High MAF of EGFR mutations and high ratio of T790M sensitizing mutations in ctDNA predict better third-generation TKI outcomes.

Clinical detection of EGFR-TKI resistance mechanism through tissue can be really challenging due to risks associated with the procedure. Thus, liquid biopsy, especially circulation tumor DNA (ctDNA) analysis, can be an adequate source for biomarker testing in targeted therapy. Our study was aimed at clinical validation of liquid biopsy next-generation sequencing (NGS) by comparison with tissue biopsy, and we also investigated clinical utility of ctDNA NGS on the prediction of TKI outcomes. Using hybrid capture panel NGS, we compared the concordance, sensitivity, and specificity of ctDNA using 39 paired plasma and tissue biopsy, and investigated the association between ctDNA genomic alterations of 147 first-generation TKI-relapsed patients and their response to first- and third-generation TKIs. The concordance for ctDNA and tissue biopsy was 84.62% among all patients, and even higher among late stage patients (88.24%). Among 147 EGFR-TKI-relapsed patients, T790M was the most common reason for resistance (40.13%). Compared with T790M-positive patients, patients only detected with sensitizing mutations (sensi-mutations) had lower mutant allele frequency (MAF) of sensi-mutations (P = 0.031). TP53 mutation showed negative impact on TKI treatments. In survival analysis of third-generation TKI, we found a positive correlation between ratio of T790M sensi-mutation and PFS (P = 0.018); also, higher MAFs of both sensi-mutation and T790M were observed in the PR group than the SD + PD group. Both ratio of T790M sensi-mutations and MAFs of EGFR mutations were associated with third-generation TKI outcomes. Thus, incorporation of high-throughput NGS into clinical trials may be crucial to identifying the response to osimertinib, as it provides more comprehensive genomic information. High concordance of ctDNA and tissue biopsy was observed. NGS of ctDNA from 147 TKI-relapsed patients showed that both high ratio of T790M sensitizing mutation (sensi-mutation) and high MAFs of mutations were all associated with better third generation TKI treatment outcomes. The quantification of both MAFs and T790M sensi-mutation ratio should be taken into consideration in some clinical situations, and incorporation of high-throughput NGS into clinical trials may be crucial to identifying the response to osimertinib, as it provides more comprehensive genomic information.

Li Y ，Zhang F ，Yuan P ，Guo L ，Jianming Y ，He J ... -  《-》

[Detection of circulating tumor DNA in epidermal growth factor receptor-TKI relapsed non-small cell lung cancer patients using next-generation sequencing and an analysis of the resistant mechanisms].

Li Y ，Zhang FS ，Guo L ，Ying JM ... -  《-》

Next-generation sequencing of tissue and circulating tumor DNA: Resistance mechanisms to EGFR targeted therapy in a cohort of patients with advanced non-small cell lung cancer.

Epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) has been considered as an effective treatment in epidermal growth factor receptor-mutant (EGFR-mutant) advanced non-small cell lung cancer (NSCLC). However, most patients develop acquired resistance eventually. Here, we compared and analyzed the genetic alterations between tissue assay and circulating tumor DNA (ctDNA) and further explored the resistance mechanisms after EGFR-TKI treatment. Amplification refractory mutation system-polymerase chain reaction (ARMS-PCR), Cobas® ARMS-PCR and next-generation sequencing (NGS) were performed on tissue samples after pathological diagnosis. Digital droplet PCR (ddPCR) and NGS were performed on plasma samples. The association between genetic alterations and clinical outcomes was analyzed retrospectively. Thirty-seven patients were included. The success rate of re-biopsy was 91.89% (34/37). The total detection rate of EGFR T790M was 62.16% (23/37) and the consistency between tissue and ctDNA was 78.26% (18/23). Thirty-four patients were analyzed retrospectively. For tissue re-biopsy, 24 patients harbored concomitant mutations. Moreover, tissue re-biopsy at resistance showed 21 patients (21/34, 61.76%) had the concomitant somatic mutation. The three most frequent concomitant mutations were TP53 (18/34, 52.94%), MET (4/34, 11.76%), and PIK3CA (4/34, 11.76%). Meanwhile, 21 patients (21/34, 61.76%) with EGFR T790M mutation. Progression-free survival (PFS) and overall survival (OS) were better in patients with T790M mutation (p = 0.010 and p = 0.017) or third-generation EGFR-TKI treatment (p < 0.0001 and p = 0.073). Interestingly, concomitant genetic alterations were significantly associated with a worse prognosis for patients with EGFR T790M mutation receiving third-generation EGFR-TKIs (p = 0.037). Multi-platforms are feasible and highly consistent for re-biopsy after EGFR-TKI resistance. Concomitant genetic alterations may be associated with a poor prognosis for patients with EGFR T790M mutation after third-generation EGFR-TKIs.

Zhang Y ，Xiong L ，Xie F ，Zheng X ，Li Y ，Zhu L ，Sun J ... -  《Cancer Medicine》

The presence and variant allele fraction of EGFR mutations in ctDNA and development of resistance.

Peripheral blood sampling for detection of EGFR T790M in cell-free circulating tumour (ct) DNA in TKI-resistant EGFR mutant (EGFRm) lung cancer is now standard. The value of more comprehensive sequencing is unknown. Prospective ctDNA analysis in patients with EGFRm NSCLC was performed using a next generation sequencing (NGS) panel of regions of 11 genes detecting single nucleotide variants and small insertions/deletions at ≥0.1% variant allele frequency (VAF) was performed. Patients were grouped according to treatment phase, including: (A) pre EGFR-TKI, (B) stable or responding to EGFR-TKI, (C) radiographic progression during EGFR-TKI, and (D) during chemotherapy treatment. Seventy-two patients with stage IV EGFRm NSCLC were enrolled and first blood samples were analysed. Primary sensitizing mutations in del19 or L858R were present in 66 (92%) and uncommon EGFRm in 6 (8%). Mutations in ctDNA were found in 53 samples (74%). T790M was detected in 3 of 4 patients with T790M-negative tissue. Other co-occurring EGFRm were found in 10 patients (7%) including K745R during first-line osimertinib. TP53 (n = 10), KRAS (n = 1), PI3KCA (n = 1) and ALK (n = 3) gene mutations also were detected. The presence of an EGFRm (excluding T790M) was associated with untreated or progressive disease, p = 0.04. In TKI-treated patients without radiologic progression, median progression free survival (PFS) was 10 months versus 2.1 months (HR 2.22, 95% CI: 0.89-5.54, p = 0.08) if an EGFRm in ctDNA was detected. If T790M was present in ctDNA, median PFS was 3.0 months versus 9.7 months (HR 4.59, 95% CI: 1.43-14.73, p = 0.005). High % VAF of both EGFRm and T790M correlated with inferior PFS (p = 0.01 and p = 0.03 respectively). In addition to the emergence of resistance mutations, the presence of the primary or co-occurring EGFRm in patients receiving EGFR-TKIs may associate with shorter PFS and may be useful in longitudinal analyses of ctDNA to direct therapy.

O'Kane GM ，Liu G ，Stockley TL ，Shabir M ，Zhang T ，Law JH ，Le LW ，Sacher A ，Shepherd FA ，Bradbury PA ，Leighl NB ... -  《-》

Predicting osimertinib-treatment outcomes through EGFR mutant-fraction monitoring in the circulating tumor DNA of EGFR T790M-positive patients with non-small cell lung cancer (WJOG8815L).

The WJOG8815L phase II clinical study involves patients with non-small cell lung cancer (NSCLC) that harbored the EGFR T790M mutation, which confers resistance to EGFR tyrosine kinase inhibitors (TKIs). The purpose of this study was to assess the predictive value of monitoring EGFR genomic alterations in circulating tumor DNA (ctDNA) from patients with NSCLC that undergo treatment with the third-generation EGFR-TKI osimertinib. Plasma samples of 52 patients harboring the EGFR T790M mutation were obtained pretreatment (Pre), on day 1 of treatment cycle 4 (C4) or cycle 9 (C9), and at diagnosis of disease progression or treatment discontinuation (PD/stop). CtDNA was screened for EGFR-TKI-sensitizing mutations, the EGFR T790M mutation, and other genomic alterations using the cobas EGFR Mutation Test v2 (cobas), droplet digital PCR (ddPCR), and targeted deep sequencing. Analysis of the sensitizing-and T790M-EGFR mutant fractions (MFs) was used to determine tumor mutational burden. Both MFs were found to decrease during treatment, whereas rebound of the sensitizing EGFR MF was observed at PD/stop, suggesting that osimertinib targeted both T790M mutation-positive tumors and tumors with sensitizing EGFR mutations. Significant differences in the response rates and progression-free survival were observed between the sensitizing EGFR MF-high and sensitizing EGFR MF-low groups (cutoff: median) at C4. In conclusion, ctDNA monitoring for sensitizing EGFR mutations at C4 is suitable for predicting the treatment outcomes in NSCLC patients receiving osimertinib (Clinical Trial Registration No.: UMIN000022076).

Sakai K ，Takahama T ，Shimokawa M ，Azuma K ，Takeda M ，Kato T ，Daga H ，Okamoto I ，Akamatsu H ，Teraoka S ，Ono A ，Ohira T ，Yokoyama T ，Yamamoto N ，Nakagawa K ，Nishio K ... -  《-》