Clinical implications of germline BCL2L11 deletion polymorphism in pretreated advanced NSCLC patients with osimertinib therapy

B-cell lymphoma 2-like 11 (BCL-2-like 11, BCL2L11, also known as BIM) deletion polymorphism (BIM-del) has been associated with resistance to first-generation epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), and is a poor prognostic factor for EGFR-mutant non-small-cell lung cancer (NSCLC) patients. Nevertheless, the impact of BIM-del in advanced NSCLC patients treated with the third-generation EGFR-TKI osimertinib remains undetermined. This study aims to evaluate the relationship between BIM-del and therapeutic efficacy of osimertinib in pretreated NSCLC patients.Patients subjected to EGFR T790 M detection and prior osimertinib treatment between December 2015 and December 2019 in our hospital were enrolled in this study. Peripheral blood samples from these patients were collected to detect BIM-del by polymerase chain reaction. Cox proportional hazards models were used to analyze the clinical outcomes of patients with and without BIM-del.In total, 152 Chinese Han NSCLC patients-including 143 T790M-positive and nine T790M-negative patients-were enrolled. BIM-del was detected in only 17.5 % of T790M-positive patients (25/143). The majority of patients were aged65 years (81.8 %, 117/143), were female (58.7 %, 84/143), were non-smokers (82.5 %, 118/143), had Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0-1 (88.8 %, 129/143), and exhibited metastases in the central nervous system (CNS) (54.5 %, 78/143). There were no associations between the BIM-del and clinical characteristics (including age, sex, histology, smoking status, stage, ECOG PS score, and CNS metastases). Patients with BIM-del had a poorer objective response rate than those without (28.0 % versus 52.5 %, p = 0.026). Besides, BIM-del was associated with a significantly shorter progression-free survival (PFS) and a moderately shorter overall survival (OS) (8.3 versus 10.5 months, p = 0.031 and 15.9 versus 25.2 months, p = 0.1, respectively). Multivariate analysis indicated that BIM-del was an independent prognostic factor for PFS but not for OS in EGFR T790 M NSCLC patients.BIM-del is associated with poor clinical responses and outcomes, and might be a negative predictive and prognostic biomarker in EGFR T790 M NSCLC patients with osimertinib treatment.