结直肠癌患者血浆循环游离DNA的RAS突变与临床特征的关系

Association of RAS mutations in circulating cell-free DNA in the plasma with clinicopathological features of colorectal cancer

目的探讨结直肠癌患者血浆循环游离DNA(cfDNA)与肿瘤组织DNA的RAS基因突变检测的一致性,以及与临床特征的关系。方法收集71例结直肠癌患者的血浆及肿瘤组织标本。采用多重荧光PCR法检测血浆标本cfDNA的RAS的基因突变状态,并与肿瘤组织标本的相应基因突变状态对比分析。分析血浆RAS基因突变状态与患者临床特征的关系。结果血浆cfDNA的RAS突变率为32.39%,组织DNA的RAS突变率为50.70%,两种标本的RAS突变检测的一致率为76.06%,血浆cfDNA与组织DNA的RAS突变检测结果一致(Kappa=0.523,P=0.000)。血浆cfDNA检测的敏感性为58.33%、特异性为94.29%、阳性预测值为91.30%、阴性预测值为68.75%。血浆cfDNA的RAS突变状态与结直肠癌患者年龄、性别、分期(Ⅳa与Ⅳb)、原发肿瘤部位、肺转移、CEA水平、CA199水平等无明显相关性,而血浆cfDNA的RAS突变与结直肠癌患者肝脏转移有相关性(P=0.045),肝转移患者较未发生肝转移的患者突变率升高。结论血浆cfDNA可以作为无法获得组织标本的结直肠癌患者的RAS基因检测的替代标本,具有临床应用价值,且结直肠癌患者肝脏转移cfDNA RAS突变率升高。

Objective To detect RAS mutations in the circulating cell-free DNA （cfDNA） in the plasma and explore the their correlation with the clinicopathological features in patients with colorectal cancer. Methods Real-time PCR was used to detect RAS mutations in plasma cfDNA and matched tumor tissue DNA samples from 71 colorectal cancer patients. The correlation of RAS mutations with the clinicopathological features of the patients were analyzed. Results Of the 71 patients with colorectal cancer, 23 （32.39%） showed RAS mutations in the cfDNA and 36 （50.7%） showed RAS mutations in tumor tissue DNA, with a concordance rate of 76.06% in the results between the two samples （Kappa=0.523）. RAS mutations in the cfDNA were not related to the patients＆#39; age （P=0.072）, gender （P=0.320）, tumor stage （IVa and IVb, P=0.450）, primary tumor position （P=0.324）, lung metastasis （P=0.237）, CEA level （P=0.284） or CA199 level （P=0.427）. The positivity rate of RAS mutations in plasma cfDNA was significantly higher in patients with liver metastasis than those without liver metastasis （P=0.045）. Conclusion Plasma cfDNA can be a reliable source of diagnostic DNA to replace the tumor tissue DNA for diagnosis of RAS mutations. RAS mutations in plasma cfDNA occur more frequently in colorectal cancer patients with liver metastasis.