Preventing endometrial cancer: updating the evidence
Elisa V. Bandera is an Associate Professor of Epidemiology, Rutgers Cancer Institute of New Jersey, Robert Wood Johnson Medical School and Rutgers School of Public Health. She is a panel member for the Continuous Update Project (CUP).
Today WCRF International released the latest CUP findings about preventing endometrial cancer. As a CUP panel member I have lead responsibility on this issue, and over the years I’ve grown more confident than ever that maintaining a healthy weight and engaging in regular exercise will reduce endometrial cancer risk.
Approximately six years ago, I led a systematic literature review and meta-analyses on food, nutrition, physical activity and endometrial cancer to support the 2007 Second Expert Report, which was the most comprehensive study of its kind. While we were aware that obesity was a strong risk factor for endometrial cancer, we were impressed with how long this relationship had been suspected – we found clinical reports noticing that endometrial cancer patients tended to be obese dating all the way back to the early 40’s!
The Second Expert Report concluded that body fatness and abdominal fatness was a convincing cause of endometrial cancer and physical activity probably decreased risk. Other areas were too unclear to draw public health conclusions.
Since then prospective studies have matured and enough endometrial cancer cases have accrued to be able to re-evaluate these associations and update our findings. A team at Imperial College London, led by Dr. Teresa Norat, has been identifying the new evidence, abstracting all the information from prospective studies and conducting meta-analyses.
So what’s new? Overall, 91 new prospective studies were found for us to factor into our conclusions.
The evidence for body fatness increasing risk remains strong for both pre-menopausal and post-menopausal women. We were able to go a step further and found that the effect was stronger for those women who have never used hormone replacement therapy. The cumulative evidence is also now stronger for abdominal obesity (measured as waist circumference or waist to hip ratio).
The evidence for physical activity reducing risk is also still strong. Additionally, there is emerging evidence from three cohort studies suggesting that sitting time may increase risk (but more evidence is needed for a firm conclusion).
Some new associations have emerged in the evidence. There is an interesting association with coffee, both caffeinated and decaffeinated, with an estimated 7% reduction in risk for every cup of coffee consumed, based on eight studies. These findings are intriguing, but we should keep in mind that excessive coffee consumption can have side effects, particularly in some people. Also, most studies have not evaluated substances added to coffee, such as cream and sugar, which may themselves pose other risks. More research is needed to explore the protective effect of coffee on cancer risk.
The evidence for glycaemic load has strengthened, with this factor shown to be a probable cause of endometrial cancer. Glycaemic load is the impact of diet on a person’s glucose level. Suggested associations with non-starchy vegetables and meat intake based on case-control data in the previous 2007 report, were not confirmed by the few prospective studies that have been published to date.
While additional studies are needed, it is a safe bet that maintaining a healthy weight and engaging in regular physical activity will reduce endometrial cancer risk, as well as having many other health benefits. In terms of food choices, eating a diet high in vegetables and low in fat and refined sugars is going to, at a minimum, help with weight control, while probably also protecting against cancer in other ways.