A comparative study of the risk factors for lung cancer in Guangdong, China

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.

Lung cancer occurrence after an episode of tuberculosis: a systematic review and meta-analysis

INTRODUCTION

People with tuberculosis experience long-term health effects beyond cure, including chronic respiratory diseases. We investigated whether tuberculosis is a risk factor for subsequent lung cancer.

METHODS

We searched PubMed, Scopus, Cochrane, Latin American and Caribbean Health Sciences Literature and the Scientific Electronic Library Online for cohort and case-control studies providing effect estimates for the association between tuberculosis and subsequent lung cancer. We pooled estimates through random-effects meta-analysis. The study was registered in PROSPERO (CDR42020178362).

RESULTS

Out of 6240 records, we included 29 cohort and 44 case-control studies. Pooled estimates adjusted for age and smoking (assessed quantitatively) were hazard ratio (HR) 1.51 (95% CI 1.30-1.76, I²=81%; five studies) and OR 1.74 (95% CI 1.42-2.13, I²=59%; 19 studies). The occurrence of lung cancer was increased for 2 years after tuberculosis diagnosis (HR 5.01, 95% CI 3.64-6.89; two studies), but decreased thereafter. Most studies were retrospective, had moderate to high risk of bias, and did not control for passive smoking, environmental exposure and socioeconomic status. Heterogeneity was high.

CONCLUSION

We document an association between tuberculosis and lung cancer occurrence, particularly in, but not limited to, the first 2 years after tuberculosis diagnosis. Some cancer cases may have been present at the time of tuberculosis diagnosis and therefore causality cannot be ascertained. Prospective studies controlling for key confounding factors are needed to identify which tuberculosis patients are at the highest risk, as well as cost-effective approaches to mitigate such risk.

Multidrug Resistance in Cancer: Understanding Molecular Mechanisms, Immunoprevention and Therapeutic Approaches

Cancer is one of the leading causes of death worldwide. Several treatments are available for cancer treatment, but many treatment methods are ineffective against multidrug-resistant cancer. Multidrug resistance (MDR) represents a major obstacle to effective therapeutic interventions against cancer. This review describes the known MDR mechanisms in cancer cells and discusses ongoing laboratory approaches and novel therapeutic strategies that aim to inhibit, circumvent, or reverse MDR development in various cancer types. In this review, we discuss both intrinsic and acquired drug resistance, in addition to highlighting hypoxia- and autophagy-mediated drug resistance mechanisms. Several factors, including individual genetic differences, such as mutations, altered epigenetics, enhanced drug efflux, cell death inhibition, and various other molecular and cellular mechanisms, are responsible for the development of resistance against anticancer agents. Drug resistance can also depend on cellular autophagic and hypoxic status. The expression of drug-resistant genes and the regulatory mechanisms that determine drug resistance are also discussed. Methods to circumvent MDR, including immunoprevention, the use of microparticles and nanomedicine might result in better strategies for fighting cancer.

Epstein–Barr Virus Infection in Lung Cancer: Insights and Perspectives

Lung cancer (LC) is the leading cause of cancer death worldwide. Tobacco smoke is the most frequent risk factor etiologically associated with LC, although exposures to other environmental factors such as arsenic, radon or asbestos are also involved. Additionally, the involvement of some viral infections such as high-risk human papillomaviruses (HR-HPVs), Merkel cell polyomavirus (MCPyV), Jaagsiekte Sheep Retrovirus (JSRV), John Cunningham Virus (JCV), and Epstein–Barr virus (EBV) has been suggested in LC, though an etiological relationship has not yet been established. EBV is a ubiquitous gamma herpesvirus causing persistent infections and some lymphoid and epithelial tumors. Since EBV is heterogeneously detected in LCs from different parts of the world, in this review we address the epidemiological and experimental evidence of a potential role of EBV. Considering this evidence, we propose mechanisms potentially involved in EBV-associated lung carcinogenesis. Additional studies are warranted to dissect the role of EBV in this very frequent malignancy.

Lung cancer in never smokers-the East Asian experience

Approximately one third of all lung cancer patients in East Asia are never-smokers. Furthermore, the proportion of lung cancer in never smokers (LCINS) has been increasing over time. Never-smokers are more often diagnosed with adenocarcinoma in East Asia, a subtype largely defined by oncogenic drivers. In this subgroup of patients, as high as 90% of patients have been found to harbor well-known oncogenic mutations and can be successfully managed with targeted therapies inhibiting specific oncogenic mutant kinases. EGFR tyrosine kinase inhibitor (EGFR-TKI) treatment has been the most important targeted therapy in lung adenocarcinoma from East Asian never-smokers as approximately 70% of these patients have the opportunity to receive EGFR-TKI treatment. Lung squamous cell carcinoma (SQCC) and small cell lung cancer (SCLC) are two common histologic types of smoking-related non-small cell lung cancer (NSCLC). The proportion of never-smokers with SQCC and SCLC in East Asian patients seems to be higher than that in Caucasian patients. Recent studies also suggest that lung SQCC and SCLC in never-smokers may be distinct subtypes. Therefore, better understanding of the biologic characteristics of these subtypes of patients may provide new insights for the treatment. In this review, we will provide an overview of East Asian experience in the treatment of advanced, never-smoking lung cancer, focusing on etiologic factors in the development of LCINS, targeted therapy for never-smokers with adenocarcinoma, distinct characteristics of never-smokers with lung SQCC and SCLC, and the role of immunotherapy in never-smokers with NSCLC.

Histology-dependent prognostic role of pERK and p53 protein levels in early-stage non-small cell lung cancer

Lung tumors represent a major health problem. In early stage NSCLC tumors, surgical resection is the preferred treatment, but 30-55% of patients will relapse within 5 years after surgery. Thus, the identification of prognostic biomarkers in early stage NSCLC patients, especially those which are therapeutically addressable, is crucial to enhance survival of these patients. We determined the immunohistochemistry expression of key proteins involved in tumorigenesis and oncogenic signaling, p53, EGFR, pAKT and pERK, and correlated their expression level to clinicopathological characteristics and patient outcome. We found EGFR expression is higher in the squamous cell carcinomas than in adenocarcinomas (p=0.043), and that nuclear p53 staining correlated with lower differentiated squamous tumors (p=0.034). Regarding the prognostic potential of the expression of these proteins, high pERK levels proved to be an independent prognostic factor for overall (p<0.001) and progression-free survival (p<0.001) in adenocarcinoma patients, but not in those from the squamous histology, and high p53 nuclear levels were identified as independent prognostic factor for progression-free survival (p=0.031) only in squamous cell carcinoma patients. We propose a role as early prognostic biomarkers for pERK protein levels in adenocarcinoma, and for nuclear p53 levels in squamous cell lung carcinoma. The determination of these potential biomarkers in the adequate histologic context may predict the outcome of early stage NSCLC patients, and may offer a therapeutic opportunity to enhance survival of these patients.

Tuberculosis, smoking and risk for lung cancer incidence and mortality

Among the exposures associated with risk for lung cancer, a history of tuberculosis (TB) is one potentially important factor, given the high prevalence of TB worldwide. A prospective cohort study was conducted to evaluate the associations of preexisting pulmonary TB with lung cancer incidence and mortality. The cohort consisted of 1,607,710 Korean adults covered by the National Health Insurance System who had a biennial national medical examination during 1997-2000. During up to 16 years of follow-up, there were 12,819 incident cases of lung cancer and 9,562 lung cancer deaths. Using Cox proportional hazards models and controlling for age, cigarette smoking and other covariates, the presence of underlying TB was significantly associated with increased risk for lung cancer incidence (HR 1.37 in men with 95% CI 1.29-1.45; HR 1.49 in women with 95% CI 1.28-1.74) and mortality (HR 1.43 in men with 95% CI 1.34-1.52; HR 1.53 in women with 95% CI 1.28-1.83). We also observed a dose-response relationship between number of cigarettes smoked daily and lung cancer risk. There was no evidence for synergism between a history of TB and smoking. The elevation in risk is relatively modest, particularly in comparison to that from smoking, and a prior history of TB is not likely to be useful risk indicator for clinical purposes. In populations with high prevalence of TB, it can be considered for incorporation into models for lung cancer risk prediction.

Environmental tobacco smoke exposure and lung cancer: A systematic review

AIM: To review evidence relating passive smoking to lung cancer risk in never smokers, considering various major sources of bias.

METHODS: Epidemiological prospective or case-control studies were identified which provide estimates of relative risk (RR) and 95%CI for never smokers for one or more of seven different indices of exposure to environmental tobacco smoke (ETS): The spouse; household; workplace; childhood; travel; social and other; and total. A wide range of study details were entered into a database, and the RRs for each study, including descriptions of the comparisons made, were entered into a linked database. RRs were derived where necessary. Results were entered, where available, for all lung cancer, and for squamous cell cancer and adenocarcinoma. “Most adjusted” results were entered based on results available, adjusted for the greatest number of potential confounding variables. “Least adjusted” results were also entered, with a preference for results adjusted at least for age for prospective studies. A pre-planned series of fixed-effects and random-effects meta-analyses were conducted. Overall analyses and analyses by continent were run for each exposure index, with results for spousal smoking given by sex, and results for childhood exposure given by source of ETS exposure. For spousal exposure, more extensive analyses provide results by various aspects of study design and definition of the RR. For smoking by the husband (or nearest equivalent), additional analyses were carried out both for overall risk, and for risk per 10 cigarettes per day smoked by the husband. These adjusted for uncontrolled confounding by four factors (fruit, vegetable and dietary fat consumption, and education), and corrected for misclassification of smoking status of the wife. For the confounding adjustment, estimates for never smoking women were derived from publications on the relationship of the four factors to both lung cancer risk and at home ETS exposure, and on the correlations between the factors. The bias due to misclassification was calculated on the basis that the proportion of ever smokers denying smoking is 10% in Asian studies and 2.5% elsewhere, and that those who deny smoking have the same risk as those who admit it. This approach, justified in previous work, balances higher true denial rates and lower risk in deniers compared to non-deniers.

RESULTS: One hundred and two studies were identified for inclusion, published in 1981 onwards, 45 in Asia, 31 in North America, 21 in Europe, and five elsewhere. Eighty-five were of case-control design and 17 were prospective. Significant (P < 0.05) associations were noted, with random-effects of (RR = 1.22, 95%CI: 1.14-1.31, n = 93) for smoking by the husband (RR = 1.14, 95%CI: 1.01-1.29, n = 45) for smoking by the wife (RR = 1.22, 95%CI: 1.15-1.30, n = 47) for workplace exposure (RR = 1.15, 95%CI: 1.02-1.29, n = 41) for childhood exposure, and (RR = 1.31, 95%CI: 1.19-1.45, n = 48) for total exposure. No significant association was seen for ETS exposure in travel (RR = 1.34, 95%CI: 0.94-1.93, n = 8) or in social situations (RR = 1.01, 95%CI: 0.82-1.24, n = 15). A significant negative association (RR = 0.78, 95%CI: 0.64-0.94, n = 8) was seen for ETS exposure in childhood, specifically from the parents. Significant associations were also seen for spousal smoking for both squamous cell carcinoma (RR = 1.44, 95%CI: 1.15-1.80, n = 24) and adenocarcinoma (RR = 1.33, 95%CI: 1.17-1.51, n = 30). Results generally showed marked heterogeneity between studies. For smoking by either the husband or wife, where 119 RR estimates gave an overall estimate of (RR = 1.21, 95%CI: 1.14-1.29), the heterogeneity was highly significant (P < 0.001), with evidence that the largest RRs were seen in studies published in 1981-89, in small studies (1-49 cases), and for estimates unadjusted by age. For smoking by the husband, the additional analyses showed that adjustment for the four factors reduced the overall (RR = 1.22, 95%CI: 1.14-1.31) based on 93 estimates to (RR = 1.14, 95%CI: 1.06-1.22), implying bias due to uncontrolled confounding of 7%. Further correction for misclassification reduced the estimate to a marginally non-significant (RR = 1.08, 95%CI: 0.999-1.16). In the fully adjusted and corrected analyses, there was evidence of an increase in Asia (RR = 1.18, 95%CI: 1.07-1.30, n = 44), but not in other regions (RR = 0.96, 95%CI: 0.86-1.07, n = 49). Studies published in the 1980’s, studies providing dose-response data, and studies only providing results unadjusted for age showed elevated RRs, but later published studies, studies not providing dose-response data, and studies adjusting for age did not. The pattern of results for RRs per 10 cigs/d was similar, with no significant association in the adjusted and corrected results (RR = 1.03, 95%CI: 0.994-1.07).

CONCLUSION: Most, if not all, of the ETS/lung cancer association can be explained by confounding adjustment and misclassification correction. Any causal relationship is not convincingly demonstrated.

COPD-related adenocarcinoma presents low aggressiveness morphological and molecular features compared to smoker tumours

OBJECTIVES

Adenocarcinoma comprises a group of diseases with heterogeneous clinical and molecular characteristics. COPD and lung cancer are strictly related; to date it is unknown if COPD-associated cancers have different features from tumours arising in non-COPD patients. Our aim was to study COPD-associated adenocarcinoma phenotypes mainly focusing on morphological and molecular aspects, in comparison to smoke-related cancer without COPD.

MATERIALS AND METHODS

From 2010 to 2013, 54 patients with adenocarcinoma (20 COPD and 34 smokers) were prospectively studied. Each patient underwent a complete clinical and instrumental assessment. Morphological studies included analysis of growth pattern, cell proliferation (Ki-67/MIB1 expression) and parameters of intra- and peri-tumoral remodelling (inflammation, fibrosis and necrosis). Genetic analysis of EGFR and KRAS mutations was also performed.

RESULTS

The two groups were comparable for the main demographic and biohumoral parameters except for increased blood basophil cell count in the COPD group. Compared to COPD, tumours of smokers presented an increased percentage of solid component (median: 20% vs 5%, p=0.02), a reduced percentage of lepidic pattern (median: 0% vs 10%, p=0.06) and higher Ki-67/MIB1 median value (55% vs 30%, p=0.02). In multivariate analysis lepidic and solid histological pattern were significantly influenced by clinical group (p=0.03 and 0.05, respectively). Concerning EGFR mutation, no differences were found between groups while KRAS mutation presented a trend of higher percentage in smokers compared to COPD (41% vs 20%, p=NS). Adenocarcinoma with KRAS mutation showed a higher value of Ki-67/MIB1 (65% vs 35%, p=0.048) and prevalent solid pattern (35% vs 10%, p=0.019) in comparison to wild-type form.

CONCLUSIONS

COPD-related adenocarcinoma presents molecular and morphological features of lower aggressiveness (increased lepidic component, reduced solid pattern, lower cell proliferation and less frequent KRAS mutation) compared to smokers. Different molecular mechanisms could be associated with the development of COPD associated cancer.

Attributable fraction of tobacco smoking on cancer using population-based nationwide cancer incidence and mortality data in Korea

Background

Smoking is by far the most important cause of cancer that can be modified at the individual level. Cancer incidence and mortality rates in Korea are the highest among all Asian countries, and smoking prevalence in Korean men is one of the highest in developed countries. The purpose of the current study was to perform a systematic review and provide an evidence-based assessment of the burden of tobacco smoking-related cancers in the Korean population.

Methods

Sex- and cancer-specific population-attributable fractions (PAF) were estimated using the prevalence of ever-smoking and second-hand smoking in 1989 among Korean adults, respectively, and the relative risks were estimated from the meta-analysis of studies performed in the Korean population for ever-smoking and in the Asian population for passive smoking. National cancer incidence data from the Korea Central Cancer Registry and national cancer mortality data from Statistics Korea for the year 2009 were used to estimate the cancer cases and deaths attributable to tobacco smoking.

Results

Tobacco smoking was responsible for 20,239 (20.9%) cancer incident cases and 14,377 (32.9%) cancer deaths among adult men and 1,930 (2.1%) cancer incident cases and 1,351 (5.2%) cancer deaths among adult women in 2009 in Korea. In men, 71% of lung cancer deaths, 55%–72% of upper aerodigestive tract (oral cavity, pharynx, esophagus and larynx) cancer deaths, 23% of liver, 32% of stomach, 27% of pancreas, 7% of kidney and 45% of bladder cancer deaths were attributable to tobacco smoking. In women the proportion of ever-smoking-attributable lung cancer was 8.1%, while that attributable to second-hand smoking among non-smoking women was 20.5%.

Conclusions

Approximately one in three cancer deaths would be potentially preventable through appropriate control of tobacco smoking in Korean men at the population level and individual level. For Korean women, more lung cancer cases and deaths were attributable to second-hand than ever-smoking. Effective control programs against tobacco smoking should be further developed and implemented in Korea to reduce the smoking-related cancer burden.

Fish consumption and lung cancer risk: systematic review and meta-analysis

There is evidence pointing to a possible role of diet on cancer etiology. Prior studies evaluating the relationship between fish consumption and lung cancer risk reported inconclusive results. The aim of this study was to achieve a comprehensive assessment of the relationship between fish consumption and lung cancer risk through systematic review and meta-analysis. Case control and cohort studies up to September 1, 2012 about fish consumption and lung cancer risk were confirmed by an online search. Separate relative risk (RR) or odds ratio (OR) estimates with 95% confidence interval (CI) of the relationship between lung cancer risk and fish consumption level from the included articles were combined by Stata11.0 software. Publication bias was evaluated by Egger's linear regression test and funnel plot. Twenty articles (17 case-control and 3 cohort studies) comprising 8799 cases of lung cancer and 17,072 noncases were included in the final analysis. The pooled results from all studies indicated that high fish consumption was significantly associated with a decreased risk of lung cancer (pooled RR: 0.79; 95% CI: 0.69-0.92). There was heterogeneity among the studies (I(2) = 73%, P < 0.05). Pooled RR in case control and cohort studies were 0.76 (95% CI: 0.63-0.91) and 0.95 (95% CI: 0.73-1.24), respectively. Omission of any single study had little effect on the combined risk estimates. This article had no publication bias. This study identifies a significant association between fish consumption and lung cancer, confirming a protective role of fish in lung cancer. More well-designed prospective studies are required to further verify the effect of fish consumption on lung cancer.

Association between chronic obstructive pulmonary disease and lung cancer: a case-control study in Southern Chinese and a meta-analysis

Background

Lung cancer and chronic obstructive pulmonary disease (COPD) share a common risk factor in cigarette smoking and a large portion of patients with lung cancer suffer from COPD synchronously. We therefore hypothesized that COPD is an independent risk factor for lung cancer. Our aim was to investigate the intrinsic linkage of COPD (or emphysema, chronic bronchitis and asthma) and lung cancer.

Methods

The present hospital-based case-control study included 1,069 patients with newly diagnosed lung cancer and 1,132 age frequency matched cancer-free controls. The odds ratios (ORs) for the associations between each previous pulmonary disease and lung cancer were estimated with logistic regression models, adjusting for age, sex, family history of cancer, BMI and pack year smoking. In meta-analysis, the pooled effects of previous pulmonary diseases were analyzed with random effects models; and stratification analyses were conducted on smoking status and ethnicity.

Results

In the case-control study, previous COPD was associated with the odds for increased risk of lung cancer (OR = 1.29, 95% confidence interval [CI] = 1.00∼1.68); so were emphysema (OR = 1.55, 95%CI = 1.03∼2.32) and chronic bronchitis (OR = 1.22, 95%CI = 0.99∼1.67); while asthma was associated with odds for decreased risk of lung cancer (OR = 0.29, 95%CI = 0.16∼0.53). These associations were more pronounced in smokers (P<.05 for all strata), but not in non-smokers. In meta-analysis, 35 studies (22,010 cases and 44,438 controls) were identified. COPD was significantly associated with the odds for increased risk of lung cancer (pooled OR = 2.76; 95% CI = 1.85–4.11), so were emphysema (OR = 3.02; 95% CI = 2.41–3.79) and chronic bronchitis (OR = 1.88; 95% CI = 1.49–2.36); and these associations were more pronounced in smokers than in non-smokers (P<.001 respectively). No significant association was observed for asthma.

Conclusion

Previous COPD could increase the risk of lung cancer, especially in smokers.

Systematic review with meta-analysis of the epidemiological evidence in the 1900s relating smoking to lung cancer

BACKGROUND

Smoking is a known lung cancer cause, but no detailed quantitative systematic review exists. We summarize evidence for various indices.

METHODS

Papers published before 2000 describing epidemiological studies involving 100+ lung cancer cases were obtained from Medline and other sources. Studies were classified as principal, or subsidiary where cases overlapped with principal studies. Data were extracted on design, exposures, histological types and confounder adjustment. RRs/ORs and 95% CIs were extracted for ever, current and ex smoking of cigarettes, pipes and cigars and indices of cigarette type and dose-response. Meta-analyses and meta-regressions investigated how relationships varied by study and RR characteristics, mainly for outcomes exactly or closely equivalent to all lung cancer, squamous cell carcinoma ("squamous") and adenocarcinoma ("adeno").

RESULTS

287 studies (20 subsidiary) were identified. Although RR estimates were markedly heterogeneous, the meta-analyses demonstrated a relationship of smoking with lung cancer risk, clearly seen for ever smoking (random-effects RR 5.50, CI 5.07-5.96) current smoking (8.43, 7.63-9.31), ex smoking (4.30, 3.93-4.71) and pipe/cigar only smoking (2.92, 2.38-3.57). It was stronger for squamous (current smoking RR 16.91, 13.14-21.76) than adeno (4.21, 3.32-5.34), and evident in both sexes (RRs somewhat higher in males), all continents (RRs highest for North America and lowest for Asia, particularly China), and both study types (RRs higher for prospective studies). Relationships were somewhat stronger in later starting and larger studies. RR estimates were similar in cigarette only and mixed smokers, and similar in smokers of pipes/cigars only, pipes only and cigars only. Exceptionally no increase in adeno risk was seen for pipe/cigar only smokers (0.93, 0.62-1.40). RRs were unrelated to mentholation, and higher for non-filter and handrolled cigarettes. RRs increased with amount smoked, duration, earlier starting age, tar level and fraction smoked and decreased with time quit. Relationships were strongest for small and squamous cell, intermediate for large cell and weakest for adenocarcinoma. Covariate-adjustment little affected RR estimates.

CONCLUSIONS

The association of lung cancer with smoking is strong, evident for all lung cancer types, dose-related and insensitive to covariate-adjustment. This emphasises the causal nature of the relationship. Our results quantify the relationships more precisely than previously.

Previous lung diseases and lung cancer risk: a systematic review and meta-analysis

BACKGROUND

In order to review the epidemiologic evidence concerning previous lung diseases as risk factors for lung cancer, a meta-analysis and systematic review was conducted.

METHODS

Relevant studies were identified through MEDLINE searches. Using random effects models, summary effects of specific previous conditions were evaluated separately and combined. Stratified analyses were conducted based on smoking status, gender, control sources and continent.

RESULTS

A previous history of COPD, chronic bronchitis or emphysema conferred relative risks (RR) of 2.22 (95% confidence interval (CI): 1.66, 2.97) (from 16 studies), 1.52 (95% CI: 1.25, 1.84) (from 23 studies) and 2.04 (95% CI: 1.72, 2.41) (from 20 studies), respectively, and for all these diseases combined 1.80 (95% CI: 1.60, 2.11) (from 39 studies). The RR of lung cancer for subjects with a previous history of pneumonia was 1.43 (95% CI: 1.22-1.68) (from 22 studies) and for subjects with a previous history of tuberculosis was 1.76 (95% CI=1.49, 2.08), (from 30 studies). Effects were attenuated when restricting analysis to never smokers only for COPD/emphysema/chronic bronchitis (RR=1.22, 0.97-1.53), however remained significant for pneumonia 1.36 (95% CI: 1.10, 1.69) (from 8 studies) and tuberculosis 1.90 (95% CI: 1.45, 2.50) (from 11 studies).

CONCLUSIONS

Previous lung diseases are associated with an increased risk of lung cancer with the evidence among never smokers supporting a direct relationship between previous lung diseases and lung cancer.

Lower risk of lung cancer after multiple pneumonia diagnoses

BACKGROUND

Although pneumonia has been suggested as a risk factor for lung cancer, previous studies have not evaluated the influence of number of pneumonia diagnoses in relation to lung cancer risk.

METHODS

The Environment And Genetics in Lung cancer Etiology (EAGLE) population-based study of 2,100 cases and 2,120 controls collected information on pneumonia more than 1 year before enrollment from 1,890 cases and 2,078 controls.

RESULTS

After adjusting for study design variables, smoking, and chronic bronchitis, pneumonia was associated with decreased risk of lung cancer [odds ratio (OR), 0.79; 95% confidence interval (CI), 0.64-0.97], especially among individuals with three or more diagnoses versus none (OR, 0.35; 95% CI, 0.16-0.75). Adjustment for chronic bronchitis contributed to this inverse association. In comparison, pulmonary tuberculosis was not associated with lung cancer (OR, 0.96; 95% CI, 0.62-1.48).

CONCLUSIONS

The apparent protective effect of pneumonia among individuals with multiple pneumonia diagnoses may reflect an underlying difference in immune response and requires further investigation and confirmation. Therefore, careful evaluation of the number of pneumonia episodes may shed light on lung cancer etiology.

Facts and fiction of the relationship between preexisting tuberculosis and lung cancer risk: a systematic review

There has been conflicting evidence concerning the possible association between tuberculosis (TB) and subsequent risk of lung cancer. To investigate whether currently published epidemiological studies can clarify this association, we performed a systematic review of 37 case-control and 4 cohort studies (published between January 1966 and January 2009) and a meta-analysis of risk estimates, with particular attention to the role of smoking, passive smoking and the timing of diagnosis of TB on this relationship. Data for the review show a significantly increased lung cancer risk associated with preexisting TB. Importantly, the association was not due to confounding by the effects of tobacco use (RR=1.8, 95% confidence interval (CI)=1.4-2.2, among never smoking individuals), lifetime environmental tobacco smoke exposure (RR=2.9, 95%CI=1.6-5.3, after controlling) or the timing of diagnosis of TB (the increased lung cancer risk remained 2-fold elevated for more than 20 years after TB diagnosis). Interestingly, the association was significant with adenocarcinoma (RR=1.6, 95%CI=1.2-2.1), but no significant associations with squamous and small cell type of lung cancer were observed. Although no causal mechanism has been demonstrated for such an association, present study supports a direct relation between TB and lung cancer, especially adenocarcinomas.

Chronic obstructive pulmonary disease and altered risk of lung cancer in a population-based case-control study

Background

Chronic obstructive pulmonary disease (COPD) has been consistently associated with increased risk of lung cancer. However, previous studies have had limited ability to determine whether the association is due to smoking.

Methodology/Principal Findings

The Environment And Genetics in Lung cancer Etiology (EAGLE) population-based case-control study recruited 2100 cases and 2120 controls, of whom 1934 cases and 2108 controls reported about diagnosis of chronic bronchitis, emphysema, COPD (chronic bronchitis and/or emphysema), or asthma more than 1 year before enrollment. We estimated odds ratios (OR) and 95% confidence intervals (CI) using logistic regression. After adjustment for smoking, other previous lung diseases, and study design variables, lung cancer risk was elevated among individuals with a history of chronic bronchitis (OR = 2.0, 95% CI = 1.5–2.5), emphysema (OR = 1.9, 95% CI = 1.4–2.8), or COPD (OR = 2.5, 95% CI = 2.0–3.1). Among current smokers, association between chronic bronchitis and lung cancer was strongest among lighter smokers. Asthma was associated with a decreased risk of lung cancer in males (OR = 0.48, 95% CI = 0.30–0.78).

Conclusions/Significance

These results suggest that the associations of personal history of chronic bronchitis, emphysema, and COPD with increased risk of lung cancer are not entirely due to smoking. Inflammatory processes may both contribute to COPD and be important for lung carcinogenesis.

Survival after surgery in stage IA and IB non-small cell lung cancer

RATIONALE

Whether histologic subtype of non-small cell lung cancer (NSCLC) has an important effect on prognosis after surgery is unknown.

OBJECTIVES

We hypothesized that we could predict mortality more effectively by integrating precise tumor size and histology rather than relying on conventional staging.

METHODS

We used the SEER (Surveillance, Epidemiology, and End Results) registry. Inclusion criteria were as follows: (1) primary squamous cell or adenocarcinoma; (2) potentially curative surgery, defined as a lobectomy or bilobectomy; (3) lymph node dissection performed; and (4) pathologic stage IA or IB.

MEASUREMENTS AND MAIN RESULTS

From 1988 to 2000, 7,965 patients were included. For both all-cause and lung cancer-associated mortality, tumor size demonstrated the strongest association (log-rank P < 0.0001 for each). When tumors were small (</=2 cm), lung cancer-associated mortality was similar for adenocarcinoma when compared with squamous cell carcinoma. When tumors were 3 cm or larger in size, lung cancer-associated mortality was higher for adenocarcinoma. The increased risk of lung cancer-associated mortality with adenocarcinoma was more pronounced in those younger than 65 years. Survival prediction using precise size and histology had much better discriminatory power than conventional TNM (tumor-node-metastasis) staging (P = 0.005).

CONCLUSIONS

Staging that takes into account size, histology, late recurrence risk, and patient age is more accurate than the current TNM system and is clinically relevant because improved prediction can facilitate better decisions on the use of adjuvant chemotherapy.

Meta-analysis of studies of passive smoking and lung cancer: effects of study type and continent

BACKGROUND

To calculate a pooled estimate of relative risk (RR) of lung cancer associated with exposure to passive smoking in never smoking women exposed to smoking spouses. This study is an updated meta-analysis that also assesses the differences between estimated risks according to continent and study type using meta-regression.

METHODS

From a total of 101 primary studies, 55 studies are included in this meta-analysis, of which, 7 are cohort studies, 25 population-based case-control and 23 non-population-based case-control studies. Twenty previously published meta-analyses are also reviewed. Fixed and random effect models and meta-regression are used to obtain pooled estimates of RR and P-value functions are used to demonstrate consistency of results.

RESULTS

The pooled RR for never-smoking women exposed to passive smoking from spouses is 1.27 (95% CI 1.17-1.37). The RR for North America is 1.15 (95% CI 1.03-1.28), Asia, 1.31 (95% CI 1.16-1.48) and Europe, 1.31 (1.24-1.52). Sequential cumulative meta-analysis shows no trend. There is no strong evidence of publication bias.

CONCLUSIONS

The abundance of evidence, consistency of finding across continent and study type, dose-response relationship and biological plausibility, overwhelmingly support the existence of a causal relationship between passive smoking and lung cancer.

Epidermal growth factor receptor mutations and their correlation with gefitinib therapy in patients with non-small cell lung cancer: a meta-analysis based on updated individual patient data from six medical centers in mainland China

BACKGROUND

Convincing data on epidermal growth factor receptor (EGFR) mutations in Chinese patients with non-small-cell lung cancer (NSCLC) remain limited. We investigated the relevance of demographic characteristics and EGFR mutations, correlations between the efficacy of gefitinib and EGFR mutations in NSCLC, and to identify individuals who would likely benefit from gefitinib.

METHODS

We conducted a meta-analysis based on updated individual patient data from six medical centers in mainland China. Outcome measures included the EGFR mutation status, demographic characteristics, response, and survival.

RESULTS

Among 506 patients with NSCLC who received EGFR mutation analysis, the EGFR mutation rate was 30.04%. Patients with adenocarcinoma had a higher mutation rate than those with non-adenocarcinoma (44.1% vs 9.2%; p < 0.00001). The EGFR mutation rate for smokers was 15.1%, lower than that for non-smokers (45.5%) (p < 0.00001). Male patients had a lower mutation rate than female patients (23.1% vs 42.9%; p < 0.0001). Multivariate analysis showed that "adenocarcinoma" and "non-smoker" were independent predictors of EGFR mutations. In a subgroup of 57 patients with complete treatment data, the response rate to gefitinib in the EGFR mutant group was 60.7%, significantly higher than that in the wild-type EGFR group (17.2%) (odds ratio, 5.78; 95% CI, 1.95-17.13; p = 0.002). "EGFR mutation", "adenocarcinoma," and "non-smoker" were independent predictors of response. Overall survival in the EGFR mutant group and the wild-type group did not differ significantly (hazard ratio, 0.60; 95% CI, 0.32-1.12; p = 0.110). "Adenocarcinoma status" was an independent prognostic factor for survival.

CONCLUSIONS

In mainland China, "adenocarcinoma" and "non-smoker" are independent predictors for EGFR mutations. Response to gefitinib favors patients with EGFR mutations. The clinical selected populations for gefitinib are non-smokers with adenocarcinoma.

Lung Cancer in Never Smokers: A Review

Lung cancer is the leading cause of cancer-related death in the United States. Although tobacco smoking accounts for the majority of lung cancer, approximately 10% of patients with lung cancer in the United States are lifelong never smokers. Lung cancer in the never smokers (LCINS) affects women disproportionately more often than men. Only limited data are available on the etiopathogenesis, molecular abnormalities, and prognosis of LCINS. Several etiologic factors have been proposed for the development of LCINS, including exposure to radon, cooking fumes, asbestos, heavy metals, and environmental tobacco smoke, human papillomavirus infection, and inherited genetic susceptibility. However, the relative significance of these individual factors among different ethnic populations in the development of LCINS has not been well-characterized. Adenocarcinoma is the predominant histologic subtype reported with LCINS. Striking differences in response rates and outcomes are seen when patients with advanced non–small-cell lung cancer (NSCLC) who are lifelong never smokers are treated with epidermal growth factor receptor tyrosine kinase (EGFR-TK) inhibitors such as gefitinib or erlotinib compared with the outcomes with these agents in patients with tobacco-associated lung cancer. Interestingly, the activating mutations in the EGFR-TK inhibitors have been reported significantly more frequently in LCINS than in patients with tobacco-related NSCLC. This review will summarize available data on the epidemiology, risk factors, molecular genetics, management options, and outcomes of LCINS.

Air pollution and lung cancer risks in China--a meta-analysis

Lung cancer is a serious health problem in China, as in the rest of the world. Many studies have already proved that air pollution as well as other environmental factors can increase the risk of lung cancer. Based on epidemiological studies carried out in China, this paper proposes odds ratios (OR) to evaluate the risk of lung cancer from indoor air pollution for the Chinese population by applying the method of meta-analysis. For domestic coal use for heating and cooking, the pooled OR values are 1.83 (95% CI: 0.62-5.41) and 2.66 (1.39-5.07) for women and both sexes, respectively. For indoor exposure to coal dust, the OR values are 2.52 (95% CI: 1.94-3.28) and 2.42 (1.62-3.63) for women and both sexes, respectively. Cooking oil vapor is another factor increasing lung cancer risk. The OR values are 2.12 (95%CI: 1.81-2.47), 1.78 (1.50-2.12) and 6.20 (2.88-13.32) for nonsmoking women, women, and both sexes, respectively. Regarding environmental tobacco smoke, the pooled OR values are 1.70 (95% CI: 1.32-2.18) and 1.64 (1.29-2.07) for nonsmoking women and both sexes, respectively. Funnel plots with statistical test have been applied to examine the publication bias, and the results implied that the analysis of coal consumption and cooking oil pollution might be affected by publication bias. The meta-analysis results confirm the association between lung cancer and indoor air pollution for the Chinese population.

Smoking-adjusted lung cancer incidence among Asian-Americans (United States)

OBJECTIVE

Chinese women residing in Asia and Hawaii have low consumption of tobacco but a high incidence of lung cancer. To explore this question further, we conducted a study of lung cancer among Chinese women residing in mainland US.

METHODS

Using data from NCI's SEER program, we identified residents of Los Angeles County, the San Francisco Metropolitan Area, and the Seattle-Puget Sound Area who were 50 years or older, diagnosed with cancer of the lung or bronchus in 1999-2001, with race specified as non-Hispanic white (n = 18,493), Chinese (n = 853), Filipino (n = 615), or Japanese (n = 282). The sex-specific observed number of lung cancer cases among each Asian sub-group was compared to the expected number of lung cancer cases for each Asian sub-group. The expected number was determined by multiplying the age-, sex-, and geographic area-adjusted incidence rates for non-Hispanic whites by the age- and sex-specific ratio of percentage of current smokers in each Asian sub-group to whites in 1990, and then by the size of the respective Asian populations.

RESULTS

Chinese women had a four-fold increased risk of lung cancer, and Filipino women a two-fold increased risk, compared to that expected based on rates in US non-Hispanic whites with a similar proportion of cigarette smokers. Lung cancer among Chinese, Filipino, and Japanese males, as well as Japanese females, did not deviate from expected risk. Among Chinese women, the increased risk was largely restricted to adenocarcinoma and large cell undifferentiated carcinoma.

CONCLUSIONS

Chinese female residents of the western US mainland have a much higher risk of lung cancer than would be predicted from their tobacco use patterns, just as they do in Asia.

COPD increases the risk of squamous histological subtype in smokers who develop non-small cell lung carcinoma

BACKGROUND

Squamous cell carcinoma has a stronger association with tobacco smoking than other non-small cell lung cancers (NSCLC). A study was undertaken to determine whether chronic obstructive pulmonary disease (COPD) is a risk factor for the squamous cell carcinoma histological subtype in smokers with surgically resectable NSCLC.

METHODS

Using a case-control design, subjects with a surgically confirmed diagnosis of squamous cell carcinoma were enrolled from smokers undergoing lung resection for NSCLC in the District Hospital of Ferrara, Italy. Control subjects were smokers who underwent lung resection for NSCLC in the same hospital and had a surgically confirmed diagnosis of NSCLC of any histological type other than squamous cell.

RESULTS

Eighty six cases and 54 controls (mainly adenocarcinoma, n = 50) were enrolled. The presence of COPD was found to increase the risk for the squamous cell histological subtype by more than four times. Conversely, the presence of chronic bronchitis was found to decrease the risk for this histological subtype by more than four times. Among patients with chronic bronchitis (n = 77), those with COPD had a 3.5 times higher risk of having the squamous cell histological subtype.

CONCLUSIONS

These data suggest that, among smokers with surgically resectable NSCLC, COPD is a risk factor for the squamous cell histological subtype and chronic bronchitis, particularly when not associated with COPD, is a risk factor for the adenocarcinoma histological subtype.

Epidemiology of environmental and occupational cancer

Environmental carcinogens, in a strict sense, include outdoor and indoor air pollutants, as well as soil and drinking water contaminants. An increased risk of mesothelioma has consistently been detected among individuals experiencing residential exposure to asbestos, while results for lung cancer are less consistent. Several good-quality studies have investigated lung cancer risk from outdoor air pollution based on measurement of specific agents. Their results tend to show an increased risk in the categories at highest exposure, with relative risks in the range 1.5. A causal association has been established between exposure to environmental tobacco smoke and lung cancer, with a relative risk in the order of 1.2. Radon is another carcinogen present in indoor air, with a relative risk in the order of 1.06 for exposure at 100 Bq/m3. In several Asian populations, an increased risk of lung cancer results among women from indoor pollution from cooking and heating. There is strong evidence of an increased risk of bladder, skin and lung cancers following consumption of water with high arsenic contamination; results for other drinking water contaminants, including chlorination by-products, are inconclusive. A total of 29 occupational agents are established human carcinogens, and another 30 agents are suspected carcinogens. In addition, at least 12 exposure circumstances entail exposure to carcinogens. Exposure is still widespread for many important occupational carcinogens, such as asbestos, coal tar, arsenic and silica, in particular in developing countries. Although estimates of the global burden of occupational and environmental cancer result in figures in the order of 2% and less than 1%, respectively, these cancers concentrate in subgroups of the population; furthermore, exposure is involuntary and can, to a large extent, be avoided.

Estrogen receptor pathways in lung cancer

Lung cancer is the leading cause of death from neoplasia in men and women in the United States. Some studies suggest that women are more susceptible than men to tobacco-induced carcinogenesis and may show higher risk than men for lung cancer development from smoking. More recently, increasing biochemical and genetic data have supported this male-female difference in response to tobacco. Estrogens may be involved in lung carcinogenesis, and estrogen receptors (ERs), mainly ERb, are present and functional in normal lung and tumor cell lines and tissues. Estrogen can directly stimulate the transcription of estrogen-responsive genes in the nucleus of lung cells, and it can also transactivate growth factor signaling pathways, in particular the epidermal growth factor pathway. Lung cancer patients currently have few effective therapeutic options. An understanding of these new developments in estrogen signaling and cross-talk pathways may pave the way for innovative combinatorial approaches for treatment of lung cancer and possibly chemoprevention.

Contribution of environmental factors to cancer risk

Environmental carcinogens, in a strict sense, include outdoor and indoor air pollutants, as well as soil and drinking water contaminants. An increased risk of mesothelioma has consistently been detected among individuals experiencing residential exposure to asbestos, whereas results for lung cancer are less consistent. At least 14 good-quality studies have investigated lung cancer risk from outdoor air pollution based on measurement of specific agents. Their results tend to show an increased risk in the categories at highest exposure, with relative risks in the range 1.5-2.0, which is not attributable to confounders. Results for other cancers are sparse. A causal association has been established between exposure to environmental tobacco smoke and lung cancer, with a relative risk in the order of 1.2. Radon is another carcinogen present in indoor air which may be responsible for 1% of all lung cancers. In several Asian populations, an increased risk of lung cancer is present in women from indoor pollution from cooking and heating. There is strong evidence of an increased risk of bladder, skin and lung cancers following consumption of water with high arsenic contamination; results for other drinking water contaminants, including chlorination by-products, are inconclusive. A precise quantification of the burden of human cancer attributable to environmental exposure is problematic. However, despite the relatively small relative risks of cancer following exposure to environmental carcinogens, the number of cases that might be caused, assuming a causal relationship, is relatively large, as a result of the high prevalence of exposure.

National burden of disease in India from indoor air pollution

In the last decade, a number of quantitative epidemiological studies of specific diseases have been done in developing countries that for the first time allow estimation of the total burden of disease (mortality and morbidity) attributable to use of solid fuels in adult women and young children, who jointly receive the highest exposures because of their household roles. Few such studies are available as yet for adult men or children over 5 years. This paper evaluates the existing epidemiological studies and applies the resulting risks to the more than three-quarters of all Indian households dependent on such fuels. Allowance is made for the existence of improved stoves with chimneys and other factors that may lower exposures. Attributable risks are calculated in reference to the demographic conditions and patterns of each disease in India. Sufficient evidence is available to estimate risks most confidently for acute respiratory infections (ARI), chronic obstructive pulmonary disease (COPD), and lung cancer. Estimates for tuberculosis (TB), asthma, and blindness are of intermediate confidence. Estimates for heart disease have the lowest confidence. Insufficient quantitative evidence is currently available to estimate the impact of adverse pregnancy outcomes (e.g., low birthweight and stillbirth). The resulting conservative estimates indicate that some 400-550 thousand premature deaths can be attributed annually to use of biomass fuels in these population groups. Using a disability-adjusted lost life-year approach, the total is 4-6% of the Indian national burden of disease, placing indoor air pollution as a major risk factor in the country.

Lung cancer and environmental tobacco smoke in a non-industrial area of China

We report results from a population-based case-control study of lung cancer and environmental tobacco smoke (ETS) among never-smokers conducted in 2 rural prefectures of China, including 200 female and 33 male lung cancer cases, and 407 female and 114 male controls, matched on age, sex and prefecture of current residence. The odds ratio (OR) for ever-exposed to ETS was 1.19 (95% CI 0.7-2.0), with a significant trend (p<0.05) with increasing exposure. ORs were 1.00, 1.04, 1.13 and 1.51 for non-exposed, <10, 10-19 and >/=20 pack-years of ETS exposure, respectively. Excess risks were limited to ETS exposures in childhood (</=18 years of age). The OR for ever-exposed to ETS in childhood, adjusting for ETS exposure in adulthood, was 1. 52 (95% CI 1.1-2.2), with a significant trend (p<0.01) with increasing pack-years of childhood exposure, 1.00, 1.43, 1.81 and 2. 95, respectively. After adjustment for ETS in childhood, there was no excess risk from adult ETS exposure. The OR for ever-exposed to ETS in adulthood was 0.90 (95% CI 0.-1.4). These results were not affected by adjustment for type of residential dwelling, type or amount of fuel used, perceived indoor smokiness, or measures of socioeconomic status, or omitting next-of-kin respondents.

Small cell lung cancer in women: risk associated with smoking, prior respiratory disease, and occupation

Small cell carcinoma of the lung (SCLC) occurs most frequently in heavy smokers, yet exhibits a lesser predominance among men than other smoking-associated lung cancers. Incidence rates have increased more rapidly in women than men and at a faster rate among women than other cell types. To investigate the importance of smoking and other risk factors, a case-control study of SCLC in women was conducted. A total of 98 women with primary SCLC and 204 healthy controls, identified by random-digit dialing and frequency matched for age, completed telephone interviews. Data collected include demographics, medical history, family cancer history, residence history, and lifetime smoking habits. Odds ratios (ORs) and 95% confidence intervals (95% CI) were calculated using logistic regression analysis. Risk for small cell carcinoma in women is strongly associated with current use of cigarettes. Ninety-seven of 98 cases had smoked cigarettes; 79% of cases were current smokers and 20% were former smokers at the time of diagnosis compared to 13% current and 34% former smokers among controls. The ORs associated with smoking are 108.7 (95% CI 14.8-801) for ever-use of cigarettes, 278.9 (95% CI 37.0-2102) for current smoking, and 31.5 (95% CI 4. 1-241) for former smoking. Risk increases steeply with pack-years of smoking and decreases with duration of smoking cessation. After adjusting for age, education, and lifetime smoking history, medical history of physician-diagnosed respiratory disease including chronic bronchitis, emphysema, pneumonia, tuberculosis, asthma, and hay fever is not associated with a significant increase in lung cancer risk. Employment in blue collar, service, or other high risk occupations is associated with a two to three-fold non-significant increase in risk for small cell carcinoma after adjusting for smoking.

Risk modification in lung cancer by a dietary intake of preserved foods and soyfoods: findings from a case-control study in Okinawa, Japan

To disclose the association of dietary intake of preserved foods and soyfoods with lung cancer risk, we analyzed the data from a case-control study conducted in Okinawa, Japan, from 1988 to 1991. The analysis, based on 333 cases and 666 age-, sex- and residence-matched population controls, provided the following major findings. (1) The more the miso soup intake, the higher the risk (test for trend: P = 0.001 for males; P = 0.043 for females). (2) Frequent intake of pickles (excluding salted fish) tended to be linked with an elevated risk in males. The adjusted odds ratio (OR) for once or twice per week or more, relative to less than once a month was 1.88 (95% confidence interval (CI): 1.26-2.81). (3) Frequent intake of soybeans was associated with a decreased risk in men (OR: 0.63, 95% CI: 0.40-0.98 for once or twice per week or more, relative to less than once a month). (4) Daily consumers of tofu were at a decreased risk, particularly for squamous cell carcinoma; the OR (95% CI) being 0.55 (0.34-0.89) in males and 0.14 (0.02-0.89) in females. These findings suggested deleterious effects of preserved foods and protective ones of soyfoods rich in isoflavones.

Genetic polymorphism of xenobiotic metabolizing enzymes among Chinese lung cancer patients

Polymorphisms in xenobiotic metabolizing enzymes have been implicated in inter-individual and inter-ethnic differences in cancer susceptibilty. Several studies have indicated an association between variant alleles of the human CYP1A1, CYP2E1 and GSTM1 genes and lung cancer. Activity of microsomal epoxide hydrolase (HYL1) has also been associated with lung cancer, and 2 variant alleles causing amino acid substitutions have been described. We have investigated genetic polymorphisms of the CYP1A1, CYP2E1, GSTM1 and HYL1 genes in 76 Chinese lung cancer patients and 122 healthy Chinese subjects. The allele frequency of the CYP1A1*2B allele was 0.21 among lung cancer patients and 0.20 in the reference group, whereas the corresponding values for the CYP1A1*2A allele were 0.34 and 0.36. The CYP2E1*5B and CYP2E1*6 alleles were less frequent among the cancer patients (0.20 and 0.22) compared with healthy subjects (0.25 and 0.26). The frequency distribution of the HYL1*2 allele was 0.49 among lung cancer patients and 0.42 in the reference group, and the corresponding frequencies for the HYL1*3 allele were 0.13 and 0.10. The homozygous GSTM1*0 genotype was found in 64% of lung cancer patients and in 66% of healthy subjects. Among heavy smokers, the frequency was 73%. The differences in the distribution of variant CYP1A1, CYP2E1 and GSTM1 alleles in lung cancer patients and healthy controls were not statistically significant. Our results indicate that the polymorphisms investigated are of minor importance as genetic susceptibility markers for lung cancer in this population. An increased risk for lung cancer in subjects carrying the HYL*3 allele was observed and suggests that polymorphism in this gene might possibly be a susceptibility factor in the Chinese population.

Difficulties in assessing the relationship between passive smoking and lung cancer

Since 1981, numerous epidemiological studies have investigated the relationship between passive smoking and lung cancer in nonsmokers. The overall evidence, predominantly relating to women, indicates a weak association with the husband's smoking and many reviewers have concluded that this demonstrates a causal effect of exposure to environmental tobacco smoke (ETS). Interpreting weak associations is notoriously difficult, however, and this paper reviews problems specific to the ETS-lung cancer relationship. After describing how to select relevant studies and appropriate data, the methods for combining evidence together ('meta-analysis') are discussed, and the need to investigate sources of heterogeneity is emphasized. Separate consideration is given to various forms of bias that may affect overall relative risk estimates, including misclassification of active smoking status, confounding, systematic case-control differences, recall bias, diagnostic bias and publication bias. Sections on dose-response, multiple ETS exposure sources and other issues follow. The problems are illustrated from the available literature. It is shown there is no significant association of lung cancer with workplace, childhood or social ETS exposure or with smoking by the wife. Though statistically significant, the association with husband's smoking is weak and heterogeneous and varies widely according to various study characteristics. The association is markedly weakened by the adjustment for smoking misclassification bias and is likely to be affected by confounding and other sources of bias. While the precise extent of all the biases remains unclear, it seems impossible to conclude with any certainty that ETS causes lung cancer.