Prognostic implications of smoking in patients with advanced lung adenocarcinoma excluding positive mutations

Background: Lung adenocarcinoma in never-smoker patients often expresses mutations including EGFR or ALK, which leads to better prognosis in never-smoker patients with indication of tyrosine kinase inhibitors (TKI). But little is known about the influence of smoking on prognosis in patients with advanced lung adenocarcinoma excluding positive mutations. Objective: This study examined the influence of smoking on overall survival of patients with stage IV lung adenocarcinoma excluding those treated with TKI on the basis of positivity of mutations. Methods: We retrospectively analyzed 129 consecutive stage IV lung adenocarcinoma cases with wild-type EGFR and without positive ALK mutations treated in our hospital between January 2011 and December 2014. Results: Out of 129 patients, 104 (81%) had a smoking history. Median age (range) and male-to-female ratio were 64 years (40-89) and 94:10 in the smoker group and 71 years (42-80) and 3:21 in the never-smoker group. PD-1 inhibitor was administrated in one smoking patient. Overall survival rate was significantly higher in never-smoker patients (p=0.031, log-rank), and median survival of patients with smoking history was 9.3 months, and 19.1 months in never-smoker patients. Conclusions: These data suggest that smoking history was a poor prognostic factor in advanced lung adenocarcinoma patients excluding positive mutations.