Clinical Significance Of Circulating Tumor DNA In Patients With Esophageal Squamous Cell Carcinoma Treated With Radiotherapy

Objective:To investigate the relationship between circulating tumor DNA content in peripheral blood and clinical features and prognosis in patients with esophageal squamous cell carcinoma treated with radiotherapy.Methods:Patients with esophageal squamous cell carcinoma who were pathologically diagnosed and treated with radiotherapy from February 2017 to September 2019 were collected。A total of 79 patients who received ctDNA examination one week before or 4～5 weeks after radiotherapy were screened。The content of ctDNA in peripheral blood of patients with esophageal squamous cell carcinoma before and after radiotherapy was determined by fluorescence quantitative PCR.DigitalPCR(dPCR)was used to detect the copy number of tumor methylated DNA in peripheral blood ctDNA of patients with esophageal squamous cell carcinoma before and after radiotherapy.The clinicopathological features and follow-up data of the patients were collected retrospectively to investigate the relationship between ctDNA level and clinicopathological characteristics and prognosis of patients before and after radiotherapy.Results:The levels of total DNA,intact DNA and tumor methylated DNA in peripheral blood of esophageal squamous cell carcinoma patients after radiotherapy were not statistically significant compared with those before radiotherapy.Univariate analysis of total DNA concentration and tumor methylated DNA expression level in peripheral blood before radiotherapy in patients with esophageal squamous cell carcinoma showed no significant correlation with prognosis(P>0.05).Total DNA concentration and tumor methylated DNA expression in peripheral blood of patients with esophageal squamous cell carcinoma after radiotherapy were positively correlated with the prognosis of the patients,and the difference was statistically significant(P<0.05).The higher of the expression level of total DNA and tumor methylated DNA in peripheral blood,the better the prognosis.There was no significant correlation between the decrease of peripheral blood total DNA and tumor methylated DNA expression level and the prognosis of patients with esophageal squamous cell carcinoma after radiotherapy(P>0.05).There was no significant correlation between the degree of SFRP2 gene methylation before and after radiotherapy and the prognosis of patients with esophageal squamous cell carcinoma(P>0.05).Multivariate analysis showed that tumor methylated DNA expression level and clinical stage in peripheral blood of patients after radiotherapy were independent prognostic factors.Conclusion:1.There was no significant change in the concentration of ctDNA in peripheral blood of ESCC patients who received radiotherapy 4～5 weeks after treatment.More time points should be selected for dynamic observation in subsequent studies.2.The expression levels of total DNA and tumor methylated DNA in peripheral blood of patients with ESCC after radiotherapy are positively correlated with the prognosis of patients.The expression level of tumor methylated DNA is an independent prognostic factor and can be used as an important reference indicator for clinical prognosis.3.The level of SFRP2 methylation in peripheral blood ctDNA does not play an important role in evaluating the prognosis of patients with esophageal cancer..