Publication-only abstracts (abstract number preceded by an "e"), published in conjunction with the 2019 ASCO Annual Meeting but not presented at the Meeting, can be found online only.
Clinical outcomes of various resistance mechanisms of osimertinib in Chinese advanced non-small cell lung cancer patients.
Metastatic Non-Small Cell Lung Cancer
Lung Cancer—Non-Small Cell Metastatic
2019 ASCO Annual Meeting
J Clin Oncol 37, 2019 (suppl; abstr e20530)
Author(s): Puyuan Xing, Li Junling, Xuezhi Hao, Yuxin Mu, Shouzheng Wang, Di Ma, Jing Lin, Hao Liu, Han Han-Zhang, Analyn Lizaso, Jianxing Xiang, Xinru Mao; National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China; Cancer Hospital Chinese Academy of Medical Science, Beijing, China; Burning Rock Biotech, Guangzhou, China
Background: Increasing efforts have been invested in elucidating the resistance mechanisms to osimertinib. Major resistance mechanisms include but not limited to acquired EGFR mutations, predominantly C797, mutations in bypass pathways and small cell lung cancer (SCLC) transformation. However, no study has comprehensively investigated clinical outcomes of various mechanisms of resistance. Methods: 103 T790M positive advanced Chinese non-small cell lung cancer (NSCLC) patients who progressed on 1st generation EGFR-TKI were enrolled. Targeted sequencing, using a panel consisting of 168 lung cancer related genes, was performed on paired plasma samples collected prior to osimertinib and after the development of disease progression (PD) to profile mutation spectrum. 7 patients with no mutation detected at PD were excluded from analyses. Results: Major acquired mutations included 25% EGFR mutations, predominantly C797 and L792, 16% MET amplification, 8% TP53 mutations, 4% KRAS mutations, 4% RET fusions, 4% ERBB2 amplification and 6.25% RB1 mutations. Acquired RB1 mutation may indicate the possibility of SCLC transformation. Approximately, 30% of patients with no known resistance mechanisms at PD. In this cohort, we had 61 patients with 19 deletion and 35 patients with EGFR L858R prior to the initiation of osimertinib. We revealed patients with 19del acquired more mutations (p= 0.014) and were more likely to acquire mutations in MAP/PI3Kpathway (p= 0.04) and TP53 at PD (p= 0.021). On the other hand, acquired ERBB2 amplifications were only detected in L858R-mutant patients (p= 0.047). Furthermore, 36 patients preserved T790M and 60 patients lost T790M at PD. Our data revealed patients retaining T790M, often associated with activation of bypass signaling pathways or continued EGFR activation through tertiary mutations, had a longer progression-free survival (PFS) (p= 0.047) and overall survival (OS) (p= 0.04) comparing to patients with T790M loss, often with diverse and EGFR-independent mechanisms. We also show that patients with acquired C797S had significantly longer PFS (p= 0.031), while patients with acquired MET amplifications had significantly shorter PFS (p= 0.033). Conclusions: Collectively, we revealed differential clinical outcomes associated with various resistance mechanisms, representing an important step in advancing the understanding of resistance mechanisms of osimertinib.