Does aspirin lower the risk of breast cancer?

A daily aspirin may give women modest protection against the most common type of breast cancer according to a study published in Breast Cancer Research. The finding reinforced earlier research indicating regular use of aspirin might reduce the risk of so-called estrogen receptor-positive breast cancer, which makes up about three quarters of breast cancer cases.

Estrogen receptor or ER-positive breast cancer is fueled by estrogen and aspirin may interfere with this hormone's activity. Researchers led by Gretchen Gierach of the National Cancer Institute, part of the National Institutes of Health, found that women who took aspirin daily cut their risk of developing this type of breast cancer by 16 percent.

The research involved about 127,000 women aged 51 to 72 from around the United States who were cancer-free when the study began. About 18 percent of the women were daily aspirin users. They were tracked for seven years and about 4,500 of them developed breast cancer.

The study did not find any relationship between aspirin and the less-common estrogen receptor-negative breast cancer. It also did not find any protective effect in women who took aspirin less than daily.

The study is the latest to suggest aspirin offers benefits beyond relieving headaches and body aches and reducing fevers. Aspirin is a common anti-inflammatory painkiller that can be used to relieve symptoms of arthritis and prevent second heart attacks and other ailments. Previous research has indicated it also may protect against colorectal cancer. It is possible that aspirin acts to reduce inflammation in cancer, which can trigger tumour growth.