Univariate and multivariate Cox analyses were applied in the training and two validation cohorts based on overall survival or progression-free survival, using the available co-variables including risk score, gender, age, race, tumor stage, tobacco smoking history, radiation therapy, KRAS mutation, and EML4-ALK mutation to validate the prognostic capacity and the independence of the 15-gene signature among other clinic-pathologic characteristics (Table 4). Here, ALK is linked to neoplasm.