Changes in Risk Factors and Increases in Screening Contribute to the Decline in Colorectal Cancer Mortality, 1975 to 2000
Article Outline
Dear Sir:
The “Annual Report to the Nation on the Status of Cancer, 1975–2006, featuring colorectal cancer trends and impact of interventions (risk factors, screening, and treatment) to reduce future rates”1 by Edwards et al was reviewed in the Gastroenterology and Hepatology News section of Gastroenterology.2 One feature of this paper was microsimulation modeling to partition out the effects of risk factors, screening, and treatment on past changes in colorectal cancer (CRC) mortality and showed that the CRC mortality rates from 1975 to 2000 decreased by 26% with a partitioning of the decline into 53% owing to screening, 35% to changes in risk factors, and 12% to treatment. Dr Robert Sandler provides the comment that “it is odd [to have a decline attributed to risk factor changes] because the important risk factors for colon cancer—obesity, physical inactivity, and red meat consumption—have gotten worse.”
However, the results of this analysis were based on prevalences between 1975 and 2000 rather than the present time. Given that there is latency in the effect of risk factors on CRC mortality, we note below the age-adjusted prevalence of risk factors between 1965 and 2000 as presented in a supplement to the report. The age-adjusted prevalence of obesity does begin to increase (from 13% to 31%) for 1965 and 2000, respectively, but not to the high levels we see now. Physical activity (adhering to guidelines) was stable—at 25% and 26%, respectively—and red meat consumption (adults consuming red meat >2 times per week) declined from 97% to 78%. Importantly, smoking, now considered to be a carcinogen for CRC,3 is a risk factor that declined from 42% to 23%. Furthermore, the relative risk for smoking (given the latency period) represents a higher relative risk for CRC than obesity.3, 4 Multivitamin use and aspirin use, both protective for CRC, had increased between 1975 and 2000. We recognize that the marked increases in obesity and in lack of physical activity that have occurred more recently in the United States will have a marked effect on CRC mortality in the future. However, this analysis was based on an earlier time period—as noted, from 1975 to 2000—and the changes in risk factors, screening, and treatment between 1975 and 2000 are consistent with a decrease in CRC mortality. The point remains that changes in risk factors take time to show an effect, but positive changes can make a contribution to reducing CRC mortality. Further analysis in the paper1, 4 showed that with a concerted effort to improve risk factors, increase screening, and further disseminate treatment, a decrease of almost 50% in CRC rates might be possible by 2020 relative to 2000.
References
- Annual report to the nation on the status of cancer, 1975–2006, featuring colorectal cancer trends and impact of interventions (risk factors, screening, and treatment) to reduce future rates. Cancer. 2010;116:544–573
- . Annual Report to the Nation Highlights Declines in Colorectal Cancer. Gastroenterology. 2010;138:799–800
- A review of human carcinogens—part E: tobacco, areca nut, alcohol, coal smoke, and salted fish. Lancet Oncol. 2009;10:1033–1034
- How much can current interventions reduce colorectal cancer mortality in the U.S.? (Mortality projections for scenarios of risk-factor modification, screening, and treatment). Cancer. 2006;107:1624–1633
Conflicts of interest The authors disclose no conflicts.
PII: S0016-5085(10)00870-X
doi:10.1053/j.gastro.2010.06.011
© 2010 AGA Institute. Published by Elsevier Inc. All rights reserved.
Refers to article:
- Annual Report to the Nation Highlights Declines in Colorectal Cancer , 22 January 2010
