Incidence and Mortality of Lung Cancer Among Never Smokers in Relationship to Secondhand Smoking: Findings From the PLCO Trial

Facing an un-met need in lung cancer screening: the never smokers

Lung cancer (LC) is the leading cause of cancer-related deaths worldwide and the second most common cancer in both men and women. In addition to smoking, other risk factors, such as environmental tobacco smoke, air pollution, biomass combustion, radon gas, occupational exposure, lung disease, family history of cancer, geographic variability, and genetic factors, play an essential role in developing LC. Current screening guidelines and eligibility criteria have limited efficacy in identifying LC cases (50%), as most screening programs primarily target subjects with a smoking history as the leading risk factor. Implementing LC screening programs in people who have never smoked (PNS) can significantly impact cancer-specific survival and early disease detection. However, the available evidence regarding the feasibility and effectiveness of such programs is limited. Therefore, further research on LC screening in PNS is warranted to determine the necessary techniques for accurately identifying individuals who should be included in screening programs.

Prevalence of Underreported Nicotine Exposure Among US Nonsmoking Adults: A Comparison of Self-Reported Exposure and Serum Cotinine Levels From NHANES 2013-2020

INTRODUCTION

Secondhand smoke (SHS) poses a significant health risk. However, individuals who do not smoke may be unaware of their exposure, thereby failing to take protective actions promptly.

AIMS AND METHODS

We assessed the prevalence of underreported nicotine exposure in a nationally representative sample of US nonsmoking adults using data from the US National Health and Examination Survey. Individuals with underreported nicotine exposure were defined as those who reported no exposure to all tobacco products (traditional tobacco, nicotine replacements, and e-cigarettes) or SHS, yet had detectable levels of serum cotinine (>0.015 ng/mL). We fitted logistic regression models to determine sociodemographic and chronic condition factors associated with underreported nicotine exposure.

RESULTS

Our analysis included 13 503 adults aged 18 years and older. Between 2013 and 2020, the prevalence of self-reported SHS exposure, serum cotinine-assessed nicotine exposure, and underreported nicotine exposure among US nonsmokers were 22.0%, 51.2%, and 34.6%, respectively. Remarkably, 67.6% with detectable serum cotinine reported no SHS exposure. Males, non-Hispanic blacks, individuals of other races (including Asian Americans, Native Americans, and Pacific Islanders), and those without cardiovascular diseases were more likely to underreport nicotine exposure than their counterparts. The median serum cotinine value was higher in respondents who reported SHS exposure (0.107 ng/mL) than in those who reported no exposure (0.035 ng/mL). We estimate that approximately 56 million US residents had underreported nicotine exposure.

CONCLUSIONS

Over a third of US nonsmokers underreport their nicotine exposure, underlining the urgent need for comprehensive public awareness campaigns and interventions. Further research into sociodemographic determinants influencing this underreporting is needed.

IMPLICATIONS

Understanding the extent of underreported nicotine exposure is crucial for developing effective public health strategies and interventions. It is imperative to bolster public consciousness about the risks associated with SHS. Additionally, surveillance tools should also incorporate measures of exposure to outdoor SHS and e-cigarette vapor to enhance the quality of data monitoring. Findings from this study can guide tobacco control initiatives and inform smoke-free air legislation.

Health effects associated with exposure to secondhand smoke: a Burden of Proof study

Despite a gradual decline in smoking rates over time, exposure to secondhand smoke (SHS) continues to cause harm to nonsmokers, who are disproportionately children and women living in low- and middle-income countries. We comprehensively reviewed the literature published by July 2022 concerning the adverse impacts of SHS exposure on nine health outcomes. Following, we quantified each exposure-response association accounting for various sources of uncertainty and evaluated the strength of the evidence supporting our analyses using the Burden of Proof Risk Function methodology. We found all nine health outcomes to be associated with SHS exposure. We conservatively estimated that SHS increases the risk of ischemic heart disease, stroke, type 2 diabetes and lung cancer by at least around 8%, 5%, 1% and 1%, respectively, with the evidence supporting these harmful associations rated as weak (two stars). The evidence supporting the harmful associations between SHS and otitis media, asthma, lower respiratory infections, breast cancer and chronic obstructive pulmonary disease was weaker (one star). Despite the weak underlying evidence for these associations, our results reinforce the harmful effects of SHS on health and the need to prioritize advancing efforts to reduce active and passive smoking through a combination of public health policies and education initiatives.

Trends and factors associated with secondhand smoke exposure among US cancer survivors, 2013-2020

BACKGROUND

Secondhand smoke (SHS) poses a significant public health threat. Cancer survivors are at a greater risk of adverse health outcomes from SHS because of its association with poor prognosis and other downstream clinical events.

METHODS

A nationally representative sample of US adults aged 20 years and older was analyzed from the National Health and Nutrition Examination Survey between 2013 and 2020. Data on indoor SHS exposure were reported by 16,778 adults who were not currently smoking (1775 cancer survivors; 15,003 individuals without a cancer history). The weighted prevalence of SHS exposure was estimated and compared across sociodemographic and health-related characteristics. Multivariable logistic regression models were fitted to identify correlates of SHS exposure.

RESULTS

Of the 1775 nonsmoking cancer survivors (mean age, 64.9 years; 57.0% female; 84.4% non-Hispanic Whites), 15.8% reported SHS exposure. No significant change in trends of SHS exposure was observed during the study period. The prevalence of SHS exposure was higher in cancer survivors who were younger, racial minorities, and had a household income below 130% of the federal poverty level. After adjustment for multiple correlates, age below 40 years, low income, smoking history, and diagnosis within 2 years were associated with SHS exposure. Cancer survivors were most likely to report that SHS exposure occurred at home or in a car.

CONCLUSIONS

The prevalence of SHS exposure among cancer survivors remained steady in the past decade. However, disparities exist in SHS exposure among cancer survivors across sociodemographic characteristics and smoking status. Smoking cessation programs should be promoted among caregivers and families of cancer survivors.

Low-dose computed tomography for lung cancer screening in Anhui, China: A randomized controlled trial

Background

Lung cancer is the leading cause of cancer-related death worldwide, with risk factors such as age and smoking. Low-dose computed tomography screening can reduce lung cancer mortality. However, its effectiveness in Asian populations remains unclear. Most Asian women with lung cancer are non-smokers who have not been screened. We conducted a randomized controlled trial to evaluate the performance of low-dose computed tomography screening in a Chinese population, including high-risk smokers and non-smokers exposed to passive smoking. The baseline data are reported in this study.

Methods

Between May and December 2019, eligible participants were randomized in a ratio of 1:1:1 to a screening (two arms) or control cohort. Non-calcified nodules/masses with a diameter >4 mm on low-dose computed tomography were considered positive findings.

Results

In total, 600 patients (mean age, 59.1 ± 6.9 years) underwent low-dose computed tomography. Women accounted for 31.5% (189/600) of patients; 89.9% (170/189) were non-smokers/passive smokers. At baseline, the incidence of lung cancer was 1.8% (11/600). The incidence of lung cancer was significantly lower in smokers than in female non-smokers/passive smokers (1.0% [4/415] vs. 4.1% [7/170], respectively; P=0.017). Stage 0-I lung cancer accounted for 90.9% (10/11) of cases.

Conclusions

We demonstrate the importance of including active smokers and female non-smokers/passive smokers in lung cancer screening programs. Further studies are needed to explore the risk factors, and long-term cost-benefit of screening Asian non-smoking women.

Clinical trial registration

http://chictr.org.cn/showproj.aspx?proj=39003, identifier ChiCTR1900023197.

Risk factors for the development of lung cancer among never smokers: A systematic review

This review aimed to summarize the up-to-date evidence on non-genetic factors for the development of never smoking lung cancer (NSLC) and to explore reasons behind the conflicting results. Relevant literature was searched in three electronic databases (PubMed, Embase and Web of Science) from 1 January 2000-31 July 2022. Cohort studies that investigated non-genetic risk factors for primary lung cancer in never smokers were included. The effect of non-genetic factors about NSLC were summarized with pooled relative risk (RR) and 95 % confidence intervals (CIs) through meta-analysis or narrative description when unexplained statistical heterogeneity was observed. The Newcastle-Ottawa Scale was used to appraise the methodological quality of included studies. Sixty cohort studies were included, covering population from Asia, Europe and America. Most included studies (42, 70.0 %) were of high methodological quality. Over 50 years old (RR = 5.26), environmental tobacco smoke (Pooled RR = 1.30), Chronic obstructive pulmonary disease (COPD) (RR = 2.67), family history of lung cancer (Pooled RR = 1.83) and higher level of neutrophil-lymphocyte ratio (RR = 1.73) increased the risk of NSLC. Dairy foods consumption (RR = 0.79), isoflavone intake (Pooled RR = 0.65), and riboflavin intake (RR = 0.62) decreased the risk among female population. Inconsistency or unclear definition for never smokers and risk factors could be observed in included studies. Most life behavior factors associated with NSLC can be modified through lifestyle changes. Future cohort studies are suggested to adopt a clearer definition on never smokers and exposure, conducting subgroup analysis when evidence indicating there is heterogeneity between genders, and explore dose-response relationship between the identified factors and NSLC.

Estimates of incidence, prevalence, mortality, and disability-adjusted life years of lung cancer in Iran, 1990-2019: A systematic analysis from the global burden of disease study 2019

BACKGROUND

Lung cancer is one of the leading cancers, with a high burden worldwide. As a developing country, Iran is facing with population growth, widespread tobacco use, demographic and epidemiologic changes, and environmental exposures, which lead to cancers becoming a severe concern of public health in Iran. We aimed to examine the burden of lung cancer and its risk factors in Iran.

METHODS

We utilized the Global Burden of Disease 2019 data and analyzed the total burden of the lung cancer and seven related risk factors by sex, age at national and sub-national levels from 1990 to 2019.

RESULTS

The lung cancer age-standardized death rate increased from 11.8 (95% Uncertainty Interval: 9.7-14.4) to 12.9 (11.9-13.9) per 100,000 between 1990 and 2019. This increase was among women from 5 (4.2-7.1) to 8 (7.2-8.8) per 100,000; in contrast, there was a decline among men from 18.5 (14.8-22.6) to 17.8 (16.2-19.4) per 100,000. The burden of lung cancer is concentrated in the advanced age groups. Smoking with 53.5% of total attributable deaths (51.0%-55.9%) was the leading risk factor. At the provincial level, there was a wide range between the lowest and highest, from 8.3 (7.0-10.0) to 19.1 (16.4-22.0) per 100,000 population in the incidence rate and from 8.7 (7.3-10.3) to 20.6 (17.7-24.0) per 100,000 population in mortality rate, respectively in Tehran and West Azerbaijan provinces in 2019.

CONCLUSION

The increasing trend of lung cancer burden among the entire Iranian population, the inter-provincial disparities, and the significant rise in burden of this cancer in women necessitate the urgent implementation and development of policies to prevent and manage lung cancer burden and strategies to reduce exposure to risk factors.

The Role of Mitochondrial miRNAs in the Development of Radon-Induced Lung Cancer

MicroRNAs are short, non-coding RNA molecules regulating gene expression by inhibiting the translation of messenger RNA (mRNA) or leading to degradation. The miRNAs are encoded in the nuclear genome and exported to the cytosol. However, miRNAs have been found in mitochondria and are probably derived from mitochondrial DNA. These miRNAs are able to directly regulate mitochondrial genes and mitochondrial activity. Mitochondrial dysfunction is the cause of many diseases, including cancer. In this review, we consider the role of mitochondrial miRNAs in the pathogenesis of lung cancer with particular reference to radon exposure.

Cost-effectiveness and health impact of lung cancer screening with low-dose computed tomography for never smokers in Japan and the United States: a modelling study

BACKGROUND

Never smokers in Asia have a higher incidence of lung cancer than in Europe and North America. We aimed to assess the cost-effectiveness of lung cancer screening with low-dose computed tomography (LDCT) for never smokers in Japan and the United States.

METHODS

We developed a state-transition model for three strategies: LDCT, chest X-ray (CXR), and no screening, using a healthcare payer perspective over a lifetime horizon. Sensitivity analyses were also performed. Main outcomes were costs, quality-adjusted life-years (QALYs), life expectancy life-years (LYs), incremental cost-effectiveness ratios (ICERs), and deaths from lung cancer. The willingness-to-pay level was US$100,000 per QALY gained.

RESULTS

LDCT yielded the greatest benefits with the lowest cost in Japan, but the ICERs of LDCT compared with CXR were US$3,001,304 per QALY gained for American men and US$2,097,969 per QALY gained for American women. Cost-effectiveness was sensitive to the incidence of lung cancer. Probabilistic sensitivity analyses demonstrated that LDCT was cost-effective 99.3-99.7% for Japanese, no screening was cost-effective 77.7% for American men, and CXR was cost-effective 93.2% for American women. Compared with CXR, LDCT has the cumulative lifetime potential for 60-year-old Japanese to save US$117 billion, increase 2,339,349 QALYs and 3,020,102 LYs, and reduce 224,749 deaths, and the potential for 60-year-old Americans to cost US$120 billion, increase 48,651 QALYs and 67,988 LYs, and reduce 2,309 deaths.

CONCLUSIONS

This modelling study suggests that LDCT screening for never smokers has the greatest benefits and cost savings in Japan, but is not cost-effective in the United States. Assessing the risk of lung cancer in never smokers is important for introducing population-based LDCT screening.

Lung cancer pathogenesis and poor response to therapy were dependent on driver oncogenic mutations

AIMS

Lung cancer was the most fatal malignancy, dominated the cancer related mortality list for years, and we tried to distinguish the lung adenocarcinoma patients at higher risk from those bearing lower therapy resistance and recurrence risk.

MATERIALS

Patients information from clinical Sequencing Cohorts and from the Regional Medical Center of the Middle-West China were included. The whole-exome sequencing was analyzed for risk evaluation.

KEY FINDINGS

We found that Smoking stimulated the oncogenic genes mutations, and the most frequently mutated genes of EGFR, KRAS, and TP53 (E/K/P) were identified. Different N stage affected the survival prognosis of patients bearing E/K/P mutations, but the T stage and AJCC stage did not. Radiation failed to prolong survival of phase II/III patients who didn't receive surgery. In those received surgery, radiation also failed to prolong survival of phase II/III patients. Radiation did not improve the prognosis in patients bearing E/K/P mutation burdens, whose differences were identified in gender or smoking-history classified groups.

SIGNIFICANCE

Smoking status and history contributed to oncogenic mutation burdens associated therapy resistance, and the aggressive treatment, especially to radiation, may lead to worse therapy response to current and past smoking behavior.

Research on lung cancer and its funding, 2004-2018

Although smoking is declining in high-income countries, the relative burden from its most well-known consequence, lung cancer, continues to increase, especially in low-income countries. We examined the amount, types, geographical origins and funding of research on lung cancer as revealed by papers in the Web of Science over the 15 years, 2004–2018. The annual number of lung cancer research papers increased over the study period from 2,157 to 8,202, but as a percentage of all biomedical research in Western Europe and North America they only accounted for one-eighth of the percentage of the disease burden. Lung cancer increased its share of cancer research from 4.4% to 6.5%, mainly because of the greatly expanded output from China in 2014–2018 which published almost one-third of the world’s total on a fractional count basis. For almost all other countries, their lung cancer presence in cancer research has declined over the 15 years. However, only 15% of the Chinese papers were co-authored internationally and its research was focussed on treatment rather than prevention. Support for lung cancer research is primarily from the government rather than charity. There is therefore an urgent need to increase support for lung cancer research, and for more international collaboration, especially in low-income countries where the disease burden is growing rapidly, and in neglected domains, such as screening and palliative care.