Age-period-cohort analysis of cancers not related to tobacco, screening, or HIV: sex and race differences

Cancer rates not explained by smoking: a county-level analysis

BACKGROUND

Debates over the importance of "lifestyle" versus "environment" contributions to cancer have been going on for over 40 years. While it is clear that cigarette smoking is the most significant cancer risk factor, the contributions of occupational and environmental carcinogens in air, water and food remain controversial. In practice, most cancer prevention messaging focuses on reducing cigarette smoking and changing other personal behaviors with little mention of environmental chemicals, despite widespread exposure to many known carcinogens. To inform decision-making on cancer prevention priorities, we evaluated the potential impact of smoking cessation on cancer rates.

METHODS

Using cancer incidence data from 612 counties in the SEER database, and county-level smoking prevalences, we investigated the impact of smoking cessation on incidence for 12 smoking-related cancer types, 2006-2016. A multilevel mixed-effects regression model quantified the association between county-level smoking prevalence and cancer incidence, adjusting for age, gender and variability over time and among counties. We simulated complete smoking cessation and estimated the effects on county-level cancer rates.

RESULTS

Regression models showed the expected strong association between smoking prevalence and cancer incidence. Simulating complete smoking cessation, the incidence of the 12 smoking-related cancer types fell by 39.8% (54.9% for airways cancers; 28.9% for non-airways cancers). And, while the actual rates of smoking-related cancers from 2006 to 2016 declined (annual percent change (APC) = - 0.8, 95% CI = - 1.0 to - 0.5%), under the scenario of smoking elimination, the trend in cancer incidence at these sites was not declining (APC = - 0.1, 95% CI = - 0.4 to + 0.1%). Not all counties were predicted to benefit equally from smoking elimination, and cancer rates would fall less than 10% in some counties.

CONCLUSIONS

Smoking prevention has produced dramatic reductions in cancer in the US for 12 major types. However, we estimate that eliminating smoking completely would not affect about 60% of cancer cases of the 12 smoking-related types, leaving no improvement in the incidence trend from 2006 to 2016. We conclude that cancer prevention strategies should focus not only on lifestyle changes but also the likely contributions of the full range of risk factors, including environmental/occupational carcinogens.

Cigarette smoking, alcohol drinking, and oral cavity and pharyngeal cancer in the Japanese: a population-based cohort study in Japan

The effects of cigarette smoking and alcohol drinking on the incidence of oral cavity and pharyngeal cancer (OCPC) in the Asian population have been poorly understood. To assess the effects of cigarette smoking, alcohol drinking, and facial flushing response on incidence of OCPC, a total of 95 525 middle-aged and older eligible individuals were followed in a large-scale population-based cohort study in Japan from 1990 to 2010. In this study, the person-years of observation were 698 006 in men and 846 813 in women, and a total of 222 cases (men=160, women=62) of OCPC were newly diagnosed during the study period. A multivariate Cox proportional-hazards model was used to assess the incidence risk of OCPC and subsites by cigarette smoking and alcohol drinking. The result showed that cigarette smoking and regular alcohol drinking were associated significantly with the incidence of OCPC in men. Compared with nonsmokers and nondrinkers, current male smokers showed a hazard ratio (HR) of 2.37 [95% confidence interval (CI)=1.51-3.70] and regular male drinkers showed an HR of 1.82 (95% CI=1.20-2.76). Cigarette smoking also increased the risk of OCPC among male heavy alcohol drinkers (HR=4.05, 95% CI=2.31-7.11). However, there was no significant association between facial flushing response and OCPC. In conclusion, cigarette smoking and alcohol drinking are independent risk factors for OCPC and its subsites in the male Japanese population.