Chronic myelomonocytic leukemia (CMML) is a clonal hematopoietic malignancy with poor prognosis. Allogeneic hematopoietic stem cell transplantation (HSCT) remains the only potentially curative treatment. Immune reconstitution (IR) is critical for improving HSCT efficacy and quality of life among survivors, yet its dynamic impact on survival and complications like chronic graft-versus-host disease (cGVHD) in CMML is poorly defined. This study aimed to investigate the dynamics of IR following HSCT in patients with CMML and evaluate its impact on post-transplant clinical outcomes.

Chronic myelomonocytic leukemia (CMML) is a myeloid malignancy exhibiting clinical and morphological features of both myelodysplastic syndromes (MDS) and myeloproliferative neoplasms (MPNs). The optimal treatment regimen remains unclear, and allogeneic hematopoietic stem cell transplantation (allo-HSCT) is currently the only known potentially curative treatment option. During allo-HSCT, the recipient's immune system undergoes reconstitution from donor-derived cells. Timely engraftment and functional recovery of the donor immune system are critical for patient recovery and long-term survival post-transplantation. While HSCT can achieve durable remission, it is associated with significant life-threatening complications, primarily mediated by rapidly reconstituted immune components. However, the cellular dynamics underlying the re-establishment of immune homeostasis between donor and recipient compartments post-HSCT remain poorly characterized. This study aims to delineate the kinetics of immune reconstitution (IR) in CMML patients following allo-HSCT, dynamically analyze its impact on clinical outcomes and prognosis, and ultimately develop and optimize immunotherapeutic strategies to enhance overall survival and improve quality of life.

Inclusion Criteria:

1. Patients with confirmed diagnosis of CMML following HSCT
2. Patients treated at Peking University People's Hospital since January 1, 2005

Exclusion Criteria:

1. Any condition that may render follow-up data unreliable, including but not limited to severe psychiatric disorders
2. Patients deemed ineligible for the study by investigators

Patients with confirmed chronic myelomonocytic leukemia (CMML)

Prerequisite criteria:

1. persistent of monocytosis in PB (absolute ≥0.5 × 109/L or relative ≥10%)
2. blast cell <20% in PB and bone marrow, excluding chronic myeloid leukemia or other MPN.

Supporting criteria :

1. dysplasia involving 1 or more myeloid lineages
2. the presence of acquired clonal cytogenetic or molecular abnormalities
3. abnormal partitioning of PB monocyte subsets (classical monocytes >94%). The requirements for CMML diagnosis include prerequisite criteria that must be met in all patients.

Then, if the monocyte count is ≥1 × 109/L, one or more supporting criteria must be met, and if the monocyte count is ≥0.5 and <1 × 109/L, the first two supporting criteria must be met.