Abstract 4899: The impact of the EGFR-T790M mutation detection by re-biopsy in EGFR mutant NSCLC patients in the retrospective analysis

Abstract

Abstract Background: EGFR-TKIs show a good anticancer effect in to most of patients with advanced non-small cell lung cancer (NSCLC) harboring EGFR activating mutations. However, it ultimately acquires resistance to EGFR-TKIs. We currently attempt to detect EGFR-T790M mutation by re-biopsy after disease progression, because the third generation EGFR-TKI osimertinib was effective against the refractory tumors with EGFR-T790M mutation. However, the re-biopsy from tumors is relatively invasive and some cases are impossible to biopsy. Therefore, it is a beneficial if we predict the EGFR-T790M mutation before re-biopsy. In this study, we analyzed the patients with disease progression after initial EGFR-TKIs to address the issues. Methods: 78 advanced NSCLC patients with EGFR mutations were enrolled from five institutions in Japan. In all patients, re-biopsy samples were obtained successfully after the resistance to initial EGFR-TKI treatment We analyzed the relationship between the emergence of EGFR-T790M mutation and clinical parameters including clinical outcomes with EGFR-TKI treatment and EGFR activating mutation status. Results: Of 78 advanced NSCLC patients with EGFR mutations, 39 patients were EGFR-T790M positive and 39 were negative based on the re-biopsy samples. Of 39 EGFR-T790M positive patients, 2 patients achieved complete response (CR), 33 partial response (PR), and 4 stable disease (SD) by initial EGFR-TKI treatment. In contrast, 1 patient experienced a CR, 19 a PR, 18 SD, and 1 progressive disease (PD) in 39 T790M negative patients. The objective response rate was higher in patients with T790M positive mutations than those with T790M negative mutations (89.7% versus 51.2%, p< 0.01). There was no statistically significant difference in progression free survival and time to failure treated with initial EGFR-TKIs between both groups. Conclusion: The response to initial EGFR-TKIs treatment might be one of good predictors for emerging of refractory tumors with EGFR-T790M mutation. Citation Format: Akihiro Yoshimura, Tadaaki Yamada, Naoko Okura, Junji Uchino, Koichi Takayama. The impact of the EGFR-T790M mutation detection by re-biopsy in EGFR mutant NSCLC patients in the retrospective analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4899.