the other breast.

It also cuts the chance of a woman developing dangerous blood clots, or endometrial cancer - both known side-effects of long-term tamoxifen use.

However, these advantages do not come cheap, as Arimidex is 10 times more expensive than tamoxifen.

At first only women considered to have a high risk of blood clots or endometrial cancer will get the drug, but this may change if trial results due next year show increases in long-term survival among women taking it.

Thousands in line

Approximately 18,000 postmenopausal women are diagnosed with early stage tumours which are sensitive to the effects of oestrogen.

Mr Mike Dixon, consultant surgeon and senior lecturer, Edinburgh Breast Unit, Western General Hospital said: "While tamoxifen has had a major impact on improving survival from breast cancer, more effective and better tolerated treatments are needed.

"The evidence to show Arimidex may further improve on the benefits already seen with tamoxifen is very exciting for both patients and doctors treating the disease."