Introduction: Approximately one-half of patients with epidermal growth factor receptor (EGFR) mutation-positive advanced/metastatic non-small-cell lung cancer (NSCLC) develop resistance to first-or second-generation EGFR tyrosine kinase inhibitors (TKIs) due to a secondary T790M mutation. This study investigated the pattern of T790M testing after EGFR TKI treatment in a real-world setting in Japan. Method: This prospective observational study enrolled patients with EGFR mutation-positive advanced/metastatic NSCLC who reported disease progression during treatment with first-or second-generation EGFR TKIs. Data regarding sampling methods for T790M mutation testing (plasma sample, cytology or tissue biopsy) and the treatment strategies after disease progression were recorded prospectively. Results: A total of 236 patients were included in the study (female, 67.4%; median age, 73.0 years), and 205 patients (86.9%) underwent rebiopsy by any of the three possible methods: plasma sampling in 137 patients (58.1%) and tissue/cytology sampling in 68 patients (28.8%) during the first rebiopsy. Overall, 80.6% of the tissue/cytology samples contained tumor cells, and 40% of these samples were positive for the T790M mutation. T790M mutations were detected in only 19.7% of plasma samples. Of the 199 patients who underwent T790M testing, 61 (30%) tested

This large, long-term analysis of EGFR mutation-positive NSCLC patients provides useful information about treatment outcomes in clinical practice. Updated analyses are required to determine real world outcomes for NSCLC patients treated with the latest available agents, including immunotherapies.

No abstract