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

• Published in: Translational lung cancer research Vol. 12; no. 4; p. 742
• Main Authors: Ma, Jun, Tan, Sze Huey, Yin, Daniel Xing Cheng, Tran, Nguyen Tuan Anh, Tan, Gek San, Lai, Gillianne Geet Yi, Ang, Mei-Kim, Kanesvaran, Ravindran, Jain, Amit, Rajasekaran, Tanujaa, Tan, Eng-Huat, Lim, Tony Kiat Hon, Tan, Daniel Shao-Weng, Lim, Darren Wan-Teck, Ng, Quan Sing, Tan, Wan Ling
• Format: Journal Article
• Language: English
• Published: China 28.04.2023
• Subjects: osimertinib; EGFR mutant; real-world data; Advanced non-small cell lung cancer (advanced NSCLC)
• ISSN: 2218-6751

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. 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. 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+ . 20% in T790M- (T790M negative) patients. OS in T790M+ patients was 22.6 . 7.9 months in T790M- patients (HR 0.43, P=0.001), and PFS was 11.2 . 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). 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.