OP-JNCS210076 1..7

Background: Smoking cessation reduces lung cancer mortality. However, little is known about whether diagnosis of lung cancer impacts changes in smoking behaviors. Furthermore, the effects of smoking cessation on the risk of second primary lung cancer (SPLC) have not been established yet. This study aims to examine smoking behavior changes after initial primary lung cancer (IPLC) diagnosis and estimate the effect of smoking cessation on SPLC risk following IPLC diagnosis. Methods: The study cohort consisted of 986 participants in the Multiethnic Cohort Study who were free of lung cancer and active smokers at baseline (1993-1996), provided 10-year follow-up smoking data (2003-2008), and were diagnosed with IPLC in 19932017. The primary outcome was a change in smoking status from “current” at baseline to “former” at 10-year follow-up (ie, smoking cessation), analyzed using logistic regression. The second outcome was SPLC incidence after smoking cessation, estimated using cause-specific Cox regression. All statistical tests were 2-sided. Results: Among 986 current smokers at baseline, 51.1% reported smoking cessation at 10-year follow-up. The smoking cessation rate was statistically significantly higher (80.6%) for those diagnosed with IPLC between baseline and 10-year follow-up vs those without IPLC diagnosis (45.4%) during the 10-year period (adjusted odds ratio 1⁄4 5.12, 95% confidence interval [CI] 1⁄4 3.38 to 7.98; P< .001). Incidence of SPLC was statistically significantly lower among the 504 participants who reported smoking cessation at follow-up compared with those without smoking cessation (adjusted hazard ratio 1⁄4 0.31, 95% CI 1⁄4 0.14 to 0.67; P1⁄4 .003). Conclusion: Lung cancer diagnosis has a statistically significant impact on smoking cessation. Quitting smoking after IPLC diagnosis may reduce the risk of developing a subsequent malignancy in the lungs. Lung cancer is the second most common cancer and the leading cause of cancer death in the United States (1). Past research has found smoking to be the strongest risk factor for lung cancer, increasing the disease incidence up to 20 times (2,3). Smoking cessation has been shown to reduce the risk of lung cancer incidence and mortality (4-6). A large prospective cohort study reported a 50%-80% reduction of lung cancer risk among individuals who had either recently quit smoking or were stable former smokers (7), and another historical cohort study reported a substantially reduced lung cancer-specific mortality after smoking cessation, with greater survival benefits associated with an earlier age at cessation (8). Several studies have examined the impact of smoking cessation on lung cancer incidence and mortality (4-9), however, little is known about whether lung cancer diagnosis is associated with changes in smoking behavior. For example, it is unknown whether lung cancer diagnosis potentially leads to smoking cessation among active smokers. Prior studies on smoking cessation among lung cancer patients were primarily based on smoking data measured cross-sectionally, with few studies fully Received: 8 April 2021; Revised: 28 June 2021; Accepted: 18 August 2021 © The Author(s) 2021. Published by Oxford University Press. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs licence (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reproduction and distribution of the work, in any medium, provided the original work is not altered or transformed in any way, and that the work is properly cited. For commercial re-use, please contact journals.permissions@oup.com 1 of 7 JNCI Cancer Spectrum (2021) 5(5): pkab076 doi: 10.1093/jncics/pkab076 First published online 23 August 2021