A systematic review and meta-analysis of circulating cell-free DNA as a diagnostic biomarker for non-small cell lung cancer

Background: Early diagnosis of non-small cell lung cancer (NSCLC) is crucial for treatment. Circulating cell-free DNA (cfDNA) is an extracellular nucleic acid found in serum, and tumor cfDNA circulating in the blood may be used as a biomarker for early diagnosis. The purpose of this study was to evaluate the application value of cfDNA as a biomarker for the diagnosis of NSCLC through meta-analysis. Methods: We searched the China National Knowledge Infrastructure (CNKI), Wanfang, VIP, PubMed, Cochrane Central Register of Controlled Trials, Embase, and Web of Science databases using the following search terms: lung cancer, NSCLC, biomarkers, circulating cfDNA, cfDNA, circulating tumor DNA (ctDNA), circulating cell-free tumor DNA, and diagnosis. The retrieval period was set until September 2021. According to PICOS (patients, intervention, comparison, outcomes, and study design) principles the inclusion criteria were: aged >= 18 years; at least 10 NSCLC cases; NSCLC patients diagnosed by histopathology or cytology; circulating cfDNA was detected; outcome data could be completely extracted. Bias risk assessment was conducted according to the QUADAS (Quality Assessment of Diagnostic Accuracy Studies). RevMan 5.3 was used for meta-analysis. Results: Eight studies met the inclusion criteria, including a total of 618 NSCLC patients and 635 healthy subjects. The overall sensitivity and specificity were 0.79 [95% confidence interval (CI): 0.75-0.82] and 0.81 (95% CI: 0.78-0.84), respectively. The area under the curve (AUC) of the summary receiving operating characteristic (SROC) curve was 0.8941. The pooled positive likelihood ratio, pooled negative likelihood ratio, and pooled diagnostic odds ratio were 5.37 (95% CI: 2.67-10.81), 0.24 (95% CI: 0.15-0.38), and 24.68 (95% CI: 8.85-68.84), respectively. The patient selection bias was high in two articles was high, unclear in one article, and low in the remaining five ones. The risk of bias in the research index test was unclear in one article, and low in the remaining seven articles. The reference standard bias, and flow and time bias of all articles was low. Conclusions: Circulating cfDNA is an efficacy biomarker in diagnosis of NSCLC. Its clinical application technology is worthy of further research.