Efficacy of osimertinib in a metastatic lung adenocarcinoma patient harboring somatic EGFR delL747_S752 and germline BIM deletion polymorphism: a case report and literature review

Background: Epidermal growth factor receptor (EGFR) exon 19 deletion (19del) and the exon 21 L858R point mutation are the most established predictive factors for the efficacy of EGFR-tyrosine kinase inhibitor (TKI) in patients with non-small cell lung cancer (NSCLC). To date, more than 50 subtypes of EGFR 19dels have been documented in NSCLC. Evidence suggests that different subtypes of 19dels exhibit different survival outcomes to EGFR-TKI treatment. Whether patients harboring EGFR Leu747_Ser752 deletion (delL747_S752) as an uncommon subtype of 19dels benefit from EGFR-TKIs has not been investigated. BIM (B-cell chronic lymphocytic leukemia/lymphoma-like 1) deletion polymorphism is common in East Asian with EGFR-mutant non-small-cell lung cancer (NSCLC). Currently, the predictive role of BIM deletion polymorphism in patients with EGFR-mutant NSCLC treated with osimertinib remains debatable.Case Description: A 34-year-old female patient was diagnosed with stage IV lung adenocarcinoma (LUAD) harboring somatic EGFR del L747_S752 and germline BIM deletion polymorphism in August 2018. She obtained benefit from the front-line treatment of osimertinib lasting for 8 months. After progression from osimertinib, the patient received bevacizumab combined with platinum-doublet chemotherapy, stereotactic radiosurgery plus osimertinib and crizotinib, anlotinib, and a programmed cell death-1 inhibitor sintilimab plus bevacizumab and docetaxel. She succumbed to her disease in June 2020 with an overall survival of 23 months. Conclusions: Our work suggests that osimertinib might be a compromised treatment option for NSCLC patients with somatic EGFR delL747_S752 and germline BIM deletion polymorphism. Development of more effective regimens are needed for this small subset of NSCLCs.