• Mahdi Sheikh, Anush Mukeriya, Oxana Shangina, Paul Brennan, and David Zaridze.
• International Agency for Research on Cancer (IARC/WHO), Genomic Epidemiology Branch, Lyon, France (M.S., P.B.).
• Ann. Intern. Med. 2021 Sep 1; 174 (9): 123212391232-1239.

BackgroundLung cancer is the leading cause of cancer death worldwide, and about one half of patients with lung cancer are active smokers at diagnosis.ObjectiveTo determine whether quitting smoking after diagnosis of lung cancer affects the risk for disease progression and mortality.DesignProspective study of patients with non-small cell lung cancer (NSCLC) who were recruited between 2007 and 2016 and followed annually through 2020.SettingN.N. Blokhin National Medical Research Center of Oncology and City Clinical Oncological Hospital No. 1, Moscow, Russia.Patients517 current smokers who were diagnosed with early-stage (IA-IIIA) NSCLC.MeasurementsProbabilities of overall survival, progression-free survival, and lung cancer-specific mortality and hazard ratios (HRs) for all-cause and cancer-specific mortality.ResultsDuring an average of 7 years of follow-up, 327 (63.2%) deaths, 273 (52.8%) cancer-specific deaths, and 172 (33.7%) cases of tumor progression (local recurrence or metastasis) were recorded. The adjusted median overall survival time was 21.6 months higher among patients who had quit smoking than those who continued smoking (6.6 vs. 4.8 years, respectively; P = 0.001). Higher 5-year overall survival (60.6% vs. 48.6%; P = 0.001) and progression-free survival (54.4% vs. 43.8%; P = 0.004) were observed among patients who quit than those who continued smoking. After adjustments, smoking cessation remained associated with decreased risk for all-cause mortality (HR, 0.67 [95% CI, 0.53 to 0.85]), cancer-specific mortality (HR, 0.75 [CI, 0.58 to 0.98]), and disease progression (HR, 0.70 [CI, 0.56 to 0.89]). Similar effects were observed among mild to moderate and heavy smokers and patients with earlier and later cancer stages.LimitationExposure measurements were based on self-reported questionnaires.ConclusionSmoking cessation after diagnosis materially improved overall and progression-free survival among current smokers with early-stage lung cancer.Primary Funding SourceInternational Agency for Research on Cancer.

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