Background: Circulating tumor DNA (ctDNA) holds great potential for cancer therapy and can provide diagnostic and prognostic information before and during treatment.

Methods: Plasma DNA samples from 97 melanoma patients, 20 healthy donors and 3 patients with benign skin tumors were analyzed by microarray analysis and droplet digital PCR (ddPCR).

Results: A microarray for simultaneous detection of six BRAF V600 mutations in ctDNA has been developed. The method allows the detection of 0.05% mutated DNA from WT DNA background. For paired samples (pre-surgery plasma and tumor tissue) isolated from 74 patients, the concordance of genotypes between tumor DNA and ctDNA was 65% (48/74). BRAF mutations in ctDNA were detected in 27/50 patients with BRAF-positive tumors and in 3/24 patients with BRAF wild-type tumors. The presence of ctDNA BRAF mutations in 23 plasma samples from melanoma patients undergoing therapy correlated significantly with tumor progression (P=0.005). The increase in cell-free DNA levels measured by ddPCR also correlated with disease progression (P=0.02). The concordance of results obtained by microarray identification of BRAF mutations and those obtained by ddPCR was 91%.

Conclusion: The novel microarray-based approach can be a useful non-invasive tool for accurate identification of ctDNA BRAF mutations to monitor disease progression.

背景：循环肿瘤DNA（ctDNA）在癌症治疗中具有巨大潜力，可以在治疗之前和期间提供诊断和预后信息。

方法：采用微阵列分析和液滴数字PCR（ddPCR）分析了97例黑素瘤患者，20名健康供体和3例皮肤良性肿瘤患者的血浆DNA样本。

结果：已经开发了一种同时检测ctDNA中六个BRAF V600突变的微阵列。该方法可从WT DNA背景中检测到0.05％的突变DNA。从74例患者中分离出的配对样品（术前血浆和肿瘤组织）中，肿瘤DNA和ctDNA的基因型一致性为65％（48/74）。在27/50例BRAF阳性肿瘤患者和3/24例BRAF野生型肿瘤患者中检测到ctDNA中的BRAF突变。在接受治疗的黑色素瘤患者的23份血浆样品中ctDNA BRAF突变的存在与肿瘤进展显着相关（P= 0.005）。通过ddPCR测量的无细胞DNA水平的增加也与疾病进展相关（P = 0.02）。通过微阵列鉴定BRAF突变获得的结果与通过ddPCR获得的结果的一致性为91％。

结论：基于微阵列的新方法可以作为准确识别ctDNA BRAF突变以监测疾病进展的有用的非侵入性工具。