Abstract: Background　Numerous studies have shown that circulating free DNA（cfDNA）has diagnostic value in prostate cancer，but there is no consensus on its accuracy.Objective　To evaluate the diagnostic value of cfDNA in prostate cancer by a Meta-analysis.Methods　Articles in Chinese and English regarding diagnosing prostate cancer using cfDNA were collected by searching databases of PubMed，EMBase，Web of Science，The Cochrane Library，CNKI，and WANFANG DATA from inception to February 2020，and were enrolled according to the inclusion and exclusion criteria.Data were extracted，including the first author's name，year of publication，country of publication，sample size，detection method and accuracy assessment indices（true-positive，false-positive，false-negative，true-negative）.Spearman correlation was used to assess whether there was a threshold effect.The SROC plot was used to examine whether the diagnostic performance curve of cfDNA presenting a “shoulder-arm” shape.The heterogeneity between the included studies was measured by the Cochran's Q test and I2 test and used for selecting an appropriate model for pooling data.Meta-analysis and Fagan's nomogram were used to estimate the diagnostic efficiency and probability of cfDNA，respectively.Results　 Twenty-two articles were included，involving 2 774 cases，1 936 of whom were diagnosed with prostatic cancer by cfDNA and 838 were not.The overall quality of the included literature was good.The pooled sensitivity，specificity，positive likelihood ratio，negative likelihood ratio，diagnostic odds ratio of cfDNA for prostate cancer diagnosis were 0.49〔95%CI（0.47，0.51）〕，0.91〔95%CI（0.89，0.92）〕，6.04〔95%CI（4.39，9.31）〕，0.52〔95%CI（0.45，0.60）〕，and 18.19〔95%CI（12.33，26.85）〕，respectively.The AUC of the SROC curve was 0.898 2.Subgroup analysis showed that the AUC value of cfDNA in the diagnosis of prostate cancer did not change significantly in each subgroup（P>0.05）.Fagan's nomogram demonstrated that using cfDNA to detect prostatic cancer increased the posttest probability to 88% from the pretest probability of 20%.Conclusion　cfDNA might be a diagnostic biomarker for prostate cancer.It may be used as a helper for prostate-specific antigen screening，but it still needed a large number of prospective stuides to support this.

Key words: Prostatic neoplasms, Circulation cell-free DNA, Meta-analysis, Diagnosis

摘要： 背景　众多研究表明循环游离DNA（cfDNA）对前列腺癌有诊断价值，但关于cfDNA检测前列腺癌的准确性并不一致。目的　进一步明确cfDNA对前列腺癌的诊断价值。方法　检索PubMed、EMBase、Web of Science、The Corchrane Library、中国知网、万方数据知识服务平台等数据库，收集所有符合纳入标准的中英文文献，提取第一作者的姓名、发表年份、国家、样本量、检测方法及研究数据参数（真阳性、假阳性、假阴性、真阴性）等信息，检索年限自建库至2020年2月。采用Spearman秩相关分析探讨有无阈值效应，并通过汇总受试者工作特征曲线（SROC曲线）判断SROC图形是否呈“肩臂状”，运用Corchran-Q检验、I2检验分析纳入研究间的异质性，并根据异质性大小选择合适模型进行合并。通过Meta分析评估cfDNA的诊断效能，绘制Fagan图评估cfDNA的诊断能力。结果　共纳入22篇文献，2 774例研究对象包括1 936例前列腺癌患者和838例非前列腺癌患者，纳入文献整体质量较好。Meta分析结果显示，cfDNA诊断前列腺癌的合并灵敏度（Sen合并）为0.49〔95%CI（0.47，0.51）〕，合并特异度（Spe合并）为0.91〔95%CI（0.89，0.92）〕，合并阳性似然比（PLR合并）为6.04〔95%CI（4.39，9.31）〕，合并阴性似然比（NLR合并）为0.52〔95%CI（0.45，0.60）〕，合并诊断比值比（DOR合并）为18.19〔95%CI（12.33，26.85）〕。相应的SROC曲线下面积（AUC）为0.898 2。亚组分析显示cfDNA对前列腺癌的诊断效能的AUC在各个亚组中并无明显改变（P>0.05）。Fagan图显示，设定验前概率为20%，然后辅以检测cfDNA，诊断前列腺癌的准确率为88%。结论　cfDNA诊断前列腺癌有一定价值，可能有助于早期发现前列腺癌，但仍有待于大量的证据进一步验证。

关键词: 前列腺肿瘤, 循环游离DNA, Meta分析, 诊断