Women who take aspirin regularly before a diagnosis of breast cancer are less likely to see the disease spread, or to die from it, a new Irish study has found.

"Our findings suggest that aspirin could play a role in reducing mortality from breast cancer by preventing the cancer spreading to nearby lymph nodes," commented the study's lead author, Dr Ian Barron, who carried out the research at Trinity College Dublin (TCD).

The study focused on almost 2,800 women with stage I, II or III breast cancer.

"We found that those women prescribed aspirin in the years immediately prior to their breast cancer diagnosis were statistically significantly less likely to present with a lymph node-positive breast cancer than non-users. The association was strongest among women prescribed aspirin regularly and women prescribed higher aspirin doses," Dr Barron said.

Lymph node positive breast cancer refers to when the cancerous cells have also been found in the lymph nodes closest to the breast. This type of cancer is usually more serious.

Dr Barron emphasised that scientists now need to establish ‘how and why' aspirin appears to have this effect. The drug is often prescribed to people at risk of cardiovascular disease as it thins the blood.

Also commenting on the findings, the study's co-author, Dr Kathleen Bennett, also of TCD, pointed out that it was observational and ‘these results do not mean that women should start taking aspirin as a precautionary measure'.

"Aspirin can have serious side-effects. We still need to identify exactly how aspirin may prevent breast cancer from spreading to the lymph nodes, which women or types of breast cancer are most likely to benefit from taking aspirin, as well as what the optimum doses might be," she noted.

The research was funded by the Irish Cancer Society and the Health Research Board and the findings are published in the US medical journal, Cancer Research.