To analyze the clinical and laboratory characteristics of acute myeloid leukemia (AML) patients with NPM1 mutation, and to explore the prognostic factors.

A total of 77 AML patients with NPM1 gene mutation admitted to Hebei Yanda Ludaopei Hospital from May 1st 2012 to December 31st 2021 were enrolled in the study, including 34 male and 43 female patients. The median age was 40 (3, 68) years old. Patients were selected and divided into 4 groups according to the morphological FAB classification. There were 29 cases (37.7%) of M1 type, 13 cases (16.9%) of M2 type, 23 cases (29.9%) of M4 type, and 12 cases (15.5%) of M5 type. The clinical characteristics, bone marrow/peripheral blood cell morphology, immunophenotype, cytogenetics, molecular biology and overall survival of different groups were retrospectively analyzed, and the risk factors affecting the prognosis of AML were also explored. Cox multivariate regression was used to analyze the clinical influencing factors of survival and prognosis.

The white blood cell counts were highest in M4 and M5 patients and lowest in M2 patients, while no significant difference in the red blood cell, hemoglobin, and platelet counts(P>0.05). Morphologically, there were significant differences in the percentage of blasts and blasts with cup-like nuclei on bone marrow (BM) and peripheral blood (PB). The proportion of blasts in BM and PB was the highest in M1 and the lowest in M2 (P<0.001). The positive rate of blasts with cup-like nuclei was the highest in M1 and the lowest in M5 of BM (P<0.001), while the highest in M2 and the lowest in M5 of PB (P=0.006). The scores of myeloperoxidase and chloroacetate esterase were all the highest in M1 and the lowest in M5 (P<0.001, 0.001, respectively). In terms of molecular biology, the occurence rate of blasts combined with DNMT3A mutation was the highest in M4 and the lowest in M2 (P=0.044), while those combined with FLT3-ITD mutation was the highest in M4 and the lowest in M5 (P=0.002). In immunophenotype, there were significant differences in the expression positivities of seven antigens including HLA-DR, CD56, CD11c, CD15, CD14, CD96 and cMPO (P<0.05). Multivariate COX regression analysis showed that no recurrence after treatment (P<0.001), complete remission after treatment (P=0.015) and transplantation (P<0.001) were correlated with overall survival (OS). No recurrence after treatment (P=0.033), transplantation (P=0.027), no mutation of FLT3-ITD (P=0.040), and hemoglobin concentration (P=0.023) were associated with relapse-free survival (RFS). Survival analysis by Kaplan-Meier curve showed that there was no significant difference in survival time between the M1, M2, M4 and M5 groups in OS and RFS.

There were significant differences in the white blood count, the percentage of blasts and blasts with cup-like nuclear morphology, cytochemical staining (MPO integration, CE integration and percentage of NAS-DCE), gene mutation (DNMT3A and FLT3-ITD) and immunophenotypes (HLA-DR, CD56, CD11c, CD15, CD14, CD96 and cMPO) between the four groups. The multivariate analysis revealed that no recurrence after treatment and transplantation were independent prognostic factors in NPM1^mut AML patients. On the other hand, FLT3-ITD mutation and hemoglobin concentration were associated with RFS and complete remission after treatment was associated with OS in the entire NPM1^mut cohort.

Acute myeloid leukemia; Cup-like nuclear morphology; NPM1; FLT3-ITD; Immunophenotype