Hormonal Replacement Therapy and the Risk of Lung Cancer in Women: An Adaptive Meta-analysis of Cohort Studies

Reproductive factors and risk of lung cancer among 300,000 Chinese female never-smokers: evidence from the China Kadoorie Biobank study

BACKGROUND

Lung cancer is the leading cause of cancer mortality among Chinese females despite the low smoking prevalence among this population. This study assessed the roles of reproductive factors in lung cancer development among Chinese female never-smokers.

METHODS

The prospective China Kadoorie Biobank (CKB) recruited over 0.5 million Chinese adults (0.3 million females) from 10 geographical areas in China in 2004-2008 when information on socio-demographic/lifestyle/environmental factors, physical measurements, medical history, and reproductive history collected through interviewer-administered questionnaires. Cox proportional hazard regression was used to estimate adjusted hazard ratios (HRs) of lung cancer by reproductive factors. Subgroup analyses by menopausal status, birth year, and geographical region were performed.

RESULTS

During a median follow-up of 11 years, 2,284 incident lung cancers occurred among 282,558 female never-smokers. Ever oral contraceptive use was associated with a higher risk of lung cancer (HR = 1.16, 95% CI: 1.02-1.33) with a significant increasing trend associated with longer duration of use (p-trend = 0.03). Longer average breastfeeding duration per child was associated with a decreased risk (0.86, 0.78-0.95) for > 12 months compared with those who breastfed for 7-12 months. No statistically significant association was detected between other reproductive factors and lung cancer risk.

CONCLUSION

Oral contraceptive use was associated with an increased risk of lung cancer in Chinese female never-smokers. Further studies are needed to assess lung cancer risk related to different types of oral contraceptives in similar populations.

Hormone replacement therapy and cancer survival: a longitudinal cohort study: protocol paper

INTRODUCTION

Hormone replacement therapy (HRT) can help women experiencing menopausal symptoms, but usage has declined due to uncertainty around risks of cancer and some cardiovascular diseases (CVD). Moreover, improved cancer survival rates mean that more women who survive cancer go on to experience menopausal symptoms. Understanding these relationships is important so that women and their clinicians can make informed decisions around the risks and benefits of HRT. This study's primary aim is to determine the association between HRT use after cancer diagnosis and the risk of cancer-specific mortality. The secondary aims are to investigate the risks of HRT on subsequent cancer, all-cause mortality and CVD.

METHODS AND ANALYSIS

We will conduct a population-based longitudinal cohort study of 18-79 year-old women diagnosed with cancer between 1998 and 2020, using the QResearch database. The main exposure is HRT use, categorised based on compound, dose and route of administration, and modelled as a time-varying covariate. Analysis of HRT use precancer and postcancer diagnosis will be conducted separately. The primary outcome is cancer-specific mortality, which will be stratified by cancer site. Secondary outcomes include subsequent cancer diagnosis, CVD (including venous thrombo-embolism) and all-cause mortality. Adjustment will be made for key confounders such as age, body mass index, ethnicity, deprivation index, comorbidities, and cancer grade, stage and treatment. Statistical analysis will include descriptive statistics and Cox proportional hazards models to calculate HRs and 95% CIs.

ETHICS AND DISSEMINATION

Ethical approval for this project was obtained from the QResearch Scientific Committee (Ref: OX24, project title 'Use of hormone replacement therapy and survival from cancer'). This project has been, and will continue to be, supported by patient and public involvement panels. We intend to the submit the findings for peer-reviewed publication in an academic journal and disseminate them to the public through Cancer Research UK.

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.

Associations between female lung cancer risk and sex steroid hormones: a systematic review and meta-analysis of the worldwide epidemiological evidence on endogenous and exogenous sex steroid hormones

Background

Published findings suggest sex differences in lung cancer risk and a potential role for sex steroid hormones. Our aim was to perform a meta-analysis to investigate the effects of sex steroid hormone exposure specifically on the risk of lung cancer in women.

Methods

The PubMed, MEDLINE, Web of Science, and EMBASE databases were searched. The pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) for female lung cancer risk associated with sex steroid hormones were calculated overall and by study design, publication year, population, and smoking status. Sensitivity analysis, publication bias, and subgroup analysis were performed.

Results

Forty-eight studies published between 1987 and 2019 were included in the study with a total of 31,592 female lung cancer cases and 1,416,320 subjects without lung cancer. Overall, higher levels of sex steroid hormones, both endogenous (OR: 0.92, 95% CI: 0.87–0.98) and exogenous (OR: 0.86, 95% CI: 0.80–0.93), significantly decreased the risk of female lung cancer by 10% (OR: 0.90, 95% CI: 0.86–0.95). The risk of lung cancer decreased more significantly with a higher level of sex steroid hormones in non-smoking women (OR: 0.88, 95% CI: 0.78–0.99) than in smoking women (OR: 0.98, 95% CI: 0.77–1.03), especially in Asia women (OR: 0.84, 95% CI: 0.74–0.96).

Conclusions

Our meta-analysis reveals an association between higher levels of sex steroid hormone exposure and the decreased risk of female lung cancer. Surveillance of sex steroid hormones might be used for identifying populations at high risk for lung cancer, especially among non-smoking women.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08437-9.

Epidemiology of lung cancer

Lung cancer is the leading cause of global cancer incidence and mortality, accounting for an estimated 2 million diagnoses and 1.8 million deaths. Neoplasms of the lungs are the second most common cancer diagnosis in men and women (after prostate and breast cancer, respectively). With increasing access to tobacco and industrialization in developing nations, lung cancer incidence is rising globally. The average age of diagnosis is 70 years old. Men are twice as likely to be diagnosed with lung cancer, which largely reflects differences in tobacco consumption, although women may be more susceptible due to higher proportions of epidermal growth factor receptor mutations and the effects of oestrogen. African American men in the US are at the highest risk of lung cancer. Family history increases risk by 1.7-fold, with a greater risk among first-degree relatives. Tobacco smoking is the greatest preventable cause of death worldwide, accounting for up to 90% of lung cancer cases, and continued consumption is projected to increase global cancer incidence, particularly in developing nations such as China, Russia, and India. Second-hand smoke among children and spouses has likewise been implicated. Radon from natural underground uranium decay is the second leading cause of lung cancer in the developed world. Occupational hazards such as asbestos and environmental exposures such as air pollution, arsenic, and HIV and Tb infection have all been implicated in lung carcinogenesis, while cannabis smoking, electronic cigarettes, heated tobacco products, and COVID-19 have been hypothesized to increase risk.

Protective effects of 17-β-oestradiol and phytoestrogen on age-induced oxidative stress and inhibition of surfactant synthesis in rat type II pneumocytes

Epidemiological data suggest protective effects of oestrogen and phytoestrogen on lung tissue. This study aimed to elucidate the role of 17-β-oestradiol and phytoestrogen in age-related inhibition of surfactant synthesis and oxidative stress in rat type II pneumocytes. Forty male and 66 female Wistar rats were used. Female rats were randomly kept intact or ovariectomized at age 12 months. At age 22 months, ovariectomized rats received 17-β-oestradiol, soy extract, or no treatment. Oxidative stress markers CO, NO, cGMP and lipid peroxide (LPO), antioxidant enzymes and phosphatidylcholine (PC) were measured in cultured type II pneumocytes isolated at ages 2, 14, 18, 22 and 24 months. Old, male and ovariectomized rats showed significantly higher CO, NO, cGMP and LPO and lower PC content and antioxidant enzymes. 17-β-oestradiol and phytoestrogen significantly reversed these effects. In conclusion, aging and oestrogen deprivation decreased PC synthesis and altered the redox status in type II pneumocytes, which were partially restored by 17-β-oestradiol or soy supplementation.

Female reproductive factors and the risk of lung cancer in postmenopausal women: a nationwide cohort study

Background

Reproductive factors and hormone use in postmenopausal women have been hypothesised to affect the risk of developing lung cancer, but the epidemiological evidence is inconsistent.

Methods

Using the Korean National Health Insurance System database, we identified 4,775,398 postmenopausal women older than 40 years who had undergone both cardiovascular health- and cancer screening between 1 January 2009 and 31 December 2014. Information about reproductive factors was obtained from a self-administered questionnaire. The risk of lung cancer was estimated using Cox proportional hazard regression models.

Results

During a median follow-up of 4.4 years, 16,556 women (15,223 non-smokers) were diagnosed with lung cancer. The risk of lung cancer was not significantly influenced by early menarche age (adjusted hazard ratio [aHR] 1.03 for menarche ≥18 vs. ≤14; 95% confidence interval [CI], 0.98–1.09) or late age at menopause (aHR 1.02 for menopause ≥55 vs. <40; 95% CI, 0.91–1.14). Furthermore, the number of children, duration of breastfeeding and use of hormone replacement therapy were not associated with the risk of lung cancer.

Conclusions

No statistically significant association was found between reproductive factors and the risk of lung cancer in postmenopausal Korean women.

Frailty Is Inversely Related to Age at Menopause and Elevated in Women Who Have Had a Hysterectomy: An Analysis of the Canadian Longitudinal Study on Aging

BACKGROUND

Frailty is a complex pathophysiological phenomenon that will impact a significant proportion of adults over the age of 65 and contributes to the risk of several adverse health outcomes. Although women have a disproportionately higher risk of frailty, the sex-specific factors related to this syndrome are not well described. Hence, we sought to examine the relationship of age at menopause, hysterectomy status, and hormone replacement therapy use with prevalent frailty in older women.

METHODS

We performed a cross-sectional analysis of the Canadian Longitudinal Study on Aging (CLSA) Baseline Comprehensive Cohort (n = 30,097, 45-85 years old). Frailty was operationalized using both the deficit accumulation (frailty index) and frailty phenotype (Fried) models. Postmenopausal women were categorized as follows: premature (30-39 years), early (40-45 years), normal (46-54 years), and late (55+ years) menopause, or hysterectomy. Associations were determined using multivariate analysis, adjusting for sociodemographics, lifestyle factors, social support, and hormone replacement therapy use.

RESULTS

Age at menopause was inversely related to frailty in older Canadian women. The frailty index decreased 1.2% of the mean (p < .001) with every year of menopause onset and was significantly higher for women in the premature (24%; p < .001) and early (7%; p < .01) menopause and hysterectomy (21%; p < .001) groups, compared to the normal menopause group. The odds for being classified as frail using Fried's criteria was higher for the premature menopause (OR = 1.33, 95% CI = 0.72-2.27) and hysterectomy (OR = 1.59, 95% CI = 1.25-2.02) groups.

CONCLUSIONS

Our study supports a role for age at menopause and hysterectomy in the risk of frailty in older women and warrants further investigation.

Hormone replacement therapy and lung cancer risk in women: a meta-analysis of cohort studies: Hormone replacement therapy and lung cancer risk

BACKGROUND

Discordant results about the causal relationship between hormone replacement therapy use (HRT) and lung cancer risk in women had been reported. We therefore conducted a meta-analysis of cohort studies to evaluate this association.

METHODS

The PubMed and Embase databases were searched. Fixed- or random-effects model was used to pool the study-specific relative risks (RRs) with corresponding 95% confidence intervals (CIs). Sensitivity analysis, publication bias, and subgroup analysis were performed.

RESULTS

A total of 13 cohort studies met the inclusion criteria. Combined results indicated that compared with nonusers, women with HRT use were at a decreased risk (RR: 0.95, 95% CI: 0.91-0.99, I = 30.8%, P for heterogeneity = .137). In subgroup analysis by geographic area, smoking statue, type of hormones, and histology type of lung cancer, no significant association between HRT use and lung cancer was observed in most subgroups except in those studies which reported risk estimates adjusted for age, body mass index, smoking, and other confounders (RR: 0.95, 95 CI: 0.91-0.99, I = 33.0%, P for heterogeneity = .214). Both Begg funnel plot and Egger test (P = .243) suggested no evidence for publication bias.

CONCLUSION

Our meta-analysis suggests ever use of HRT is associated with a decreased risk of lung cancer in women.

The influence of hormone replacement therapy on lung cancer incidence and mortality

OBJECTIVE

Data regarding the effects of hormone replacement therapy (HRT) on non-small cell lung cancer (NSCLC) are mixed. We hypothesized HRT would have a protective benefit with reduced NSCLC incidence among women in a large, prospective cohort.

METHODS

We used data from the multicenter randomized Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (1993-2001). Participants were women aged 50 to 74 years followed prospectively for up to 13 years for cancer screening. The influence of HRT on the primary outcome of NSCLC incidence and secondary outcomes of all-cause and disease-specific mortality were assessed with Kaplan-Meier analysis and Cox proportional hazard models adjusting for covariates.

RESULTS

In the overall cohort of 75,587 women, 1147 women developed NSCLC after a median follow-up of 11.5 years. HRT use was characterized as 49.4% current users, 17.0% former users, and 33.6% never users. Increased age, smoking, comorbidities, and family history were associated with increased risk of NSCLC. On multivariable analysis, current HRT use was associated with reduced risk of NSCLC compared with never users (hazard ratio, 0.80; 95% confidence interval, 0.70-0.93; P = .009). HRT or oral contraception use was not associated with significant differences in all-cause mortality or disease-specific mortality.

CONCLUSIONS

These data represent among the largest prospective cohorts suggesting HRT use may have a protective effect on the development of NSCLC among women; the physiological basis of this effect merits further study; however, the results may influence discussion surrounding HRT use in women.

Sex steroid metabolism and actions in non-small cell lung carcinoma

Despite recent development in targeted therapies, lung cancer still remains the leading cause of cancer death. Therefore, a better understanding of its pathogenesis and progression could contribute to improving the eventual clinical outcome of the patients. Results of recently published several in vitro and clinical studies indicated the possible involvement of sex steroids in both development and progression of non-small cell lung carcinoma (NSCLC). Therefore we summarized the reported clinical relevant information of the sex steroids, their receptors and steroid metabolizing enzymes related to NSCLC in this mini-review. In addition, we also reviewed the potential "endocrine therapy", targeting sex steroid actions and/or metabolism in NSCLC patients.

Perioperative outcome of lung cancer surgery in women: results from a Spanish nationwide prospective cohort study

Background

To assess possible differences in the perioperative profile between men and women in lung cancer surgery.

Methods

A prospective cohort multicenter study was design, in which consecutive patients undergoing curative intent surgery for lung cancer in 24 Thoracic Services throughout Spain were included. Clinical features, tumor- and surgery-related data, postoperative complications, and mortality were recorded.

Results

There were 2,566 men and 741 women. Women were younger than men [mean (SD) age, 61.8 (10.8) vs. 66.5 (9.1) years, P<0.0001] and showed a more favorable preoperative characteristics, with significantly higher percentages of ECOG grade 0 and lower percentages of active smokers (28.4% vs. 33.9%; pack-years 18.8 vs. 26.9) and comorbidities [chronic obstructive pulmonary disease (COPD), diabetes, hypertension, cardiac disorders]. There were significant differences (P<0.001) in histological types and TNM stages with adenocarcinoma (70.1% vs. 46.4%) and IA stage (41.5% vs. 33.6%) more frequent in women. The use of VATS or thoracotomy was similar. The rate of pneumonectomy was higher in men (10.9%) than in women (5.1%) (P<0.001) but the distributions of other procedures were similar. Postoperative complications (pneumonitis, atelectasis, air leak, hemorrhage, fistula, empyema, wound dehiscence, and need of reintubation) were lower in women. Significant differences (P<0.0001) in the severity of postoperative complications (Clavien-Dindo classification) were also found, with higher percentages of grades I (51.6% vs. 43%) and II (37.5% vs. 33%) and lower percentages of grades III and IV among women. The mean length of hospital stay was 7.8 (7.1) days in men versus 6.3 (5.0) days in women, and the 30-day mortality rate 0.3% in women versus 2.9% in men (P<0.0001). The percentage of readmissions within 30 days after surgery was also higher in men (8.6% vs. 2.8%).

Conclusions

This multicenter nationwide study of lung cancer surgery with curative intent shows that the perioperative profile is better in women than in men.

Biases Inherent in Studies of Coffee Consumption in Early Pregnancy and the Risks of Subsequent Events

Consumption of coffee by women early in their pregnancy has been viewed as potentially increasing the risk of miscarriage, low birth weight, and childhood leukemias. Many of these reports of epidemiologic studies have not acknowledged the potential biases inherent in studying the relationship between early-pregnancy-coffee consumption and subsequent events. I discuss five of these biases, recall bias, misclassification, residual confounding, reverse causation, and publication bias. Each might account for claims that attribute adversities to early-pregnancy-coffee consumption. To what extent these biases can be avoided remains to be determined. As a minimum, these biases need to be acknowledged wherever they might account for what is reported.

The epidemiology of lung cancer

The incidence and mortality from lung cancer is decreasing in the US due to decades of public education and tobacco control policies, but are increasing elsewhere in the world related to the commencement of the tobacco epidemic in various countries and populations in the developing world. Individual cigarette smoking is by far the most common risk factor for lung carcinoma; other risks include passive smoke inhalation, residential radon, occupational exposures, infection and genetic susceptibility. The predominant disease burden currently falls on minority populations and socioeconomically disadvantaged people. In the US, the recent legalization of marijuana for recreational use in many states and the rapid growth of commercially available electronic nicotine delivery systems (ENDS) present challenges to public health for which little short term and no long term safety data is available.

The 2017 hormone therapy position statement of The North American Menopause Society

The 2017 Hormone Therapy Position Statement of The North American Menopause Society (NAMS) updates the 2012 Hormone Therapy Position Statement of The North American Menopause Society and identifies future research needs. An Advisory Panel of clinicians and researchers expert in the field of women's health and menopause was recruited by NAMS to review the 2012 Position Statement, evaluate new literature, assess the evidence, and reach consensus on recommendations, using the level of evidence to identify the strength of recommendations and the quality of the evidence. The Panel's recommendations were reviewed and approved by the NAMS Board of Trustees.Hormone therapy (HT) remains the most effective treatment for vasomotor symptoms (VMS) and the genitourinary syndrome of menopause (GSM) and has been shown to prevent bone loss and fracture. The risks of HT differ depending on type, dose, duration of use, route of administration, timing of initiation, and whether a progestogen is used. Treatment should be individualized to identify the most appropriate HT type, dose, formulation, route of administration, and duration of use, using the best available evidence to maximize benefits and minimize risks, with periodic reevaluation of the benefits and risks of continuing or discontinuing HT.For women aged younger than 60 years or who are within 10 years of menopause onset and have no contraindications, the benefit-risk ratio is most favorable for treatment of bothersome VMS and for those at elevated risk for bone loss or fracture. For women who initiate HT more than 10 or 20 years from menopause onset or are aged 60 years or older, the benefit-risk ratio appears less favorable because of the greater absolute risks of coronary heart disease, stroke, venous thromboembolism, and dementia. Longer durations of therapy should be for documented indications such as persistent VMS or bone loss, with shared decision making and periodic reevaluation. For bothersome GSM symptoms not relieved with over-the-counter therapies and without indications for use of systemic HT, low-dose vaginal estrogen therapy or other therapies are recommended.This NAMS position statement has been endorsed by Academy of Women's Health, American Association of Clinical Endocrinologists, American Association of Nurse Practitioners, American Medical Women's Association, American Society for Reproductive Medicine, Asociación Mexicana para el Estudio del Climaterio, Association of Reproductive Health Professionals, Australasian Menopause Society, Chinese Menopause Society, Colegio Mexicano de Especialistas en Ginecologia y Obstetricia, Czech Menopause and Andropause Society, Dominican Menopause Society, European Menopause and Andropause Society, German Menopause Society, Groupe d'études de la ménopause et du vieillissement Hormonal, HealthyWomen, Indian Menopause Society, International Menopause Society, International Osteoporosis Foundation, International Society for the Study of Women's Sexual Health, Israeli Menopause Society, Japan Society of Menopause and Women's Health, Korean Society of Menopause, Menopause Research Society of Singapore, National Association of Nurse Practitioners in Women's Health, SOBRAC and FEBRASGO, SIGMA Canadian Menopause Society, Società Italiana della Menopausa, Society of Obstetricians and Gynaecologists of Canada, South African Menopause Society, Taiwanese Menopause Society, and the Thai Menopause Society. The American College of Obstetricians and Gynecologists supports the value of this clinical document as an educational tool, June 2017. The British Menopause Society supports this Position Statement.

Epidemiology of Second Primary Tumors in Women With Ovarian Cancer

OBJECTIVE

The last large study of second primary tumors (SPTs) in women with ovarian cancer was published in 1996, prior to major changes in the differential diagnosis and treatment. The present study reports on the incidence of SPTs in a contemporary cohort of patients with a diagnosis of ovarian cancer.

METHODS

Ovarian cancer patients with a diagnosis of an ovarian malignancy between 1992 and 2012 were identified and characterized from 13 registries of the Surveillance, Epidemiology, and End Results database.

RESULTS

Of 41,073 women with a diagnosis of an ovarian malignancy between 1992 and 2012, 1831 (4.5%) developed a microscopically confirmed SPT. There was no significant difference in the risk of developing an SPT at all sites between women with an ovarian cancer and the general population. There was an elevated risk of site-specific SPTs of the small intestine, vagina, thyroid gland, and acute nonlymphocytic leukemia in ovarian cancer patients compared with the general Surveillance, Epidemiology, and End Results population. Conversely, the risk of lung and non-Hodgkin lymphoma was significantly decreased in women with ovarian cancer. An elevated risk of SPTs was observed in women with mucinous, endometrioid, and germ cell tumors. White women had an overall decreased risk of developing a second primary solid tumor, whereas American Indian and Asian/Pacific Islander women had an overall increased risk of an SPT at any site.

CONCLUSIONS

The incidence of SPTs in women with ovarian cancer was not significantly different as compared with the general population. However, divergent rates of SPTs in relation to histology, latency, age, and race were observed.

Influence of estrogen in non-small cell lung cancer and its clinical implications

Lung cancer (LC) is the leading cause of cancer death in men worldwide and has significantly increased in women. Differences in non-small cell lung cancer (NSCLC) behavior, prognosis, and response to treatment have been reported by sex and hormonal status, with premenopausal women presenting the worst prognosis compared to postmenopausal women and men. Additionally, the use of hormonal replacement therapy significantly increases NSCLC mortality; supporting the role of estrogen signaling in the pathogenesis of LC. The mechanisms by which estrogen promotes lung carcinogenesis have not been fully elucidated. Estrogen, through its receptor, can stimulate LC cell proliferation, death resistance, angiogenesis, migration and metastasis. Estrogen also induces expression of pro-inflammatory proteins and ligands that promote tumor evasion, suggesting that estrogen might modify the microenvironment and anti-tumor immune response. Recent reports have shown an interaction between the epidermal growth factor receptor (EGFR) pathway and estrogen signaling in lung adenocarcinoma, whence, combined treatment based on tyrosine kinase inhibitors (TKIs) and antiestrogen therapy is beginning to be evaluated. This review focuses on the differences in NSCLC behavior by sex and hormonal status, highlighting the role of estrogen and its receptors in lung carcinogenesis and LC prognosis. Due to the importance of estrogen in NSCLC development and progression we finally discuss the potential of antiestrogen therapy in LC treatment and show the results from preclinical and clinical trials.

Hormone therapy and lung cancer mortality in women: Systematic review and meta-analysis

The mortality of lung cancer presents a significant difference between the sexes. A role of hormone therapy (HT) in lung cancer mortality has been suggested, but the evidence is inconclusive. We sought to elucidate this issue with a meta-analysis. We conducted a systematic literature search in both Pubmed and Embase. Studies that reported the association of HT and mortality of lung cancer cases were included. Pooled hazard ratio (HR) was computed as the effect size to reflect the association between HT and lung cancer mortality. In total, 11 studies were included in the meta-analysis. The pooled HR of HT in relation to lung cancer mortality was 0.97 (95% CI 0.83-1.12, I²=59.2%, p=0.006) in all studies disregarding study design, and it was 0.80 (95% CI: 0.69-0.92, I²=21.4%, p=0.278) in prospective cohort studies. Results of this meta-analysis were robust, and there was no indication of significant differences in association in small and large studies. We observed a protective role of HT use in lung cancer mortality in pooled prospective cohorts, but not in pooled retrospective cohorts and post hoc analyses of randomized controlled trials. Future studies that address smoking, type and time of HT, menopausal status, and histology are warranted.

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.

Menopausal hormone therapy in cancer survivors: A narrative review of the literature

Decision making regarding the use of menopausal hormone therapy (MHT) for the treatment of bothersome menopausal symptoms in a cancer survivor can be complex, and includes assessment of its impact on disease-free or overall survival. Estrogen receptors are present in several cancer types, but this does not always result in estrogen-mediated tumor proliferation and adverse cancer-related outcomes. Estrogen may even be protective against certain cancers. Menopausal hormone therapy is associated with an increased risk of recurrence and mortality after diagnosis of some cancer types, but not others. We provide a narrative review of the medical literature regarding the risk of cancer recurrence and associated mortality with initiation of MHT after the diagnosis of breast, gynecologic, lung, colorectal, hematologic cancers, and melanoma. Menopausal hormone therapy may be considered for management of bothersome menopausal symptoms in women with some cancer types (e.g., colorectal and hematologic cancer, localized melanoma, and most cervical, vulvar and vaginal cancers), while nonhormonal treatment options may be preferred for others (e.g., breast cancer). In women with other cancer types, recommendations are less straightforward, and the use of MHT must be individualized.

Dietary intakes of citrus fruit and risk of gastric cancer incidence: an adaptive meta-analysis of cohort studies

OBJECTIVES:

In the context of supplementary antioxidants having no anticancer effect, it is important to update the meta-analysis to evaluate whether there is an association between intake of citrus fruit and gastric cancer risk.

METHODS:

The list of articles to be searched was established using citation discovery tools provided by PubMed and Scopus. The effect size of each article to be used in meta-analysis was calculated using the interval-collapse method. Summary effect size (sES) and 95% confidence intervals (CI) were obtained by conducting this meta-analysis. Random effect dose–response meta-regression (DRMR) was performed to investigate the dose–response relationship.

RESULTS:

A total of five cohort studies were selected. The result was 13% reduction of gastric cancer according to the intake of citrus fruit (sES, 0.87; 95% CI, 0.76 to 0.99; I-squared=69.6%). In subgroup analysis, it was found that the intake of citrus fruit inhibited cardia gastric cancer (CGC) (sES, 0.67; 95% CI, 0.55 to 0.81; I-squared=46.1%) and as a result of DRMR, 100 g of citrus fruit intake per day inhibits CGC by 40% (relative risk, 0.60; 95% CI, 0.44 to 0.83).

CONCLUSIONS:

It is suggested that the intake of citrus fruit inhibits the development of CGC. This conclusion can be used as a primary prevention measure in the future when the incidence of CGC may be on the rise.

Osteoporosis: Modern Paradigms for Last Century's Bones

The skeleton is a metabolically active organ undergoing continuously remodelling. With ageing and menopause the balance shifts to increased resorption, leading to a reduction in bone mineral density and disruption of bone microarchitecture. Bone mass accretion and bone metabolism are influenced by systemic hormones as well as genetic and lifestyle factors. The classic paradigm has described osteoporosis as being a “brittle bone” disease that occurs in post-menopausal, thin, Caucasian women with low calcium intakes and/or vitamin D insufficiency. However, a study of black women in Africa demonstrated that higher proportions of body fat did not protect bone health. Isoflavone interventions in Asian postmenopausal women have produced inconsistent bone health benefits, due in part to population heterogeneity in enteric bacterial metabolism of daidzein. A comparison of women and men in several Asian countries identified significant differences between countries in the rate of bone health decline, and a high incidence rate of osteoporosis in both sexes. These studies have revealed significant differences in genetic phenotypes, debunking long-held beliefs and leading to new paradigms in study design. Current studies are now being specifically designed to assess genotype differences between Caucasian, Asian, African, and other phenotypes, and exploring alternative methodology to measure bone architecture.

Citation Discovery Tools for Conducting Adaptive Meta-analyses to Update Systematic Reviews

OBJECTIVES

The systematic review (SR) is a research methodology that aims to synthesize related evidence. Updating previously conducted SRs is necessary when new evidence has been produced, but no consensus has yet emerged on the appropriate update methodology. The authors have developed a new SR update method called 'adaptive meta-analysis' (AMA) using the 'cited by', 'similar articles', and 'related articles' citation discovery tools in the PubMed and Scopus databases. This study evaluates the usefulness of these citation discovery tools for updating SRs.

METHODS

Lists were constructed by applying the citation discovery tools in the two databases to the articles analyzed by a published SR. The degree of overlap between the lists and distribution of excluded results were evaluated.

RESULTS

The articles ultimately selected for the SR update meta-analysis were found in the lists obtained from the 'cited by' and 'similar' tools in PubMed. Most of the selected articles appeared in both the 'cited by' lists in Scopus and PubMed. The Scopus 'related' tool did not identify the appropriate articles.

CONCLUSIONS

The AMA, which involves using both citation discovery tools in PubMed, and optionally, the 'related' tool in Scopus, was found to be useful for updating an SR.

Human papillomavirus infection and risk of lung cancer in never-smokers and women: an 'adaptive' meta-analysis

OBJECTIVES:

The incidence of lung cancer in Koreans is increasing in women and in both men and women with a never-smoking history. Human papillomavirus (HPV) infection has been suggested as a modifiable risk factor of lung cancer in never-smokers and women (LCNSW). This systematic review (SR) aimed to evaluate an association between HPV infection and lung cancer risk in LCNSW.

METHODS:

Based on a prior SR and some expert reviews, we identified refereed, cited, or related articles using the PubMed and Scopus databases. All case-control studies that reported the odds ratio of HPV infection in LCNSW were selected. An estimate of the summary odds ratio (SOR) with 95% confidence intervals (CI) was calculated.

RESULTS:

A total of four case-control studies were included. The fixed-effect model was applied because of homogeneity (I-squared=0.0%). The SORs in women and in never-smokers were 5.32 (95% CI, 1.75 to 16.17) and 4.78 (2.25 to 10.15) respectively.

CONCLUSIONS:

These results showed a significant effect of HPV infection in LCNSW. It is evident that developing a preventive plan against LCNSW may be necessary.

Modifiable risk factors of lung cancer in "never-smoker" women

Korean women with a history of never smoking and with adenocarcinoma showed an increasing trend in lung cancer occurrence during 2002 to 2012. The two modifiable factors of never-smoker lung cancer in women are hormone and oncogenic virus infection. Based on previous studies, hormone replacement therapy (HRT) and human papillomavirus (HPV) infection might afford protection or be a risk factor, respectively. It is necessary to perform a pooled analysis of cohort studies to evaluate HRT and never-smoker lung cancer in women and a systematic review of case-control studies to determine the association between HPV infection and never-smoker lung cancer.