Over the last decade, no fewer than a dozen studies have suggested an association between frequent aspirin or NSAID use and a reduced risk for breast and ovarian cancer, but almost all the research has been observational.
In one of the most widely reported studies, Columbia University researchers questioned close to 3,000 women with and without breast cancer about their aspirin use.
They found a 20% lower breast cancer risk among women who said they were regular aspirin users, compared to infrequent aspirin users.
Just last year, Brigham and Women's researchers reported that breast cancer survivors who took aspirin regularly had a lower risk of cancer recurrence or death from their disease than women who did not take aspirin; the breast cancer survivors also had a lower risk of having their cancer spread beyond the breast.
The researchers followed 4,000 female nurses enrolled in the ongoing Nurses Health Study (NHS) who had been treated for breast cancer at least a year earlier.