This comes from a long-term study of 2.7 million women published recently in the Journal of the National Cancer Institute. Aspirin cut the risk by 13%, while ibuprofen lowered it by a fifth.
However, experts warned long-term use of painkillers can have serious side-effects. Both these pain killers are non-steroidal antiinflammatories, which can cause stomach ulceration. However, it is their ability to interfere with inflammation that appears to be key to their role in breast cancer.
Two body chemicals which help produce inflammation, COX1 and 2, are thought to play roles in the development of cancer by influencing how cells divide and die, the production of new blood vessels that can "feed" tumours, and influence the body's immune responses. It appears NSAIDS inhibit these chemicals.
Women taking either aspirin or ibuprofen regularly had a 12% lower chance of developing breast cancer compared to those who did not use them at all, while regular ibuprofen use appeared to have the biggest effect.
