Su Fei, Zheng Ke, Fu Yiyun, Wu Qian, Tang Yuan, Wang Weiya, Jiang Lili
Department of Pathology, West China Hospital of Sichuan University, Chengdou 610041, China.
Zhongguo Fei Ai Za Zhi. 2018 May 20;21(5):389-396. doi: 10.3779/j.issn.1009-3419.2018.05.06.
Epidermal growth factor receptor (EGFR) gene mutation is closely related to the EGFR-TKI target treatment and prognosis of lung adenocarcinoma patients. The mutation status of EGFR is limited by tissue detection. The purpose of this study was to investigate the difference of EGFR mutants in plasmacirculating cell-free DNA (cfDNA) obtained from patients with non-small cell lung cancer (NSCLC) in three groups: pre-therapy, after traditional chemotherapy and targeted therapy. The aim of this study was to analyze whether the plasma cfDNA could effectively determine the EGFR mutations and monitor the drug resistant gene T790M, as well as its prognostic prediction value in patients with targeted therapy.
ARMS (amplification refractory mutation system)-PCR was used to detect EGFR mutations in 107 (50 of pre-therapy, 29 after traditional chemotherapy and 28 after targeted therapy) cases of paired plasma and tumor tissue specimens, followed by comparing their concordance. The sensitivity, specificity and the prognostic value of plasma cfDNA detection were also observed.
The total rate of EGFR mutation was 56% (60/107) in all plasma samples and 77.6% (83/107) in corresponding tumor tissues. Completely the same mutants and wild-type EGFR were found in 68.2% cases of paired specimens. The sensitivity of plasma cfDNA detection was 72.3% and the specificity was up to 100%. Patients were sub-categorized according to therapy. The results showed that the highest consistent rate of cfDNA and tumor tissues was found in the group of pre-therapy (74%, 37/50). Whereas, the lowest consistent rate was observed in the targeted therapy group (57.1%, 16/28). It indicated that the targeted treatment could change the EGFR status in plasma cfDNA. Further analyses on inconsistent cases in this group revealed that 50% of them were compound EGFR mutations with T790M. Thereby, it suggested that targeted therapy might induce the emergence of drug resistance gene T790M. This speculation was confirmed by survival analyses. Based on plasma cfDNA results, patients with T790M mutant had significantly worse progression-free survival (PFS) and overall survival (OS).
For EGFR testing, ARMS-PCR on plasma cfDNA is a promising methodology with the highest specificity and effective sensitivity. It is useful for EGFR testing in patients before treatment, especially the late-stage patients. Simultaneously, plasma cfDNA could be used to monitor the drug resistant mutation, T790M status and predict prognosis after targeted therapy.
表皮生长因子受体（EGFR）基因突变与肺腺癌患者的EGFR-TKI靶向治疗及预后密切相关。EGFR的突变状态受组织检测限制。本研究旨在探讨非小细胞肺癌（NSCLC）患者在治疗前、传统化疗后及靶向治疗后三组血浆循环游离DNA（cfDNA）中EGFR突变体的差异。本研究的目的是分析血浆cfDNA能否有效检测EGFR突变并监测耐药基因T790M，以及其在靶向治疗患者中的预后预测价值。
采用ARMS（扩增阻滞突变系统）-PCR检测107例（治疗前50例、传统化疗后29例、靶向治疗后28例）配对血浆和肿瘤组织标本中的EGFR突变，随后比较它们的一致性。还观察了血浆cfDNA检测的敏感性、特异性及预后价值。
所有血浆样本中EGFR突变总率为56%（60/107），相应肿瘤组织中为77.6%（83/107）。68.2%的配对标本中发现完全相同的突变体和野生型EGFR。血浆cfDNA检测的敏感性为72.3%，特异性高达100%。根据治疗情况对患者进行亚分类。结果显示，治疗前组cfDNA与肿瘤组织的一致性率最高（74%，37/50）。而靶向治疗组的一致性率最低（57.1%，16/28）。这表明靶向治疗可改变血浆cfDNA中的EGFR状态。对该组不一致病例的进一步分析显示，其中50%为伴有T790M的复合EGFR突变。因此，提示靶向治疗可能诱导耐药基因T790M的出现。生存分析证实了这一推测。基于血浆cfDNA结果，T790M突变患者的无进展生存期（PFS）和总生存期（OS）明显更差。
对于EGFR检测，血浆cfDNA的ARMS-PCR是一种具有最高特异性和有效敏感性的有前景的方法。它对治疗前患者尤其是晚期患者的EGFR检测有用。同时，血浆cfDNA可用于监测耐药突变、T790M状态并预测靶向治疗后的预后。
