Thiotepa-Containing Conditioning Regimen for Allogeneic HSCT in Chronic Myelomonocytic Leukemia

Inclusion Criteria: * Age ≥ 18 years, any sex/gender. * Confirmed diagnosis of chronic myelomonocytic leukemia (CMML) according to the 2022 WHO classification. * Intermediate-2 or high-risk CMML based on CPSS or CPSS-mol score, and planned to receive allo-HSCT. * Has a suitable hematopoietic stem cell donor: * For haploidentical donor: at least 5/10 HLA match at HLA-A, -B, -C, -DQB1, and -DRB1. * For unrelated donor: at least 9/10 HLA match at the same five loci. * For matched sibling donor: 10/10 HLA match at the same five loci. * Hematopoietic cell transplantation comorbidity index (HCT-CI) ≤ 2, with generally good health and no significant organ abnormalities or major comorbidities. * Adequate organ function as defined below: * Left ventricular ejection fraction (LVEF) ≥ 50%, and no uncontrolled tachycardia or bradycardia-tachycardia syndrome. * Total bilirubin ≤ 1.5 × upper limit of normal (ULN); ALT ≤ 2 × ULN; AST ≤ 2 × ULN. * Serum creatinine ≤ 1.5 × ULN. * Baseline oxygen saturation \> 92%. * Pulmonary function: DLCO (corrected for hemoglobin) ≥ 40%, FEV1 ≥ 50%. * Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2. * Agrees not to participate in any other interventional study during the treatment period. * Willing and able to provide written informed consent, understand the nature, purpose, and procedures of the study, and voluntarily comply with study requirements. Exclusion Criteria: * Previous allogeneic HSCT for CMML that later relapsed. * Unwilling or unable to receive the study treatment regimen. * Active hepatitis B or C, or chronic active hepatitis; known human immunodeficiency virus (HIV) infection. * Active uncontrolled infection, including: hemodynamic instability related to infection, new or worsening signs/symptoms of infection, new infection lesions on imaging, or persistent fever without explanation despite no symptoms/signs. * History of stroke or intracranial hemorrhage within 6 months before enrollment. * Known pregnancy (positive urine pregnancy test), or currently breastfeeding. * Diagnosis of another malignancy within the past 2 years, except for localized skin cancer, superficial bladder cancer, carcinoma in situ of the cervix, breast cancer, or localized prostate cancer (Gleason score ≤ 6) that has been treated with curative intent. * Any other condition that, in the investigator's judgment, makes the patient unsuitable for study participation.