The discovery could greatly improve the quality of life for younger breast cancer sufferers when doctors try to kill off any remaining cancerous tissue.

Standard treatment for breast cancer starts with surgery to remove the tumour. Surgery is followed by radiation treatment or chemotherapy to destroy any parts of the cancer that may have spread.

But chemotherapy - which consists of regular doses of a powerful cocktail of anti-cancer drugs - has extremely unpleasant side effects including nausea, hair loss, diarrhoea and reduced ability to stave off infections.

Three pieces of research into hormone alternatives were presented on Monday at the American Society of Clinical Oncology's annual meeting in Atlanta.

Pre-menopausal benefits

The hormone treatment could prove an effective option for tackling hormone responsive tumours.

The growth of these tumours is partially dependent on the female hormone oestrogen. Scientists believe three out of every five breast cancers are hormone responsive.

Tamoxifen has already shown potential as a preventive treatment

Scientists started to look at hormone therapy after spotting a side effect of chemotherapy - damage to the ovaries. This reduces oestrogen levels and stops menstruation.

Studies have shown that those women who stop menstruating after chemotherapy appear to do better than those who continue, suggesting that starving a cancer of oestrogen can improve the chances of survival.

It is almost standard now for young women who have not started the menopause to get chemotherapy after surgery, but the new research offers hope of an alternative.

Hormone therapy

The three research teams looked at the effect of a hormone therapy known as Luteinising Hormone Releasing Hormone (LHRH) agonist.

This therapy causes oestrogen levels to drop to those found in women after the menopause, and causes menstruation to stop. However, this is reversible after treatment ends.

The teams' research used two drugs - Zoladex (or goserelin) and Tamoxifen - and involved more than 5,000 women.

Although the studies were not the same in design, early findings suggest:

• Hormonal therapy using both drugs could be more effective than chemotherapy alone in women with hormone-responsive tumours
• The benefits seen are linked to the reduced levels of oestrogen
• Side effects - such as hot flushes - occurred but they were not as severe as those associated with chemotherapy

High hopes

Professor Jakesz, lead researcher with one of the groups, said: "It is early days, but already our results show a significantly increased recurrence-free survival rate for patients on the hormone therapy combination."

Professor Jakesz's group, based in Austria, found that the hormone treatment on its own was more effective than chemotherapy on its own.

Another team, based at the Karolinska Hospital in Sweden, also have high hopes for their research.

Professor Rutqvist, who presented the team's findings, said: "Chemotherapy, while effective for a lot of women, is not without its problem side effects, which many of our patients find difficult to bear.

"Goserelin, on the other hand, is well tolerated and could offer this patient group an effective alternative to chemotherapy, whether given in combination with tamoxifen or not."

Preventive use

However, Dr John Toy, director of clinical programmes at the Cancer Research Campaign, doubted the hormone therapy would actually take the place of chemotherapy.

"Hormone treatment on its own may be more effective than chemotherapy on its own, but the best results are probably going to be found when you give both," he said.

"One potential interesting use (for hormone therapy) would be to use it as a preventive treatment in women who are already at risk of breast cancer.

"We already know that tamoxifen can be used like that, but it does have side effects."