The presence of mutations found in both extracellular DNA (cfDNA) and tumor tissue can serve as evidence of the tumor origin of the cfDNA. The aim of this study was to determine the mutational status of cfDNA in plasma and to compare that with the mutational changes in DNA of the tumor to identify possible sources and origin of the cfDNA. Material and methods. The methodology for conducting the metaanalysis is carried out in accordance with the provisions of «Preferred reporting parameters for systematic reviews and metaanalysis (PRISMA)». In accordance with the inclusion criteria, 28 studies involving 3371 people were combined to perform the meta-analysis, in which the comparison of the mutational status of the EGFR gene in the cfDNA of plasma and tumor tissue was carried out. In a laboratory study, 13 patients with a diagnosis of non-small cell lung cancer adenocarcinoma (76.9%) and squamous cell carcinoma were evaluated. Results. Metaanalysis showed that there was no heterogeneity between studies (Q=0.001699, I2=0), the average percentage of concordance of the mutational status of the tumor DNA and the cfDNA in blood was 88.1% (95% CI 86.96—89.18%). In the study of genetic changes in tumor samples and cfDNA in plasma from patients with non-small cell lung cancer, it was shown that the activating mutation in the EGFR gene in our sample was present in 2 patients. Also, the same mutation was detected in plasma cfDNA in 50% of samples from these patients. The remaining patients had no mutation in either the tumor samples or in the plasma cfDNA. Therefore, the percentage of concordance of the mutational status of the tumor and the cfDNA of the blood (concordance) was 92.3% (95% CI 63.9—99.8%). Conclusions. It can be concluded that the results of this study may indicate a possible tumor origin of the cfDNA, which opens up new possibilities for understanding the biological role of the cfDNA in plasma.