Demographic and clinical characteristics of the NSCLC patients.

Abbreviations: ECOG, Eastern Cooperative Oncology Group; SD, stand deviation.*P values refer to the comparison between early stage patients with surgery and advanced patients with chemotherapy. Student's t-test was used to compare age as a continuous variable; chi-square test was used to compare categorical variables, except for ECOG performance status, where Fisher's exact test was used.†Comparisons between never smokers and ever smokers.