循环肿瘤DNA（ctDNA）是肿瘤特征描述和治疗期间残留疾病监测的宝贵资源；然而，在转移性结直肠癌（mCRC）常规临床实践中，它尚未被引入。在这项回顾性的探索性研究中，我们评估了ctDNA在接受化疗加别嘌呤单抗治疗的mCRC患者中的作用。在治疗开始前，对53位患者的肿瘤组织进行了RAS和BRAF状态的表征。在基线、第一次临床评估和疾病进展时采集了血浆样本。使用Ion S5 XL仪器上的Oncomine Colon cfDNA检测仪进行ctDNA分析。在基线时，从血浆样本中检测到44位患者的RAS、BRAF或PIK3CA突变。观察到ctDNA与肿瘤组织突变之间存在高度一致性（KRAS 100%，NRAS 97.9%，BRAF 97.9%，PIK3CA 90%）。与高变异等位基因频率（VAF）相比，低基线VAF与较长的中位无进展生存期（PFS）相关（15.9 v 12.2个月，P = 0.02）。在第一次评估中，VAF大幅下降的患者观察到较高的PFS（12.29个月[95% CI，9.03至17.9] vs 8.15个月[95% CI，2.76至N/A]，P = 0.04）和总生存期（34.1个月[95% CI，21.68至N/A] vs 11.1个月[95% CI，3.71至N/A]，P = 0.003）。ctDNA分析在mCRC患者的分子特征描述和肿瘤反应监测中具有用处。释放的ctDNA的定量变化与临床结果相关。

Plasma circulating tumor DNA (ctDNA) is a valuable resource for tumor characterization and for monitoring of residual disease during treatment; however, it is not yet introduced in metastatic colorectal cancer (mCRC) routine clinical practice. In this retrospective exploratory study, we evaluated the role of ctDNA in patients with mCRC treated with chemotherapy plus bevacizumab.Fifty-three patients were characterized for RAS and BRAF status on tumor tissue before the start of treatment. Plasma was collected at baseline, at first clinical evaluation, and at disease progression. ctDNA analysis was performed using Oncomine Colon cfDNA Assay on the Ion S5 XL instrument.At baseline, from a plasma sample, RAS, BRAF, or PIK3CA mutations were detected in 44 patients. A high correspondence was observed between ctDNA and tumor tissue mutations (KRAS 100%, NRAS 97.9%, BRAF 97.9%, PIK3CA 90%). Low baseline variant allele frequency (VAF) was found to be associated with longer median progression-free survival (PFS) compared with those with high VAF (15.9 v 12.2 months, P = .02). A higher PFS {12.29 months (95% CI, 9.03 to 17.9) v 8.15 months (95% CI, 2.76 to not available [NA]), P = .04} and overall survival (34.1 months [95% CI, 21.68 to NA] v 11.1 months [95% CI, 3.71 to NA], P = .003) were observed in patients with large decline in VAF at first evaluation.ctDNA analysis is useful for molecular characterization and tumor response monitoring in patients with mCRC. Quantitative variations of released ctDNA are associated with clinical outcomes.