After investigating the clinical implications of BIM deletion polymorphism in advanced lung adenocarcinoma treated with gefitinib, we found that patients with BIM deletion genotypes had poor progression-free survival and overall survival after gefitinib treatment and were more likely to experience acquired gefitinib resistance, highlighting the clinical potential of the polymorphism in patient-tailored decisions during epidermal growth factor receptor-tyrosine kinase inhibitor therapy. Background: Proapoptotic protein Bcl-2elike 11 (BIM) is a crucial tumor suppressor gene in lung cancer development. A 2903-bp genomic deletion polymorphism is present in BIM intron 2, which alters RNA splicing and impairs the generation of the death-inducing isoform of BIM and resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs). In the present study, we investigated the clinical implications of this genetic polymorphism in patients with advanced lung adenocarcinoma treated with gefitinib. Materials and Methods: After genotyping the BIM deletion polymorphism in 111 patients with stage IIIB or IV lung adenocarcinoma receiving gefitinib, the hazard ratio (HR) and 95% confidence interval (CI) for progression-free survival and overall survival were estimated using Cox proportional hazards models. Results: Possession of >= 1 deletion allele of the BIM polymorphism was observed in 18.02% of the patients. The BIM deletion polymorphism was an independent indicator of a shorter PFS (7.5 months vs. 11.3 months; HR, 2.38; 95% CI, 1.30-4.34; P = .005) and shorter OS (9.9 months vs. 27.5 months; HR, 2.53; 95% CI, 1.37-4.65; P = .003). Additionally, patients carrying the BIM deletion allele were more likely to experience acquired gefitinib-resistant disease. Conclusion: Our results indicate that the BIM deletion polymorphism might be a promising germline biomarker for gefitinib treatment in Chinese patients with lung adenocarcinoma. (C) 2018 Elsevier Inc. All rights reserved.