Corelationship of Lymphocyte Subsets and Prognosis in Juvenile Myelomonocytic Leukemia

Objective: Juvenile Myelomonocytic Leukemia (JMML) is a rare hematopoietic stem cell malignant clonal disease in children and has the characteristics of MDS/MPN. Due to the poor response of JMML to chemotherapy, hematopoietic stem cell transplantation (HSCT) is currently the only cure method for JMML. Currently, there are some reports on the distribution of lymphocyte subsets in MDS. A significant lymphocytopenia was observed in MDS patients compared with similarly aged healthy people. Another study form Polish found patients with MDS have more CD3+T cells than healthy donors. But there are few related reports in JMML. The objective of this study is to analyze relationship between the distribution of lymphocyte subsets and prognosis in JMML patients, and explore new risk stratification indicatorsfor JMML personalized therapy.

Method: This study retrospectively collected JMML patients clinical data from Institute of Hematology & Blood Diseases Hospital of CAMS during Jan 2008 and Nov 2022. All completed complete blood count and peripheral blood classification, fetal hemoglobin (HbF), granulocyte colony-stimulating factor (GM-CSF) high sensitivity, bone marrow morphology, immune typing, molecular biology, cytogenetics and other tests. We analyzed the relationship between distribution of lymphocyte and prognosis in these patients.

Result: 96 newly diagnosed JMML patients were admitted to this study. The median age at diagnosis was 25 (2-82) months, and male to female was 3.8:1. 66 cases underwent lymphocyte subsets by flow cytometry. Median percentage of lymphocytes is 34.3%(1.8%-90.4%, normal range: 20%-40%), median percentage of CD3+T cells is 54.85%(10.3%-91%, normal range: 57%-88%), median percentage of CD3+CD4+ T cells is 30.95%(3.54%-53%, normal range: 27%-58%), median percentage of CD3+CD8+ T cells is 18.4%(2%-49.1%, normal range: 16%-45%), median percentage of NK cells is 13.95%(2.3%-50.3%, normal range: 3%-32%), and median percentage of B cells is 23.25%(4%-69.6%, normal range: 4%-18%). These cases were followed-up to Jan 2023, with a median follow-up time of 12 months (1-104 months). The overall survival (OS) rate was 52.67%, with a median OS time of 12 months (0-103 months). There were significant differences in the percentage of CD3+T cells (30.89% ± 9.46% vs 59.05% ± 10%, P<0.01) and CD3+CD4+T cells (14.87% ± 5.82% vs 35% ± 5.41%, P<0.01) between children with single NRAS mutation and compound mutations (≥2 classical five Ras pathway mutation ). In PTPN11 mutation patients, there is a significant positive correlation between OS and the percentage of lymphocytes (P=0.018).

Conclusion: Our study shows differences in percentage of CD3+ T cells and CD3+CD4+ T cells between patients with NRAS mutation and compound mutations. Patients with PTPN11 mutation and higher percentage of lymphocytes will have better prognosis.