Clinical significance of BIM deletion polymorphism in non-small cell lung cancer with epidermal growth factor receptor mutation

11052 Background: Germ line alterations in the proapoptotic protein BCL2-like 11 (BIM) can have a crucial role in how a tumor responds to treatment. To clarify the clinical usefulness of detecting BIM deletion polymorphism in non-small cell lung cancer (NSCLC) with positive epidermal growth factor receptor (EGFR) mutation we examined the prognosis in patients with or without the BIM changes. Methods: Seventy NSCLC patients with positive EGFR mutation treated with EGFR-tyrosine kinase inhibitor (EGFR-TKI) between January 2008 and January 2013 were enrolled in this study. BIM deletion polymorphism was analyzed by PCR in 58 peripheral blood samples, 24 formalin-fixed paraffin-embedded (FFPE) slides of surgical specimens (lung tissue in 20, brain tissue in 4), and 12 samples that included both blood and tissue specimens. We performed retrospective analyses on clinical characteristics, response rate and toxicity of EGFR-TKI, and estimated the prognosis in patients with or without BIM deletion polymorphism. Results: BIM deletion polymorphism was present in 13 of 70 patients (18.6%) with homozygous deletion in 1 and heterozygous deletion in 12. There was no discordance between the two types of samples among the 12 patients. There were no significant differences between patients with or without BIM deletion polymorphism on clinical characteristics, response rate to EGFR-TKI and incidence of EGFR-TKI toxicity. Patients with BIM deletion polymorphism showed significantly shorter PFS that in patients without BIM deletion polymorphism (median: 216 days vs. 430 days, p < 0.001). There was no significant difference in OS. In multivariate analyses using the Cox regression model, BIM deletion polymorphism (hazard ratio = 4.2, p< 0.001, 95% CI = 2.026-8.777) was identified as an independent factor for shorter PFS. Conclusions: BIM deletion polymorphism could be detected by PCR on peripheral blood samples and FFPE slides of surgical specimens. BIM deletion polymorphism has emerged as an independent prognostic factor for shorter PFS. Therefore, new treatment strategies should be established for patients with BIM deletion polymorphism.