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

Abstract

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.

FIGURE 1

Flowchart of the search process and results for studies looking at radon and lung cancer in never-smokers. ^#: these 24 studies are unique individual studies included in the four pooled data analyses. Accordingly, Barros-Dios et al. [33], which appears in two of the four pooled data analyses, is only counted once.

FIGURE 2

Adjusted excess relative risk (aERR) and 95% CI per 100 Bq·m⁻³ (radon exposure) for diagnosis of lung cancer. ^#: Barros-Dios et al. [66] in this pooled study contributed to the “ever-smoker” meta-analysis. p=0.32 for test of difference between aERRs for never-smokers and ever-smokers.

FIGURE 3

Adjusted excess relative risk (aERR) and 95% CI per100 Bq·m⁻³ (radon exposure) for diagnosis of lung cancer in never-smokers stratified by sex. p=0.027 for difference between male and female aERRs.