Clinical And Genomic Characteristics Of Small Cell Lung Cancer In Never Smokers Results From A Retrospective Multicenter Cohort Study

BACKGROUND Small cell lung cancer (SCLC) has the strongest association with smoking among lung cancers. The characteristics of never smokers with SCLC is not known.RESEARCH QUESTION: Are the clinical characteristics, prognostic factors, survival, genomic alterations, and tumor mutational burdens of SCLC in patients who have never smoked different from those who have smoked?STUDY DESIGN AND METHODS: A retrospective multicenter cohort study of patients with clinician-confirmed SCLC was performed with the use of a longitudinal and nationally representative electronic medical records database. Smoking history was assessed through technology-enabled abstraction and confirmed for never smokers via chart review. Genomic characteristics of never smoker patients with SCLC were examined with the use of a next-generation sequencing-based gene panel and whole exome sequencing.RESULTS: One hundred of 5,632 patients (1.8%) with SCLC were never smokers. Relative to smokers, never smokers were more likely to be female (66.0% vs 52.4%; P = .009) and present with extensive stage (70.0% vs 62.2%; P = .028). Never smokers had a higher proportion of patients in age groups 35 to 49 years (7.0% vs 3.0%; P = .006) and >= 80 years (17.0% vs 8.2%; P = .006). Known risk factors for lung cancer were found in <20% of never smokers. There were no overall survival differences between never smokers and smokers. Among patients with available genomic data (n = 9), never smoker SCLC were characterized by lower tumor mutational burden, a lower frequency of TP53 mutations, and an absence of mutational signatures related to tobacco exposure.INTERPRETATION: The sex- and age-specific distribution of SCLC among never smokers, along with differences that were identified by genomic analyses, suggests a distinct biology of SCLC in never smokers compared with smokers.