Data from three international trials involving more than 4,000 women showed that switching from standard therapy to Arimidex after two years can reduce death rates by 29 per cent.

The drug is currently licensed for the after-surgery treatment of post-menopausal women with early invasive breast cancer fuelled by the sex hormone oestrogen.

However, it is still awaiting a green light from the National Institute for Health and Clinical Excellence (Nice), which issues guidelines on the use of new treatments in England and Wales.

Nice is not due to consider Arimidex until November next year. Meanwhile, the drug has already been given the seal of approval by Scotland's drug-vetting body.

Three quarters of post-menopausal women with breast cancer have a form of the disease that is sensitive to the hormone. Without oestrogen, the tumours find it hard to survive.

Tamoxifen, which blocks the activity of oestrogen without preventing its production, is currently the standard treatment for hormone-sensitive breast cancers.

Earlier research showed that a five year course of treatment, which involved switching from tamoxifen to Arimidex after two years, cut the chances of recurrence by 26%. This was over and above the 50% reduction due to tamoxifen.

The new meta-analysis study, pooling together data from three similarly designed international trials, provides the first definitive evidence of improved survival with Arimidex.

A total of 13,000 women die from breast cancer each year in the UK. Many of these deaths could be prevented by using Arimidex, the research suggests.

He analysed information from three major trials, Austrian Breast and Colorectal Cancer Study Group (ABCSG) 8, Arimidex-Nolvadex (Arno) 95, and Italian Tamoxifen Arimidex (ITA).

The findings, presented at the San Antonio Breast Cancer Symposium in Texas, USA, not only showed a dramatic death reduction, but also 45 per cent fewer cases of disease recurrence.

Jeffrey Tobias, Professor of Cancer Medicine at University College London Hospitals, said: "Survival is the ultimate goal in the treatment of early breast cancer, and these results provide compelling evidence that anastrozole has the potential to save the lives of significantly more cancer patients who are post-menopausal and hormone-receptor positive.

Mike Baum, Emeritus Professor of Surgery at University College London, said: "Importantly, we know that the risk of the cancer returning peaks in the first two years after surgery, and that women should be given an AI (aromatase inhibitor) at the earliest opportunity to minimise the risk in this crucial period. These significant new data highlight that for those women who are already taking tamoxifen, greater benefit may still be achieved by replacing tamoxifen with Arimidex."

Dr Emma Pennery, Nurse Consultant at the charity Breast Cancer Care, said: The goal of adjuvant (additional) therapy is to keep patients free from recurrence and risk of serious side effects for as long as possible. This is very encouraging news for women with breast cancer."

I have just been switched from Tamoxifen to Arimidex after having had a single mastectomy in November 2004 and finishing chemo and radiotherapy which was completed August 2005. Tamoxifen made me very achey and the hot sweats were dreadful so on a visit to the Oncologist the drug was changed and this was November and already I feel quite a lot better. The bonus of my own GP understanding and being able to prescribe this has also helped greatly. I cannot praise too highly the care and attention I have received from all the NHS staff in Nottingham.

I have been treated with Arimidex for over 3 years but not for early stage breast cancer. I first had breast cancer nearly 10 years ago and then discovered that I had secondary breast cancer (spread to the lungs and bones) in Feb 2002. As my tumours were oestrogen receptive my wonderful oncologist suggested Arimidex but I was also pre menopausal, so I was put through a chemical menopause to ensure that the Arimidex worked. The results have been extraordinary. After 6 months the 19 tumours in my lungs had disappeared and my bones too are free of any tumours. It is true that Arimidex patients could be prone to Osteoporosis but I am also taking a drug called Bonefos- one of the group of bisphosphonates- to strengthen the bones. Both of these drugs are prescribed by my NHS doctor. I hope all women are offered this treatment as it is not only remarkably effective but I have suffered no side effects to date.

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