DataSheet_1_Longitudinal Circulating Tumor DNA Profiling in Metastatic Colorectal Cancer During Anti-EGFR Therapy.pdf

BackgroundMetastatic colorectal cancer (mCRC) is a heterogenous disease with limited precision medicine and targeted therapy options. Monoclonal antibodies against epidermal growth factor receptor (EGFR) have been a crucial treatment option for mCRC. However, proper biomarkers for predicting therapeutic response remain unknown. As a non-invasive test, circulating tumor DNA (ctDNA) is appropriately positioned to reveal tumor heterogeneity and evolution, as it can be used in real-time genomic profiling. To evaluate the significance of ctDNA in monitoring the dynamic therapeutic response and prognosis of mCRC, we detected the baseline and dynamic changes of ctDNA in mCRC patients receiving anti-EGFR therapies.
MethodsA single-center study was conducted retrospectively. Plasma samples from mCRC patients who received anti-EGFR therapies were collected at baseline and continuous treatment points. The ctDNA was extracted and sequenced with a target panel of tumor-related genes via next-generation sequencing (NGS). Clinical information was also collected and analyzed.
ResultsWe conducted dynamic sampling of 22 mCRC patients, analyzed 130 plasma samples, obtained a baseline genomic mutation profile of the patients. In total, 54 variations were detected in 22 plasma samples, with a positive rate of 77.3% (17/22). TP53 was the most mutated gene (59.1%, 13/22), followed by APC (18.2%, 4/22). There was a high concordance rate of genomic characteristics between the tumor tissue test by polymerase chain reaction and ctDNA test by NGS. The mutation discrepancy increased with an extended course of treatment. During remission TP53 and APC were the most frequently decreased clonal mutations and KRAS, NRAS, ERBB2 and PIK3CA were the most decreased subclonal mutations. Both mutation types were increased during progression. The ctDNA decreased earlier than did the responses of computed tomography and traditional tumor markers (carbohydrate antigen 19-9 and carcinoembryonic antigen [CEA]). Lactate dehydrogenase level (P = 0.041), CEA level (P = 0.038), and primary lesion site (P = 0.038) were independent risk factors that influenced overall survival. Moreover, patients with RAS mutations tended to have a worse prognosis (P = 0.072).
ConclusionsThis study demonstrates that ctDNA is a promising biomarker for monitoring the dynamic response to treatment and determining the prognosis of mCRC.

背景：转移性结直肠癌（metastatic colorectal cancer, mCRC）是一种异质性疾病，精准医学与靶向治疗选择有限。抗表皮生长因子受体（epidermal growth factor receptor, EGFR）单克隆抗体一直是mCRC的关键治疗手段。然而，目前仍缺乏可准确预测治疗响应的合格生物标志物。循环肿瘤DNA（circulating tumor DNA, ctDNA）作为一种无创检测手段，能够实时进行基因组分型，因此非常适合用于揭示肿瘤异质性与演化过程。为评估ctDNA在监测mCRC患者动态治疗响应及预后中的价值，本研究对接受抗EGFR治疗的mCRC患者的ctDNA基线水平与动态变化进行了检测。
方法：本研究为单中心回顾性研究。收集接受抗EGFR治疗的mCRC患者的血浆样本，采集时点包括基线期与持续治疗期间的多个时间点。通过下一代测序（next-generation sequencing, NGS）结合肿瘤相关基因靶向测序Panel，对提取的ctDNA进行测序。同时收集并分析患者的临床信息。
结果：本研究对22例mCRC患者进行了动态采样，共分析130份血浆样本，获取了患者的基线基因组突变图谱。在22份基线血浆样本中共检测到54个变异，阳性率为77.3%（17/22）。TP53是突变频率最高的基因（59.1%，13/22），其次为APC（18.2%，4/22）。聚合酶链反应（polymerase chain reaction, PCR）检测的肿瘤组织基因组特征与NGS检测的ctDNA基因组特征具有较高的一致性；随着治疗疗程延长，基因组突变的不一致性逐渐升高。在疾病缓解阶段，TP53与APC是丰度下降最显著的克隆突变，而KRAS、NRAS、ERBB2及PIK3CA则是丰度下降最明显的亚克隆突变；在疾病进展阶段，这两类突变的丰度均出现升高。ctDNA水平的变化早于计算机断层扫描（computed tomography, CT）及传统肿瘤标志物[糖链抗原19-9（carbohydrate antigen 19-9, CA19-9）与癌胚抗原（carcinoembryonic antigen, CEA）]的响应变化。乳酸脱氢酶水平（P=0.041）、CEA水平（P=0.038）及原发灶部位（P=0.038）是影响总生存期的独立危险因素。此外，携带RAS突变的患者预后往往更差（P=0.072）。
结论：本研究证实，ctDNA可作为一种极具潜力的生物标志物，用于监测mCRC患者的动态治疗响应并判断其预后。