The results of the latest study may support the use of anastrozole, rather than tamoxifen, as the future treatment of choice

Michael Baum, University College Hospital, London

The results of the trials were presented at a breast cancer conference in San Antonio, Texas, USA.

They showed encouraging results in post-menopausal women with oestrogen positive cancer.

About 80% of women past the menopause with breast cancer have the oestrogen positive type, where the female hormone affects the cells.

One study showed how the drug Arimidex, known under the generic name anastrozole, helped women with early breast cancer.

After an average of 30 months' treatment and 33 months' of follow-up, 317 of the 3,125 women taking Arimidex suffered relapses, compared to 379 of the 3,116 given tamoxifen.

Life expectancy increased

"The results of the latest study may support the use of anastrozole, rather than tamoxifen, as the future treatment of choice," said Michael Baum of University College Hospital, London, who presented the results.

In another study, 324 women in the late stages of cancer in Germany, Spain, France and Britain, took either tamoxifen or an aromatase inhibitor, called Femara, known by the generic name letrozole.

New drugs carry fewer side effects

Tumours shrank in 60% of women who took Femara for four months, compared to 41% of women taking tamoxifen.

Those taking Femara also lived longer.

Dr Matthew Ellis, who presented the results of the study to the conference said: "Letrozole is associated with a higher rate of tumour shrinkage... and a better one and two-year survival than tamoxifen.

"For the patients who receive Femara, an extra eight patients per 100 were alive after a year.

"Obviously that is a very significant improvement."

Further research

Tamoxifen also reduces cases of breast cancer in healthy women with a high risk of the disease, but it is not known if the new generation of drugs can reproduce that effect.

A second study in Belgium, by Dr Martine Piccart of 453 women taking Femara and 454 taking tamoxifen showed overall average survival was 34 months with Femara and 30 months with tamoxifen.

these findings are at an early stage and we need to be cautious about over-analysing them

Professor Jack Cuzick, Imperial Cancer Research Fund

Dr Piccart said 64% of patients were alive two years after starting Femara, compared to 58% of tamoxifen patients.

Breast cancer is the second biggest cancer killer of women in the industrialised world after lung cancer.

The Imperial Cancer Research Fund (ICRF) has welcomed the findings.

The ICRF's Professor Jack Cuzick said: "These are exciting results.

"However, these findings are at an early stage and we need to be cautious about over-analysing them.

"Full evaluation must wait until we have more results and clearer evidence on the effect the drug has on breast cancer mortality rates."

It is unlikely the new drugs will be fully available in the UK for some time, cancer experts warned.