目的 检测结直肠癌患者血浆游离DNA（cell-free DNA, cfDNA）甲基化水平，并分析其临床应用价值。方法 收集38例大连大学附属新华医院就诊的CRC患者（Ⅰ~Ⅲ期）及38例健康体检者的血标本，采用化学发光法检测血清CEA水平；提取CRC组及健康体检者血浆cfDNA，行高通量甲基化靶向测序检测，计算甲基化评分，并分析其与CRC患者临床病理参数的关系；ROC曲线评估cfDNA和CEA单独及联合检测筛查CRC的临床价值。结果 与健康对照组相比，CRC组cfDNA浓度差异无统计学意义（34.41±5.00 vs 36.59±4.46, t=0.326，P=0.745），而cfDNA甲基化评分显著升高（0.53±0.27 vs 0.26±0.18, t=6.134，P<0.001）。伴有淋巴结转移CRC患者cfDNA甲基化阳性率较无淋巴结转移者显著升高（88.9% vs 60%，χ2=4.323，P=0.038），但在不同性别、年龄、肿瘤位置分组中的差异均无统计学意义（P均＞0.05）。ROC曲线分析结果显示，cfDNA甲基化检测筛查CRC的ROC曲线下面积（AUCROC）为0.892（95%CI: 0.814~0.970），血清CEA为0.81（95%CI: 0.707~0.909），二者联合检测的AUCROC0.93（95%CI: 0.8674~0.9967）。cfDNA甲基化检测的敏感性为84.21%，特异性为86.84%（cut-off值为0.2805）；CEA单独检测敏感性为42.1%，特异性为97.3%（cut-off值为4.0）；cfDNA甲基化联合CEA检测其敏感性显著升高（89.47%），特异性为91.89%，准确性高达90.67%。结论 血浆cfDNA甲基化检测在CRC筛查中的敏感性和特异性较高，并且与淋巴结转移相关，具有较好的临床应用价值。
Abstract: Objective To detect the methylation level of plasma cell-free DNA ( cfDNA) in patients with colorectal cancer ( CRC)，and analyze its clinical significance. Methods The blood samples from 38 CRC patients ( Stage I -I ) and 38 healthy controls were collected，and serum carcinoembry onic antigen( CEA) levels were detected by a chemiluminescence assay. Plasma cfDNA was extracted from blood samples, and detected by high-throughput targeted methylation sequencing. Then, the methylation score of cfDNA was calculated and its relationship with the clinicopathological parameters of CRC patients was analyzed. The clinical values of cfDNA alone and combined with CEA in the screening of CRC were evaluated by the ROC curve. Results There was no significant difference in the concentration of cfDNA between CRC patients and healthy controls (34.41+5.00 vs 36.59+4.46, t=0.326, P=0.745), but the methy lation score of cfDNA in CRC patients was significantly higher than that of healthy controls (0.53+0.27 vs 0.26+0.18, t=6.134, P<0.001). The positive rate of cfDNA methylation in CRC patients with lymph node metastasis was significantly higher than that in patients without lymph node metastasis ( 88.9% vs 60%,2 =4.323, P= 0.038), but there was no significant diference between different gender, age and tumor location groups ( P>0.05). The ROC curve analysis showed that the areas under the ROC curve ( AUCR0C) of cfDNA methylation, serum CEA and the combination of them in the screening of CRC were 0.892 ( 95%CI: 0.814-0.970)， 0.810 ( 95%CI: 0.707-0.909) and 0.930 (95%CI: 0.867 4-0.996 7), respectively. The sensitivity, speeificity and cut-off value of efDNA methylation in the screening of CRC were 84.21%, 86.84% and 0.280 5, respectively, and those of serum CEA alone were 42. 1 %，97.3% and 4.0, respectively. The sensitivity, specifity and accuracy of cfDNA methylation combined with serum CEA in the screening of CRC were 89.47%, 91.89% and 90.67%, respectively. Conclusion The detection of plasma cfDNA methylation has high sensitivity and specificity in the screening of CRC, and is related to lymph node metastasis, which has a good clinical application value.