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Cancer Intervention and Surveillance Modeling Network

Modeling to guide public health research and priorities

Comparative Analyses

Quantifying the impact of tobacco control policies on lung cancer mortality in the United States

Using five CISNET lung cancer models and detailed information on cigarette smoking, the CISNET lung group is quantifying the impact of tobacco control policies and increased awareness of the health effects of smoking following the seminal Surgeon General's report on lung cancer mortality in the United States between 1975 and 2000. The CISNET group is quantifying the levels of smoking and associated lung cancer deaths that would have occurred if the tobacco control efforts starting mid-century had never been initiated, as well as quantifying the number of lung cancer deaths that would have been avoided had tobacco control been perfect (i.e., if following the Surgeon General's report all current smokers quit and there was no new initiation).

These projections will serve to highlight the number of lung cancer deaths that were avoided due to the tobacco control efforts that did occur, and it will highlight an upper bound on how many more deaths could have been avoided if the efforts had been perfect. The results of this modeling are being prepared for a special issue of a journal. In addition to the population-based models, this project will result in the development of other sophisticated tools for the investigation of the association between smoking habits and human health. These include life tables for mortality associated with specific levels of smoking and a smoking history generator that allows the stochastic simulation of smoking habits by birth cohort while adjusting for smoking-related mortality.

Hypothesized Impact of Tobacco Control Policies on U.S. Smoking Prevalence

Hypothesized impact of tobacco control policies on US smoking prevalence

Hypothesized impact of tobacco control policies on U.S. smoking prevalence. Percentage of smokers among the white U.S. male population in a given year (1900–2000) by given year at birth (different colors). Solid lines represent the percentage of smokers estimated based on National Health Interview Survey data. Dashed lines represent the percentages (hypothesized) that would have been observed if tobacco control efforts had never been initiated.

Quantifying the potential benefits and harms of CT screening for lung cancer

Five CISNET groups have been engaged in a comparative modeling analysis that aims to predict the impact of CT screening on survival, mortality, and overdiagnosis. Initial efforts have focused on simulating the Mayo CT trial, which did not have a control arm. By simulating Mayo CT, the groups can evaluate how well different models of the natural history of lung cancer predict the observed outcomes in the screened group and the degree to which the models vary in their predictions for the simulated control group. While much of the debate on CT screening has been focused on a mortality benefit versus no benefit and substantial overdiagnosis, the truth probably lies between these two extremes. One CISNET affiliate group has already published a simulation of this study (McMahon 2008) but because of the complexity and uncertainty in this area, there will be significant benefit from a careful assessment of how reproducible their results are across five groups. This comparative analysis will help to better frame the debate concerning CT screening by conceptually linking specific outcomes to underlying proposed models of the natural history of lung cancer and the operating characteristics of CT screening. Once the results of CT screening trials are published, these models will be poised to allow translation to the population level, reconcile differences between trials conducted under different study protocols, as well as identification of guidelines for optimal screening strategies by targeting age-groups, risk-groups, and screening frequencies that are different than those tested in trials and would not be feasible to test without additional studies.

Simulation of the Mayo Lung Project

The Mayo Lung Project was a randomized study conducted in the 1970's to determine if a regimen of chest x-rays and sputum cytology could reduce lung cancer mortality. The study found no mortality benefit for this regimen, but a persistent excess of cases in the intervention arm, suggesting overdiagnosis. Three CISNET modeling teams are simulating this trial, since the long-term follow-up provides a unique window, albeit through the lens of an older technology, to better understand the natural history of lung cancer, and to determine estimates of overdiagnosis and potential mortality gains that are consistent with the observed data.