Hormone replacement therapy as a risk factor for non-small cell lung cancer: results of a case-control study

Role of sex hormones in lung cancer

Lung cancer represents the world's leading cause of cancer deaths. Sex differences in the incidence and mortality rates for various types of lung cancers have been identified, but the biological and endocrine mechanisms implicated in these disparities have not yet been determined. While some cancers such as lung adenocarcinoma are more commonly found among women than men, others like squamous cell carcinoma display the opposite pattern or show no sex differences. Associations of tobacco product use rates, susceptibility to carcinogens, occupational exposures, and indoor and outdoor air pollution have also been linked to differential rates of lung cancer occurrence and mortality between sexes. While roles for sex hormones in other types of cancers affecting women or men have been identified and described, little is known about the influence of sex hormones in lung cancer. One potential mechanism identified to date is the synergism between estrogen and some tobacco compounds, and oncogene mutations, in inducing the expression of metabolic enzymes, leading to enhanced formation of reactive oxygen species and DNA adducts, and subsequent lung carcinogenesis. In this review, we present the literature available regarding sex differences in cancer rates, associations of male and female sex hormones with lung cancer, the influence of exogenous hormone therapy in women, and potential mechanisms mediated by male and female sex hormone receptors in lung carcinogenesis. The influence of biological sex on lung disease has recently been established, thus new research incorporating this variable will shed light on the mechanisms behind the observed disparities in lung cancer rates, and potentially lead to the development of new therapeutics to treat this devastating disease.

Plausible Role of Estrogens in Pathogenesis, Progression and Therapy of Lung Cancer

Malignant neoplasms are among the most common diseases and are responsible for the majority of deaths in the developed world. In contrast to men, available data show a clear upward trend in the incidence of lung cancer in women, making it almost as prevalent as breast cancer. Women might be more susceptible to the carcinogenic effect of tobacco smoke than men. Furthermore, available data indicate a much more frequent mutation of the tumor suppressor gene-p53 in non-small cell lung cancer (NSCLC) female patients compared to males. Another important factor, however, might lie in the female sex hormones, whose mitogenic or carcinogenic effect is well known. Epidemiologic data show a correlation between hormone replacement therapy (HRT) or oral contraceptives (OCs), and increased mortality rates due to the increased incidence of malignant tumors, including lung cancer. Interestingly, two types of estrogen receptors have been detected in lung cancer cells: ERα and ERβ. The presence of ERα has been detected in tissues and non-small-cell lung carcinoma (NSCLC) cell lines. In contrast, overexpression of ERβ is a prognostic marker in NSCLC. Herein, we summarize the current knowledge on the role of estrogens in the etiopathogenesis of lung cancer, as well as biological, hormonal and genetic sex-related differences in this neoplasm.

Reproductive factors and lung cancer risk: a comprehensive systematic review and meta-analysis

BACKGROUND

A number of studies have investigated the association between reproductive factors and lung cancer risk, however findings are inconsistent. This meta-analysis aimed to evaluate the association between female reproductive factors and lung cancer risk.

METHODS

We conducted a comprehensive systematic search to identify relevant and eligible studies published before 18th December 2019. Inter-study heterogeneity was assessed using the Q test and I2 statistic. Based on the heterogeneity of each reproductive factor, fixed or random effects models were used to calculate the summary odds ratios (ORs) and 95% confidence intervals (CIs). Subgroup analyses by study design, lung cancer subtypes, smoking status, and ethnicity were also performed.

RESULTS

A total of 66 studies with 20 distinct reproductive factors were included in this meta-analysis. Comparing the highest and lowest categories (reference) of each reproductive factor, parity (OR = 0.83, 95% CI = 0.72-0.96), menstrual cycle length (OR = 0.79, 95% CI = 0.65-0.96), and age at first birth (OR = 0.85, 95% CI = 0.74-0.98), were significantly associated with a lower risk of overall lung cancer. On the contrary, non-natural menopause was significantly associated with higher lung cancer risk (OR = 1.52, 95% CI = 1.25-1.86). Among never-smokers, a significant negative association was found between parity and lung cancer risk. Both parity and non-natural menopause were statistically significant in case-control studies.

CONCLUSION

These results suggest that certain reproductive factors may be associated with lung cancer risk. Future studies should further validate the associations, and investigate the underlying mechanisms.

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.

Hormone Use, Reproductive History, and Risk of Lung Cancer: The Women's Health Initiative Studies

INTRODUCTION

Results from the Women's Health Initiative clinical trials demonstrated no increase in the risk of lung cancer in postmenopausal women treated with hormone therapy (HT). We conducted a joint analysis of the Women's Health Initiative observational study data and clinical trials data to further explore the association between estrogen and estrogen-related reproductive factors and lung cancer risk.

METHODS

Reproductive history, oral contraceptive use, and postmenopausal HT were evaluated in 160,855 women with known HT exposures. Follow-up for lung cancer was through September 17, 2012; 2467 incident lung cancer cases were ascertained, with median follow-up of 14 years.

RESULTS

For all lung cancers, women with previous use of estrogen plus progestin of less than 5 years (hazard ratio = 0.84; 95% confidence interval = 0.71-0.99) were at reduced risk. A limited number of reproductive factors demonstrated associations with risk. There was a trend toward decreased risk with increasing age at menopause (ptrend = 0.04) and a trend toward increased risk with increasing number of live births (ptrend = 0.03). Reduced risk of non-small-cell lung cancer was associated with age 20-29 years at first live birth. Risk estimates varied with smoking history, years of HT use and previous bilateral oophorectomy.

CONCLUSIONS

Indirect measures of estrogen exposure to lung tissue, as used in this study, provide only weak evidence for an association between reproductive history or HT use and risk of lung cancer. More detailed mechanistic studies and evaluation of risk factors in conjunction with estrogen receptor expression in the lung should continue as a role for estrogen cannot be ruled out and may hold potential for prevention and treatment strategies.

Pharmacogenetics of chemotherapy-induced nausea and vomiting

Chemotherapy-induced nausea and vomiting (CINV) is associated with distressing adverse effects observed in patients during cytotoxic chemotherapy. One of the potential factors explaining suboptimal response to currently used antiemetics is variability in genes encoding enzymes and proteins that play a role in the action of antiemetic drugs. Pharmacogenomics studies of CINV are sparse and focus mainly on polymorphisms associated with serotonin receptor, drug metabolism and drug transport. Currently, the role of pharmacogenetics in mechanisms of CINV has not been fully unraveled, and it is premature to implement results of pharmacogenetic association studies of antiemetic drugs in clinical practice. More uniform studies, with genetic profiles and biomarkers relevant for the proposed target and transporter mechanisms, are needed.

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.

Hormone use and risk for lung cancer: a pooled analysis from the International Lung Cancer Consortium (ILCCO)

BACKGROUND

The association between oral contraceptive (OC) use, hormone replacement therapy (HRT) and lung cancer risk in women is still debated.

METHODS

We performed a pooled analysis of six case-control studies (1961 cases and 2609 controls) contributing to the International Lung Cancer Consortium. Potential associations were investigated with multivariable unconditional logistic regression and meta-analytic models. Multinomial logistic regressions were performed to investigate lung cancer risk across histologic types.

RESULTS

A reduced lung cancer risk was found for OC (odds ratio (OR)=0.81; 95% confidence interval (CI): 0.68-0.97) and HRT ever users (OR=0.77; 95% CI: 0.66-0.90). Both oestrogen only and oestrogen+progestin HRT were associated with decreased risk (OR=0.76; 95% CI: 0.61-0.94, and OR=0.66; 95% CI: 0.49-0.88, respectively). No dose-response relationship was observed with years of OC/HRT use. The greatest risk reduction was seen for squamous cell carcinoma (OR=0.53; 95% CI: 0.37-0.76) in OC users and in both adenocarcinoma (OR=0.79; 95% CI: 0.66-0.95) and small cell carcinoma (OR=0.37; 95% CI: 0.19-0.71) in HRT users. No interaction with smoking status or BMI was observed.

CONCLUSION

Our findings suggest that exogenous hormones can play a protective role in lung cancer aetiology. However, given inconsistencies with epidemiological evidence from cohort studies, further and larger investigations are needed for a more comprehensive view of lung cancer development in women.

Hormone replacement therapy in females can decrease the risk of lung cancer: a meta-analysis

The purpose of the present meta-analysis was to determine the relationship between hormone replacement therapy (HRT) and lung cancer risk in females. Publications were reviewed and obtained through a PubMed, EMBASE database and Cochrane Library literature search up to May, 2012. The detailed numbers of patients in different groups, odd ratios (ORs) and corresponding 95% confidence intervals (CIs) were collected and estimated using a random-effects model. Twenty five studies entered into the meta-analysis. The total number of participates and lung cancer patients was 656,403 and 11,442, respectively. The OR of all 25 studies was 0.91 (95%CI  = 0.83 to 0.99) and P value was 0.033. In stratified analyses, the positive association between HRT use and decreased lung cancer risk was also found in the patients with BMI<25 kg/m² (OR = 0.65, P = 0.000), and never smokers patients (OR = 0.86, P = 0.042). However, HRT use in patients with artificial menopause could increase the lung cancer risk, OR = 1.51(P = 0.001). The result of Egger's test did not show any evidence of publican bias (P = 0.069). In conclusion, our meta-analysis on HRT and lung cancer risk suggests that HRT use is correlated with decreased lung cancer risk in female, especially in female with BMI<25 kg/m² and never smokers.

Reproductive and hormonal factors and the risk of lung cancer: the EAGLE study

Evidence about the role for reproductive and hormonal factors in the etiology of lung cancer in women is conflicting. To clarify this question, we examined 407 female cases and 499 female controls from the Environment And Genetics in Lung cancer Etiology population-based case-control study. Subjects were interviewed in person using a computer-assisted personal interview to assess demographics, education, smoking history, medical history, occupational history, reproductive and hormonal factors. Associations of interest were investigated using logistic regression models, adjusted for catchment area and age (matching variables), cigarette smoking (status, pack-years and time since quitting). Additional confounding variables were investigated but did not substantially affect the results. We observed a reduced risk of lung cancer among women with later age at first live birth [≥31 years: odds ratio (OR) = 0.57, 95% confidence interval (CI) = 0.31-1.06, p-trend = 0.05], later age at menopause (≥51 years: OR = 0.49, 95%CI = 0.31-0.79, p-trend = 0.003) and longer reproductive periods (≥41 years: OR = 0.44, 95%CI = 0.25-0.79, p-trend = 0.01). A reduced risk was also observed for hormone replacement therapy (OR = 0.63, 95%CI = 0.42-0.95, p = 0.03) and oral contraceptive use (OR = 0.67, 95%CI = 0.45-1.00, p = 0.05) but no trend with duration of use was detected. Menopausal status (both natural and induced) was associated with an augmented risk. No additional associations were identified for other reproductive variables. This study suggests that women who continue to produce estrogens have a lower lung cancer risk. Large studies with great number of never smoking women, biomarkers of estrogen and molecular classification of lung cancer are needed for a more comprehensive view of the association between reproductive factors and lung cancer risk.

Use of the cytokinesis-blocked micronucleus assay to detect gender differences and genetic instability in a lung cancer case-control study

BACKGROUND

Although tobacco exposure is the predominant risk factor for lung cancer, other environmental agents are established lung carcinogens. Measuring the genotoxic effect of environmental exposures remains equivocal, as increases in morbidity and mortality may be attributed to coexposures such as smoking.

METHODS

We evaluated genetic instability and risk of lung cancer associated with exposure to environmental agents (e.g., exhaust) and smoking among 500 lung cancer cases and 500 controls using the cytokinesis-blocked micronucleus (CBMN) assay. Linear regression was applied to estimate the adjusted means of the CBMN endpoints (micronuclei and nucleoplasmic bridges). Logistic regression analyses were used to estimate lung cancer risk and to control for potential confounding by age, gender, and smoking.

RESULTS

Cases showed significantly higher levels of micronuclei and nucleoplasmic bridges as compared with controls (mean ± SEM = 3.54 ± 0.04 vs. 1.81 ± 0.04 and mean ± SEM = 4.26 ± 0.03 vs. 0.99 ± 0.03, respectively; P < 0.001) with no differences among participants with or without reported environmental exposure. No differences were observed when stratified by smoking or environmental exposure among cases or controls. A difference in lung cancer risk was observed between nonexposed male and female heavy smokers, although it was not statistically significant (I(2) = 64.9%; P value for Q statistic = 0.09).

CONCLUSIONS

Our study confirms that the CBMN assay is an accurate predictor of lung cancer and supports the premise that heavy smoking may have an effect on DNA repair capacity and in turn modulate the risk of lung cancer.

IMPACT

Identifying factors that increase lung cancer risk may lead to more effective prevention measures.

Prevention of tobacco carcinogen-induced lung cancer in female mice using antiestrogens

Increasing evidence shows that estrogens are involved in lung cancer proliferation and progression, and most human lung tumors express estrogen receptor β (ERβ) as well as aromatase. To determine if the aromatase inhibitor anastrozole prevents development of lung tumors induced by a tobacco carcinogen, alone or in combination with the ER antagonist fulvestrant, ovariectomized female mice received treatments with the tobacco carcinogen 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanone (NNK) along with daily supplements of androstenedione, the substrate for aromatase. Placebo, anastrozole and/or fulvestrant were administered in both an initiation and a promotion protocol of lung tumorigenesis. The combination of fulvestrant and anastrozole given during NNK exposure resulted in significantly fewer NNK-induced lung tumors (mean = 0.5) compared with placebo (mean = 4.6, P < 0.001), fulvestrant alone (mean = 3.4, P < 0.001) or anastrozole alone (mean = 2.8, P = 0.002). A significantly lower Ki67 cell proliferation index was also observed compared with single agent and control treatment groups. Beginning antiestrogen treatment after NNK exposure, when preneoplastic lesions had already formed, also yielded maximum antitumor effects with the combination. Aromatase expression was found mainly in macrophages infiltrating preneoplastic and tumorous areas of the lungs, whereas ERβ was found in both macrophages and tumor cells. Antiestrogens, especially in combination, effectively inhibited tobacco carcinogen-induced murine lung tumorigenesis and may have application for lung cancer prevention. An important source of estrogen synthesis may be inflammatory cells that infiltrate the lungs in response to carcinogens, beginning early in the carcinogenesis process. ERβ expressed by inflammatory and neoplastic epithelial cells in the lung may signal in response to local estrogen production.

The 2012 hormone therapy position statement of: The North American Menopause Society

OBJECTIVE

This position statement aimed to update the evidence-based position statement published by The North American Menopause Society (NAMS) in 2010 regarding recommendations for hormone therapy (HT) for postmenopausal women. This updated position statement further distinguishes the emerging differences in the therapeutic benefit-risk ratio between estrogen therapy (ET) and combined estrogen-progestogen therapy (EPT) at various ages and time intervals since menopause onset.

METHODS

An Advisory Panel of expert clinicians and researchers in the field of women's health was enlisted to review the 2010 NAMS position statement, evaluate new evidence, and reach consensus on recommendations. The Panel's recommendations were reviewed and approved by the NAMS Board of Trustees as an official NAMS position statement.

RESULTS

Current evidence supports the use of HT for perimenopausal and postmenopausal women when the balance of potential benefits and risks is favorable for the individual woman. This position statement reviews the effects of ET and EPT on many aspects of women's health and recognizes the greater safety profile associated with ET.

CONCLUSIONS

Recent data support the initiation of HT around the time of menopause to treat menopause-related symptoms and to prevent osteoporosis in women at high risk of fracture. The more favorable benefit-risk ratio for ET allows more flexibility in extending the duration of use compared with EPT, where the earlier appearance of increased breast cancer risk precludes a recommendation for use beyond 3 to 5 years.

Hormone therapy and risk of lung cancer: a meta-analysis

BACKGROUND

The association between hormone therapy (HT) use and lung cancer risk is inconsistent in epidemiological studies. This meta-analysis was conducted to examine the association between HT and lung cancer risk.

METHODS

We searched MEDLINE (PubMed), EMBASE, and the Cochrane Library in April 2008. All articles searched were independently reviewed and selected by two evaluators according to predetermined inclusion and exclusion criteria.

RESULTS

We included a total of 11 studies (8 case-control studies and 3 prospective cohort studies), involving a total of 220,599 participants. When all studies were pooled, the odds ratio (OR) of HT use for lung cancer risk was 0.87 (95% confidence interval (CI) 0.74-1.02). In subgroup meta-analyses, there was no association among cohort studies (relative risk (RR) 1.01; 95% CI 0.74-1.38), while there was a significant association between HT use and lung cancer risk among case-control studies (OR 0.81; 95% CI 0.68-0.97) based on a random-effects model. No significant association between HT use and lung cancer risk was observed in most of the subgroup meta-analyses by methodological quality of study, type of HT use, duration of HT use, and histology of lung cancer, while significant protective effects were observed among former and never smokers except for current smokers. However, cumulative meta-analyses based on year of publication showed a distinct trend toward a protective effect of HT use on lung cancer risk in the recent studies.

CONCLUSIONS

Overall, the findings of this meta-analysis do not support the hypothesis that there is a link between HT use and lung cancer risk. Our findings should be evaluated in further prospective cohort studies.

Body mass index and risk of lung cancer among never, former, and current smokers

BACKGROUND

Although obesity has been directly linked to the development of many cancers, many epidemiological studies have found that body mass index (BMI)--a surrogate marker of obesity--is inversely associated with the risk of lung cancer. These studies are difficult to interpret because of potential confounding by cigarette smoking, a major risk factor for lung cancer that is associated with lower BMI.

METHODS

We prospectively examined the association between BMI and the risk of lung cancer among 448 732 men and women aged 50-71 years who were recruited during 1995-1996 for the National Institutes of Health-AARP Diet and Health Study. BMI was calculated based on the participant's self-reported height and weight on the baseline questionnaire. We identified 9437 incident lung carcinomas (including 415 in never smokers) during a mean follow-up of 9.7 years through 2006. Multivariable Cox proportional hazards regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) with adjustment for lung cancer risk factors, including smoking status. To address potential bias due to preexisting undiagnosed disease, we excluded potentially unhealthy participants in sensitivity analyses. All statistical tests were two-sided.

RESULTS

The crude incidence rate of lung cancer over the study follow-up period was 233 per 100 000 person-years among men and 192 per 100 000 person-years among women. BMI was inversely associated with the risk of lung cancer among both men and women (BMI ≥35 vs 22.5-24.99 kg/m(2): HR = 0.81, 95% CI = 0.70 to 0.94 and HR = 0.73, 95% CI = 0.61 to 0.87, respectively). The inverse association was restricted to current and former smokers and was stronger after adjustment for smoking. Among smokers, the inverse association persisted even after finely stratifying on smoking status, time since quitting smoking, and number of cigarettes smoked per day. Sensitivity analyses did not support the possibility that the inverse association was due to prevalent undiagnosed disease.

CONCLUSIONS

Our results suggest that a higher BMI is associated with a reduced risk of lung cancer in current and former smokers. Our inability to attribute the inverse association between BMI and the risk of lung cancer to residual confounding by smoking or to bias suggests the need for considering other explanations.

Unopposed estrogen and estrogen plus progestin menopausal hormone therapy and lung cancer risk in the NIH-AARP Diet and Health Study Cohort

PURPOSE

Previous studies have reported that lung cancer risk may be decreased, increased, or unaffected by prior use of menopausal hormone therapy (MHT).

METHODS

To assess this issue further, we examined relationships among 118,008 women, ages 50-71 years who were recruited during 1995-1996 for the NIH-AARP Diet and Health Study and in whom 2,097 incident lung carcinomas were identified during follow-up through 2006. Multivariable Cox proportional hazards models estimated relative risks (RR) and 95% confidence intervals (CIs) associated with various measures of self-reported MHT use.

RESULTS

We found no evidence that either estrogen therapy (ET)-only or estrogen plus progestin therapy (EPT) use was substantially related to subsequent lung cancer risk (respective RRs and 95% CIs for ever use = 0.97, 0.86-1.09 and 1.03, 0.90-1.17). There were no significant variations according to currency or duration of use of either formulation, nor was there evidence that risks varied within subgroups defined by cigarette smoking or body size. The absence of effect was seen for nearly all lung cancer subtypes, with the exception of an increased risk of undifferentiated/large cell cancers associated with long-term ET-only use (p (trend) = 0.02), a relationship not observed among EPT users.

CONCLUSIONS

Our results failed to support any substantial alterations in lung cancer risk associated with use of either unopposed estrogen or estrogen plus progestin MHT, even when detailed exposure measures and other risk predictors were considered.

Risks and benefits of dietary isoflavones for cancer

A high intake of fruits and vegetables is associated with a lower risk of cancer. In this context, considerable attention is paid to Asian populations who consume high amounts of soy and soy-derived isoflavones, and have a lower risk for several cancer types such as breast and prostate cancers than populations in Western countries. Hence, interest focuses on soyfoods, soy products, and soy ingredients such as isoflavones with regard to their possible beneficial effects that were observed in numerous experiments and studies. The outcomes of the studies are not always conclusive, are often contradictory depending on the experimental conditions, and are, therefore, difficult to interpret. Isoflavone research revealed not only beneficial but also adverse effects, for instance, on the reproductive system. This is also the case with tumor-promoting effects on, for example, breast tissue. Isoflavone extracts and supplements are often used for the treatment of menopausal symptoms and for the prevention of age-associated conditions such as cardiovascular diseases and osteoporosis in postmenopausal women. In relation to this, questions about the effectiveness and safety of isoflavones have to be clarified. Moreover, there are concerns about the maternal consumption of isoflavones due to the development of leukemia in infants. In contrast, men may benefit from the intake of isoflavones with regard to reducing the risk of prostate cancer. Therefore, this review examines the risks but also the benefits of isoflavones with regard to various kinds of cancer, which can be derived from animal and human studies as well as from in vitro experiments.

Reproductive and hormonal factors and lung cancer risk in the NIH-AARP Diet and Health Study cohort

BACKGROUND

Lung cancer exhibits unique patterns among women including high adenocarcinoma rates among nonsmokers. Inconsistent findings about hormonal factors on risk may reflect incomplete control for confounding, misclassification of exposures, or insufficient attention to variation by histology.

METHODS

Among 185,017 women, ages 50 to 71 years, recruited during 1995 and 1996 for the NIH-AARP (American Association of Retired Persons) Diet and Health Study, we identified 3,512 incident lung cancers (including 276 in never smokers) in follow-up through December 2006. Multivariable Cox proportional hazards models estimated relative risks (RR) and 95% CIs for self-reported hormonally related risk factors.

RESULTS

After adjustment for smoking and other confounders, subjects with late menarche were at reduced risk, with the association specific for adenocarcinomas (RR = 0.72 for menarche 15+ vs. <11, P(trend) < 0.01). Subjects with early ages at ovarian cessation (either from natural menopause or bilateral oophorectomy) were at an increased risk for adenocarcinomas and squamous cell tumors, but the associations were strongest for smokers, suggesting either residual confounding or an enhanced effect of menopausally related factors among subjects with decreased endogenous estrogens. In contrast, we saw no relationships of risk with either parity, age at first birth, or exogenous hormone use.

CONCLUSIONS

Elevated levels of hormones may adversely affect lung function early in life while assisting with cellular and immunologic responses later in life. Additional attention toward the role of hormonal factors may further our understanding of lung carcinogenesis.

IMPACT

Our findings provide some support for a role of hormonal factors in the etiology of lung cancer, although the mechanisms appear complicated.

Reproductive and hormonal factors and the risk of nonsmall cell lung cancer

Although exposure to estrogen may directly influence or modify the association between cigarette smoking and lung cancer risk, results from epidemiologic studies examining the association between reproductive and hormonal factors and risk of lung cancer among women have been inconsistent. Between 1998 and 2008, 430 women diagnosed with nonsmall cell lung cancer, 316 hospital controls and 295 population controls were recruited into the multi-center Maryland Lung Cancer Study. Conditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) according to reproductive and hormonal exposures adjusting for age, smoking, passive smoking, education and household income. Results were similar for hospital and population based controls, so the control groups were combined. Reduced risks of lung cancer were observed among women with greater parity (≥ 5 vs. 1-2 births: OR = 0.50, 95% CI = 0.32, 0.78, p-trend = 0.002) and later ages at last birth (≥ 30 vs. <25 years old: OR = 0.68, 95% CI = 0.48, 0.98, p-trend = 0.04). After mutual adjustment parity, but not age at last birth, remained significantly inversely associated with risk (p-trend = 0.01). No associations were found for nonsmall cell lung cancer risk with age at menarche, age at first birth, menopausal status, oral contraceptive use or menopausal hormone use, including use of oral estrogens. Compatible with findings from recent epidemiologic studies, we observed a reduction in the risk of nonsmall cell lung cancer with increasing number of births. Other reproductive and hormonal exposures, including menopausal hormone therapy use, were not associated with risk.

Lung cancer in women: role of estrogens

The incidence of lung cancer in females is increasing, in contrast to that seen in males. In addition, the proportion of lung cancer cases in women attributable to smoking is approximately half of that seen in males. Female sex hormones, especially estrogen, may play a key role in this. Estrogen receptors ERalpha and ERbeta have been detected on lung cancer cells and there is new evidence suggesting that hormone-replacement therapy may increase both the incidence of, and mortality from, lung cancer in women. Laboratory evidence lends credence to the carcinogenic effects of estrogens in lung cancer. This article summarizes the current evidence on their role in lung cancer.

Lung cancer among postmenopausal women treated with estrogen alone in the women's health initiative randomized trial

BACKGROUND

In the Women's Health Initiative (WHI) randomized controlled trial, use of estrogen plus progestin increased lung cancer mortality. We conducted post hoc analyses in the WHI trial evaluating estrogen alone to determine whether use of conjugated equine estrogen without progestin had a similar adverse influence on lung cancer.

METHODS

The WHI study is a randomized, double-blind, placebo-controlled trial conducted in 40 centers in the United States. A total of 10 739 postmenopausal women aged 50-79 years who had a previous hysterectomy were randomly assigned to receive a once-daily 0.625-mg tablet of conjugated equine estrogen (n = 5310) or matching placebo (n = 5429). Incidence and mortality rates for all lung cancers, small cell lung cancers, and non-small cell lung cancers in the two randomization groups were compared by use of hazard ratios (HRs) and 95% confidence intervals (CIs) that were estimated from Cox proportional hazards regression analyses. Analyses were by intention to treat, and all statistical tests were two-sided.

RESULTS

After a mean of 7.9 years (standard deviation = 1.8 years) of follow-up, 61 women in the hormone therapy group were diagnosed with lung cancer compared with 54 in the placebo group (incidence of lung cancer per year = 0.15% vs 0.13%, respectively; HR of incidence = 1.17, 95% CI = 0.81 to 1.69, P = .39). Non-small cell lung cancers were of comparable number, stage, and grade in both groups. Deaths from lung cancer did not differ between the two groups (34 vs 33 deaths in estrogen and placebo groups, respectively; HR of death = 1.07, 95% CI = 0.66 to 1.72, P = .79).

CONCLUSION

Unlike use of estrogen plus progestin, which increased deaths from lung cancer, use of conjugated equine estrogen alone did not increase incidence or death from lung cancer.

Reproductive factors, hormone use, and risk for lung cancer in postmenopausal women, the Nurses' Health Study

BACKGROUND

There is increasing evidence suggesting that female hormones may play a significant role in lung cancer development. We evaluated the associations between reproductive factors, exogenous hormone use, and lung cancer incidence in the Nurses' Health Study.

METHODS

We assessed age at menopause, age at menarche, type of menopause, parity, age at first birth, postmenopausal hormone (PMH) use, and past oral contraceptive use in 107,171 postmenopausal women. Cox models were used to estimate the hazard ratios for each exposure, adjusting for smoking and other covariates.

RESULTS

We identified 1,729 lung cancer cases during follow-up from 1984 to 2006. Menopause onset before 44 years of age (hazard ratio, 1.39; 95% confidence interval, 1.14-1.70) and past oral contraceptive use for >5 years (hazard ratio, 1.22; 95% confidence interval, 1.05-1.42) were associated with increased lung cancer risk. These associations were strongest in current smokers and small cell histology. In never smokers, increased parity was associated with decreased risk among parous women (P trend = 0.03), whereas in current smokers, older age at first birth was associated with increased risk (P trend = 0.02). PMH use was not associated with overall lung cancer incidence. However, nonsignificant results of increased risk in adenocarcinoma were seen with current PMH use.

CONCLUSIONS

Our findings suggest female hormones may influence lung carcinogenesis, although the effect is likely modest, varied by histologic subtype, and altered by smoking.

IMPACT

Further investigation of the pathophysiology of female hormones in lung cancer subtypes and their interaction with smoking will lead to better understanding of lung carcinogenesis.

Early changes in pulmonary gene expression following tobacco exposure shed light on the role of estrogen metabolism in lung carcinogenesis

This perspective on Meireles et al. (beginning on p. 707 in this issue of the journal) discusses the increasing evidence for the role of female steroid hormones in lung cancer development and progression. The novel work of Meireles et al. is the first evidence for the rapid upregulation by tobacco smoke of a key cytochrome P450 gene that can metabolize estrogens such as beta-estradiol to potentially carcinogenic catechol and quinine forms, as well as the first evidence for the colocalization of beta-estradiol and estrogen receptors in murine airway epithelium. Actions of estrogens that contribute to lung carcinogenesis, especially in the presence of tobacco smoke, may involve both reactive intermediates that damage DNA and steroid hormone receptor signaling that promotes growth.

Lung cancer and hormone replacement therapy: association in the vitamins and lifestyle study

PURPOSE

Lung cancer is the leading cause of cancer-related mortality among women. The role of hormone replacement therapy (HRT) in lung cancer development is unclear.

PATIENTS AND METHODS

We evaluated a prospective cohort of 36,588 peri- and postmenopausal women aged 50 to 76 years from Washington State recruited in 2000 to 2002 (Vitamins and Lifestyle [VITAL] Study). Lung cancer cases (n = 344) were identified through the Seattle-Puget Sound Surveillance, Epidemiology, and End Results cancer registry during 6 years of follow-up. Hazard ratios (HRs) associated with use and duration of specific HRT formulations were calculated for total incident lung cancer, specific morphologies, and cancer by stage at diagnosis.

RESULTS

After adjusting for smoking, age, and other potential confounders, there was an increased risk of incident lung cancer associated with increasing duration of estrogen plus progestin (E+P) use (HR = 1.27 for E+P use 1 to 9 years, 95% CI, 0.91 to 1.78; and HR = 1.48 for E+P use > or = 10 years, 95% CI, 1.03 to 2.12; P for trend = .03). There was no association with duration of unopposed estrogen use. Duration of E+P use was associated with an advanced stage at diagnosis (P for trend = .03).

CONCLUSION

Use of E+P increased the risk of incident lung cancer in a duration-dependent manner, with an approximate 50% increased risk for use of 10 years or longer. These findings may be helpful for informing women of their risk of developing lung cancer and delineating important pathways involved in hormone metabolism and lung cancer.

Estrogen receptor signaling in lung cancer

Lung cancer has long been thought of as a cancer that mainly affects men, but over the past several decades, because of the high increase in tobacco use by women, there has been a corresponding dramatic increase in lung cancer among women. Since 1998, lung cancer deaths in women have surpassed those caused by breast cancer in the United States. Annual lung cancer deaths among US women currently surpass those caused by breast, ovarian, and cervical cancers combined. Women are more likely than men to be diagnosed with adenocarcinoma and small cell carcinoma of the lung compared to squamous cell carcinoma, and never-smokers diagnosed with lung cancer are almost three times more likely to be female than male. These observations in the population, coupled to the findings that both estrogen receptors (ERs) and aromatase, the enzyme that synthesizes 17beta-estradiol, are expressed by lung tumors, suggest a role for female steroid hormones in control of lung cancer growth. Preclinical data and clinical data are increasingly emerging to support this concept, and to suggest that a local production of estrogen and expression of ERs occurs in lung tumors that arise in men as well as in women. An additional protein that recognizes 17beta-estradiol with high affinity, GPR30, also is expressed in lung tumors at high levels and may be responsible for some of the proliferation signals induced by estrogen.

Menopausal hormone therapy and risk of lung cancer-Systematic review and meta-analysis

OBJECTIVES

Lung cancer rates increase among women in many regions of the world. To explore whether menopausal hormone therapy (MHT) plays a role.

METHODS

We conducted a systematic search of the literature and performed meta-analyses of cohort studies (C), case-control studies (CC), randomized controlled trials (RCTs), and cancer registry studies (CR) to analyse the impact of estrogen therapy (ET), estrogen/progestin therapy (EPT) and any hormone therapy (HT) on lung cancer risks. We explored associations between ever-use of therapies and risks, analysed annual changes of risk, and the impact of therapies on histological subtypes. We calculated summary odds ratios, relative risks, 95% confidence intervals (CI; fixed-effects model), and assessed heterogeneity across studies. Eighteen studies were eligible (9 CC, 4 C, 3 RCT, 2 CR).

RESULTS

We found a significant increase of risk - 76.2% - in non-smoking women with adenocarcinoma (CI 1.072-2.898) reporting ever-use of HT. Estrogen plus progestin therapy does not change the risk; however, the pooled analysis of 2 RCTs points at an increased risk (RR 1.359; CI 1.031-1.791). Our further results should be interpreted with caution as significances were found in analyses only when smoking and non-smoking women, various hormone regimens, or histological subtypes, respectively, were pooled.

CONCLUSIONS

Dedicated studies designed to more adequately delineate the role of MHT are necessary to substantiate whether use of MHT is a risk factor for this or other types of lung cancer.

Hormone replacement therapy and cardioprotection: a new dawn? A statement of the Study Group on Cardiovascular Disease in Women of the Italian Society of Cardiology on hormone replacement therapy in postmenopausal women

Cardiovascular disease is the leading cause of death in women in Western countries. Despite preventive strategies, in the past decades the incidence of cardiovascular events has shown a decline in men but a rise in women, matching the growth of the population of postmenopausal women. Several epidemiological findings suggest the causative pathophysiological role of ovarian hormone deficiency in the development of cardiovascular disease in women. Observational and randomized studies have suggested that hormone replacement therapy in early postmenopause could be beneficial from a cardiovascular point of view. Conversely, aging, time since menopause and presence of cardiovascular risk factors or cardiovascular disease may decrease its efficacy and increase the risk of cardiovascular events. It is plausible that the unfavorable effects of the estrogen/progestin combination used in the randomized studies are not related to the hormone preparation per se but rather to the use of hormones in the less receptive group of women, older and with cardiovascular risk factors. Clinical judgment, choice of the right dose and estrogen/progestin combination are of pivotal importance to maximize the beneficial effect of estrogen replacement therapy/hormone replacement therapy, especially if given within a reasonable time after the menopause to women who need the therapy for the relief of menopausal symptoms.