Estimating Cancer Preventability:
Q and A with AICR/WCRF Expert Panel Member Tim Byers
Tim Byers, MD, MPH, is the Interim Director of the University of Colorado Cancer Center and Associate Dean for Public Health Practice at the Colorado School of Public Health. He is a member of the AICR/WCRF Expert Panel that authored the policy report, Policy and Action for Cancer Prevention.
Q. How have you put these preventability figures together?
A. We have taken the findings of the AICR/WCRF Expert Report, which established the degree to which diet, physical activity and body fatness influence cancer risk, and combined them with information from national surveys on obesity in the US as well as cancer incidence data.
In this case, the Expert Report found a convincing link between excess body fat and risk of several cancers. So we looked at data from US surveys to find out how much of the population is overweight and obese. We then worked out the percentage of those specific cancers that would be prevented if everyone in the US maintained a healthy weight.
The final step was to translate that preventable percentage into real-number estimates. To do that, we applied our preventability estimates to the US incidence of those cancers that are linked to excess body fat.
Q. Why haven’t you included smoking in this? What is the total level of preventability including smoking?
A. The AICR/WCRF Expert Report and the Policy Report only looked at food, nutrition, physical activity and body weight. Other cancer preventability factors -- such as smoking, infectious agents, radiation and industrial chemicals -- were outside the remits for these reports. However, the Panel emphasized the importance of avoiding smoking and exposure to tobacco smoke as key to cancer prevention.
Most cancer is preventable by not smoking (which includes avoiding other exposure to tobacco smoke) and by following the recommendations in the 2007 WCRF/AICR Diet and cancer report.
Q. How certain are you these estimates are correct?
A. We need to be clear that these are estimates, not precise figures. We are being open about the fact that we have had to make a number of assumptions in coming to these figures. But we believe these estimates are as good as it is possible to achieve, given the available data.
FOR A DETAILED BREAKDOWN OF THESE PREVENTABILITY ESTIMATES AND THE METHODOLOGY BEHIND THEM, SEE APPENDIX A OF THE AICR/WCRF REPORT POLICY AND ACTION FOR CANCER PREVENTION.