Detection Of Circulating Tumor DNA In Peripheral Blood And The Significance In Early Diagnosis Of Lung Cancer

Research Background:Lung cancer(LC)is the most rapidly growing cancer disease in China and the world,which seriously threatens the health of the population.In the past 30 years,mortality of lung cancer has increased significantly,lung cancer is the leading cause of cancer related deaths.In China,with the morbidity and mortality being the first of all malignancies in male and the second only to breast cancer in female.At present,more than 80%of lung cancer is non-small cell lung cancer(NSCLC).In this research we mainly focused on patients with NSCLC.Nowadays,the best treatment of NSCLC is formulated mainly according to the clinical manifestation,clinical staging and morphological diagnosis of patients in the clinic.In patients with early lung cancer(I A,I B),they can be cured by simple surgical treatment;for patients with stage II A and IIB,the NSCLC may be controlled in the ideal state under the help of surgery plus postoperative ad.juvant chemotherapy.Howevernfor the patients in stage III A,stage III B or even stage IV,the disease is only treated by means of chemotherapy,radiotherapy,targeted therapy,immunotherapy,or multi-disciplinary therapy,and the prognosis of lung cancer is very poor,so the early diagnosis of non-small cell lung cancer is very valuable.The pseudopositive results of CT and the non-specificity of tumor markers such as CEA make them unsuitable for early diagnosis of lung cancer.Currently,the diagnosis of lung cancer mainly depends on biopsy of tumor tissues taken by means of puncture,bronchoscope and surgery.But this is an invasive operation,and its positive rate is affected by the tumor size,tumor growth area,the heterogeneity of tumor,drugs and other internal and external factors,so the operation has its limitations.Currently,researchers have found that the circulating tumor DNA(ctDNA)in peripheral blood of patients with NSCLC is only derived from tumor tissues,which contains all the genetic information of tumor tissues.By detecting the DNA of circulating tumor in peripheral blood and detecting the gene changes of circulating turmor DNA,the changes of tumor diseases can be monitored dynamically so that the optimal treatment plan is formulated.With the continuous development of sequencing technology,the detection of ctDNA will play an important role in the early diagnosis of NSCLC.Research Objective:We selected some patients as the research objects,who have found small pulmo-nary nodules by examining low dose CT before surgery and the pulmonary nodules were confirmed as stage I,stage II lung cancer by postoperative pathology.CtDNA was detected and sequenced in the preoperative peripheral blood of these patients.On the one hand,by comparing the results obtained with the results of postoperative pathological examination,we are able to evaluate the sensitivity of ctDNA detection in early lung cancer patients.We get some blood test CEA.We evaluated the sensitivity differences between ctDNA and CEA.On the other hand,by analyzing the correlation between rate of ctDNA detection and general clinical data,we assessed the value of detection of ctDNA in the diagnosis of early lung cancer.Research Materials and Methods:In this study,41 patients who were treated by thoracic surgery in the Second Hospital of Shandong University from January 2017 to November 2017 were given preoperative blood samples.All 41 patients have found small pulmonary nodules in chest CT before operation.And the pulmonary nodules were confirmed as stage I,stage Ⅱ lung cancer by postoperative pathology.After blood samples were collected,plasma was isolated by high speed centrifugation.Plasma DNA was extracted by magnetic bead method with universal genomic DNA extraction kit.CfDNA was extracted by QIAamp Circulating Nucleic Acid Kit.Agilent’s liquid phase chip capture system was used to efficiently enrich the DNA of the specific target area of human,and then high-throughput and high-depth sequencing was carried out on Illumina Hiseq platform.The number of AF was used as the result of ctDNA detection.The AF was the ratio of the number of mutation sequences of tumor samples to the number of reference sequences of tumor samples,namely the mutation frequency of genes.Statistical analysis was performed by SPSS 17.0.Student’ s t-test was used to determine the statistical significance between control and test groups.P<0.05 was regarded as significant difference.Research Results;Compared with the pathological results of tumor tissue,the sensitivity of detection of circulating tumor DNA in plasma was 80.49%(33/41).We found CEA in 15 patients with peripheral blood,the sensitivity of which is 36.59%(15/41).The sensitivity of detection of ctDNA was significantly higher than that of CEA.Clinical data analysis:In Ⅰ,Ⅱ period lung cancer patients,no significant statistical differences between the results of ctDNA detection in the plasma and the general clinical data were found.These general clinical data cover pathological type,pathological stage,tumor size,age,gender,smoking history.Research Conclusion:Based on the preliminary result,we found that the detection of circulating tumor DNA in plasma is highly sensitive to the diagnosis of the early lung cancer compared to CEA,and no significant statistical differences between the results of ctDNA detection in the plasma and the general clinical data were found.These general clinical data cover pathological type,pathological stage,tumor size,age,gender,smoking history.Tt has the potential value of diagnosis of early lung cancer.But at the same time,we should stick to the gold standard of tissue biopsy as the first means of diagnosis of NSCLC.