OBJECTIVES T790M mutations inEGFR-mutated non-small cell lung cancer (NSCLC) account for nearly 50% of acquired resistance mechanisms to EGFR-TKIs. Earlier studies suggested that tumor T790M could also be detected in TKI-naïve EGFR-mutated NSCLC. The aim of the study is to assess the prevalence and clinical significance of quantification of tumor pre-treatment T790M subclones. MATERIALS AND METHODS We analyzed 366 EGFR-mutated NSCLC patients of the real-life IFCT Biomarkers France study with available pre-treatment formalin-fixed paraffin-embedded (FFPE) tumor DNA before treatment by first/second-generation EGFR-TKI. We used ultra-sensitive Droplet Digital Polymerase Chain Reaction (ddPCR) QX200 (BIO-RAD®, Hercules, CA, USA). All samples were tested in duplicate. RESULTS ddPCR identified T790M in 19/240 specimens (8%). T790M-positive and T790M-negative populations were not different for clinical baseline characteristics. T790M Variant Allele Frequency (VAF) was > 0.01% <0.1%, > 0.1% <1%, > 1% <10%, and >10% in five (26.3%), six (31.6%), six (31.6%), and two (10.5%) patients, respectively. T790M VAF was >0.1% in 11/13 (84%) patients with rapid (<3 months) or usual progression (3-20 months) compared to 0/3 with low progression (>20 months) (p = 0.02). In a Cox model, T790M mutation positivity was correlated with overall survival (OS) and progression-free survival (PFS) for 10% > VAF >1% (hazard ratio [HR] = 2.83, 95% confidence interval [CI] 1.13-7.07, p = 0.03; HR=3.62, 95%CI 1.43-4.92, p = 0.007, respectively) and for VAF >10% (HR = 19.14, 95%CI 4.35-84.26, p < 0.001; HR = 17.89, 95%CI 2.21-144.86, p = 0.007, respectively). CONCLUSION Ultra-sensitive detection of tumor T790M mutation concerned 8% of EGFR-mutated TKI-naïve NSCLC patients and has a negative prognostic value only for T790M VAF over 1%.

中文翻译：

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第一代/第二代TKI对EGFR突变的非小细胞肺癌（NSCLC）的肿瘤预治疗T790M亚克隆进行超灵敏定量的独立预后价值，取决于变异等位基因频率（VAF）：法国合作性胸腔镜的结果组间（IFCT）生物标志物法国项目。

目的EGFR突变的非小细胞肺癌（NSCLC）中的T790M突变占获得性对EGFR-TKIs耐药机制的近50％。较早的研究表明，在TKI初始EGFR突变的NSCLC中也可以检测到T790M肿瘤。这项研究的目的是评估量化的肿瘤预处理T790M亚克隆的流行率和临床意义。材料和方法我们在第一代/第二代EGFR-TKI治疗之前，对366例IFCT Biomarkers France真实生活中EGFR突变的NSCLC患者进行了福尔马林固定石蜡包埋（FFPE）肿瘤DNA预处理治疗。我们使用了超灵敏的液滴数字聚合酶链反应（ddPCR）QX200（BIO-RAD®，美国大力神，美国）。所有样品均一式两份进行测试。结果ddPCR在19/240个样本（8％）中鉴定出T790M。T790M阳性和T790M阴性人群的临床基线特征无差异。T790M变异等位基因频率（VAF）在五个（26.3％），六个（31.6％），六个（31.6％）中> 0.01％<0.1％，> 0.1％<1％，> 1％<10％和> 10％ ）和两名（10.5％）患者。快速（<3个月）或正常进展（3-20个月）的11/13患者中的T790M VAF> 0.1％，而低进展（> 20个月）的0/3患者则为T790M VAF（p = 0.02）。在Cox模型中，对于10％> VAF> 1％（危险比[HR] = 2.83，95％置信区间[CI] 1.13-），T790M突变阳性与总生存期（OS）和无进展生存期（PFS）相关。 7.07，p = 0.03; HR = 3.62，95％CI 1.43-4.92，p = 0.007）和VAF> 10％（HR = 19.14，95％CI 4.35-84.26，p <0.001; HR = 17.89，95 ％CI 2.21-144.86，p = 0.007，分别）。结论超敏感检测T790M肿瘤突变涉及EGFR突变的TKI初治NSCLC患者的8％，并且仅对1％以上的T790M VAF具有阴性预后价值。