Abstract:Objective To compare the changes of circulating free DNA (cfDNA), common tumor markers in advanced malignant tumors, and to explore the clinical value of cfDNA. Methods A retrospective study was conducted on 30 patients with advanced malignant tumors who could be evaluated by imaging in the oncology department of Nanjing Second Hospital from January 2020 to December 2020, to observe the changes of cfDNA, tumor markers and imaging features during the treatment. Through the detection of serum cfDNA and tumor markers ［carcinoembryonic antigen (CEA), cancer antigen (CA)199, alpha-fetoprotein (AFP), neuron specific enolase (NSE)］ and the imaging evaluation (CT or MRI) before treatment, the consistency was observed between the changes of cfDNA and the levels of tumor markers and imaging evaluation in monitoring treatment efficacy. Results The cfDNA levels were increased in 25 of 30 patients with advanced malignant tumor at baseline (detectable rate 83.33%) and positively correlated with the size (r=0.804,P<0.01) and number of tumor lesions(r=0.580,P<0.01). The higher the tumor load in vivo, the higher the cfDNA level (P<0.05).The levels of cfDNA and the levels of tumor markers changed in the same direction in 20 cases and changed in the opposite direction in 8 cases. After two cycles of anti-tumor therapy, imaging evaluation showed no case of complete response (CR), 3 cases of partial response (PR), 22 cases of stable disease (SD) and 5 cases of progressive disease (PD). Spearman correlation analysis showed that the continuous increase of cfDNA was negatively correlated with the disease control rate by imaging evaluation (r=-0.553, P<0.01). Conclusion The cfDNA has a certain predictive effect on the disease assessment and curative effect evaluation, and can be used as a serological biomarker to dynamically observe the changes of advanced malignant tumors.