The Study On The Relationship Between Circulating Tumor Dnaand Radiotherapy Efficacy In Non-small Cell Lung Cancer

Objective:To investigate the value of ctDNA in predicting the efficacy of radiotherapy in non-small cell lung cancer.Methods:From April 2016 to December 2017,20 patients with stage IIIb who were pathologically diagnosed of non-small cell lung cancer were included in the study.They all received radical radiotherapy at the Department of Radiation Oncology in Chongqing Cancer Hospital with complete data.The patients were given chest CT before radiotherapy.The maximum cross-sectional area of the tumor was recorded as the baseline size.4 ml peripheral blood were collected within 1 week before radiotherapy,10 times after radiotherapy,and 20 times after radiotherapy respectively.And plasma were separated using a low-temperature high-speed centrifuge.The plasma DNA was extracted by LIFE magnetic bead method with the plasma DNA extraction kit.The target gene was verified by gel electrophoresis.Moreover,real-time PCR was used to amplify and accurately quantify EGFR gene,and the ct DNA concentration was recorded.1 month after radiotherapy,the maximum sectional area of the tumor was measured by chest CT,and the efficay was evaluated.At last,to analyze the correlation between the total amount of ctDNA and the therapeutic effect ofradiotherapy.Results:1.Compared with the ct DNA concentration before radiotherapy(3.07~7.31 ng/?L,median 4.63 ng/?L),the ctDNA concentration of all patients after 10 times of radiotherapy increased(3.90~8.92 ng/?L,median 6.69 ng/?L),while the ctDNA concentration decreased after 20 timers of radiotherapy in all the patients(2.24~6.53 ng/?L,median 3.48 ng/?L).2.20 patients with non-small cell lung cancer were randomly divided into groups PR and group SD with the cut off value of regression rate 0.5,of which 7 cases in group PR and 13 cases in group SD.The regression rate was between 0.012% and 0.771%.There was no significant difference in ctDNA concentration between before and after radiotherapy(P = 0.431,0.742,0.109),and between the baseline value and after radiotherapy(P = 0.095,0.051).However,there was a statistically significant difference between10 times after radiotherapy and 20 times after radiotherapy(P= 0.031).3.The baseline value before radiotherapy was positively correlated with the maximum cross-sectional area of ??the tumor before treatment(r=0.819,P=0.002).The regression rate was not correlated with the ctDNA concentration before radiotherapy and 10 times after radiotherapy(before radiotherapy:r=-0.207,P=0.382;10 times after radiotherapy:r=0.190,P=0.421).However,it was negatively correlated with ctDNA concentration 20 times after radiotherapy(r=-0.525,P=0.017).Compared with baseline values??before radiotherapy,ctDNA concentration after radiotherapy was not correlated with the regression rate(10 times after radiotherapy :r=0.596,P =0.06;20 times after radiotherapy :r=-0.575,P=0.08).But ctDNA concentration of 20 times after radiation was negatively correlated with the remission rate comprared with 10 times after radiation(r=-0.692,P=0.01).Conclusion : 1.ctDNA concentration correlates with tumor load;2.Thevariation trend of ctDNA concentration is related to the short-term efficacy of radiotherapy.Monitoring ctDNA concentration during radiotherapy may predict the efficay early.And quantitative ctDNA analysis is expected to be a new molecular biomarker to evaluate the efficacy of radiotherapy for non-small cell lung cancer,which deserves further investigation.