Lung cancer risk in never-smokers:An overview of environmental and genetic factors

Lung cancer is the leading cause of cancer-related mortality globally,accounting for 1.8 million deaths in 2020.While the vast majority are caused by tobacco smoking,15%-25%of all lung cancer cases occur in lifelong neversmokers.The International Agency for Research on Cancer(IARC)has classified multiple agents with sufficient evidence for lung carcinogenesis in humans,which include tobacco smoking,as well as several environmental exposures such as radon,second-hand tobacco smoke,outdoor air pollution,household combustion of coal and several occupational hazards.However,the IARC evaluation had not been stratified based on smoking status,and notably lung cancer in never-smokers(LCINS)has different epidemiological,clinicopathologic and molecular characteristics from lung cancer in ever-smokers.Among several risk factors proposed for the development of LCINS,environmental factors have the most available evidence for their association with LCINS and their roles cannot be overemphasized.Additionally,while initial genetic studies largely focused on lung cancer as a whole,recent studies have also identified genetic risk factors for LCINS.This article presents an overview of several environmental factors associated with LCINS,and some of the emerging evidence for genetic factors associated with LCINS.An increased understanding of the risk factors associated with LCINS not only helps to evaluate a never-smoker’s personal risk for lung cancer,but also has important public health implications for the prevention and early detection of the disease.Conclusive evidence on causal associations could inform longer-term policy reform in a range of areas including occupational health and safety,urban design,energy use and particle emissions,and the importance of considering the impacts of second-hand smoke in tobacco control policy.

Widening socioeconomic disparity in lung cancer incidence among men in New South Wales, Australia, 1987–2011

Objective：We assessed the trends in lung cancer incidence over a 25-year period by socioeconomic groups for men in New South Wales（NSW）,Australia.Methods：Men diagnosed with lung cancer between 1987 and 2011 were divided into five quintiles according to an Index of Education and Occupation（IEO）.We assessed relative socioeconomic differences over time by calculating age-standardized incidence ratios（SIRs）by 5-year period of diagnosis,and estimated absolute differences by comparing the observed and expected numbers of cases using the highest IEO quintile as the reference.Results：Lung cancer incidence for men decreased from 1987 to 2011 for all IEO quintiles,with a greater rate of decline for men living in the highest IEO areas.Thus,the relative disparity increased significantly over the 25-year period（P=0.0006）.For example,the SIR for the lowest IEO quintile increased from 1.28 during 1987–1991 to 1.74during 2007–2011.Absolute differences also increased with the proportion of＂potentially preventable＂cases doubling from 14.5% in 1987–1991 to 30.2% in 2007–2011.Conclusions：Despite the overall decline in lung cancer incidence among men in NSW over the past 25 years,there was a significant increase in disparity across socioeconomic areas in both relative and absolute terms.