The Efficacy and Safety of Stereotactic Radiotherapy Bridging Allogeneic Hematopoietic Stem Cell Transplantation for the Treatment of Hematological Malignance Patients With Extramedullary Infiltrating

Inclusion Criteria: Subjects who meet all of the following criteria are eligible for enrollment in this study: * Age between 18 and 60 years. * A confirmed diagnosis of a hematologic malignancy, including but not limited to Acute Myeloid Leukemia (AML), Acute Lymphoblastic Leukemia (ALL), Chronic Myeloid Leukemia (CML), Myelodysplastic Syndromes (MDS), Non-Hodgkin Lymphoma (NHL), Hodgkin Lymphoma (HL), and Multiple Myeloma (MM). * Diagnosis of extramedullary disease/lesions confirmed by one of the following: pathological biopsy, cytology, or at least one imaging modality (including PET-CT, contrast-enhanced CT, or contrast-enhanced MRI). * Presence of a suitable donor and scheduled to undergo allogeneic hematopoietic stem cell transplantation (allo-HSCT). * Karnofsky Performance Status (KPS) score \> 60% or Eastern Cooperative Oncology Group Performance Status (ECOG PS) score of 0 to 2. * Has not participated in any other clinical trial involving cell-based or immunotherapies for the treatment of the primary disease. * The subject voluntarily agrees to participate in the study, demonstrates good compliance, and is willing to cooperate with follow-up procedures. * A signed informed consent form must be obtained prior to the initiation of any study-related procedures. For subjects aged 18 years or older, consent is to be provided by the subject or their immediate family member. If, in the physician's judgment, obtaining consent directly from the subject is not in the patient'…