Real world efficacy of osimertinib in second line/beyond in patients with metastatic EGFR+ non-small cell lung cancer and role of paired tumour-plasma T790M testing at tyrosine kinase inhibitor resistance.

Background: Osimertinib is a third-generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) approved for use in EGFR-mutant lung cancer. We examined its performance in the second/subsequent line after resistance to first- and second-generation (1/2G) EGFR-TKI.
Methods: We reviewed electronic records of 202 patients who received osimertinib from July 2015 to January 2019 in the second/subsequent line after progression on prior EGFR-TKI. Of these, complete data from 193 patients were available. Clinical data including patient characteristics, primary EGFR mutation, T790M mutation status, presence of baseline brain metastases (BM), first-line EGFR-TKI use, and survival outcomes were extracted, and results retrospectively analyzed.
Results: Of 193 evaluable patients, 151 (78.2%) were T790M+ (T790M positive) with 96 (49.2%) tissue confirmed; 52% of patients received osimertinib in the second line setting. After median follow up of 37 months, median progression-free survival (PFS) of the entire cohort was 10.3 [95% confidence interval (CI): 8.64-11.50] months and median overall survival (OS) was 20 (95% CI: 15.61-23.13) months. Overall response rate (ORR) to osimertinib was 43% (95% CI: 35.9-50.3%); 48.3% in T790M+ vs . 20% in T790M- (T790M negative) patients. OS in T790M+ patients was 22.6 vs . 7.9 months in T790M- patients (HR 0.43, P=0.001), and PFS was 11.2 vs . 3.1 months respectively (HR 0.52, P=0.01). Tumour T790M+ was significantly associated with longer PFS (P=0.007) and OS (P=0.01) compared to tumour T790M- patients, however this association was not seen with plasma T790M+. Of the 22 patients with paired tumor/plasma T790M testing, response rate (RR) to osimertinib was 30% for those plasma T790M+/tumour T790M-, compared to 63% and 67% for those who were plasma T790M+/tumour T790M+ and plasma T790M-/tumour T790M+, respectively. By multivariable analysis (MVA), Eastern Cooperative Oncology Group (ECOG) performance status ≥2 was associated with shorter OS (HR 2.53, P<0.001) and PFS (HR 2.10, P<0.001), whereas presence of T790M+ was associated with longer OS (HR 0.50, P=0.008) and PFS (HR 0.57, P=0.027).
Conclusions: This cohort demonstrated the efficacy of osimertinib in second line/beyond for EGFR+ (EGFR mutation-positive) non-small cell lung cancer (NSCLC). Tissue T790M result appeared more predictive of osimertinib efficacy compared to plasma, highlighting potential T790M heterogeneity and the advantage with paired tumor-plasma T790M testing at TKI resistance. T790M- disease at resistance remains an unmet treatment need.
Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tlcr.amegroups.com/article/view/10.21037/tlcr-22-661/coif). JM reports travel support for meetings from AstraZeneca. GGYL reports honoraria from Amgen and consulting/advisory role for Merck, AstraZeneca, Pfizer, Bristol Myers Squibb and Roche. MKA reports support for meetings from AstraZeneca, Boehringer Ingelheim, Ipsen; honoraria from Boston Scientific and consulting/advisory role for Merck. RK reports research funding support from Sanofi (Inst), Janssen Pharmaceuticals (Inst); honoraria from Astellas Pharma, Novartis, Janssen Pharmaceuticals, MSD Oncology, Bristol-Myers Squibb, consulting/advisory role for Pfizer, Astellas Pharma, Novartis, Mundipharma. TR reports honoraria and Speakers’ Bureau from Novartis, consulting/advisory role for Ipsen and Eisai. TKHL reports honoraria for AstraZeneca and consulting/advisory role for MSD. DSWT reports research funding from Novartis (Inst), GlaxoSmithKline (Inst), AstraZeneca (Inst); honoraria from Bristol-Myers Squibb, Takeda Pharmaceuticals, Novartis, Roche and Pfizer; consulting/advisory role for Novartis, Merck, Loxo, AstraZeneca, Roche, Pfizer. DWTL reports research funding from Bristol-Myers Squibb (Inst), honoraria from Boehringer Ingelheim, consulting/advisory role for Roche, AstraZeneca, MSD Oncology, Novartis and Boehringer Ingelheim and stock ownership from Clearbridge Biomedics. QSN reports research funding from Novartis, MSD Oncology and Bayer; honoraria from MSD Oncology, AstraZeneca and Pierre Fabre and consulting/advisory role for Boehringer Ingelheim. WLT reports educational grant support from AstraZeneca; honoraria from Novartis, Merck, and Amgen; support for meetings from AstraZeneca, Ipsen, Boehringer Ingelheim, Bristol-Myers Squibb (Inst), and DKSH. The other authors have no conflicts of interest to declare.
(2023 Translational Lung Cancer Research. All rights reserved.)