A new report by the American Institute for Cancer Research and World Cancer Research Fund International estimates that nearly 60 percent, or 29,500 cases, of endometrial cancer annually could be prevented if women maintained a healthy weight and got regular exercise. The recently published report on preventing endometrial, or uterine, cancer, found that obesity and a sedate lifestyle add to the risk. The disease primarily strikes women over 60, killing more than 8,000 a year. Rutgers Cancer Institute of New Jersey epidemiologist Elisa Bandera, the panel lead of this report which analyzed global research on diet, exercise and weight and their influence on the disease, talks about the findings.
This is the first systematic update of the research on lifestyle and endometrial cancer risk since 2007. Overall, what's new here?
Bandera: For the update, we now have more prospective data for dietary factors and interesting associations emerged with coffee consumption and glycemic load. Coffee consumption was associated with reduced risk while glycemic load increased risk. There is also growing evidence that longer sitting time increases endometrial cancer risk.
But the research for sitting time – sedentary living – was not strong enough to make a conclusion.
Bandera: There were only three studies at this time but they all suggested increased risk. We could not be certain based on the limited data that the association was independent of BMI. However, sitting time has been emerging as an important risk factor for other cancers, independent of physical activity. In other words, it is not sufficient to go to the gym three times a week. We have to remember to get up out of our chairs and move and avoid extended period of sittings in front of the television or the computer.
How much more research is there now on endometrial cancer prevention compared to the last report?
Bandera: There are more studies, but particularly more prospective studies evaluating dietary factors, which were lacking in the first report. Still, only few prospective studies have evaluated some of the dietary exposures and endometrial cancer risk compared to the number of studies that have evaluated them in relation to breast or colorectal cancers.
Why is having prospective data so important?
Bandera: The previous report's conclusions were based on mainly findings from case-control studies, which are generally considered weaker than cohort or prospective studies.
Case-control studies compare the experiences and exposures (for example dietary intake) of participants with the disease to a comparison group (participants without the disease). Because some of the participants have the disease at the time they are interviewed, that may influence their recall and reporting of dietary intake and other factors. On the other hand, prospective or cohort studies, start with a large population free of the disease at the time of interview. Therefore, we can be certain that the disease did not affect reporting of dietary intake and other factors under investigation and more certain about cause-effect
You're an expert in risk factors relating to endometrial and other women's cancers; was there anything that surprised you here?
Bandera: In the first report, there was a suggestion that non-starchy vegetables decreased risk and meat consumption increased risk, which was not apparent in the update. The first report's results were based on case-control data, which are known to have limitations, as mentioned earlier. There are now only a few prospective studies evaluating these factors, which failed to replicate the earlier findings. More studies are needed though to be able to draw any conclusions.
Of all the risk factors, it looks like excess body fat has the greatest affect on a woman's risk of this cancer. Yes?
Bandera: Yes, by far excess body weight is the most important risk factor for endometrial cancer (other than using estrogen supplements without progesterone, which was not the focus of this report.) The link between obesity and endometrial cancer is the most consistent and strong association found in the nutrition and cancer literature. Obese women have more than double the risk of developing this type of cancer, compared to women who are lean. And the risk increases as BMI increases. Weight gain from early adulthood to adulthood was also associated with increased risk, with an estimated 16% increased risk per 5 kilogram [11 pounds] gain in weight.
A 2010 report found that people with type 2 diabetes are at increased risk of endometrial cancer. Could this relate to obesity and increased risk?
Bandera: Obesity increases the risk of diabetes, so they are both related. However, some studies have found that diabetes can increase risk independent of BMI. Both obesity and diabetes lead to hyperinsulinemia, which has been shown to stimulate the growth of endometrial cancer cells.
Being physically active reduces risk; does this include activities such as housework and gardening?
Bandera: Most studies have evaluated recreational and occupational activity and they tended to suggest an inverse association. In general, moderate and vigorous activities are more beneficial, meaning activities that require an effort, but any level of activity is better than none.
This is the first time the report linked a glycemic load diet to risk of endometrial cancer – or any cancer. Can you explain how a woman can use this information as she chooses what to eat?
Bandera: The bottom line is that not all carbohydrates are equal. For example, we want to choose whole grains instead of refined grains and generally a plant-based diet high in vegetables, fruit and beans, in moderate amounts that favor weight control.
What is the basic takeaway from this report?
Bandera: The findings on endometrial cancer are important reminders of the major impact of obesity on cancer. While there are individual choices that can be made for weight control, there is urgent need for communities to facilitate healthy lifestyles for obesity prevention, including access to fresh fruits and vegetables and healthy foods in general, as well as safe and well-lighted streets to walk, jog, bicycle, and play.