Abstract
BackgroundPopulation-based studies showed an over 50% decrease in lung cancer risk after quitting smoking for 5–6 years, but the beneficial effect in silicotics remains unknown. We aimed to rectify this knowledge gap using a large historical cohort of 3185 Chinese silicotics since 1981 and followed-up till 2014.MethodsBaseline information on workers’ socio-demographics, smoking habits, occupational history, and medical history was collected. Smoking status was reassessed during follow-up. Multiple Cox proportional hazards model was performed to evaluate the impact of smoking cessation on lung cancer mortality.ResultsOverall, 1942 deaths occurred and 188 lung cancer deaths were identified. Compared with never quitters, silicotics who were new quitters had almost halved their lung cancer risk [hazard ratio (HR) = 0.51, 95%CI: 0.34–0.76], while persistent quitters had a 53% risk reduction (HR = 0.47, 95%CI: 0.33–0.66). Lung cancer mortality approximately halved after quitting smoking for 10 years. While the risk kept decreasing with years since cessation, it did not reverse back to that of never smokers. Persistent quitters with small opacities tended to have higher beneficial effects than those with large opacities.ConclusionsSmoking cessation for 10 years halved lung cancer mortality among silicotics, while the beneficial effect was prominent for patients with small opacities.
Highlights
Lung cancer remains the most common cancer with respect to both incidence and mortality worldwide, including Hong Kong.[1,2]Silicosis is among the most important occupational diseases in Hong Kong,[3] resulting from prolonged exposure to dust containing respirable crystalline silica during various types of work, including quarrying, tunneling, mining, and sandblasting.[4]
Compared with the never quitters, a significantly negative gradient (p = 0.001 for trend test) of lung cancer mortality was observed with increasing years since smoking cessation for all silicotics, despite the significant risk reduction did not manifest in the first 10 years of cessation
The risk of lung cancer mortality among all silicotics was nearly halving within 20 years since cessation (HR = 0.54, 95%CI: 0.35–0.83), and it further decreased by 68% (HR = 0.32, 95%CI: 0.48–0.81) if the smokers continued to abstain from cigarette smoking for 30 years or more
Summary
Lung cancer remains the most common cancer with respect to both incidence and mortality worldwide, including Hong Kong.[1,2]Silicosis is among the most important occupational diseases in Hong Kong,[3] resulting from prolonged exposure to dust containing respirable crystalline silica during various types of work, including quarrying, tunneling, mining, and sandblasting.[4]. Lung cancer remains the most common cancer with respect to both incidence and mortality worldwide, including Hong Kong.[1,2]. Population-based studies showed an over 50% decrease in lung cancer risk after quitting smoking for 5–6 years, but the beneficial effect in silicotics remains unknown. Silicotics who were new quitters had almost halved their lung cancer risk [hazard ratio (HR) = 0.51, 95%CI: 0.34–0.76], while persistent quitters had a 53% risk reduction (HR = 0.47, 95%CI: 0.33–0.66). Lung cancer mortality approximately halved after quitting smoking for 10 years. CONCLUSIONS: Smoking cessation for 10 years halved lung cancer mortality among silicotics, while the beneficial effect was prominent for patients with small opacities
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