Regular Aspirin Use Leads To A Small Reduction In Breast Cancer Risk

Some pills in a bottleA new study, published in the journal Breast Cancer Research in April this year has found that women who take an aspirin a day have a modestly reduced risk of developing breast cancer compared to women who never use aspirin.

The study, conducted by researchers at the US National Cancer Institute in Rockville, USA, focused on 136,408 women aged between 51 and 72 and who were free of cancer at the beginning of the study in 1996-1997.

By the end of 2003, 4501 (3.3%) of the women had developed breast cancer. The study found no association between the use of non-aspirin NSAID’s and breast cancer or between occasional aspirin use and breast cancer. The study did however find that daily aspirin users were 7% less likely to develop breast cancer and in particular 16% less likely to develop ER-positive breast cancer than those who did not use aspirin at all.

Around 18% of the study participants reported daily aspirin use, a further 16% used aspirin 1 to 6 times a week, 32% used aspirin between once a week and once a year while 34% of the women had not used aspirin in the past year.

ER positive breast cancer is the most common form of breast cancer making up around 75% of total cases. ER positive cancer means the breast cancer cells have estrogen receptors on their surface. Breast cancers can also be classified as progesterone-receptor positive (PR+) or negative (PR-) depending on the presence of progesterone receptors on the cancerous cells . ER positive breast cancers typically have a slightly better prognosis than ER-negative breast cancers because they are more likely to respond to hormonal therapy.

Aspirin inhibits the action of the COX-2 enzyme which is responsible for inflammation and pain. The over expression of the COX-2 has been implicated in many steps of cancer development including the inhibition of cell death (apoptosis) and the increased division of cancerous cells.