Sex differences in lung-cancer risk associated with cigarette smoking

The changing landscape of small cell lung cancer

BACKGROUND

Small-cell lung cancer (SCLC) is characterized by rapid proliferation and early dissemination. The objective of this study was to examine the demographic trends and outcomes in SCLC.

METHODS

The authors queried the National Cancer Institute's Surveillance, Epidemiology, and End Results database to assess the trends in incidence, demographics, staging, and survival for SCLC from 1975 to 2019. Trends were determined using joinpoint analysis according to the year of diagnosis.

RESULTS

Among the 530,198 patients with lung cancer, there were 73,362 (13.8%) with SCLC. The incidence per 100,000 population peaked at 15.3 in 1986 followed by a decline to 6.5 in 2019. The percentage of SCLC among all lung tumors increased from 13.3% in 1975 to a peak of 17.5% in 1986, declining to 11.1% by 2019. There was an increased median age at diagnosis from 63 to 69 years and an increased percentage of women from 31.4% to 51.2%. The percentage of stage IV increased from 58.6% in 1988 to 70.8% in 2010, without further increase. The most common sites of metastasis at diagnosis were mediastinal lymph nodes (75.3%) liver (31.6%), bone (23.7%), and brain (16.4%). The 1-year and 5-year overall survival rate increased from 23% and 3.6%, respectively, in 1975-1979 to 30.8% and 6.8%, respectively, in 2010-2019.

CONCLUSIONS

The incidence of SCLC peaked in 1988 followed by a gradual decline. Other notable changes include increased median age at diagnosis, the percentage of women, and the percentage of stage IV at diagnosis. The improvement in 5-year overall survival has been statistically significant but clinically modest.

Age-specific incidence trends of 32 cancers in China, 1983 to 2032: Evidence from Cancer Incidence in Five Continents

The long-term incidence trends of 32 cancers in China remained unclear. Cancer statistics for young population were often presented in aggregate, masking important heterogeneity. We aimed to assess the incidence trends of 32 cancers in China from 1983 to 2032, stratified by sex and age groups. Data on cancer incidence from 1983 to 2017 were extracted from Cancer Incidence in Five Continents Volumes VI-XII. The age-period-cohort model was utilized to assess age and birth cohort effects on the temporal trends of 32 cancers in China, while the Bayesian age-period-cohort model was utilized to project future trends from 2018 to 2032. An increase in cohort effects is observed in some cancers such as thyroid and kidney cancers. Eight of the 12 obesity-related cancers may rise in the 0-14 age group, and nine in the 15-39 age group from 2013 to 2032. Liver and stomach cancers show an increasing trend among the younger population, contrasting with the observed declining trend in the middle-aged population. There has been a significant rise in the proportions of cervical cancer among females aged 40-64 (4.3%-19.1%), and prostate cancer among males aged 65+ (1.1%-11.8%) from 1983 to 2032. Cancer spectrum in China is shifting toward that in developed countries. Incidence rates of most cancers across different age groups may increase in recent cohorts. It is essential to insist effective preventive interventions, and promote healthier lifestyles, such as reducing obesity, especially among younger population.

Recent advances in small cell lung cancer: the future is now?

Small cell lung cancer is a relevant clinical issue as it is a highly malignant cancer, often diagnosed in advanced stage. Similarly to non-small cell lung cancer, tobacco smoking is currently the main risk factor. Its incidence, at least in males, has declined over the past decades, due to the worldwide decreased percentage of active smokers. The typical small cells of this tumor type are characterized by a high Proliferation Index, chromosomal deletions such as 3p(14-23) involving the tumor-suppressor gene FHIT, alterations of the MYC or Notch family proteins and the frequent expression of neuroendocrine markers. The combination of thoracic radiotherapy and chemotherapy is the standard treatment for limited stage disease, while platinum-based chemotherapy is the most effective choice for extensive stage disease. Unfortunately, whatever chemotherapy is used, the results are disappointing. No regimen has proved to be effective in the long run, indeed small cell lung cancer rapidly progresses after a frequent initial strong response, and the mortality rate remains still high. The advent of immunotherapy is actually changing the landscape in oncology. As well as in other cancers, recent trials have demonstrated the efficacy of the combination of immune checkpoint inhibitors and chemotherapy, opening new perspectives for the future of our patients.

Sex and Gender Differences in Lung Cancer and Chronic Obstructive Lung Disease

Two highly prevalent pulmonary diseases, lung cancer and chronic obstructive lung disease (COPD), show both sex and gender differences in their presentations and outcomes. Sex differences are defined as biological differences associated with the male vs female genotype, and gender differences are defined as behavioral or social differences that primarily arise because of gender identity. The incidence of both lung cancer and COPD has increased dramatically in women over the past 50 years, and both are associated with chronic pulmonary inflammation. Development of COPD is also a risk factor for lung cancer. In this review, the main differences in lung cancer and COPD biology observed between men and women will be summarized. Potential causative factors will be discussed, including the role of estrogen in promoting pro-growth and inflammatory phenotypes which may contribute to development of both lung cancer and COPD. Response of the innate and adaptive immune system to estrogen is a likely factor in the biology of both lung cancer and COPD. Estrogen available from synthesis by reproductive organs as well as local pulmonary estrogen synthesis may be involved in activating estrogen receptors expressed by multiple cell types in the lung. Estrogenic actions, although more pronounced in women, may also have importance in the biology of lung cancer and COPD in men. Effects of estrogen are also timing and context dependent; the multiple cell types that mediate estrogen action in the lungs may confer both positive and negative effects on disease processes.

Women and Lung Cancer

The world is witnessing a global epidemic of lung cancer in women. Cigarette smoking remains the dominant risk factor in both sexes, but multiple observations suggest that important sex-related distinctions in lung cancer exist. These include differences in histologic distribution, prevalence in never-smokers, frequency of activating EGFR mutations, likelihood of DNA adduct accumulation, and survival outcomes. Important questions such as whether women are more susceptible to carcinogenic effects of smoking or derive more benefit from lung cancer screening merit more study. A deeper understanding of sex-related differences in lung cancer may lead to improved outcomes for both women and men.

The smoking estrogens - a potential synergy between estradiol and benzo(a)pyrene

According to recent statistics, Lung Cancer (LC) is one of the most frequently diagnosed tumor types, representing nearly 12% of all global cancer cases. Moreover, in recent years, an increased mortality rate and incidence of this cancer were observed, especially among nonsmokers. Lung cancer patients are often characterized by poor prognosis and low survival rates, which encourages the scientific community to investigate the biochemical and molecular processes leading to the development of this malignancy. Furthermore, the mechanisms of LC formation and progression are not yet fully elucidated due to their high complexity, as well as a multitude of environmental, genetic, and molecular factors involved. Even though LC's association with exposure to cigarette smoke is indisputable, current research provides evidence that the development of this cancer can also be affected by the presence of estrogens and their interaction with several tobacco smoke components. Hence, the main goal of this brief review was to investigate reports of a possible synergy between 17β estradiol (E2), the most biologically active estrogen, and benzo(a)pyrene (BaP), a strongly carcinogenic compound produced as a result of incomplete tobacco combustion. The literature sources demonstrate a possible carcinogenic synergy between estrogens, especially E2, and BaP, a toxic tobacco smoke component. Therefeore, the combined effect of disturbed estrogen production in cancer cells, as well as the molecular influence exerted by BaP, could explain the increased aggressiveness and rate of LC development. Summarizing, the synergistic effect of these risk factors is an interesting area of further research.

Description of a Lung Cancer Hotspot: Disparities in Lung Cancer Histology, Incidence, and Survival in Kentucky and Appalachian Kentucky

INTRODUCTION

Kentucky is recognized as the state with the highest lung cancer burden for more than 2 decades, but how lung cancer differs in Kentucky relative to other US populations is not fully understood.

PATIENTS AND METHODS

We examined lung cancer reported to the Surveillance, Epidemiology, and End Results (SEER) Program by Kentucky and the other SEER regions for patients diagnosed between 2012 and 2016. Our analyses included histologic types, incidence rates, stage at diagnosis, and survival in Kentucky and Appalachian Kentucky relative to other SEER regions.

RESULTS

We found that both squamous cell carcinomas and small-cell lung cancers represent larger proportions of lung cancer diagnoses in Kentucky and Appalachian Kentucky than they do in the SEER registries. Furthermore, age-adjusted cancer incidence rates were higher in Kentucky for every subtype of lung cancer examined. Most notably, for Appalachian women the rate of small-cell carcinomas was 3.5-fold higher, and for Appalachian men the rate of squamous cell carcinoma was 3.1-fold higher, than the SEER rates. In Kentucky, lung cancers were diagnosed at later stages and lung cancer survival was lower for adenocarcinoma and neuroendocrine carcinomas than in SEER registries. Squamous cell carcinomas and small-cell carcinomas were most lethal in Appalachian Kentucky.

CONCLUSION

Together, these data highlight the considerable disparities among lung cancer cases in the United States and demonstrate the continuing high burden and poor survival of lung cancer in Kentucky and Appalachian Kentucky. Strategies to identify and rectify causes of these disparities are discussed.

The molecular basis of gender disparities in smoking lung cancer patients

AIMS

Gender disparities exist in smoking-related lung cancer epidemiology, but the molecular basis has not been explored so far. We aimed at identifying genes with gender-bias expression pattern in smoking lung cancer patients for understanding the molecular basis of gender bias in smokers using meta-analysis of microarray gene expression data.

MATERIALS AND METHODS

Transcriptome of around 1100 samples from 13 studies were used in the meta-analysis to identify 'Lung Cancer genes specific to Female-Smokers' (LCFS) and 'Lung Cancer genes specific to Male-Smokers' (LCMS). The expression profiles of these genes were validated with an independent microarray report and TCGA-RNA-sequencing data. The molecular interactions, pathway, and other functional annotations were portrayed for the key genes identified.

KEY FINDINGS

We identified 1159 gender-biased genes in smoking lung cancer patients. Of these, 400 and 474 genes showed differential expression in cancerous compared to normal lung of women (LCFS) and men (LCMS), respectively. While many up-regulated LCFS were involved in 'immune responses' including T-cell activation, leukocyte cell-cell adhesion, the LCMS were mainly involved in 'positive regulation of gene expression', signaling pathways including RAS, VEGF, insulin-receptor signaling, and 'cell cycle'.

SIGNIFICANCE

The strategic-method identified genes, particularly, SNX20, GIMAP6, MTMR2, FAM171B, IDH1, MOBP, FBXO17, LPXN and WIPF1, which were consistently differentially expressed in at least 4 studies, and in agreement with RNA-Seq data. Exploring their functions could be beneficial to the gender-based diagnosis, prognosis, and treatment of lung cancer in smokers. The current meta-analysis supports existing knowledge of sexual-dimorphism of immune responses in cancer.

Gender-specific aspects of epidemiology, molecular genetics and outcome: lung cancer

Lung cancer remains the leading cause of cancer-related deaths worldwide in women and men. In incidence, lung cancer ranks second, surpassed by breast cancer in women and prostate cancer in men. However, the historical differences in mortality and incidence rate between both sexes have changed in the last years. In the last decades, we have also witnessed an increased number of lung cancer in female never-smokers. These disparities have grown our interest in studying the impact of the gender and sex in the presentation of lung cancer. The aetiology is yet to be fully elucidated, but the data are clear so far: there is a growing divide between lung cancer presentation in women and men that will change our management and study of lung cancer. This article aims to review the sex and gender differences in lung cancer.

Influence of Estrogen on the NSCLC Microenvironment: A Comprehensive Picture and Clinical Implications

Lung cancer mortality represents the leading cause of cancer related deaths in the United States and worldwide. Almost half of these deaths occur in female patients, making lung cancer the most common cause of cancer mortality in women with a higher annual mortality rate than breast, uterine, and ovarian cancers combined. The distinct epidemiological, histological and biological presentation of non-small cell lung cancer (NSCLC) in women combined with extensive preclinical data have demonstrated that the female sex hormone β-estradiol (E2) plays an important role in NSCLC tumorigenesis, prognosis, and treatment response. Estrogen receptors are widely expressed on stromal and immune cells, and estrogen-linked signaling pathways are known to be involved in regulating the response of both the innate and adaptive immune system. Immune evasion has been recognized as a “hallmark” of cancer and immunotherapy has re-defined standard of care treatment for NSCLC. Despite these advancements, the low response rates observed in patients treated with immune checkpoint inhibitors has led to a search for mediators of immunosuppression and ways to augment the action of these agents. We focus on emerging data describing sex differences that modulate immunotherapy efficacy in NSCLC, immunosuppressive properties of E2 that lead to a pro-tumor microenvironment (TME), and the translational potential of altering the immune microenvironment by targeting the estrogen signaling pathway. E2-induced modulation affects multiple cell types within the TME, including cancer-associated fibroblasts, tumor infiltrating myeloid cells, and tumor infiltrating lymphocytes, all of which interplay with lung tumor cells via E2 and estrogen receptor engagement, ultimately shaping the TME that may, in part, be responsible for the sex-based disparities observed in NSCLC. An improved understanding of the role of the estrogen pathway in NSCLC anti-cancer immunity may lead to novel therapeutic approaches for altering the TME to improve the efficacy of immunotherapy agents.

Lung Cancer in Women: A Modern Epidemic

Lung cancer in women is a modern epidemic and a major health crisis. Cigarette smoking remains the most important risk factor for lung cancer, and unfortunately smoking rates are either stabilized or continue to increase among women. Women may not be more susceptible to the carcinogenic effects of tobacco, but the biology of lung cancer differs between the sexes. This paper summarizes the biological sex differences in lung cancer, including molecular abnormalities, growth factor receptors, hormonal influences, DNA repair capacity, as well as differences in the histology and treatment outcomes of lung cancer in women.

Diagnostic and Prognostic Performance of Blood Plasma Glycan Features in the Women Epidemiology Lung Cancer (WELCA) Study

Lung cancer is the leading cause of cancer death in women living in the United States, which accounts for approximately the same percentage of cancer deaths in women as breast, ovary, and uterine cancers combined. Targeted blood plasma glycomics represents a promising source of noninvasive diagnostic and prognostic biomarkers for lung cancer. Here, 208 samples from lung cancer patients and 207 age-matched controls enrolled in the Women Epidemiology Lung Cancer (WELCA) study were analyzed by a bottom-up glycan "node" analysis approach. Glycan features, quantified as single analytical signals, including 2-linked mannose, α2-6 sialylation, β1-4 branching, β1-6 branching, 4-linked GlcNAc, and antennary fucosylation, exhibited abilities to distinguish cases from controls (ROC AUCs: 0.68-0.92) and predict survival in patients (hazard ratios: 1.99-2.75) at all stages. Notable alterations of glycan features were observed in stages I-II. Diagnostic and prognostic glycan features were mostly independent of smoking status, age, gender, and histological subtypes of lung cancer.

The estrogen pathway as a modulator of response to immunotherapy

Lung cancer is the leading cause of cancer deaths worldwide, with a 5-year survival rate of about 18%. Thus, there is a great need for novel therapeutic approaches to treat non-small-cell lung cancer (NSCLC). Immune checkpoint inhibitors (ICIs) have improved outcomes for a subset of patients, especially those with high programmed death-ligand 1 expression and/or high tumor mutational burden, but have failed in the majority of patients. Increasing evidence suggests that the estrogen signaling pathway may be a therapeutic target in metastatic NSCLC and that the estrogen pathway may play a role in sex-based responses to ICIs. This report will review the epidemiologic, preclinical and clinical data on the estrogen pathway in NSCLC, its implications in sex-based responses to ICIs and the potential use of antiestrogen therapy in combination with ICIs.

Epidemiological Study of Lung Cancer Incidence in Lebanon

Background and Objectives: Lung cancer (LC) is the most common cancer in the world. Developing countries in the Middle East and North Africa (MENA) region, including Lebanon, have witnessed a great increase in the incidence rates of this disease. The aim of our study is to investigate the incidence rates of lung cancer in Lebanon from 2005 to 2015 and to compare these rates to other countries from the MENA region and other regions of the world. Material and Methods: Lung cancer data for the years 2005-2015 were collected from the National Cancer Registry of Lebanon and stratified by gender and age group. Age-specific and age-standardized incidence rates were calculated and analyzed using joinpoint regression. Age-standardized incidence rates to the world population (ASR(w)) for other countries were obtained from two online databases. Results: Lung cancer ranked as the second most common cancer in Lebanon and accounted for 9.2% of all newly diagnosed cancers. Lung cancer ASR(w) showed a significantly increasing trend over the period studied for males and females. Lung cancer ASR(w) among males in Lebanon came second after Malta when compared to other MENA countries, but it was among the lowest when compared to non-MENA countries. For females, Lebanon ranked first when compared to other MENA countries but was among the lowest when compared to countries in other regions of the world. The lung cancer incidence rate increased with age in both sexes and 89.2% of patients were 50 years of age or older. Conclusion: Lebanon has the highest incidence of LC in females and the second highest for males in the MENA region. The lung cancer incidence rate is on the rise and older age groups are much more burdened by this disease than the young ones. Several risk factors, particularly smoking, play a role in increased LC incidence among the Lebanese population.

Tobacco and Alcohol Consumption Rates among Chinese Women of Reproductive Age in 2004⁻2011: Rate and Sociodemographic Influencing Factors

Background: Smoking and alcohol consumption have become major public health problems among Chinese women. In this study we explore the behavioral trends in smoking and alcohol consumption of Chinese women. We also explored the changes in the sociodemographic factors that affect the smoking and alcohol consumption behaviors of Chinese women at different reproductive stages. Methods: We used the Chinese Health and Nutrition Survey data for 2004 to 2011 to investigate the trends and influential factors of tobacco and alcohol consumption among Chinese women. Data for tobacco and alcohol consumption (consumption of beer or any other alcoholic beverage and smoking of cigarettes) were extracted using questionnaires. We applied the χ² test to examine the trends of alcohol and tobacco consumption among Chinese women over the period of 2004 to 2011. We conducted two penalized logistic regressions with age as the continuous and classification variable (18–23, 24–29, 30–44, and 45–49 years), and independent variables included residence, age, and marital status. Results: Drinking rates among Chinese women significantly changed over the period of 2004 to 2011 (p = 0.018). Age was related to tobacco consumption rates for 2009 and 2011 (p < 0.05). Marital status was associated with tobacco consumption rates for 2004, 2009, and 2011 (p < 0.05). Tobacco and alcohol consumption rates from 2004 to 2011 were positively correlated (p < 0.05). Over the period of 2004 to 2011, alcohol consumption rates were higher among women living in urban areas than those among women living in rural areas (p < 0.05). High educational attainment was related to alcohol consumption. Educational attainment levels of secondary or primary schooling and university or above were related to alcohol consumption rates for 2004 to 2011 (p < 0.05). Employed women were more likely to consume alcohol than unemployed women in 2004, 2006, and 2011 (p < 0.05). Data from 2004 to 2011 showed that tobacco and alcohol use were correlated (p < 0.05) and that women aged 45–49 years old were more likely to consume tobacco than other women (p < 0.05); Conclusions: The drinking behavior of Chinese women changed considerably over the period of 2004 to 2011. Our results provide further insight on the smoking and drinking behaviors of Chinese women at different reproductive stages and the factors that influence such behaviors. Therefore, our findings on trends and factors that influence rates of tobacco and alcohol use allow for a better understanding of the smoking and drinking behaviors of Chinese women.

Different inhibitory potential of sex hormones on NNK detoxification in vitro: A possible explanation for gender-specific lung cancer risk

Smoking women are probably at a higher risk to develop lung cancer than men. Different explanations exist for these findings, a gender-specific impairment of tobacco carcinogen metabolism being one of them. In this study, we examined the inhibition of NNK reduction to NNAL, the first and most important detoxication step of this tobacco-specific carcinogen. It is mediated by different carbonyl reductases of the SDR (CBR1 and 11βHSD1) and AKR (AKR1B10, AKR1C1, AKR1C2 and AKR1C4) superfamilies. Inhibition constants of NNK reduction were determined with male (testosterone) and female (estradiol, progesterone) sex hormones and the contraceptives ethinylestradiol and drospirenone in A549 cells and with purified enzymes. Female sex hormones turned out to be stronger inhibitors than testosterone. The gestagen progesterone and its synthetic derivative drospirenone are the strongest inhibitors with Ki-values similar to hormone levels in pregnant women or women using hormonal contraceptives. Therefore, pregnancy or hormonal contraception may commit these women as high risk groups. The results of this study support the hypothesis that women bear a higher lung cancer risk when smoking because of female sex hormones acting as inhibitors of NNK detoxication.

Sex hormones reduce NNK detoxification through inhibition of short-chain dehydrogenases/reductases and aldo-keto reductases in vitro

Carbonyl reduction is an important metabolic pathway for endogenous and xenobiotic substances. The tobacco specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK, nicotine-derived nitrosamine ketone) is classified as carcinogenic to humans (IARC, Group 1) and considered to play the most important role in tobacco-related lung carcinogenesis. Detoxification of NNK through carbonyl reduction is catalyzed by members of the AKR- and the SDR-superfamilies which include AKR1B10, AKR1C1, AKR1C2, AKR1C4, 11β-HSD1 and CBR1. Because some reductases are also involved in steroid metabolism, five different hormones were tested for their inhibitory effect on NNK carbonyl reduction. Two of those hormones were estrogens (estradiol and ethinylestradiol), another two hormones belong to the gestagen group (progesterone and drospirenone) and the last tested hormone was an androgen (testosterone). Furthermore, one of the estrogens (ethinylestradiol) and one of the gestagens (drospirenone) are synthetic hormones, used as hormonal contraceptives. Five of six NNK reducing enzymes (AKR1B10, AKR1C1, AKR1C2, AKR1C4 and 11β-HSD1) were significantly inhibited by the tested sex hormones. Only NNK reduction catalyzed by CBR1 was not significantly impaired. In the case of the other five reductases, gestagens had remarkably stronger inhibitory effects at a concentration of 25 μM (progesterone: 66-88% inhibition; drospirenone: 26-87% inhibition) in comparison to estrogens (estradiol: 17-51% inhibition; ethinylestradiol: 14-79% inhibition) and androgens (14-78% inhibition). Moreover, in most cases the synthetic hormones showed a greater ability to inhibit NNK reduction than the physiologic derivatives. These results demonstrate that male and female sex hormones have different inhibitory potentials, thus indicating that there is a varying detoxification capacity of NNK in men and women which could result in a different risk for developing lung cancer.

Exploring estrogenic activity in lung cancer

It is well known that a connection between xenobiotics inhalation, especially tobacco combustion and Lung Cancer development is strongly significant and indisputable. However, recent studies provide evidence indicating that another factors such as, estrogens are also involved in lung carcinoma biology and metabolism. Although the status of estrogen receptors (ER), in both cancerous and healthy lung tissue has been well documented, there is still inconclusive data with respect of which isoform of the receptor is present in the lungs. However according to several studies, ERβ appears to be predominant form. Apart from ERs, estrogens can work through a recently discovered G-coupled estrogen receptor. Binding with both types of the receptors causes a signal, which leads to i.e. enhanced cell proliferation. There are many published reports which suggest that estrogen can be synthesized in situ in lung cancer. Some disturbances in the activity and expression levels of enzymes involved in estrogen synthesis were proved. This suggests that increased amounts of sex-steroid hormones can affect cells biology and be the reason of the accelerated development and pathogenesis of lung cancer. There also exist phenomena which associate estrogenic metabolism and tobacco combustion and its carcinogenic influence on the lungs. Compounds present in cigarette smoke induce the activity of CYP1B1, the enzyme responsible for estrogenic metabolism and synthesis of their cateholic derivatives. These structures during their redox cycle are able to release reactive oxygen species or form DNA adduct, which generally leads to destruction of genetic material. This process may explain the synergistic effect of smoking and estrogens on estrogen-dependent lung cancer development.

Are male and female smokers at equal risk of smoking-related cancer: evidence from a Swedish prospective study

This study examines sex differences in the relative risks of lung cancer and other smoking-related cancers (i.e. cancers of the upper respiratory tract, oesophagus, pancreas, bladder, and renal pelvis). Data on smoking habits in 1963 from a random sample of 56,000 men and women were linked with information on new cases of cancer for 1964 - 89. Compared with people who have never smoked, the relative risks of lung cancer at different levels of pack-years completed in 1963 (>5, 6 - 15, 16 - 25 and 25+ pack-years) were 1.6, 4.4, 14.2, and 17.9 for men, and 2.1, 6.3, 10.3, and 16.5 for women. The corresponding relative risks of other smoking-related cancers were 1.8, 3.0 5.4, and 6.4 for men, and 2.0, 3.1, 5.0, and 6.5 for women. These results suggest that men and women have similar relative risks of smoking-related cancers at different levels of smoking.

Molecular epidemiology of lung cancer and geographic variations with special reference to EGFR mutations

Lung cancer is a leading cause of cancer-related mortality in many countries. Although recent advances in targeted therapy against driver oncogenes have significantly improved patient outcome, cure of this disease is still exceptional. Although tobacco is a known cause of lung cancer, not all smokers develop lung cancer, and conversely many patients, especially Asian female patients with lung cancer, are lifetime never-smokers. Therefore, efforts to understand the basis for different susceptibilities to lung cancer among individuals with different genetic, biologic, ethnic, and social backgrounds are important to help develop effective preventive measures. Lung cancer in never-smokers has many different characteristics to lung cancer in smokers, such as adenocarcinoma predominance and high frequency of epidermal growth factor receptor (EGFR) mutation yet low number of genetic changes. Epidemiologic studies suggest that East Asians are more susceptible to smoking-unrelated lung cancer but less susceptible to smoking-related lung cancer compared with Caucasians. Mutations in the EGFR gene are more common in Asian females and never-smokers. Our case-control study suggests that EGFR mutation occurs independent of smoking, and that the apparent low frequency of EGFR mutations in smokers may be the result of dilution by smoking-related lung cancer. The frequencies of three EGFR gene polymorphisms associated with increased protein expression are significantly different between East Asians and Caucasians, favoring lower protein expression in East Asians. Although these may be associated with preferred expression of the EGFR mutant allele, it is difficult to explain the frequent EGFR mutation in Asian patients. Genome wide association studies (GWAS) revealed several loci related to lung cancer susceptibility. In the future, GWAS may identify loci that are specifically related to EGFR-targeted carcinogenesis, leading to identification of carcinogens that induce EGFR mutations and effective prevention measures.

Gender susceptibility for cigarette smoking-attributable lung cancer: a systematic review and meta-analysis

OBJECTIVES

As the primary cause of lung cancer, whether smoking confers the same risk of lung cancer for women as men is unclear. Therefore, we aimed to compare male and female susceptibility for cigarette smoking-attributable lung cancer.

METHODS

A systematic review and meta-analysis was conducted by searching articles published up to July 2013 in three online databases (MEDLINE, EMBASE, and Cochrane Database). All studies estimated the association of cigarette smoking with the risk of lung cancer between men and women, respectively. A random effects model with inverse variance weighting was used to pool data. Male to female ratio of relative risk (RRR) was calculated to compare male and female susceptibility for cigarette smoking-attributable lung cancer.

RESULTS

47 articles containing 404,874 individuals were included in the final analysis. Compared with non-smokers, male to female RRR was 1.61 (95%CI: 1.37, 1.89) among current smokers. Based on pathological type, adenocarcinoma had the highest RRR (1.42; 95%CI: 0.86, 2.35), followed by squamous cancer and small cell lung cancer. Furthermore, compared with non-smoking men, current smoking men had higher risk of lung cancer than women in spite of smoking quantity, smoking duration or years since quitting.

CONCLUSIONS

These findings indicated that males had higher susceptibility for cigarette smoking-attributable lung cancer than females. It is contradicted with traditional opinion that females would be more easily suffered from cigarette smoking-attributable health problems than males. Hence, tobacco control is very crucial in both males and females.

Targeting the estrogen pathway for the treatment and prevention of lung cancer

The estrogen signaling pathway is involved in the biology of non-small-cell lung cancer and represents a novel therapeutic target for lung cancer. This is supported by epidemiological evidence, preclinical studies and recent data from clinical trials. Antiestrogens and inhibitors of estrogen synthesis have been shown to inhibit lung tumor growth as well as prevent lung tumorigenesis in preclinical models both in vitro and in vivo. Two clinical trials testing the effectiveness of hormonal strategies in advanced non-small-cell lung cancer have recently been completed with promising results. Future work in this field should focus on identification of patients that would benefit from hormone modulators so that they can be used earlier in the course of disease or for chemoprevention.

Heavy smoking and lung cancer: are women at higher risk? Result of the ICARE study

Background:

Whether women are more or equally susceptible to the carcinogenic effects of cigarette smoke on the lungs compared with men is a matter of controversy. Using a large French population-based case–control study, we compared the lung cancer risk associated with cigarette smoking by gender.

Methods:

The study included 2276 male and 650 female cases and 2780 male and 775 female controls. Lifetime smoking exposure was represented by the comprehensive smoking index (CSI), which combines the duration, intensity and time since cessation of smoking habits. The analysis was conducted among the ever smokers. All of the models were adjusted for age, department (a regional administrative unit), education and occupational exposures.

Results:

Overall, we found that the lung cancer risk was similar among men and women. However, we found that women had a two-fold greater risk associated with a one-unit increase in CSI than men of developing either small cell carcinoma (OR=15.9, 95% confidence interval (95% CI) 7.6, 33.3 and 6.6, 95% CI 5.1, 8.5, respectively; P<0.05) or squamous cell carcinoma (OR=13.1, 95% CI 6.3, 27.3 and 6.1, 95% CI 5.0, 7.3, respectively; P<0.05). The association was similar between men and women for adenocarcinoma.

Conclusion:

Our findings suggest that heavy smoking might confer to women a higher risk of lung cancer as compared with men.

Differential Effect of Active Smoking on Gene Expression in Male and Female Smokers

Smoking is the second leading cause of preventable death in the United States. Cohort epidemiological studies have demonstrated that women are more vulnerable to cigarette-smoking induced diseases than their male counterparts, however, the molecular basis of these differences has remained unknown. In this study, we explored if there were differences in the gene expression patterns between male and female smokers, and how these patterns might reflect different sex-specific responses to the stress of smoking. Using whole genome microarray gene expression profiling, we found that a substantial number of oxidant related genes were expressed in both male and female smokers, however, smoking-responsive genes did indeed differ greatly between male and female smokers. Gene set enrichment analysis (GSEA) against reference oncogenic signature gene sets identified a large number of oncogenic pathway gene-sets that were significantly altered in female smokers compared to male smokers. In addition, functional annotation with Ingenuity Pathway Analysis (IPA) identified smoking-correlated genes associated with biological functions in male and female smokers that are directly relevant to well-known smoking related pathologies. However, these relevant biological functions were strikingly overrepresented in female smokers compared to male smokers. IPA network analysis with the functional categories of immune and inflammatory response gene products suggested potential interactions between smoking response and female hormones. Our results demonstrate a striking dichotomy between male and female gene expression responses to smoking. This is the first genome-wide expression study to compare the sex-specific impacts of smoking at a molecular level and suggests a novel potential connection between sex hormone signaling and smoking-induced diseases in female smokers.

Cigarette smoking and lung cancer risk according to histologic type in Japanese men and women

Although cigarette smoking is a well-known risk factor for lung cancer, histology-specific risk has not been fully clarified in Japan. This case-control study evaluated the associations between smoking and lung cancer risk according to sex and histologic type. From among patients aged 30 years and over admitted to a single hospital in Japan between 1997 and 2009, 1670 lung cancer cases and 5855 controls were selected. History of smoking, quantity and duration of smoking, and passive smoking from spouses were assessed using a self-administered questionnaire. Odds ratios (ORs) and 95% confidence intervals (CIs) for each exposure were estimated by unconditional logistic regression. Ever-smoking was significantly associated with a higher risk of squamous cell and small cell carcinoma. The OR for these two histologic types combined was larger in women (OR = 24.98, 95% CI: 13.50-46.23) than in men (OR = 9.43, 95% CI: 5.73-15.51). Analysis of the quantity and duration of smoking showed that the OR for each exposure level tended to be larger in women than in men. For adenocarcinoma, clear positive associations with quantity and duration-related factors were observed among men, and a significant positive association with passive smoking from spouses was found among non-smoking women (OR = 1.44, 95% CI: 1.06-1.95). These results suggest sex- and histologic type- differences in the association of smoking with lung cancer risk. Although smoking control should be continued to prevent lung cancers, further studies are required to better clarify differences in smoking-related lung cancer risk between the sexes and histologic types.

Are women who smoke at higher risk for lung cancer than men who smoke?

Worldwide lung cancer incidence is decreasing or leveling off among men, but rising among women. Sex differences in associations of tobacco carcinogens with lung cancer risk have been hypothesized, but the epidemiologic evidence is conflicting. We tested sex-smoking interaction in association with lung cancer risk within a population-based case-control study, the Environment and Genetics in Lung Cancer Etiology (EAGLE) Study (Lombardy, Italy, 2002-2005). Detailed lifetime smoking histories were collected by personal interview in 2,100 cases with incident lung cancer and 2,120 controls. Odds ratios and 95% confidence intervals for pack-years of cigarette smoking were estimated by logistic regression, adjusted for age, residence area, and time since quitting smoking. To assess sex-smoking interaction, we compared the slopes of odds ratios for logarithm of pack-years in a model for men and women combined. Overall, the slope for pack-years was steeper in men (odds ratio for female-smoking interaction = 0.39, 95% confidence interval: 0.24, 0.62; P < 0.0001); after restriction to ever smokers, the difference in slopes was much smaller (odds ratio for interaction = 0.63, 95% confidence interval: 0.29, 1.37; P = 0.24). Similar results were found by histological type. Results were unchanged when additional confounders were evaluated (e.g., tobacco type, inhalation depth, Fagerström-assessed nicotine dependence). These findings do not support a higher female susceptibility to tobacco-related lung cancer.

Lung cancer in women

Recent biological advances in tumor research provide clear evidence that lung cancer in females is different from that in males. These differences appear to have a direct impact on the clinical presentation, histology, and outcomes of lung cancer. Women are more likely to present with lung adenocarcinoma, tend to receive a diagnosis at an earlier age, and are more likely to be diagnosed with localized disease. Women may also be more predisposed to molecular aberrations resulting from the carcinogenic effects of tobacco, but do not appear to be more susceptible than men to developing lung cancer. The gender differences found in female lung cancer make it mandatory that gender stratification is used in clinical trials in order to improve the survival rates of patients with lung cancer.

Retrospective cohort study of smoking and lung cancer incidence in rural prefecture, Japan

OBJECTIVES

We conducted an epidemiological study of the relationship between lung cancer incidence and smoking, with special reference to the benefits of smoking cessation for reducing lung cancer incidence, to promote a local smoking control program.

METHODS

The study was a retrospective cohort study. The population studied was 16,383 male examinees of lung cancer health examinations in 1995 in Tottori Prefecture, Japan. Smoking status from the questionnaire during the health examination was used as the exposure variable. Endpoint (lung cancer incidence) was obtained from the Tottori population-based cancer registry. A multivariable analysis using the Cox proportional hazard model was adapted for statistical analysis. The average follow-up period was 4.3 years.

RESULTS

The hazard ratio of current smokers for the incidence of lung cancer was 4.9, whereas that of ex-smokers was 2.2. The dose-response relationship between lung cancer incidence and lifetime cigarette consumption (pack year) was determined. The ratio increased among younger subjects (under 65 years old). The hazard ratio of ex-smokers decreased with years just after quitting smoking, and reached the level of never smokers after 10-19 years from smoking cessation.

CONCLUSIONS

We reconfirmed that the magnitude of risk estimates of smoking for lung cancer incidence was similar to those of previous studies, and smoking cessation was effective for reducing lung cancer risk.

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.

Lung cancer in women: the differences in epidemiology, biology and treatment outcomes

Although the prevalence of lung cancer in men has been decreasing, it has been increasing in women. Without a doubt, lung cancer is a major health problem for women in the USA, not only owing to its high incidence rate but, more alarming, the high mortality rate. Lung cancer kills more women each year than breast, ovarian and uterine cancers combined. One of the most important risk factors for the development of lung cancer in both men and women is cigarette smoking. Unfortunately, the prevalence of smoking among women has increased significantly since 1980, which is a major concern as epidemiologic data suggest that women may be more susceptible to developing lung cancer than men. Many will argue, however, that after adjusting for tobacco exposure, some studies have failed to show that women are at a higher risk for developing lung cancer. Indeed, the increased risk of lung cancer in women remains controversial. There is, however, little controversy to the fact that the biology of lung cancer differs between the sexes. This paper summarizes the explanations for the sex differences in lung cancer, including differences in molecular abnormalities, growth factor receptors, hormonal influences, differences in cytochrome P-450 enzymes and DNA repair capacity, as well as variations in treatment outcomes.

Epidemiology of lung cancer in women: risk factors, survival, and screening

OBJECTIVE

Lung cancer remains the leading cause of cancer mortality in both men and women. Tobacco use causes the vast majority of lung cancer in women but does not explain all cases, because about one in five women who develop lung cancer have never smoked.

CONCLUSION

Environmental exposures, genetic predisposition, hormonal factors, and viral infection may all play a role in lung cancer in women. A better understanding may provide an avenue to more effective screening, diagnosis, and therapy.

Smoking reduces survival in young females with lung adenocarcinoma after curative resection

The aim of this study was to investigate effects of smoking on the overall survival of young female lung adenocarcinoma patients after curative resection. A total of 282 surgically treated young females (younger than 40) with histologically confirmed primary lung adenocarcinoma were studied retrospectively. Overall survivals (OS) and related prognostic factors were analyzed. The 5-year OS of current-smokers and non-smokers were 20 and 36.6%, respectively (P = 0.03). As for patients with stage I disease, the 5-year OS of current-smokers and non-smokers were 50 and 68.8%, respectively, (P = 0.02). Smoking (RR = 3.15, CI 1.726-8.786) was identified as an independent prognostic factor. Current-smokers (21.4 vs. 14.5%, P = 0.03) and non-smokers (37.9 vs. 28.8%, P = 0.02) all benefited from adjuvant chemotherapy. Among young female patients with adenocarcinoma, current-smokers have a lower survival rate than non-smokers, especially patients with stage I disease.

Gender is a risk factor for lung cancer

Results of epidemiological studies suggest that, after one controls for the number of cigarettes smoked, women have a three times higher risk of getting lung cancer than men. Although the mechanism(s) explaining this gender-dependent difference in lung cancer risk is not known, it is thought that endocrine factors may play an important role. Normal human bronchial epithelial cells contain estrogen receptors and synthesize 17β-estradiol (E(2)) and estrone (E(1)), which can undergo further metabolism into the catechol estrogens, 4-hydroxyestradiol (4-OHE(2)) and 4-hydroxyestrone (4-OHE(1)), respectively. Catechol estrogens are formed from E(2) by the actions of cytochrome p450 1B1 (CYP1B1). CYP1B1 is present in normal human bronchial epithelial) cells, and its activity is increased by cigarette smoking. Both 4-OHE(1) and 4-OHE(2) are mutagenic and carcinogenic and may exert their biological effects by inducing DNA adducts in cancer-related genes, including the tumor suppressor gene p53 and the proto-oncogene K-ras. Women with lung cancer have a different p53 mutational spectrum and a higher frequency of K-ras mutations than do men with lung cancer. Both clinical and basic research studies support the hypothesis that E(2) and cigarette smoking are cofactors in lung carcinogenesis in women. More specifically, cigarette smoke stimulates metabolism of E(2) into the genotoxic metabolites, 4-OHE(1) and 4-OHE(2,) which interact with DNA in cancer-related genes, including the tumor suppressor gene, p53, and the proto-oncogene K-ras, two genes frequently mutated in patients with lung cancer. E(2) may stimulate cellular proliferation and enhance tumor growth.

Sex differences in susceptibility to PAHs is an intrinsic property of human lung adenocarcinoma cells

Recent epidemiological studies have disputed whether females are at increased risk of lung cancer compared to males. However, several molecular studies are in support of an increased susceptibility to tobacco smoke carcinogens among females. Our earlier findings suggest that women display higher levels of smoking-induced bulky/hydrophobic DNA adducts which may be related to an increased expression of CYP1A1 in their lungs, compared to men. In this in vitro study, 11 lung adenocarcinoma cell lines, 6 of male and 5 of female origin, were exposed to benzo[a]pyrene, cigarette smoke condensate (CSC), or vehicle control. Subsequent expression analysis of genes in the polycyclic aromatic hydrocarbon bioactivation pathway was conducted with Real-Time RT-PCR. DNA adducts were measured in benzo[a]pyrene-exposed cells by ³²P-postlabelling analysis, and CYP1 activity was measured by EROD assay. Analysis of benzo[a]pyrene-DNA adducts showed higher levels of adducts in cell lines from women compared to cell lines from men (p=0.03). The results also revealed significant sex differences in CYP1A1 gene expression, both in untreated cells (p=0.03), and in cells exposed to benzo[a]pyrene (p=0.017) and cigarette smoke condensate (p=0.0043). In CSC-exposed cells, significantly higher levels of CYP1 activity was found in cell lines of female origin (p=0.049). These results are in support of the previously published in vivo data, providing evidence for a higher susceptibility to PAH of women's lungs.

Haplotypes of estrogen receptor-beta and risk of non-small cell lung cancer in women

Epidemiologic and biologic evidence suggests that lung cancer has different clinical and biological characteristics in women, and that estrogen may contribute to the pathogenesis of non-small cell lung cancer (NSCLC). We investigated whether germline variation in the estrogen receptor-beta gene (ESR2) is associated with lung cancer risk among 1021 female cases and 826 female controls enrolled in the Lung Cancer Susceptibility Study at the Massachusetts General Hospital from 1992 to 2004. Four haplotype-tagging polymorphisms (htSNPs) (rs3020450, rs1256031, rs1256049, rs4986938) captured the common genetic variation across the ESR2 locus from a set of markers culled from healthy controls from a public database and sequencing the coding regions of 95 breast cancer cases. Using the expectation-maximization algorithm, five common haplotypes were resolved (CCGC (43%), TCAT (287%), TCAC (11%), CCAC (9%) and CCAT (6%)). Multivariate logistic regression was used to estimate adjusted odds ratios (OR) and their 95% confidence intervals (95% CI) for individual htSNPs and haplotype scores. Neither the four individual htSNPs nor their resolved haplotypes were associated with lung cancer risk in the entire population, nor in strata defined by parity (yes versus no), age (<50 years versus ≥ 50 years) or smoking history (current-, former-, never-smokers). Our findings indicate that ESR2 is not associated with risk of lung cancer in women.

Women and tobacco dependence

Millions of American girls and women have been drawn to smoking by an industry that has been clearly and systematically targeting women of all ages and life circumstances. Tobacco marketing strategies skillfully link cigarette use to typical female values. Biologically speaking, women are especially vulnerable to the legion of health problems of tobacco use. Smoking is a critical hazard for women in their reproductive years, particularly when they are pregnant.

Parity and risk of lung cancer in women

Patterns of lung cancer incidence suggest that gender-associated factors may influence lung cancer risk. Given the association of parity with risk of some women's cancers, the authors hypothesized that childbearing history may also be associated with lung cancer. Women enrolled in the Lung Cancer Susceptibility Study at Massachusetts General Hospital (Boston, Massachusetts) between 1992 and 2004 (1,004 cases, 848 controls) were available for analysis of the association between parity and lung cancer risk. Multivariate logistic regression was used to estimate adjusted odds ratios and 95% confidence intervals. After results were controlled for age and smoking history, women with at least 1 child had 0.71 times the odds of lung cancer as women without children (odds ratio = 0.71, 95% confidence interval: 0.52, 0.97). A significant linear trend was found: Lung cancer risk decreased with increasing numbers of children (P < 0.001). This inverse association was stronger in never smokers (P = 0.12) and was limited to women over age 50 years at diagnosis (P = 0.17). Age at first birth was not associated with risk. The authors observed a protective association between childbearing and lung cancer, adding to existing evidence that reproductive factors may moderate lung cancer risk in women.

Emerging drugs for small-cell lung cancer

Small-cell lung cancer (SCLC) is a rapidly progressing tumor in which chemotherapy has a limited impact on survival. Unfortunately, little progress has been made in the medical management of SCLC during the last 30 years, which is best exemplified by the fact that standard first-line chemotherapy has remained platinum-based over time. On the other hand, improvements in survival have been obtained only with the introduction of innovative radiation strategies such as accelerated hyperfractionation to the thorax for limited-stage disease and prophylactic cranial irradiation for both limited- and extensive-stage disease. However, recent advances in the understanding of SCLC biology have renewed the interest in the clinical development of active drugs for SCLC. In this review, we address the most promising agents under clinical evaluation, discussing both novel chemotherapeutic agents and targeted agents. Particularly, amrubicin, a fully synthetic anthracycline, is a very active agent for SCLC, and ongoing Phase III trials are evaluating this agent either in the first-line setting of extensive-stage or relapsed disease. Among targeted agents, anti-angiogenic strategies and Bcl-2 inhibitors represent the most promising approaches, and they are being specifically tested in combination with and/or as maintenance therapy after first-line platinum-based chemotherapy.

Lung cancer: a biologically different disease in women?

Lung cancer is now the leading cancer killer of women, having surpassed breast cancer in 1987. Over 30,000 more US women are expected to die from lung cancer than from breast cancer annually. The vast majority of lung cancer cases are attributable to smoking, and smoking prevalence rates remain unacceptably high in US women. Mounting evidence suggests that there are significant differences in lung cancer between the sexes. Although the magnitude of the effect of smoking on the development of lung cancer may not be different, smoking appears to have an impact on the histology of lung cancer. Hormonal and biologic effects may play a role in lung cancer carcinogenesis, and may impact treatment response. A more thorough understanding of the biologically different aspects of lung cancer across different populations may lead to innovations in prevention and treatment.

Smoking and the risk of upper aero digestive tract cancers for men and women in the Asia-Pacific region

Although smoking is an established causal factor for upper aero digestive tract cancer (UADTC), most of the evidence originates from the West. Thus, we analysed data from 455,409 subjects in the Asia Pacific Cohort Studies Collaboration. Over a median of around six years follow-up, 371 deaths from UADTC were observed. The hazard ratio (95% confidence interval) for current smokers, compared with those who had never smoked, was 2.36 (1.76 – 3.16), adjusted for age and alcohol drinking. Tobacco control policies are urgently required in Asia to prevent millions of deaths from UADTC that smoking will otherwise cause.

Estimation of the effects of smoking and DNA repair capacity on coefficients of a carcinogenesis model for lung cancer

Numerous prospective and retrospective studies have clearly demonstrated a dose-related increased lung cancer risk associated with cigarette smoking, with evidence also for a genetic component to risk. In this study, using the two-stage clonal expansion stochastic model framework, for the first time we investigated the roles of both genetic susceptibility and smoking history in the initiation, clonal expansion, and malignant transformation processes in lung carcinogenesis, integrating information collected by a case-control study and a large-scale prospective cohort study. Our results show that individuals with suboptimal DNA repair capacity have enhanced transition rates of key events in carcinogenesis.

Lung cancer occurrence in never-smokers: an analysis of 13 cohorts and 22 cancer registry studies

BACKGROUND

Better information on lung cancer occurrence in lifelong nonsmokers is needed to understand gender and racial disparities and to examine how factors other than active smoking influence risk in different time periods and geographic regions.

METHODS AND FINDINGS

We pooled information on lung cancer incidence and/or death rates among self-reported never-smokers from 13 large cohort studies, representing over 630,000 and 1.8 million persons for incidence and mortality, respectively. We also abstracted population-based data for women from 22 cancer registries and ten countries in time periods and geographic regions where few women smoked. Our main findings were: (1) Men had higher death rates from lung cancer than women in all age and racial groups studied; (2) male and female incidence rates were similar when standardized across all ages 40+ y, albeit with some variation by age; (3) African Americans and Asians living in Korea and Japan (but not in the US) had higher death rates from lung cancer than individuals of European descent; (4) no temporal trends were seen when comparing incidence and death rates among US women age 40-69 y during the 1930s to contemporary populations where few women smoke, or in temporal comparisons of never-smokers in two large American Cancer Society cohorts from 1959 to 2004; and (5) lung cancer incidence rates were higher and more variable among women in East Asia than in other geographic areas with low female smoking.

CONCLUSIONS

These comprehensive analyses support claims that the death rate from lung cancer among never-smokers is higher in men than in women, and in African Americans and Asians residing in Asia than in individuals of European descent, but contradict assertions that risk is increasing or that women have a higher incidence rate than men. Further research is needed on the high and variable lung cancer rates among women in Pacific Rim countries.

Comparison of aspects of smoking among the four histological types of lung cancer

BACKGROUND

The magnitude of the link between cigarette smoking and lung cancer may vary by histological type.

METHODS

We used polytomous logistic regression to evaluate whether aspects of smoking have different effects across four histological types in the Nurses' Health Study.

RESULTS

From 1976 to 2002, we identified 1062 cases of lung cancer: squamous cell (n = 201), small cell (n = 236), adenocarcinoma (n = 543) and large cell carcinoma (n = 82), among 65 560 current or former smokers. Risk reduction after quitting ranged from an 8% reduction (relative risk (RR): 0.92, 95% CI 0.91 to 0.94) to a 17% reduction (RR: 0.83, 95% CI 0.80 to 0.86) per year for adenocarcinoma and small cell carcinoma, respectively, with a 9% reduction observed for large cell carcinoma and an 11% reduction observed for squamous cell carcinoma. The association of age at smoking initiation and former cigarette smoking was similar across types, while the association of smoking duration differed. The risk of adenocarcinoma increased by 6% per year of smoking, compared to 7% for large cell, 10% for squamous cell and 12% for small cell. The 6% difference between adenocarcinoma and small cell carcinoma is equivalent to a 3.2 to 9.7-fold increase in risk for 20 years of smoking.

CONCLUSIONS

The effects of the number of cigarettes smoked per day and years since quitting smoking are different across the major types of lung cancer, which are fully appreciated at long durations of smoking and smoking cessation. Smoking prevention and cessation should continue to be the focus of public health efforts to reduce lung cancer incidence and mortality.

Women and lung cancer

OBJECTIVES

There is expanding evidence that lung cancer has a multitude of sex differences. This article will review these differences and discuss nursing implications for women with lung cancer.

DATA SOURCES

Research and journal articles.

CONCLUSION

Understanding the sex differences of lung cancer is essential for individualizing care for women with lung cancer.

IMPLICATIONS FOR NURSING PRACTICE

Nurses play an integral role throughout the trajectory of illness for women with lung cancer. Understanding the sex differences will help nurses to individualize the care for this population to meet their specific needs.