Application Of Circulating Tumor DNA In Diffuse Large B-cell Lymphoma

Background and objective: Circulating tumor DNA(ctDNA)derives from tumor cells through processes of apoptosis and necrosis,shedding into the bloodstream as a specific tumor biomarker.With the rapid development of the next-generation sequencing,the sensitivity of ctDNA detection has been greatly improved.Tumor liquid biopsy based on ctDNA can reveal an average of the overall tumor-specific genetic lesions.Detection of ctDNA has a wide range of applications such as auxiliary diagnosis,therapeutic evaluation,drug resistance surveillance,minimal residual disease monitoring,recurrence prediction and prognosis assessment of malignant tumors.A series of foreign studies have shown that dynamic monitoring of ctDNA based on the next-generation sequencing has a great significance for molecular monitoring of diffuse large B cell lymphoma,which will be conducive to therapeutic efficacy and prognosis assessment,recurrence prediction and so on.However there is no similar study in the Chinese population,and the utility of this technology for patients with DLBCL in China needs clinical studies to verify.This study detected ctDNA in Chinese DLBCL patients before and after two cycles chemotherapy,which aimed to explore the potential value of ctDNA based on tumor specific VDJ rearrangement by NGS in diagnosis,therapeutic outcome prediction and prognosis evaluation of DLBCL.Methods: Forty-seven newly diagnosed and untreated DLBCL patients were collected from our hospital,and their clinical characteristics were recorded.Those who could not receive R-CHOP chemotherapy because of organ disfunction or other reasons were excluded.Ultimately,thirty-eight patients were enrolled and received standard R-CHOP immunochemotherapy.All enrolled patients accepted ctDNA detection by NGS before and after two cycles of immunochemotherapy using 10 ml of peripheral blood samples.Enhanced CT or PET-CT was used to evaluate systemic lymph node size and metabolism at the baseline and post-treatment.The therapeutic effectwas evaluated according to the efficacy standards.All data was analyzed by SPSS 22.0 and P values<0.05 were deemed to have statistically differences.Results:1.A total of thirty-eight DLBCL patients were included in the study,including twenty-one males and seventeen females.The median age was 61.5 years with a range from 31 to 77 years.Twenty-two cases were of primary lymph nodes,the other sixteen cases were of primary outside the lymph nodes.Among them,there were twelve cases of Ann Arbor Ⅰ-Ⅱ stage,twenty-six cases of Ⅲ-Ⅳ stage,thirteen cases with B symptoms,twenty-six cases with IPI score 0 ～ 2,twelve cases with 3 ～ 5,seven cases with bone marrow involvement,six cases of GCB subtype,thirty-two of non-GCB subtype,eight cases with CD5 positive and twenty cases with Bcl-2/MYC double expression.2.Thirty-one patients had positive ctDNA before initial treatment,while seven patients were negative.The positive rate of ctDNA detection was 81.6%,which was significantly higher than that of LDH(P=0.001).According to the ctDNA test results at diagnosis,the patients were divided into ctDNA positive group and negative group.The clinical characteristics of the two groups were compared.The ratio of Bcl-2/ MYC double expression was significantly higher in the ctDNA positive group(P=0.038).There were no significant differences in other clinical characteristics.3.All included patients were evaluated for efficacy after 4 courses of R-CHOP chemotherapy.There were no significant differences in CR rate and OR rate between the two groups.4.There were no significant differences in PFS and OS between the ctDNA positive and negative patients at diagnosis.5.After two courses of chemotherapy,54.8% of patients turned ctDNA negative,while45.2% of patients still had positive ctDNA.The ctDNA still positive group had a later disease stage(P=0.021),B symptoms(P=0.031),increased LDH levels(P=0.012),high-risk IPI score(P<0.0001),and bone marrow involvement(P=0.012).6.Thirty-one DLBCL patients of newly diagnosed ctDNA-positive were evaluated for efficacy after 4 courses of R-CHOP chemotherapy.The CR rate in the ctDNA turning negative group was significantly higher than that in the still positive group(58.8% vs 7.1%,P=0.007),while the OR rate was not significantly different.7.DLBCL patients with ctDNA turning negative after two courses of chemotherapy had a better PFS and OS(P=0.036 and P=0.030)with the estimated one year PFS was 91.7% and one year OS was 100.0%.8.An analysis of other clinical parameters related to prognosis through K-M survival analysis showed that the variables had significant influences in PFS were disease stage(P=0.030)and LDH level(P=0.031);in OS were age(P=0.019),IPI score(P=0.001),extra nodal involvement(P=0.035)and LDH level(P=0.049).Conclusion: The detection of plasma ctDNA in newly diagnosed DLBCL patients had a high positive rate,which was significantly higher than the increase rate of LDH and wouldn’t be affected by factors such as disease stage and sites.Circulating tumor DNA detection could contribute to the diagnosis and residual monitoring of DLBCL.Whether the ctDNA turned negtive after two courses of chemotherapy was conducive to early prediction of therapeutic efficacy and prognosis evaluation.As a new tumor biomarker,ctDNA had the advantages of minimal invasion,free of radiation exposure,dynamic monitoring,etc.It had potential value in the diagnosis,residual monitoring,efficacy evaluation,and prognosis prediction of DLBCL.