Aspirin’s cancer-fighting power comes from its anti-inflammatory effects, which reduce the chronic inflammation suspected to play a role in the development of cancer, says study author Susanne Krüger Kjær, M.D., of the Danish Cancer Society Research Center and the Department of Obstetrics and Gynecology at Copenhagen University Hospital, both in Copenhagen, Denmark. So why were non-aspirin pain relievers—which may also reduce inflammation—found to be less effective at curbing cancer? “This may reflect differences in the way these drugs induce their effect on inflammation,” says Kjær.