A breast cancer treatment which blocks the growth of tumours has been hailed as a breakthrough by Irish scientists.
The protein works by blocking the growth of cancer
Researchers at Ireland's Royal College of Surgeons have developed a protein which attacks a hormonal growth factor which stimulates cancer cells.
Pre-clinical trials on mice have shown it is particularly effective at slowing the growth of secondary tumours, which tend to be much harder to treat.
But UK experts warned it would be years before the treatment was available.
Nearly 13,000 women die each year from breast cancer.
But as treatment has improved in recent years the survival rate has gone up - three quarters live for at least five years, according to Cancer Research UK.
Breast cancer is often treated by chemotherapy, radiotherapy and surgery, but lead researcher Dr Judith Harmey said secondary cancer growth, particularly in the bone, was the biggest risk for patients.
"It has been shown in a pre-clinical model that the treatment can inhibit breast tumour growth, increase survival by 30% and reduce secondary growths in bones.
"We are absolutely delighted, it [the treatment] has worked better than ever expected.
"Possibly in the future it will be used, but it is some way down the line, we have to make it in pharmaceutical form and check for toxicity."
The protein works by blocking IGF1, which helps cancer cells grow.
Dr Harmey, whose work is being funded by the Irish Cancer Society, added using the genetically-engineered protein was less intrusive, toxic and more specific than chemotherapy.
"This approach would be what is called a targeted approach, which tends away from using chemotherapy as it kills normal cells as well as tumour cells.
"The targeted one hits the tumour only."
Ed Yong, science information officer at Cancer Research UK, said it was too early to know if the protein's potential would be realised.
"These findings are very preliminary but are certainly promising. More research is needed to determine if this new protein has a future as a cancer treatment.
"And it will eventually have to undergo rigorous clinical trials in humans.
"Cancer Research UK is supporting studies aimed at finding similar agents, which can block the development of a tumour's blood vessels.
"These molecules effectively starve tumours, making them a potentially powerful way of treating cancers." .