P2.13-18 A Multicenter Prospective Biomarker Study to Explore Mechanisms of Afatinib Resistance Based on Digita PCR and Next-Generation Sequencing

Abstract

Listen

Translate article

Afatinib is an oral irreversible blocker of ErbB-family kinases and shows a pronounced anti-tumor efficacy for advanced non–small cell lung cancer (NSCLC) positive for activating mutations of EGFR. We applied digital polymerase chain reaction (dPCR) and next-generation sequencing (NGS) to explore mechanisms of afatinib resistance. Eligible patients had advanced lung adenocarcinoma with EGFR activating mutations. Tumor and plasma samples were collected before afatinib treatment and after treatment failure with disease progression (systemic progressive disease, SPD). DNA from the samples was analyzed by dPCR and NGS. Thirty-five patients were enrolled, with a median follow-up time of 15.8 months. Among 25 patients with SPD, tumor, plasma, or both samples were available for 18, 23, and 16 individuals, respectively. dPCR and NGS detected EGFR T790M mutation in 13 (56.5%) and 11 (47.8%) of 23 plasma samples at SPD, with sensitivity and specificity compared with tumor samples being 83.3% and 70.0% (dPCR) and 50.0% and 70.0% (NGS), respectively. Applying the ratio of the number of T790M alleles to that of activating mutations (T/A) for determination of the T790M positivity improved the sensitivity and specificity of plasma analysis compared with tumor analysis to 83.3% and 100% (dPCR) and 57.1% and 100% (NGS), respectively. Among 25 patients with SPD, the T790M mutation of EGFR alone (n = 11), copy number gain (CNG) of NRAS (n = 1), CNG of MET (n = 1), CNG of EGFR plus T790M (n = 1), and CNG and E545K of PIK3CA plus T790M of EGFR (n = 1) were identified by NGS as putative resistance mechanisms against afatinib. No tumor showed transformation to small cell carcinoma. Median progression-free survival was longer in patients with than in those without T790M at SPD (15.1 versus 10.9 months, P =0.25). Median time to SPD was much longer in patients with than in those without T790M at SPD (17.9 versus 10.9 months, P =0.18). Assessment of T/A ratio with dPCR or NGS improved specificity of plasma analysis for determination of T790M positivity compared with tumor analysis. dPCR and NGS analysis in tumor and plasma samples shed light on exploring mechanisms of afatinib resistance.