... continued from page 39 [Smoking is a major cause of 12 types of cancer]
The statistical models showed the expected strong association between smoking prevalence and cancer incidence. Simulating complete smoking cessationin 1996, the incidence of the 12 smoking-related cancer types in 2016 was 39.8% lower than actual rates. But not all counties were predicted to benefit equally from smoking elimination. The models estimated that if smoking had been completely eliminated, rates of cancer for which smoking is a known risk factor would have fallen less than 10% in some counties, many of them urban with elevated environmental exposures. For example, our follow-up analysis of lung cancer incidence rates in Allegheny County Pennsylvania, where high levels of air pollution and radon are a concern, concluded that lung cancer rates would have declined by 11%, compared to an average reduction in lung cancer rates across all counties of 62%.In addition, while the actual rates of all smoking-related cancers during the 2006 to 2016 time perioddeclined by almost 1% per year, under the scenario of smoking elimination, the trend in incidence of these cancer types was flat, not declining.
Our results can be summarized as follows. First, we estimated that about 60% of the cancers at tumor sites considered to be smoking-related would still occur even if smoking were completely eliminated. Second, the degree to which smoking elimination would reduce cancer incidence rates would not be uniformly distributed across the country. Our models predicted that some counties would have only modest reductions in cancer from eliminating smoking and by extension higher rates of cancers remaining. Third, under the same simulated condition of no smoking, the 11-year trend in the incidence rate of these 12 types of cancer would be stable – neither rising nor falling – indicating that smoking cessation is almost entirely responsible for the reductions in incidence that have occurred over this time period and suggesting missed opportunities for other prevention strategies.
Conclusions and new directions
Overall cancer incidence in the U.S. has been falling over the past several decades. This has been attributed largely to the reduction in smoking prevalence, especially among men. Smoking prevention has produced dramatic reductions in cancer in the US for 12 major types of cancer. However, we estimate that eliminating smoking completely would not affect about 60% of cancer cases of the 12 smoking-related types, leaving no net improvement in the trend in new cases of cancer from 2006 to 2016. Smoking elimination would benefit some counties much less than others.
Without detracting from the importance of tobacco control, these findings suggest that progress in the primary prevention of cancer must include many strategies, not only those focused on healthy lifestyles. A particular opportunity is environmental chemicals which are ubiquitous and also elevated in particular states, regions and
How might people and organizations concerned about cancer begin to take action onother cancer risk factors in addition to smoking, in particular environmental and occupational carcinogens? A first step is acknowledging the importance of these exposures as cancer prevention opportunitiesand providing and accessing information about steps that can be taken to reduce them. Expanding state cancer coalitions to include people with environmental expertise and lived experience of environmental exposures is another; these coalitions shape statewide cancer control plans. Leveraging the capacity of businesses already investing in safer alternatives and advocating for policies that incentivize a shift from reliance on toxic chemicals are also opportunities. We commend the Centers for Disease Control and National Association of Chronic Disease Directors for the recent launch of a webinar series for cancer prevention leaders on this topic which will provide examples of effective interventions and strategies for impactful partnerships and policies. And we applaud the research institutions, professional associations, non-governmental organizations and community groups that are elevating attention to the contribution of environmental and occupational chemicals to cancer and providing invaluable resources on these issues.
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