Comparative study of lung cancer between smokers and non-smokers: A real-world study based on the whole population from Tianjin City, China

INTRODUCTION The purpose of this study was to examine the prevalence, clinical characteristics, and changing trends of non-smokers with lung cancer (LC) based on data from a population-wide cancer registry in northern China. METHODS The study used LC incidence and follow-up data from 2010 to 2019 from the Cancer Registry System of Tianjin city, which included 82769 cases. Trends in the incidence and proportion of non-smokers with LC were examined by joinpoint regression analysis. Life table and Cox survival analyses were used to calculate the survival rates and compare the death hazard ratios (HRs) in different groups, respectively. RESULTS Among the 82769 new diagnosis cases of LC during 2010 to 2019, there were 34589 (41.8%) current smokers, 14913 (18.0%) ex-smokers, 28123 (34.0%) non-smokers, and 5144 (6.2%) unknowns. The proportion of non-smokers changed slightly from 2010 (35.36%) to 2019 (36.87%) (annual percentage change, APC=-0.01%, p>0.05). This proportion declined in men (2010 vs 2019; 22.06% vs 20.66%) and increased in women (2010 vs 2019; 53.02% vs 62.35%), and in the 0-44 years age group it showed an upward trend from 2015 to 2019 (APC=4.82%, 95% CI: 1.8-7.9). Compared with smokers with LC, non-smokers with LC were predominantly females (64.15% vs 27.26%), had a predominantly adenocarcinoma histological subtypes (76.71% vs 42.22%), and had a 20% lower risk of death than smokers (HR=0.80; 95% CI: 0.78-0.81). CONCLUSIONS The proportion of non-smokers with LC was relatively high in northern China, with an increasing trend in the proportion of females and younger age groups. Non-smokers with LC had different epidemiological and clinical characteristics compared with smokers with LC.