Lung cancer in never-smokers - what are the differences?

Introduction: Characteristics of never-smokers with lung cancer are still not fully clarified. The aim of this study was to compare never-smokers and ever-smokers with non-small cell lung cancer (NSCLC) regarding patient and tumor characteristics.

Methods: All consecutive newly NSCLC patients with known smoking status diagnosed between 2011 and 2015 were included in this retrospective cohort study. Clinical, histological, and molecular characteristics were compared between ever-smokers and never-smokers.

Results: Of the 558 included patients, 125 (22.4%) were never-smokers. These patients were more likely to be female (74% vs. 7%, p < .001), older (67 vs. 66 years-old, p = .019), and have adenocarcinoma (93% vs. 65%, p < .001). Never-smokers took longer to seek medical care after the symptoms onset (3 vs. 2 months, p < .001), regardless of the symptoms, histological type, or gender (OR: 1.2 [1.4-2.0]). The metastatic pattern was different in never-smokers: pleural metastases were more frequent (OR: 2.1 [1.1-4.0]), regardless of the histological type and gender. Never-smokers had a higher prevalence of ALK translocations (26% vs. 4%, p < .001) and EGFR mutations (36% vs. 8%, p < .001). The type of EGFR mutation was also significantly different between groups.

Conclusions: Never-smokers with NSCLC present distinct demographic and clinical characteristics. The characteristics of tumor also differ between never-smokers and ever-smokers, which may suggest different carcinogenic pathways.