Immunophenotype And Clinical Characteristics Of Acute Myeloid Leukemia With Positive FLT3-ITD

Background Acute myeloid leukemia（AML）is a malignant hematological tumor of bone marrow stem cells,which is highly heterogeneous.In recent years,with high-throughput sequencing technology and in-depth research on the molecular biology of AML patients,more and more gene mutations related to the treatment and prognosis of AML have been discovered.FMS-like tyrosine kinase 3（fms related receptor tyrosine kinase 3,FLT3）is a receptor tyrosine kinase（RTK）activated by a transmembrane ligand,usually expressed by hematopoietic stem/progenitor cells,and It plays a key role in the hematopoietic process of normal people（such as proliferation,differentiation and survival）.The internal tandem duplication（ITD）of FLT3 proximal membrane domain is the most common type of mutation in AML,and it occurs in approximately 30%of AML patients.In addition,related studies have shown that FLT3gene mutations are closely related to the poor prognosis of AML patients.FLT3-ITD mutant AML patients have disordered leukemia cell antigen expression,high peripheral blood white blood cell count,hemoglobin count,bone marrow blast cell ratio,low remission rate of induction chemotherapy,easy to merge NPM1 mutation,high recurrence rate,and short survival time.Objective To investigate the mutation rate and occurrence of FLT3-ITD mutation in acute myeloid leukemia（AML）;to study the clinical characteristics and immunophenotype of acute myeloid leukemia patients with or without FLT3-ITD mutation,and to analyze the mutation The relationship between the survival and prognosis of patients,so as to have a deeper understanding of the FLT3-ITD mutation,and provide precise guidance for the individualized treatment of newly diagnosed AML patients.Methods From December 2016 to December 2018,103 newly diagnosed AML patients（except acute promyelocytic leukemia）admitted to the Department of Hematology of our hospital were selected,and the patients were classified according to whether they were associated with FLT3-ITD mutations.Divided into two groups,including 24 FLT3-ITD⁺AML patients（positive group）and 79 FLT3-ITD-AML patients（negative group）.Use PCR combined with gene sequencing to detect mutant genes such as FLT3-ITD and NPM1;perform Wright and immunohistochemical staining on bone marrow fluid smears;observe the morphology of bone marrow cells and the proportion of original cells under a microscope;flow cytometry analyzer The patient’s immunophenotype was analyzed and the antigen expression rate was calculated respectively;the chromosome karyotype was detected by bone marrow culture method and G-banding technique,and the karyotype was divided into a good prognosis group,a medium prognosis group and a poor prognosis group.The SPSS software was used to calculate the overall response rate（OR）,progression-free survival time（PFS）and overall survival time（OS）of the two groups of patients.All patients were diagnosed by the relevant FAB and WHO standards,and the standard"3+7"regimen was mainly used for chemotherapy,that is,"anthracyclines+cytarabine for injection".Results 1.Clinical parameters of FLT3-ITD⁺AML patients:There were 24 cases of FLT3-ITD mutation in 103 patients with first-onset AML,and the mutation rate was23.30%（24/103）.There was no significant difference between 24 FLT3-ITD+AML patients and 79 FLT3-ITD^-patients in gender,age and platelet count（P>0.05）.The peripheral blood white blood cell count,hemoglobin count,and the proportion of bone marrow blasts in FLT3-ITD⁺AML patients were significantly higher than those in FLT3-ITD-group（P<0.05）.2.Immune phenotype of FLT3-ITD⁺AML patients:In this paper,a total of 16 leukemia cell antigens were tested,and a total of 6 antigens had statistical differences in the expression rate of leukemia cell antigens.There was a statistically significant difference in the expression rates of CD56,CD13,CD34,CD38,CD7,and CD33 antigens between the two groups.The expression levels of CD13 and CD34 antigens in FLT3-ITD⁺AML patients were significantly lower than those in FLT3-ITD-AML patients（P<0.05）,And the CD56,CD33,CD7 and CD38 antigen expression levels were significantly higher than the FLT3-ITD-AML group（P<0.05）.3.Cytogenetic characteristics of FLT3-ITD⁺AML patients:Normal karyotypes accounted for the highest proportion of patients in both groups.FLT3-ITD⁺AML patients accounted for 66.67%（16/24）of normal karyotypes,while The proportion of FLT3-ITD⁺AML patients with poor prognosis was significantly higher than that of FLT3-ITD-AML group（37.5%vs16.46%;χ²=4.853,P=0.028）.4.Molecular morphological classification of FLT3-ITD+AML patients:According to the French,British and American（FAB）and World Health Organization（WHO）classifications,103patients with new-onset AML were M₀1cases,M₁11cases,M₂48cases,M₄24cases,M₅16cases,M₆2cases and M₇1cases.Among 24 FLT3-ITD⁺AML patients,the incidence of M2 subtype was the highest,accounting for 41.7%（10/24）,followed by M5,M1,M4,and M6,while M0 and M7 had the lowest incidence.5.Clinical treatment effect:The CR rate of FLT3-ITD+AML patients after the first course of standard induction chemotherapy was 20.83%,which was significantly lower than 44.30%of FLT3-ITD-AML patients（χ²=4.261,P=0.039）,FLT3-ITD+Median OS time for AML patients was 9.5 months,median PFS was 9 months;median OS time for FLT3-ITD-AML patients was 17 months,median PFS was 16 months,OS for FLT3-ITD+AML patients,PFS was significantly lower than FLT3-ITD-group（χ²=7.241,P=0.007;χ²=6.858,P=0.009）.6.FLT3-ITD⁺AML combined with NPM1mutation:62.50%of FLT3-ITD+AML patients jointly expressed NPM1 mutation,which was significantly higher than FLT3-ITD-AML patients（χ²=15.294,P<0.001）,the difference was statistically significant.OS and PFS of AML patients in FLT3-ITD+/NPM1+group were longer than FLT3-ITD+/NPM1-group（χ²=1.501,P=0.220;χ²=1.413,P=0.235）,but the difference was not statistically significant.Conclusion 1.FLT3-ITD⁺newly diagnosed AML patients have disordered leukemia cell antigen expression,the proportion of peripheral blood leukocytes,hemoglobin,and bone marrow leukemia cells is high,the CR rate of the first course of chemotherapy and the total response rate of treatment are low,PFS and OS are significantly shortened,and the treatment effect is poor.It is suggested that the activating mutation of FLT3-ITD is a poor prognostic indicator of AML patients.2.The incidence of FLT3-ITD⁺AML patients was 23.30%,mainly distributed in M₂and M₅,and the expression in AML patients with normal karyotype was higher than that of abnormal karyotype.3.FLT3-ITD mutation is easy to merge with NPM1 mutation.Compared with FLT3-ITD single mutation,the proportion of bone marrow blast cells in patients with FLT3-ITD⁺/NPM1⁺mutation is significantly higher,the CR rate in the first course of chemotherapy is higher,and the prognosis is better.