Department of Comprehensive Clinical Oncology, Faculty of Medical Sciences, Kyushu University, Fukuoka.
Research Institute for Diseases of the Chest, Graduate School of Medical Sciences, Kyushu University, Fukuoka.
Ann Oncol. 2017 Jan 1;28(1):136-141. doi: 10.1093/annonc/mdw531.
Analysis of circulating cell-free DNA (cfDNA) is under intensive investigation for its potential to identify tumor somatic mutations. We have now explored the usefulness of such liquid biopsy testing with both the digital polymerase chain reaction (dPCR) and next-generation sequencing (NGS) during treatment of patients with the epidermal growth factor receptor (EGFR) inhibitor afatinib.
Eligible patients had advanced lung adenocarcinoma with EGFR activating mutations and were treated with afatinib. Plasma samples were collected before and during (4 and 24 weeks) afatinib treatment as well as at disease progression. Tumor and plasma DNA were analyzed by dPCR and NGS.
Thirty-five patients were enrolled. The objective response rate and median progression-free survival (PFS) were 77.1% and 13.8 months, respectively. Tumor and plasma DNA were available for 32 patients. dPCR and NGS detected EGFR activating mutations in 81.3% and 71.9% of baseline cfDNA samples, respectively. In 19 patients treated with afatinib for ≥24 weeks, the number of EGFR mutant alleles detected in cfDNA by dPCR declined rapidly and markedly after treatment onset, becoming undetectable or detectable at only a low copy number (<10 copies per milliliter) at 4 weeks. Median PFS was slightly longer for patients with undetectable EGFR mutant alleles in cfDNA at 4 weeks than for those in whom such alleles were detectable (14.3 versus 10.0 months). A total of 45 somatic mutations was identified in baseline tumor DNA, and 30 (66.7%) of these mutations were identified in cfDNA by NGS. Allele frequency for somatic mutations in cfDNA determined by NGS changed concordantly during afatinib treatment with the number of EGFR mutant alleles determined by dPCR.
Monitoring of cfDNA by dPCR is informative for prediction of afatinib efficacy, whereas that by NGS is reliable and has the potential to identify mechanisms of treatment resistance.
分析循环无细胞 DNA（cfDNA）是目前研究的热点，它具有识别肿瘤体细胞突变的潜力。我们现在已经探索了液体活检检测在使用表皮生长因子受体（EGFR）抑制剂阿法替尼治疗患者中的应用，检测方法包括数字聚合酶链反应（dPCR）和下一代测序（NGS）。
入组患者为携带 EGFR 激活突变的晚期肺腺癌患者，接受阿法替尼治疗。在阿法替尼治疗前（基线）和治疗中（4 周和 24 周）以及疾病进展时采集血浆样本。通过 dPCR 和 NGS 分析肿瘤和血浆 DNA。
共入组 35 例患者。客观缓解率和中位无进展生存期（PFS）分别为 77.1%和 13.8 个月。32 例患者有肿瘤和血浆 DNA 可供分析。dPCR 和 NGS 分别在 81.3%和 71.9%的基线 cfDNA 样本中检测到 EGFR 激活突变。在 19 例接受阿法替尼治疗≥24 周的患者中，dPCR 检测到的 cfDNA 中 EGFR 突变等位基因数在治疗开始后迅速且明显下降，在 4 周时几乎无法检测到或仅以低拷贝数（<10 拷贝/毫升）检测到。在 4 周时 cfDNA 中无法检测到 EGFR 突变等位基因的患者中位 PFS 略长于可检测到 EGFR 突变等位基因的患者（14.3 个月比 10.0 个月）。在基线肿瘤 DNA 中鉴定出 45 个体细胞突变，其中 30 个（66.7%）通过 NGS 在 cfDNA 中鉴定到。通过 NGS 确定的 cfDNA 中体细胞突变的等位基因频率在阿法替尼治疗期间与 dPCR 确定的 EGFR 突变等位基因数一致地变化。
dPCR 监测 cfDNA 对预测阿法替尼疗效具有信息价值，而 NGS 监测可靠，并具有识别治疗耐药机制的潜力。
