The BIM Deletion Polymorphism and its Clinical Implication in Patients with EGFR-Mutant Non-Small-Cell Lung Cancer Treated with EGFR Tyrosine Kinase Inhibitors

IntroductionA germline BIM deletion polymorphism has been proposed to predict poor treatment response to certain kinase inhibitors. The purpose of this study was to explore whether the BIM deletion polymorphism predicts treatment efficacy of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in Korean patients with EGFR-mutant non-small-cell lung cancer (NSCLC).MethodsPeripheral blood samples from a total of 205 patients with EGFR-mutant NSCLC who were treated with EGFR TKIs between July 2008 and April 2013 were included. The incidence of BIM deletions in these samples was detected by polymerase chain reaction. We compared the clinical outcomes in patients with and without the polymorphism after treatment with EGFR TKIs (gefitinib or erlotinib).ResultsThe BIM deletion polymorphism was present in 15.6% (32 of 205) of patients. One patient was homozygous for the deletion, and the remaining 31 had heterozygous deletions. The majority of patients were younger than 65 years (74%), female (68%), never smokers (76%), and had stage IV NSCLC (67%). There were no associations between the BIM deletion polymorphism and clinicopathological features including gender, age, smoking status, histology, stage, and number of metastasis sites. Patients with and without the BIM deletion polymorphism had similar objective response rates (91 vs. 84%, p = 0.585). Progression-free survival and overall survival did not differ significantly between patients with and without the BIM deletion polymorphism (median progression-free survival 12 vs. 11 months, p = 0.160; median overall survival 31 vs. 30 months, p = 0.452). Multivariate analysis identified significantly predictive markers for clinical outcomes of EGFR TKIs including Eastern Cooperative Oncology Group performance status 0-1, adenocarcinoma histology, recurrent disease, and EGFR mutation type. The results were validated in an independent cohort of 69 NSCLC patients.ConclusionsIt remains to be determined whether the BIM deletion polymorphism provides intrinsic resistance or decreased sensitivity to EGFR TKIs in EGFR-mutant NSCLC patients.