Lung adenocarcinoma patients with high CXCL9 levels had an 80% reduced risk of death relative to patients with low CXCL9 levels (HR = 0.20, 95% CI: 0.05–0.78, p = 0.021), and those in the TCGA validation cohort were at a 29% reduced risk of death (HR = 0.71, 95% CI: 0.45–0.99, p = 0.044). This evidence concerns the gene CXCL9 and lung adenocarcinoma.