Regular use of non-steroidal anti-inflammatory drugs (NSAIDs)*, such as aspirin, may be associated with a decreased risk of endometrial cancer in women who are obese (women with a body mass index (BMI) of 30 kg/m² or higher).

There is some evidence that NSAIDs may also be associated with a decreased risk of endometrial cancer in women who are overweight (women with a BMI between 25 and 30 kg/m²). There is no evidence of an association between taking an NSAID and risk of endometrial cancer in women in the healthy weight range.

The risk of endometrial cancer has been shown to be up to 16% lower in obese or overweight women who take aspirin or another NSAID at least once a week compared to women who do not take one of these medicines. However, no decrease in risk is seen in obese or overweight women who take aspirin every day. This is probably because aspirin taken every day is usually a much lower dose used to help prevent heart attacks.

The protective effects of NSAIDs in obese and overweight women may be due to the anti-inflammatory effects of these medicines. Women who are obese or overweight have certain proteins and other factors in their blood caused by inflammation. These factors may increase the risk of endometrial cancer. By reducing the inflammation seen in obese or overweight women, NSAIDs may help to reduce the risk of endometrial cancer.

*NSAIDs are anti-inflammatory medicines used to treat pain, fever and inflammation. Aspirin is an example of an NSAID that can also be used to prevent heart attacks in some people when used at a low dose.