Residential radon exposure and lung cancer histology and stage: a population-based ecological study in Central Germany

PURPOSE: Residential radon exposure is recognised as one of the leading environmental risk factors for lung cancer and acts synergistically with tobacco smoking. Thuringia, Germany, exhibits high geogenic radon potential; however, population-level associations with lung cancer histology and stage at diagnosis remain insufficiently characterised. METHODS: We conducted a retrospective ecological analysis of 893 lung cancer cases (2018-2022) from the Thuringian State Cancer Registry. Cases from 96 communities were classified as high- or low-radon exposure based on geogenic radon potential and soil radon activity. Demographics, histology and stage were compared between groups. RESULTS: Population-level lung cancer incidence did not differ significantly between low- and high-radon communities, consistent with age- and sex-adjusted Poisson regression showing no association with residential radon exposure (adjusted IRR 1.05, p = 0.473). However, all cases in women younger than 50 years occurred in high-radon communities. Adenocarcinoma was nominally more frequent (56% vs. 48%, p = 0.04), and among patients with small cell lung cancer (SCLC), extensive-stage disease was more common (64% vs. 49%, p = 0.04), with combined SCLC occurring exclusively; however, these findings were not significant after correction for multiple testing. CONCLUSION: In this ecological analysis, residential radon exposure was not associated with annual lung cancer incidence but was linked to tumour histology and stage at diagnosis. Given the ecological design and lack of smoking and occupational exposure data, these findings are hypothesis-generating and warrant further investigation to clarify radon's role in lung cancer biology and prevention.