The characteristics of the BM and non-BM patients were compared using Chi-square tests. The association between EGFR mutations (mutated vs. WT) and overall BM (BM at the diagnosis of lung cancer and SBM) was determined using a multivariable logistic regression analysis. For those NSCLC patients without BM at the diagnosis of lung cancer, we tested the association between the presence of mutated-EGFR and SBM using a time-to-event analysis considering death as a competing risk (Fine and Gray's sub-distribution hazard model). To compare the exon 19, L858R and WT groups, we conducted a separate model (both logistic and time-to-event models) incorporating the details of EGFRs. Regarding the covariate selection, only the covariates that were significant (P < 0.05) in the univariate model were included in the multivariable model. In addition to analyzing the NSCLC patients of all-stage disease, we also performed a subgroup analysis that only included patients of stage IIIB-IV disease. Therefore, we performed multiple tests involving four comparisons for each outcome (overall BM in Table 2 and SBM in Table 3). To prevent the problem of type-I error inflation, we set the alpha level to 0.05/4 = 0.0125 in the multivariable model (Tables 2 and 3). In addition, we depicted OS using the Kaplan-Meier method and compared group differences (i.e., EGFR mutations) using log-rank tests. Finally, the distribution of vimentin expression in lung cancer specimens was categorized into a dichotomous variable (positive vs. negative), and the difference between the mutated- and WT-EGFR groups was compared using Fisher's exact test. Generally, P < 0.05 was considered as significant. Data analyses were conducted using SPSS 22 (Armonk, NY: IBM Corp) and R 3.1.3 (R Core Team, Vienna, Austria).