Scientists at a Welsh University are carrying out pioneering research into the prevention of the most common cancer for women.
Breast cancer is the most common form of the illness among women
Breast cancer is the most common cancer in the UK for women, with the chances of contracting the disease increasing dramatically with age.
Women have a one in 15,000 chance of contracting breast cancer before the age of 25, but that rises to one in 200 at the age of 50 and just one in 15 at 70.
Ten year trials at Cardiff University are looking at how to prevent the cancer in women who are in high-risk groups.
Five years into the work scientists have already carried out trials on the drug tamoxifen which is now being used to prevent the disease.
And they are now trialling a new drug called arimidex which they believe could be even more successful in preventing the onset of breast cancer.
Professor Robert Mansel, of Cardiff University, said: "We have found that tamoxifen does help to prevent breast cancer in women with a high risk of (contracting) it.
It is hoped the new drug can prevent breast cancer
"The problem we've had with the trial is that although (tamoxifen) is effective, it has quite a bit in the way of side-effects.
"We are looking for a better drug to do the same prevention with fewer side effects."
Around 7,000 women across the world have been taking tamoxifen tablets every day for the past five years and the Cardiff scientists are now looking for more recruits to take part in the next trials.
Trial participant Susan Davies took part in the tamoxifen trials in Cardiff.
She said: "You are helping medical research and you are helping yourself.
"Even after I've finished this trial the study is going to keep and eye on me and that gives me a great sense of security."