Lung cancer in never-smokers: a case-control study in a radon-prone area (Galicia, Spain)

Overview of radon gas in groundwater around the world: Health effects and treatment technologies

The natural radioactive decay of uranium in rocks and soils gives rise to the presence of radon in groundwater. The existence of radon in groundwater at activity levels way higher than the reference limits set by US-EPA and WHO was widely covered in literature. The exposure to elevated levels of radon in ground and drinking water have been reported in literature to cause adverse health impacts. The aim of the present paper is to give an overview of radon gas in groundwater followed by the safe limits suggested by international organizations and agencies such as US-EPA and WHO. The paper also discusses the health effects associated with the exposure to radon levels and the estimation of the annual effective dose through ingestion and inhalation. This is followed by the radon levels around the world as well as the corresponding annual effective doses reported in literature. The determination techniques of radon levels in water covered in literature such as liquid scintillation counting, gamma-ray spectrometry and emanometry were also discussed and reviewed in the present work. Next, the paper sheds light on the most frequently used treatment techniques such as aeration, adsorption, filtration as well as biological techniques and evaluates their efficiency in mitigating radon levels in water. The paper also highlights the main precautions and future mitigation plans for radon in groundwater as well as delved onto future research perspectives of radon. It was found out that the type of rock played a key role in determining the radon levels. For instance, granitic rock types were reported to contribute to the elevation in the groundwater radon levels due to their characteristic permeability as a result of the formed fractures as well as their natural incorporation of high levels of uranium. Some of the reported radon levels in groundwater in literature were way higher than the guidelines set by the World Health Organization (WHO) for drinking water and US-EPA alternative higher maximum contaminant level. This review paper could be of importance to researchers working on the evaluation as well as the treatment of radon gas in water as it will provide a critical and state of the art review on radon gas in groundwater.

Radon exposure risks among residents proximal to gold mine tailings in Gauteng Province, South Africa: a cross-sectional preliminary study protocol

Gold mine tailings, a legacy of the mining industry, harbors significant amount of radon gas, a classified human carcinogen. Radon exposure, especially near tailings, is a significant public health threat, potentially leading to increased risk of lung cancer, leukemia, and chronic obstructive pulmonary disease (COPD). These health problems are often associated with lower survival rates and significant financial burdens. This ongoing research aim to evaluating the relationship between indoor radon exposure and lung cancer, leukemia, and COPD risks among residents proximal to gold mine tailings in Gauteng Province, South Africa. This cross-sectional preliminary study focus on two distinct groups: Riverlea (exposed group, <2 km to Gold mine tailings) and Orlando East (unexposed group, >2 km to Gold mine tailings). Indoor radon levels is measured using AlphaE monitors, while health risks (lung cancer, leukemia, and COPD) linked to exposure are evaluated through interview-administered questionnaire and secondary data from Gauteng Health Department. Of the 476 residents randomly selected for this study, 300 have already participated, with balanced representation from both the exposed and unexposed groups. The study will compare indoor radon levels and health outcomes between the two groups. This study's results could aid in creating targeted interventions and policies to mitigate indoor radon exposure risks and safeguard vulnerable communities from this significant public health hazard.

An overview on the relationship between residential radon and lung cancer: what we know and future research

We aim to provide an overview of the research available on indoor radon and lung cancer, with a special focus on Spanish investigations. Early studies on underground miners established the link between radon and lung cancer, which was later confirmed for the general population by residential case-control studies. Spain contributed with extensive evidence, including 5 multicentric, hospital-based, case-control studies in the last 30 years, exploring diverse aspects, such as radon's effect on never-smokers, molecular pathways linking radon exposure to lung cancer risk, survival rates, mortality burden, and occupational exposure. There is a well-established causal association between radon with lung cancer. Despite pioneering research performed in our country by the Galician Radon Laboratory, particularly on driver genes, the evidence on the potential molecular pathways which makes radon a carcinogen is sparse. Also, relevant questions on the potential association of radon exposure with the induction of other diseases are still pending.

Social determinants of health and lung cancer surgery: a qualitative study

Introduction

Social determinants of health (SDOH) are non-clinical factors that may affect the outcomes of cancer patients. The purpose of this study was to describe the influence of SDOH factors on quality of life (QOL)-related outcomes for lung cancer surgery patients.

Methods

Thirteen patients enrolled in a randomized trial of a dyadic self-management intervention were invited and agreed to participate in semi-structured key informant interviews at study completion (3 months post-discharge). A conventional content analysis approach was used to identify codes and themes that were derived from the interviews. Independent investigators coded the qualitative data, which were subsequently confirmed by a second group of independent investigators. Themes were finalized, and discrepancies were reviewed and resolved.

Results

Six themes, each with several subthemes, emerged. Overall, most participants were knowledgeable about the concept of SDOH and perceived that provider awareness of SDOH information was important for the delivery of comprehensive care in surgery. Some participants described financial challenges during treatment that were exacerbated by their cancer diagnosis and resulted in stress and poor QOL. The perceived impact of education varied and included its importance in navigating the healthcare system, decision-making on health behaviors, and more economic mobility opportunities. Some participants experienced barriers to accessing healthcare due to insurance coverage, travel burden, and the fear of losing quality insurance coverage due to retirement. Neighborhood and built environment factors such as safety, air quality, access to green space, and other environmental factors were perceived as important to QOL. Social support through families/friends and spiritual/religious communities was perceived as important to postoperative recovery.

Discussion

Among lung cancer surgery patients, SDOH factors can impact QOL and the patient's survivorship journey. Importantly, SDOH should be assessed routinely to identify patients with unmet needs across the five domains. SDOH-driven interventions are needed to address these unmet needs and to improve the QOL and quality of care for lung cancer surgery patients.

How Does Environmental and Occupational Exposure Contribute to Carcinogenesis in Genitourinary and Lung Cancers?

Environmental and occupational exposures have been associated with an increased risk of different types of cancers, although the exact mechanisms of higher carcinogenesis risk are not always well understood. Lung cancer is the leading cause of global cancer mortality, and, also, genitourinary neoplasms are among the main causes of cancer-related deaths in Western countries. The purpose of this review is to describe the main environmental and occupational factors that increase the risk of developing lung and genitourinary cancers and to investigate carcinogenesis mechanisms that link these agents to cancer onset. Further objectives are to identify methods for the prevention or the early detection of carcinogenic agents and, therefore, to reduce the risk of developing these cancers or to detect them at earlier stages.

Radon prevalence in domestic water in the Ría de Vigo coastal basin (NW Iberian Peninsula)

The Ría de Vigo catchment is situated in the largest radon-prone area of the Iberian Peninsula. High local indoor radon (²²²Rn) levels are the preeminent source of radiation exposure, with negative effects on health. Nevertheless, information on radon levels of natural waters and the potential human exposure risks associated with their domestic use is very sparse. To elucidate the environmental factors increasing human exposure risk to radon during domestic water use, we undertook a survey of local water sources, including springs, rivers, wells, and boreholes, over different temporal scales. Continental waters were highly enriched in ²²²Rn: activities ranged from 1.2 to 20.2 Bq L^-1 in rivers and levels one to two orders of magnitude higher were found in groundwaters (from 8.0 to 2737 Bq L^-1; median 121.1 Bq L^-1). The geology and hydrogeology of local crystalline aquifers support one order of magnitude higher ²²²Rn activities in groundwater stored in deeper fractured rock compared to that contained within the highly weathered regolith at the surface. During the mean dry season, ²²²Rn activities nearly doubled in most sampled waters in comparison to the wet period (from 94.9 during the dry season to 187.3 Bq L^-1 during wet period; n = 37). Seasonal water use and recharge cycles and thermal convection are postulated to explain this variation in radon activities. The high ²²²Rn activities cause the total effective dose of radiation received from domestic use of untreated groundwaters to exceed the recommended 0.1 mSv y^-1. Since more than 70% of this dose comes from indoor water degassing and subsequent ²²²Rn inhalation, preventative health policy in the form of ²²²Rn remediation and mitigation measures should be implemented prior to pumping untreated groundwater into dwellings, particularly during the dry period.

Human Health Impacts of Residential Radon Exposure: Updated Systematic Review and Meta-Analysis of Case-Control Studies

This study investigated the impact of residential radon exposure on human cancers (i.e., lung cancer and childhood leukemia) through a systematic review and meta-analysis of case−control studies. A total of 9724 articles obtained from electronic databases were assessed; however, only 55 case−control studies were eligible after manually screening and eliminating unnecessary studies. The causal associations were addressed by determining the meta-analysis’s estimated size effects (i.e., ORs/RRs) of the meta-analysis. Residential radon was revealed to significantly increase the incidence of lung cancer and childhood leukemia with pooled ORs of 1.38 [1.19; 1.60] (I2 = 90%; p < 0.00001) and 1.43 [1.19; 1.72] (I2 = 0% and p = 0.51), respectively. In addition, subgroup analyses were performed to reduce the heterogeneity of the initial meta-analyses. The results provided strong evidence that inhaling radon in the indoor environments is closely associated with the development of lung cancer and childhood leukemia in patients living in Europe and areas with high radon levels (≥100 Bq/m3).

Radon and Lung Cancer: Current Trends and Future Perspectives

Simple Summary

Radon represents the main risk factor of lung cancer in non-smokers and the second one in smoking patients. In Europe, there are several radon-prone areas, but regulatory policies may vary between countries. Radon causes DNA damage and high genomic tumor instability, but its exact carcinogenesis mechanism in lung cancer remains unknown. Molecular drivers in NSCLC are more often described in non-smoker patients and a potential association between radon exposure and oncogenic-driven NSCLC has been postulated. This is an updated review on indoor radon exposure and its role in lung cancer carcinogenesis, especially focusing on its potential relation with NSCLC with driver genomic alterations. We want to contribute to rising knowledge and awareness on this still silent but preventable lung cancer risk factor.

Abstract

Lung cancer is a public health problem and the first cause of cancer death worldwide. Radon is a radioactive gas that tends to accumulate inside homes, and it is the second lung cancer risk factor after smoking, and the first one in non-smokers. In Europe, there are several radon-prone areas, and although the 2013/59 EURATOM directive is aimed to regulate indoor radon exposition, regulating measures can vary between countries. Radon emits alpha-ionizing radiation that has been linked to a wide variety of cytotoxic and genotoxic effects; however, the link between lung cancer and radon from the genomic point of view remains poorly described. Driver molecular alterations have been recently identified in non-small lung cancer (NSCLC), such as somatic mutations (EGFR, BRAF, HER2, MET) or chromosomal rearrangements (ALK, ROS1, RET, NTRK), mainly in the non-smoking population, where no risk factor has been identified yet. An association between radon exposure and oncogenic NSCLC in non-smokers has been hypothesised. This paper provides a practical, concise and updated review on the implications of indoor radon in lung cancer carcinogenesis, and especially of its potential relation with NSCLC with driver genomic alterations.

Characteristics and clinical outcomes of patients with nonsmoking small cell lung cancer in Korea

BACKGROUND

The aim of this study was to investigate the characteristics and clinical outcomes of patients with nonsmoking small cell lung cancer (SCLC) using a nationwide registry in Korea.

METHODS

The Korean Association for Lung Cancer developed a registry in cooperation with the Korean Central Cancer Registry (KCCR) and surveyed approximately 10% of recorded lung cancer cases.

RESULTS

From 2014 to 2016, the KCCR registered 1,043 patients newly diagnosed with SCLC among a total of 8,110 lung cancer patients. In subgroup analysis, Kaplan meier survival analysis showed that the overall survival (OS) was significantly shorter in the nonsmoking subgroup than the ever-smoking subgroup of SCLC patients with extensive disease (6.99 vs. 9.68 months; P = 0.016). Among SCLC patients with limited disease, OS was also shorter in the nonsmoking subgroup, without statistical significance (19.4 vs. 23.5 months; P = 0.247). In a multivariate analysis using a Cox regression model, never smoking was not associated with shorter OS, but older age, extensive stage, poor performance status (Eastern Cooperative Oncology Group grade ≥ 2), male sex, no prophylactic cranial irradiation, and no active treatment (chemotherapy and/or radiotherapy) were associated with poor prognosis.

CONCLUSION

This evaluation of an unbiased nationwide survey dataset revealed that a significant proportion of Korean SCLC patients were never-smokers. No history of smoking appeared to be a significant prognostic factor according to the univariate analysis but was confirmed to be statistically insignificant through a multivariate analysis of the total population. Reasons for a poor prognosis may include the possibility that a high rate of the elderly population is composed of nonsmokers who did not receive active treatment.

Radon, Tobacco Exposure and Non-Small Cell Lung Cancer Risk Related to BER and NER Genetic Polymorphisms

INTRODUCTION

Tobacco consumption and radon exposure are considered the first and second most common causes of lung cancer, respectively. The aim of this study was to analyze both whether selected genetic polymorphisms in loci that are in DNA repair pathways, are related to non-small-cell lung cancer (NSCLC) and whether they may modulate the association between residential radon exposure and lung cancer in both smokers and never smokers.

METHODS

A multicentre, hospital-based, case-control study with 826 cases and 1201 controls was designed in a radon-prone area. Genotyping was determined in whole blood and residential radon exposure was measured in participants' dwellings.

RESULTS

Attending to tobacco exposure, the variant in the gene NBN (rs1805794) was associated with lung cancer in never smokers (OR 2.72; 95%1.44-5.2) and heavy smokers (OR 3.04; 95%CI 1.21-7.69). The polymorphism with the highest lung cancer association was OGG1 (rs125701), showing an OR of 8.04 (95%CI 1.64-58.29) for its homozygous variant genotype in heavy smokers. Attending to indoor radon exposure (>200Bq/m3), rs1452584, for its homozygous variant genotype, showed the highest association (OR 3.04 (95%CI 1.15-8.48).

CONCLUSION

The genes analyzed seem to have no association with the fully adjusted model, but they might modulate lung cancer association when different categories of tobacco consumption are considered (i.e. heavy smokers). This association may similarly be elevated for those individuals having high indoor radon exposures, though at a minor extent.

Fruits and Vegetables and Lung Cancer Risk in Never Smokers. A Multicentric and Pooled Case-Control Study

BACKGROUND

The etiology of lung cancer in never smokers is partly unknown. We aimed to assess the effect of fruits and vegetables consumption on lung cancer risk in never smokers.

METHODS

We pooled five multicenter case-control studies performed in Northwestern Spain. Cases and controls were all never smokers. All lung cancer cases had anatomopathological confirmed diagnoses. We performed a multivariate logistic regression to analyze the effect of different types of fruits and vegetables consumption on lung cancer risk.

RESULTS

A total of 438 cases and 781 controls were included. We observed that a consumption from one to six times per week shows a negative association with lung cancer risk for: kiwis (OR 0.67; 95%CI 0.46-0.95), oranges (OR 0.55; 95%CI 0.37-0.80), turnip tops (OR 0.48; 95%CI 0.34-0.66), "berza gallega" (OR 0.70; 95%CI 0.51-0.97) and broccoli (OR 0.55; 95%CI 0.35-0.83) compared to less than once a week consumption. On the other hand, we found an increased risk for lung cancer with a daily consumption of tomatoes, carrots and potatoes.

CONCLUSIONS

Oranges, kiwis, turnip tops, berza gallega and broccoli may play a protective role on lung cancer development in never smokers while tomatoes, carrots and potatoes might have some association with this disease.

Residential radon and lung cancer characteristics at diagnosis

PURPOSE

This study sought to ascertain whether there might be an association between radon concentrations and age, gender, histologic type, and tumor stage at diagnosis.

MATERIALS AND METHODS

Lung cancer cases from different multicenter case-control studies were analyzed, and clinical data were retrieved from electronic health records and personal interviews. A radon device was placed in all dwellings of participants, and we then tested the existence of an association between residential radon and lung cancer characteristics at diagnosis.

RESULTS

Of the total of 829 lung cancer cases included, 56.7% were smokers or ex-smokers. There was no association between indoor radon concentrations and age, gender, histologic type or tumor stage at diagnosis. Median indoor radon concentrations increased with age at diagnosis for men, but not for women. When analyzing participants exposed to more than 1000 Bq/m3, a predominance of small cell lung cancer and a higher presence of advanced stages (IIIB and IV) were observed.

CONCLUSIONS

There seems to be no association between radon and age, gender, histologic type or tumor stage at diagnosis. Higher radon exposure is more frequent in the case of small-cell lung cancer.

Systematic review and meta-analysis of residential radon and lung cancer in never-smokers

Background

Globally, radon is the leading risk factor for lung cancer in never-smokers (LCINS). In this study, we systematically reviewed and meta-analysed the evidence of the risk of LCINS associated with residential radon exposure.

Methods

Medline and Embase databases were searched using predefined inclusion and exclusion criteria to identify relevant studies published from 1 January 1990 to 5 March 2020 focused on never-smokers. We identified four pooled collaborative studies (incorporating data from 24 case–control studies), one case–control study and one cohort study for systematic review. Meta-analysis was performed on the results of the four pooled studies due to different measures of effect and outcome reported in the cohort study and insufficient information reported for the case–control study. In a post hoc analysis, the corresponding risk for ever-smokers was also examined.

Results

Risk estimates of lung cancer from residential radon exposure were pooled in the meta-analysis for 2341 never-smoker cases, 8967 never-smoker controls, 9937 ever-smoker cases and 12 463 ever-smoker controls. Adjusted excess relative risks (aERRs) per 100 Bq·m⁻³ of radon level were 0.15 (95% CI 0.06–0.25) for never-smokers and 0.09 (95% CI 0.03–0.16) for ever-smokers, and the difference between them was statistically insignificant (p=0.32). The aERR per 100 Bq·m⁻³was higher for men (0.46; 95% CI 0.15–0.76) than for women (0.09; 95% CI −0.02–0.20) among never-smokers (p=0.027).

Conclusion

This study provided quantified risk estimates for lung cancer from residential radon exposure among both never-smokers and ever-smokers. Among never-smokers in radon-prone areas, men were at higher risk of lung cancer than women.

Globally, radon is the leading cause of lung cancer in never-smokers. Yet its quantified link with lung cancer risk among never-smokers is not known. This study computes the risk estimate of lung cancer from residential radon exposure among never-smokers.https://bit.ly/32frCbq

Small-cell lung cancer in never-smokers

Background

Lung cancer is a public health problem worldwide. Small-cell lung cancer (SCLC) is the most aggressive histologic type, with a 5-year survival <10%. SCLC is closely associated with tobacco consumption and infrequent in never-smokers. We aim to describe SCLC characteristics in never-smokers recruited in a radon-prone area.

Patients and methods

We designed a multicentric case series where SCLC cases were recruited consecutively following histologic confirmation. Detailed information was obtained for indoor radon exposure, occupation and environmental tobacco smoke. We also collected different clinical characteristics such as extended or limited disease at diagnosis.

Results

We recruited 32 never-smoking SCLC cases. Median age was 75 years and 87.5% were women; 47% had extended disease. Median radon concentration was 182 Bq/m³. There were no statistically significant differences in residential radon concentration neither regarding age at diagnosis nor regarding sex. The most frequent symptoms were constitutional syndrome (23.1%) and coughing (23.1%). As much as 63% of cases had an Eastern Cooperative Oncology Group Study (ECOG) status of 0-2. The 1- and 2-year survival rates were 34.4% and 21.9%, respectively. The 2-year survival rate with a localized tumor was 26.7%, compared with 18.8% for extended disease.

Conclusions

These results show, for the first time, that indoor radon might not be associated with SCLC characteristics at diagnosis in never-smokers, and also confirms the low survival of this aggressive type of lung cancer also for never-smokers.

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Small-cell lung cancer in never-smokers is an infrequent disease.

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Risk factors are poorly characterized, and we have observed that residential radon may have a role (182 Bq/m³ as average).

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In this study, 1- and 2-year survival rates were 34.4% and 21.9%, respectively.

Lung emphysema and lung cancer: what do we know about it?

Emphysema and lung cancer (LC) are two diseases which share common risk factors, e.g., smoking. In recent years, many studies have sought to analyse this association. By way of illustration, we conducted a review of the scientific literature of the studies published to date, whose main designated aim was to demonstrate the relationship between emphysema and LC, and this association's influence on the histology, prognosis and molecular mechanisms responsible. We included over 40 studies (ranging from case-control and cohort studies to systematic reviews and meta-analyses), which highlight the association between emphysema and LC, independently of smoking habit. These studies also report a possible influence on histology, with adenocarcinoma being the most frequent lineage, and an association with poor prognosis, which affects both survival and post-operative complications. Oxidative stress, which generates chronic inflammatory status as well as the presence of certain polymorphisms in various genes (CYP1A1, TERT, CLPTM1L, ERK), gives rise-in the case of patients with emphysema-to alteration of cellular repair mechanisms, which in turn favours the proliferation of neoplastic epithelial cells responsible for the origin of LC.

Ecological level analysis of primary lung tumors in dogs and cats and environmental radon activity

Background

Epidemiologic studies suggest residential radon exposure might increase the risk of primary lung cancer in people, but these studies are limited by subject mobility. This limitation might be overcome by evaluating the association in pets.

Hypothesis

Primary pulmonary neoplasia (PPN) rate is higher in dogs and cats residing in counties with a high radon exposure risk (Environmental Protection Agency [EPA] zone 1) compared to zones 2 (moderate radon exposure risk) and 3 (low radon exposure risk).

Animals

Six hundred ninety client‐owned dogs and 205 client‐owned cats with PPN.

Methods

Retrospective review of medical records at 10 veterinary colleges identified dogs and cats diagnosed with PPN between 2010 and 2015. Each patient's radon exposure was determined by matching the patient's zip code with published county radon exposure risk. County level PPN rates were calculated using the average annual county cat and dog populations. The PPN counts per 100 000 dog/cat years at risk (PPN rates) were compared across radon zones for each species.

Results

The PPN rate ratio in counties in high radon zone (1) was approximately 2‐fold higher than in counties in lower radon zones for dogs (rate ratio zone 1 to 2, 2.49; 95% confidence interval [CI], 1.56‐4.00; rate ratio zone 1 to 3, 2.29; 95% CI, 1.46‐3.59) and cats (rate ratio zone 1 to 2, 2.13; 95% CI, 0.95‐4.79; zone 1 to 3, 1.81; 95% CI, 0.9‐3.61).

Conclusions and Clinical Importance

Exposure to household radon might play a role in development of PPN in dogs and cats.

Lung cancer risk and residential radon exposure: A pooling of case-control studies in northwestern Spain

BACKGROUND

Through a pooled case-control study design, we have assessed the relationship between residential radon exposure and lung cancer risk. Other objectives of the study were to evaluate the different risk estimates for the non-small cell lung cancer histological types and to assess the effect modification of the radon exposure on lung cancer risk by tobacco consumption.

METHODS

We collected individual data from various case-control studies performed in northwest Spain that investigated residential radon and lung cancer. Cases had a confirmed anatomopathological diagnosis of primary lung cancer and controls were selected because they were undergoing ambulatory evaluation or surgical procedures that were unrelated to tobacco use. Residential radon was measured using alpha track detectors. Results were analyzed using logistic regression.

RESULTS

3704 participants were enrrolled, 1842 cases and 1862 controls. Data show that lung cancer risk increases with radon exposure, finding a significant association of radon exposure with lung cancer at radon exposures above 50 Bq/m³. The estimated adjusted OR for individuals exposed to concentrations >200 Bq/m³ was 2.06 (95% CI: 1.61-2.64) compared with those exposed to ≤50 Bq/m³. Within a smoking category, lung cancer risk increases markedly as radon concentration increases, reaching an OR of 29.3 (95% CI: 15.4-55.7) for heavy smokers exposed to more than 200 Bq/m.³ CONCLUSIONS: This study confirms that residential radon exposure is a risk factor for lung cancer well below action levels established by international organizations. As expected, there is also an effect modification between radon exposure and tobacco consumption.

Lung cancer survival in never-smokers and exposure to residential radon: Results of the LCRINS study

We aimed to evaluate lung cancer survival in never-smokers, both overall and specifically by sex, exposure to residential-radon, age, histological type, and diagnostic stage. We included lung cancer cases diagnosed in a multicentre, hospital-based, case-control-study of never-smoker patients, diagnosed from January-2011 to March-2015 (Lung Cancer Research In Never Smokers study). 369 never-smokers (79% women; median age 71 years; 80% adenocarcinoma; 66% stage IV) were included. Median overall survival, and at one, 3 and 5 years of diagnosis was 18.3 months, 61%, 32% and 22%, respectively. Higher median survival rates were obtained for: younger age, adenocarcinoma, actionable mutations, and earlier-stage at diagnosis. Higher indoor radon showed a higher risk of death in multivariate analysis. Median lung cancer survival in never-smokers seems higher than that in ever-smokers. Patients with actionable mutations have a significantly higher survival. Higher indoor-radon exposure has a negative effect on survival.

Radon Biomonitoring and microRNA in Lung Cancer

Radon is the number one cause of lung cancer in non-smokers. microRNA expression in human bronchial epithelium cells is altered by radon, with particular reference to upregulation of miR-16, miR-15, miR-23, miR-19, miR-125, and downregulation of let-7, miR-194, miR-373, miR-124, miR-146, miR-369, and miR-652. These alterations alter cell cycle, oxidative stress, inflammation, oncogene suppression, and malignant transformation. Also DNA methylation is altered as a consequence of miR-29 modification induced by radon. Indeed miR-29 targets DNA methyltransferases causing inhibition of CpG sites methylation. Massive microRNA dysregulation occurs in the lung due to radon expose and is functionally related with the resulting lung damage. However, in humans this massive lung microRNA alterations only barely reflect onto blood microRNAs. Indeed, blood miR-19 was not found altered in radon-exposed subjects. Thus, microRNAs are massively dysregulated in experimental models of radon lung carcinogenesis. In humans these events are initially adaptive being aimed at inhibiting neoplastic transformation. Only in case of long-term exposure to radon, microRNA alterations lead towards cancer development. Accordingly, it is difficult in human to establish a microRNA signature reflecting radon exposure. Additional studies are required to understand the role of microRNAs in pathogenesis of radon-induced lung cancer.

Residential Radon and Histological Types of Lung Cancer: A Meta-Analysis of Case‒Control Studies

Epidemiological studies on residential radon exposure and the risk of histological types of lung cancer have yielded inconsistent results. We conducted a meta-analysis on this topic and updated previous related meta-analyses. We searched the databases of Cochrane Library, Embase, PubMed, Web of Science and Chinese National Knowledge Infrastructure for papers published up to 13 November 2018. The pooled odds ratio (OR) and 95% confidence interval (CI) were calculated using fixed and random effects models. Subgroup and dose‒response analyses were also conducted. This study was registered with PROSPERO (No. CRD42019127761). A total of 28 studies, which included 13,748 lung cancer cases and 23,112 controls, were used for this meta-analysis. The pooled OR indicated that the highest residential radon exposure was significantly associated with an increased risk of lung cancer (OR = 1.48, 95% CI = 1.26–1.73). All histological types of lung cancer were associated with residential radon. Strongest association with small-cell lung carcinoma (OR = 2.03, 95% CI = 1.52–2.71) was found, followed by adenocarcinoma (OR = 1.58, 95% CI = 1.31–1.91), other histological types (OR = 1.54, 95% CI = 1.11–2.15) and squamous cell carcinoma (OR = 1.43, 95% CI = 1.18–1.74). With increasing residential radon levels per 100 Bq/m³, the risk of lung cancer, small-cell lung carcinoma and adenocarcinoma increased by 11%, 19% and 13%, respectively. This meta-analysis provides new evidence for a potential relationship between residential radon and all histological types of lung cancer.

Elemental and mutational analysis of lung tissue in lung adenocarcinoma patients

Background

This study aimed to observe the association between trace element concentrations in lung tissue from lung adenocarcinoma cancer (LADC) patients and mutations in the epidermal growth factor receptor (EGFR) and KRAS genes.

Methods

LADC patients who had undergone lung resection were included in this study. Furthermore, twenty patients without lung cancer were included in this study as the control group. Samples were separately collected from both tumor and peritumor tissues. The mutational status was assessed for EGFR mutations, ALK rearrangements and KRAS mutations. Based on these analyses, patients were grouped into three groups: EGFR mutation, KRAS mutation and wild-type groups. The concentrations of various trace elements in the lung tissues were measured by a particle-induced X-ray emission (PIXE) system, and the results were analyzed for statistical significance.

Results

A total of 110 LADC patients were included in this study. The median age was 70 years, and 60% of the participants were female. Moreover, 18% and 20% of patients were EGFR- and KRAS-positive, respectively. Thirty-two trace elements were measured, and 18 trace elements were detectable. The concentrations of Fe, Co, Ni, Cu, Zn and Br were significantly higher in the KRAS mutation and wild-type groups than in the control group regardless of whether the samples were from tumor or peritumor tissues. For these 6 trace elements, the concentrations were significantly higher in smokers than in non-smokers. Considering the effect of smoking, differences in the trace element concentrations between each mutational group remained.

Conclusions

Trace elements in the lung may play a role in development of LADC in both smokers and never-smokers. However, prospective studies with larger sample sizes are needed to support this hypothesis.

Health Effects of Radon Exposure

Radon is a naturally occurring radioactive material that is formed as the decay product of uranium and thorium, and is estimated to contribute to approximately half of the average annual natural background radiation. When inhaled, it damages the lungs during radioactive decay and affects the human body. Through many epidemiological studies regarding occupational exposure among miners and residential exposure among the general population, radon has been scientifically proven to cause lung cancer, and radon exposure is the second most common cause of lung cancer after cigarette smoking. However, it is unclear whether radon exposure causes diseases other than lung cancer. Media reports have often dealt with radon exposure in relation to health problems, although public attention has been limited to a one-off period. However, recently in Korea, social interest and concern about radon exposure and its health effects have increased greatly due to mass media reports of high concentrations of radon being released from various close-to-life products, such as mattresses and beauty masks. Accordingly, this review article is intended to provide comprehensive scientific information regarding the health effects of radon exposure.

Indoor Radon in EGFR- and BRAF-Mutated and ALK-Rearranged Non-Small-Cell Lung Cancer Patients

BACKGROUND

Radon gas is the leading cause of lung cancer in the nonsmoking population. The World Health Organization (WHO) recommends indoor concentrations of < 100 Bq/m³. Several molecular alterations have been described in non-small-cell lung cancer (NSCLC), mainly in nonsmokers, with no risk factors identified. We studied the role of indoor radon in NSCLC patients harboring specific driver alterations.

PATIENTS AND METHODS

We assessed the radon concentration from EGFR-, BRAF-mutated (m), and ALK-rearranged (r) NSCLC patients measured by an alpha-track detector placed in their homes between September 2014 and August 2015. Clinical characteristics were collected prospectively, and pathologic samples were reviewed retrospectively.

RESULTS

Forty-eight patients were included (36 EGFRm, 10 ALKr, 2 BRAFm). Median radon concentration was 104 Bq/m³ (IQR 69-160) overall, and was 96 Bq/m³ (42-915) for EGFRm, 116 (64-852) for ALKr, and 125 for BRAFm, with no significant differences. Twenty-seven patients (56%) had indoor radon above WHO recommendations, 8 (80%) of 10 ALKr, 2 (100%) of 2 BRAFm, and 17 (47%) of 36 EGFRm.

CONCLUSION

The median indoor radon concentration was above the WHO recommendations, with no differences between EGFR, ALK, and BRAF patients. Concentrations above the WHO recommendations were most common with ALKr and BRAFm. These findings should be validated in larger studies.

Lung cancer and residential radon in never-smokers: A pooling study in the Northwest of Spain

BACKGROUND

Using a pooled case-control study design, including only never-smokers, we have assessed the association of residential radon exposure with the subsequent occurrence of lung cancer. We also investigated whether residential radon poses a different risk specifically for adenocarcinoma.

METHODS

We pooled individual data from different case-control studies conducted in recent years in Northwestern Spain which investigated residential radon and lung cancer. All participants were never-smokers. Cases had a confirmed biopsy of primary lung cancer. Hospital controls were selected at pre-surgery units, presenting for non-complex surgical procedures. They were interviewed using a standardized instrument. Residential radon was measured using alpha track detectors at the Galician Radon Laboratory at the University of Santiago de Compostela.

RESULTS

A total of 1415 individuals, 523 cases and 892 controls were included. We observed an odds ratio of 1.73 (95%CI: 1.27-2.35) for individuals exposed to ≥ 200 Bq/m³ compared with those exposed to ≤100 Bq/m³. Lung cancer risk for adenocarcinoma was 1.52 (95%CI: 1.14-2.02) using the same categories for radon exposure.

CONCLUSIONS

Residential radon is a clear risk factor for lung cancer in never-smokers. Our data suggest that radon exposure is associated with all histological types of lung cancer and also with adenocarcinoma, which is currently the most frequent histological type for this disease.

Alcohol consumption and lung cancer risk in never smokers: a pooled analysis of case-control studies

Background

Lung cancer is the deadliest cancer in developed countries but the etiology of lung cancer risk in never smokers (LCRINS) is largely unknown. We aim to assess the effects of alcohol consumption, in its different forms, on LCRINS.

Methods

We pooled six multi-center case-control studies developed in the northwest of Spain. Cases and controls groups were composed of never smokers. We selected incident cases with anatomopathologically confirmed lung cancer diagnoses. All participants were personally interviewed. We performed two groups of statistical models, applying unconditional logistic regression with generalized additive models. One considered the effect of alcohol type consumption and the other considered the quantity of each alcoholic beverage consumed.

Results

A total of 438 cases and 863 controls were included. Median age was 71 and 66, years, respectively. Adenocarcinoma was the predominant histological type, comprising 66% of all cases. We found that any type of wine consumption posed an OR of 2.20 OR 95%CI 1.12-4.35), and spirits consumption had an OR of 1.90 (95%CI 1.13-3.23). Beer consumption had an OR of 1.33 (95%CI 0.82-2.14). These results were similar when women were analyzed separately, but for men there was no apparent risk for any alcoholic beverage. The dose-response analysis for each alcoholic beverage revealed no clear pattern.

Conclusions

Wine and spirits consumption might increase the risk of LCRINSs, particularly in females. These results have to be taken with caution given the limitations of the present study.

Meta-analysis of case-control studies on the relationship between lung cancer and indoor radon exposure

Indoor exposure to natural radon is a factor that influences lung cancer risk worldwide. The present study includes a meta-analysis of epidemiological data on the relationship between lung cancer and indoor radon. Altogether, 31 case-control studies with 20,703 cases, 34,518 controls and 140 individual odds ratio (OR) estimates are included in the meta-analysis. Weighted median OR was calculated for five radon intervals. The following parameters were used for the weighting: standard error of OR, duration of radon concentration measurement, and relative number of controls in reference intervals. The dependence of the weighted median OR on the radon concentration was estimated applying linear non-threshold and threshold models. The results obtained suggest a significant linear no-threshold exposure-effect relationship for radon concentrations above 100 Bq/m³, with a slope of 0.14 (95% confidence interval 0.08-0.21) per 100 Bq/m³.

Indoor radon in Spanish workplaces. A pilot study before the introduction of the European Directive 2013/59/Euratom

OBJECTIVE

To explore whether there is a possible problem regarding indoor radon concentration surpassing the new European Directive 2013/59/Euratom threshold in Spanish workplaces. We also aim to find out whether radon concentration might be associated with certain characteristics of workplaces.

METHOD

We performed a cross-sectional study to measure indoor radon concentrations in Spanish workplaces including five different sectors (education, public administration, the health sector, the tourist sector and the private sector). To be measured, the workplace should be occupied permanently by at least one worker. Alpha-track type radon detectors were placed for at least three months and read at the Galician Radon Laboratory at the University of Santiago de Compostela. A descriptive analysis was performed on radon distribution by sector, building characteristics and number of workers affected.

RESULTS

We faced enormous difficulties in finding volunteers for this study. Galicia and Madrid had the highest number of measurements. Of a total of 248 measurements, 27% had concentrations above 300 Bq/m³. Median radon concentration was 251 Bq/m³ in Galicia, followed by Madrid, with 61.5 Bq/m³. Forty-six percent of the workplaces measured in Galicia had radon concentrations higher than 300 Bq/m³ followed by 10.6% in Madrid. Nineteen percent of all workers were exposed to more than 300 Bq/m³ and 6.3% were exposed to radon concentrations higher than 500 Bq/m³.

CONCLUSION

Indoor radon exposure might be a relevant problem in Spanish workplaces and the number of affected workers could be high. The prevalence of workers exposed to high radon concentrations probably depends on the geographical area.

Use of Magnetic Resonance Imaging for N-Staging in Patients with Non-Small Cell Lung Cancer. A Systematic Review

INTRODUCTION

The aim of this study is to assess the diagnostic value of the magnetic resonance imaging (MRI) in differentiating metastasic from non-metastatic lymph nodes in NSCLC patients compared with computed tomography (CT) and fluorodeoxyglucose (FDG) - positron emission tomography (PET) or both combined.

METHODS

Twenty-three studies (19 studies and 4 meta-analysis) with sample size ranging between 22 and 250 patients were included in this analysis. MRI, regardless of the sequence obtained, where used for the evaluation of N-staging of NSCLC. Histopathology results and clinical or imaging follow-up were used as the reference standard. Studies were excluded if the sample size was less than 20 cases, if less than 10 lymph nodes assessment were presented or studies where standard reference was not used. Papers not reporting sufficient data were also excluded.

RESULTS

As compared to CT and PET, MRI demonstrated a higher sensitivity, specificity and diagnostic accuracy in the diagnosis of metastatic or non-metastatic lymph nodes in N-staging in NSCLC patients. No study considered MRI inferior than conventional techniques (CT, PET or PET/CT). Other outstanding results of this review are fewer false positives with MRI in comparison with PET, their superiority over PET/CT to detect non-resectable lung cancer, to diagnosing infiltration of adjacent structures or brain metastasis and detecting small nodules.

CONCLUSION

MRI has shown at least similar or better results in diagnostic accuracy to differentiate metastatic from non-metastatic mediastinal lymph nodes. This suggests that MRI could play a significant role in mediastinal NSCLC staging.

Meta-analysis of thirty-two case-control and two ecological radon studies of lung cancer

A re-analysis has been carried out of thirty-two case-control and two ecological studies concerning the influence of radon, a radioactive gas, on the risk of lung cancer. Three mathematically simplest dose-response relationships (models) were tested: constant (zero health effect), linear, and parabolic (linear-quadratic). Health effect end-points reported in the analysed studies are odds ratios or relative risk ratios, related either to morbidity or mortality. In our preliminary analysis, we show that the results of dose-response fitting are qualitatively (within uncertainties, given as error bars) the same, whichever of these health effect end-points are applied. Therefore, we deemed it reasonable to aggregate all response data into the so-called Relative Health Factor and jointly analysed such mixed data, to obtain better statistical power. In the second part of our analysis, robust Bayesian and classical methods of analysis were applied to this combined dataset. In this part of our analysis, we selected different subranges of radon concentrations. In view of substantial differences between the methodology used by the authors of case-control and ecological studies, the mathematical relationships (models) were applied mainly to the thirty-two case-control studies. The degree to which the two ecological studies, analysed separately, affect the overall results when combined with the thirty-two case-control studies, has also been evaluated. In all, as a result of our meta-analysis of the combined cohort, we conclude that the analysed data concerning radon concentrations below ~1000 Bq/m3 (~20 mSv/year of effective dose to the whole body) do not support the thesis that radon may be a cause of any statistically significant increase in lung cancer incidence.

A statewide investigation of geographic lung cancer incidence patterns and radon exposure in a low-smoking population

BACKGROUND

Lung cancer is the leading cause of cancer-related mortality in Utah despite having the nation's lowest smoking rate. Radon exposure and differences in lung cancer incidence between nonmetropolitan and metropolitan areas may explain this phenomenon. We compared smoking-adjusted lung cancer incidence rates between nonmetropolitan and metropolitan counties by predicted indoor radon level, sex, and cancer stage. We also compared lung cancer incidence by county classification between Utah and all SEER sites.

METHODS

SEER*Stat provided annual age-adjusted rates per 100,000 from 1991 to 2010 for each Utah county and all other SEER sites. County classification, stage, and sex were obtained from SEER*Stat. Smoking was obtained from Environmental Public Health Tracking estimates by Ortega et al. EPA provided low (< 2 pCi/L), moderate (2-4 pCi/L), and high (> 4 pCi/L) indoor radon levels for each county. Poisson models calculated overall, cancer stage, and sex-specific rates and p-values for smoking-adjusted and unadjusted models. LOESS smoothed trend lines compared incidence rates between Utah and all SEER sites by county classification.

RESULTS

All metropolitan counties had moderate radon levels; 12 (63%) of the 19 nonmetropolitan counties had moderate predicted radon levels and 7 (37%) had high predicted radon levels. Lung cancer incidence rates were higher in nonmetropolitan counties than metropolitan counties (34.8 vs 29.7 per 100,000, respectively). Incidence of distant stage cancers was significantly higher in nonmetropolitan counties after controlling for smoking (16.7 vs 15.4, p = 0.02*). Incidence rates in metropolitan, moderate radon and nonmetropolitan, moderate radon counties were similar. Nonmetropolitan, high radon counties had a significantly higher incidence of lung cancer compared to nonmetropolitan, moderate radon counties after adjustment for smoking (41.7 vs 29.2, p < 0.0001*). Lung cancer incidence patterns in Utah were opposite of metropolitan/nonmetropolitan trends in other SEER sites.

CONCLUSION

Lung cancer incidence and distant stage incidence rates were consistently higher in nonmetropolitan Utah counties than metropolitan counties, suggesting that limited access to preventative screenings may play a role in this disparity. Smoking-adjusted incidence rates in nonmetropolitan, high radon counties were significantly higher than moderate radon counties, suggesting that radon was also major contributor to lung cancer in these regions. National studies should account for geographic and environmental factors when examining nonmetropolitan/metropolitan differences in lung cancer.

Residential radon and cancer mortality in Galicia, Spain

Residential radon exposure is a serious public health concern, and as such appears in the recommendations of European Code Against Cancer. The objective of this study was to assess the association between residential radon levels and mortality due to different types of cancer, using misaligned data analysis techniques. Mortality data (observed cases) for each of the 313 Galician municipalities were drawn from the records of the National Statistics Institute for the study period (1999-2008). Expected cases were computed using Galician mortality rates for 14 types of malignant tumors as reference, with a total of 56,385 deaths due to the tumors analyzed. The effect estimates of indoor radon (3371 sampling points) were adjusted for sociodemographic variables, altitude, and arsenic topsoil levels (1069 sampling points), using spatial/geostatistical models fitted with stochastic partial differential equations and integrated nested Laplace approximations. These models are capable of processing misaligned data. The results showed a statistical association between indoor radon and lung, stomach and brain cancer in women in Galicia. Apart from lung cancer (relative risk (RR)=1.09), in which a twofold increase in radon exposure led to a 9% rise in mortality, the association was particularly relevant in stomach (RR=1.17) and brain cancer (RR=1.28). Further analytical epidemiologic studies are needed to confirm these results, and an assessment should be made of the advisability of implementing interventions targeting such exposure in higher-risk areas.

Influence of architectural style on indoor radon concentration in a radon prone area: A case study

Indoor radon is a major health concern as it is a known carcinogenic. Nowadays there is a trend towards a greater energy conservation in buildings, which is reflected in an increasing number of regulations. But, can this trend increase the indoor radon concentration? In this paper, we selected a radon prone area in Spain and focused on single-family dwellings constructed in a variety of architectural styles. These styles ranged from 1729 up to 2014, with varying construction techniques (from local resources to almost universally standard building materials) and regulations in force (from none to the Spanish regulation in force). The ²²⁶Ra concentrations in soil and surface radon exhalation rates were rather similar in this area, mean values ranging 70-126Bq/kg and 49-100mBq/m²·s, respectively. Indoor radon concentration was generally greater than the contribution from soil exhalation (surface exhalation rates), especially in New dwellings (1980-2014). Its concentration in dwellings built in the Traditional style (1729-1940) was significantly lower than in the new houses. This can be consequence of the air tightness of the dwellings as a consequence of the different regulations in force. In the period covered by the Traditional style, there was no regulation in force, and dwelling had loose air tight. Whereas in recent times, there are mandatory regulations assuring a better air tightness of the buildings. Refurbishment of Traditional dwellings also seems to increase the indoor radon concentration, as they must also comply with the regulations in force.

Association between lung cancer somatic mutations and occupational exposure in never-smokers

Occupational exposure constitutes a common risk factor for lung cancer. We observed molecular alterations in 73% of never-smokers, 35% of men and 8% of women were exposed to at least one occupational carcinogen. We report herein associations between molecular patterns and occupational exposure.BioCAST was a cohort study of lung cancer in never-smokers that reported risk factor exposure and molecular patterns. Occupational exposure was assessed via a validated 71-item questionnaire. Patients were categorised into groups that were unexposed and exposed to polycyclic aromatic hydrocarbons (PAH), asbestos, silica, diesel exhaust fumes (DEF), chrome and paints. Test results were recorded for EGFR, KRAS, HER2, BRAF and PIK3 mutations, and ALK alterations.Overall, 313 out of 384 patients included in BioCAST were analysed. Asbestos-exposed patients displayed a significantly lower rate of EGFR mutations (20% versus 44%, p=0.033), and a higher rate of HER2 mutations (18% versus 4%, p=0.084). ALK alterations were not associated with any occupational carcinogens. The DEF-exposed patients were diagnosed with a BRAF mutation in 25% of all cases. Chrome-exposed patients exhibited enhanced HER2 and PIK3 mutation frequency.Given its minimal effects in the subgroups, we conclude that occupational exposure slightly affects the molecular pattern of lung cancers in never-smokers. In particular, asbestos-exposed patients have a lower chance of EGFR mutations.

Environmental tobacco smoke exposure and EGFR and ALK alterations in never smokers' lung cancer. Results from the LCRINS study

Environmental tobacco smoke (ETS) exposure is a main risk factor of lung cancer in never smokers. Epidermal Growth Factor Receptor (EGFR) mutations and ALK translocations are more frequent in never smokers' lung cancer than in ever-smokers. We performed a multicenter case-control study to assess if ETS exposure is associated with the presence of EGFR mutations and its types and if ALK translocations were related with ETS exposure. All patients were never smokers and had confirmed lung cancer diagnosis. ETS exposure during childhood showed a negative association on the probability of EGRF mutation though not significant. Exposure during adulthood, at home or at workplace, did not show any association with EGFR mutation. The mutation type L858R seemed the most associated with a lower probability of EGFR alterations for ETS exposure at home in adult life. There is no apparent association between ETS exposure and ALK translocation. These results might suggest that ETS exposure during childhood or at home in adult life could influence the EGFR mutations profile in lung cancer in never smokers, reducing the probability of presenting EFGR mutation.

Residential radon in Galicia: a cross-sectional study in a radon-prone area

Residential radon exposure is a major public health problem. It is the second greatest cause of lung cancer, after smoking, and the greatest in never-smokers. This study shows the indoor radon exposure distribution in Galicia and estimates the percentage of dwellings exceeding reference levels. It is based on 3245 residential radon measurements obtained from the Galician Radon Map project and from controls of two previous case-control studies on residential radon and lung cancer. Results show a high median residential radon concentration in Galicia (99 Bq m^-3), with 49.3% of dwellings having a radon concentration above 100 Bq m^-3 and 11.1% having a concentration above 300 Bq m^-3. Ourense and Pontevedra, located in South Galicia, are the provinces with the highest median indoor radon concentrations (137 Bq m^-3 and 123.5 Bq m^-3, respectively). Results also show lower radon levels in progressively higher building storeys. These high residential radon concentrations confirm Galicia as a radon-prone area. A policy on radon should be developed and implemented in Galicia to minimize the residential radon exposure of the population.

Residential radon and lung cancer: a cohort study in Galicia, Spain

Case-control studies show an association between residential radon and lung cancer. The aim of this paper is to investigate this association through a cohort study. We designed an ambispective cohort study using the Galician radon map, Spain, with controls drawn from a previous case-control study. Subjects were recruited between 2002 and 2009. The data were cross-checked to ascertain lung cancer incidence and then analysed using a Cox regression model. A total of 2,127 subjects participated; 24 lung cancer cases were identified; 76.6% of subjects were drawn from the radon map. The adjusted hazard ratio was 1.2 (95%CI: 0.5-2.8) for the category of subjects exposed to 50Bq/m3 or more. This risk rose when subjects from the case-control study were analyzed separately. In conclusion, we did not observe any statistically significant association between residential radon exposure and lung cancer; however, it appears that with a sample of greater median age (such as participants from the case-control study), the risk of lung cancer would have been higher.

Residential radon exposure and brain cancer: an ecological study in a radon prone area (Galicia, Spain)

We aimed to know if radon concentration is associated with municipal mortality due to brain cancer in Galicia, Spain. We designed an ecological study taking as study unit Galician municipalities. To be included, municipalities had to have at least three radon measurements. We correlated radon concentrations with municipal mortality due to these malignant tumors during the period 1999-2008. We calculated the relative risk of dying of brain cancers for each municipality and correlated this value with municipal radon concentration using Spearman's Rho. 251 municipalities were included, with close to 3,500 radon measurements and an average of 14 radon measurements at each municipality. We observed a significant correlation between residential radon with brain cancer mortality for males and females and the intensity of the correlation was higher for females. These results were reinforced when the analysis was restricted to municipalities with more than 5 radon measurements: Spearman's Rho 0.286 (p-value < 0.001) and Spearman's Rho 0.509 (p-value < 0.001) for males and females, respectively. These results suggest an association between residential radon and brain cancer mortality. More research using more robust epidemiological designs is needed to confirm these findings.

Residential radon and COPD. An ecological study in Galicia, Spain

PURPOSE

Radon is a human lung carcinogen but it might be linked with other respiratory diseases. We aimed to assess the relationship between residential radon exposure and COPD (chronic obstructive pulmonary disease) prevalence and hospital admissions at a municipal level.

MATERIALS AND METHODS

We designed an ecological study where we included those municipalities with at least three radon measurements. Using mixed Poisson regression models, we calculated the relative risk (RR) for COPD for each 100 Bq/m³ of increase in radon concentration and also the relative risk for COPD using a cut-off point of 50 Bq/m³. We did not have individual data on cigarette smoking and therefore we used a proxy (bladder cancer standardized mortality rate) that has proved to account for tobacco consumption. We performed separate analyses for sex and also sensitivity analysis considering age and rurality.

RESULTS

A total of 3040 radon measurements and 49,393 COPD cases were included. The relative risk for COPD prevalence was 0.95 (95% CI: 0.92-0.97) while for hospital admissions the RR was 1.04 (95% CI: 1.00-1.10) for each 100 Bq/m³. Relative risks were higher for women compared to men. Using a categorical analysis with a cut-off point of 50 Bq/m³, the RR for COPD prevalence was 1.06 (95% CI: 1.02-1.10) and for hospital admissions it was 1.08 (95% CI: 1.00-1.17) for women living in municipalities with more than 50 Bq/m³. All risks were also higher for women. No relevant differences were observed for age, rurality or other categories for radon exposure.

CONCLUSION

While the influence of radon on COPD prevalence is unclear depending on the approach used, it seems that residential radon might increase the risk of hospital admissions in COPD patients. Women have a higher risk than men in all situations. Since this is an ecological study, results should be interpreted cautiously.

Residential radon, EGFR mutations and ALK alterations in never-smoking lung cancer cases

The aim of this study was to assess if residential radon exposure might cause EGFR mutations or ALK rearrangements in never-smokers.We designed a multicentre case-control study in a radon-prone area (Galicia, Spain); only lung cancer cases were included in the study. We obtained residential radon measurements and clinical information for all the participants. We compared the median values of residential radon between patients with EGFR mutations or ALK rearrangements versus those without them.323 patients were included. Median age was 70 years and 19.5% were males. 42 and 15% of patients were EGFR- and ALK-positive, respectively. The most frequent EGFR alterations were exon 19 deletions and exon 21 (L858R) single-point substitution mutations. ALK-positive patients were 10 years younger than ALK-negative patients. Residential radon levels were two-fold higher in patients with exon 19 deletions compared with patients with exon 21 (L858R) single-point substitution mutations (216 versus 118 Bq·m^-3; p=0.057). There were no differences in residential radon levels by EGFR mutation status. ALK-positive patients (n=12) essentially had two-fold residential radon levels compared with ALK-negative patients (290 versus 164 Bq·m^-3, respectively).Residential radon may have a role in the molecular signature of lung cancer in never-smokers, although more studies with larger sample sizes are needed to support this hypothesis.