Difficulties in assessing the relationship between passive smoking and lung cancer

Lung cancer risk in never-smokers: a population-based case-control study of epidemiologic risk factors

BACKGROUND

We conducted a case-control study in the greater Toronto area to evaluate potential lung cancer risk factors including environmental tobacco smoke (ETS) exposure, family history of cancer, indoor air pollution, workplace exposures and history of previous respiratory diseases with special consideration given to never smokers.

METHODS

445 cases (35% of which were never smokers oversampled by design) between the ages of 20-84 were identified through four major tertiary care hospitals in metropolitan Toronto between 1997 and 2002 and were frequency matched on sex and ethnicity with 425 population controls and 523 hospital controls. Unconditional logistic regression models were used to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI) for the associations between exposures and lung cancer risk.

RESULTS

Any previous exposure to occupational exposures (OR total population 1.6, 95% CI 1.4-2.1, OR never smokers 2.1, 95% CI 1.3-3.3), a previous diagnosis of emphysema in the total population (OR 4.8, 95% CI 2.0-11.1) or a first degree family member with a previous cancer diagnosis before age 50 among never smokers (OR 1.8, 95% CI 1.0-3.2) were associated with increased lung cancer risk.

CONCLUSIONS

Occupational exposures and family history of cancer with young onset were important risk factors among never smokers.

The "father of stress" meets "big tobacco": Hans Selye and the tobacco industry

The concept of stress remains prominent in public health and owes much to the work of Hans Selye (1907-1982), the "father of stress." One of his main allies in this work has never been discussed as such: the tobacco industry. After an analysis of tobacco industry documents, we found that Selye received extensive tobacco industry funding and that his research on stress and health was used in litigation to defend the industry's interests and argue against a causal role for smoking in coronary heart disease and cancer. These findings have implications for assessing the scientific integrity of certain areas of stress research and for understanding corporate influences on public health research, including research on the social determinants of health.

Lung cancer in never smokers: clinical epidemiology and environmental risk factors

More than 161,000 lung cancer deaths are projected to occur in the United States in 2008. Of these, an estimated 10 to 15% will be caused by factors other than active smoking, corresponding to 16,000 to 24,000 deaths annually. Thus lung cancer in never smokers would rank among the most common causes of cancer mortality in the United States if considered as a separate category. Slightly more than half of the lung cancers caused by factors other than active smoking occur in never smokers. As summarized in the accompanying article, lung cancers that occur in never smokers differ from those that occur in smokers in their molecular profile and response to targeted therapy. These recent laboratory and clinical observations highlight the importance of defining the genetic and environmental factors responsible for the development of lung cancer in never smokers. This article summarizes available data on the clinical epidemiology of lung cancer in never smokers, and several environmental risk factors that population-based research has implicated in the etiology of these cancers. Primary factors closely tied to lung cancer in never smokers include exposure to known and suspected carcinogens including radon, second-hand tobacco smoke, and other indoor air pollutants. Several other exposures have been implicated. However, a large fraction of lung cancers occurring in never smokers cannot be definitively associated with established environmental risk factors, highlighting the need for additional epidemiologic research in this area.

Environmental tobacco smoke and lung cancer among Chinese nonsmoking males: might adenocarcinoma be the culprit?

No studies have specifically reported the association of lung adenocarcinoma with environmental tobacco smoke (ETS) exposure among nonsmoking males. The objective of this study was to examine the exposure-response relation between ETS exposure and lung cancer among nonsmoking males. In particular, the association with adenocarcinoma of the lung was studied. This is a population-based, case-referent study in Hong Kong during 2004-2006. A total of 132 Chinese male nonsmokers with newly diagnosed primary lung cancer and 536 nonsmoking community referents were interviewed about ETS exposures from the household and/or workplace, including ever ETS exposure, sources of exposure, number of smoking cohabitants/coworkers, and smoker-years. Univariate logistic regression analyses showed a weak association between all lung cancers and ever ETS exposure from the household and/or workplace (odds ratio (OR) = 1.11, 95% confidence interval (CI): 0.74, 1.67), but an increased risk was restricted to adenocarcinoma (OR = 1.68, 95% CI: 1.00, 2.38). After adjustment for family cancer history and other confounders, excess risk (OR = 1.62, 95% CI: 0.91, 2.88) still persisted for adenocarcinoma, although it was no longer statistically significant. Exposure-response relations for adenocarcinoma were found with increasing levels of all ETS indices when exposures from the household and workplaces were combined. The consistent exposure-response relations between ETS exposures and adenocarcinoma suggested a probable causal link, which would have to be confirmed by future larger studies.

The roles of smoking and cooking emissions in lung cancer risk among Chinese women in Hong Kong

BACKGROUND

We conducted this case-control study to evaluate smoking effect on lung cancer conditional on the level of exposure to cooking emissions and to explore whether there is a joint effect of these two risk factors.

SUBJECTS AND METHODS

We selected 279 newly diagnosed primary lung cancer cases and 322 community controls from Hong Kong females, frequency matched by age group, and collected relevant data. We applied logistic regression to estimate lung cancer risk related to smoking and cooking fume exposure, expressed as total cooking dish-years, while adjusting for various potential confounding factors.

RESULTS

Current smoking was associated with four-fold increased risk, and ex-smoking with two-fold risk, which was not much influenced by cooking dish-years. No increased risk was observed in environmental tobacco smoking. Increasing intakes of yellow/orange vegetables and multivitamins were significant protective factors in all models. In the analysis of joint effect, the combination of smoking and cooking dish-years tended to have a greater risk than exposure to cooking fumes alone. There was a dose-response gradient with total dish-years in nonsmokers, but not in smokers. Smoking was more strongly associated with nonadenocarcinoma, whereas exposure to cooking fumes appeared to be related to both adenocarcinoma and nonadenocarcinoma.

CONCLUSION

We confirmed the important roles of smoking and cooking emissions in lung cancer risk among the women. These two major risk factors appeared to act independently.

Challenging the epidemiologic evidence on passive smoking: tactics of tobacco industry expert witnesses

OBJECTIVE

To analyse the statements given by tobacco industry defence witnesses during trial testimonies and depositions in second-hand smoke cases and in parallel, to review criticisms of epidemiology in industry-funded publications in order to identify strategies for discrediting epidemiologic evidence on passive smoking health effects.

METHODS

A collection of depositions and trial testimony transcripts from tobacco industry-related lawsuits filed in the United States during the 1990s, was compiled and indexed by the Tobacco Deposition and Trial Testimony Archive (DATTA). Statements in DATTA made by expert witnesses representing the tobacco industry relating to the health effects of passive smoking were identified and reviewed. Industry-supported publications within the peer-reviewed literature were also examined for statements on exposure misclassification, meta-analysis, and confounding.

RESULTS

The witnesses challenged causation of adverse health effects of passive smoking by citing limitations of epidemiologic research, raising methodological and statistical issues, and disputing biological plausibility. Though not often cited directly by the witnesses, the defence tactics mirrored the strategies used in industry-funded reports in the peer-reviewed literature.

CONCLUSION

The tobacco industry attempted to redirect the focus and dialogue related to the epidemiologic evidence on passive smoking. This approach, used by industry experts in trial testimony and depositions, placed bias as a certain alternative to causation of diseases related to passive smoking and proposed an unachievable standard for establishing the mechanism of disease.

Parental smoking and childhood cancer: results from the United Kingdom Childhood Cancer Study

There are strong a priori reasons for considering parental smoking behaviour as a risk factor for childhood cancer but case - control studies have found relative risks of mostly only just above one. To investigate this further, self-reported smoking habits in parents of 3838 children with cancer and 7629 control children included in the United Kingdom Childhood Cancer Study (UKCCS) were analysed. Separate analyses were performed for four major groups (leukaemia, lymphoma, central nervous system tumours and other solid tumours) and more detailed diagnostic subgroups by logistic regression. In the four major groups, after adjustment for parental age and deprivation there were nonsignificant trends of increasing risk with number of cigarettes smoked for paternal preconception smoking and nonsignificant trends of decreasing risk for maternal preconception smoking (all P-values for trend >0.05). Among the diagnostic subgroups, a statistically significant increased risk of developing hepatoblastoma was found in children whose mothers smoked preconceptionally (OR=2.68, P=0.02) and strongest (relative to neither parent smoking) for both parents smoking (OR=4.74, P=0.003). This could be a chance result arising from multiple subgroup analysis. Statistically significant negative trends were found for maternal smoking during pregnancy for all diagnoses together (P<0.001) and for most individual groups, but there was evidence of under-reporting of smoking by case mothers. In conclusion, the UKCCS does not provide significant evidence that parental smoking is a risk factor for any of the major groups of childhood cancers.

Molecular epidemiology of smoking and lung cancer

Lung cancer is the single most common cause of death, and almost all of it is due to tobacco smoking. Before the widespread use of cigarettes in this century, lung cancer was a rare illness. Tobacco smoke is a complex mixture of numerous mutagens and carcinogens. Over the last 40 years, the type of cigarettes most frequently used has been changing, namely the increased use of low tar and nicotine cigarettes. This has been accompanied by an increased risk of lung cancer due to a smokers' need to maintain blood nicotine levels, which in turn causes the need for smoking more cigarettes per day and deeper inhalation. This phenomena has led to the increasing rates of lung adenocarcinoma, compared to squamous cell carcinoma. It also probably explains, in part, the greater risk of lung cancer in women compared to men (in addition to some biological differences). The study of lung cancer involves many types of biomarkers, including those that measure exposure, the biologically effective dose and harm. The use of these has allowed us to understand many parts of lung carcinogenesis. Genetic susceptibilities play a large role in lung cancer risk. They govern smoking behavior (affecting dopamine reward mechanisms due to nicotine and nicotine metabolism), carcinogen metabolism and detoxification, DNA repair, cell cycle control and other cellular responses. The need for the study of lung cancer is highlighted by the need to improve cessation rates and reduce exposure among persons who cannot quit smoking, for better prevention strategies for former smokers and an understanding of environmental tobacco smoke risk.

Epidemiology of tobacco carcinogenesis

Tobacco smoking is a worldwide epidemic. Tobacco smoke is an established human carcinogen that contains more than 50 carcinogens, among the most potent of which are polycyclic aromatic hydrocarbons (PAHs) and tobacco- specific nitrosamines (TSNs). Over the last 40 years, the level of tar and nicotine in cigarettes has decreased, along with the level of PAHs, but the level of TSNs has increased. Also, decreases in nicotine content can lead to an attendant increase in smoking in order for an individual to maintain his or her blood nicotine levels. Several factors determine the biologically effective dose of carcinogens, including the number of cigarettes smoked per day, type of cigarette, smoking topography, carcinogen metabolism, and DNA repair. Many studies have shown a relationship between tobacco smoke exposure, carcinogen-DNA adduct formation, tumor specific mutations (eg, p53 mutational spectra), and cancer risk. Genetically determined host capacity can influence these outcomes and the risk for tobacco addiction. Current areas of interest include determining whether women are indeed at greater risk of lung cancer compared with men, and if blacks are at higher risk than women. Also, newer methods can probably clarify the role of environmental tobacco smoke in carcinogenesis.

Accuracy of recall in health-related quality-of-life assessment among men treated for prostate cancer

PURPOSE

To determine the accuracy of patient recall of health-related quality of life (HRQOL) in men who have undergone radical prostatectomy for early-stage prostate cancer.

PATIENTS AND METHODS

Patients enrolled onto a longitudinal, observational cohort study of HRQOL after radical prostatectomy for early-stage prostate cancer were asked to assess their baseline HRQOL before surgery. They were later asked to recall their baseline HRQOL at intervals of 7 to 37 months after surgery. The two views of baseline HRQOL (actual and recall) were compared. HRQOL was measured with established instruments (the RAND 12-Item Short-Form Health Survey and a validated short form of the University of California Los Angeles Prostate Cancer Index) that addressed impairment in the physical, mental, urinary, bowel, and sexual domains.

RESULTS

Overall, recall was poor. Patients tended to remember their baseline HRQOL as being better than it actually was. This effect was particularly striking for urinary and sexual function. Greater education and younger age diminished this effect in some domains. The effect did not vary with time since surgery.

CONCLUSION

Men undergoing radical prostatectomy for early-stage prostate cancer do not accurately recall their pretreatment HRQOL when asked several months or years later. This recall bias is constant throughout a period of 6 months to 3 years after surgery. By collecting data before treatment and observing subjects longitudinally, investigators can ensure that HRQOL changes are analyzed in the context of any impairment that may have been present at baseline. If a longitudinal study is not feasible, then great caution must be used if patients are asked to recall their pretreatment HRQOL.