Inclusion Criteria:

• Documented informed consent of the participant and/or legally authorized representative

  • Assent, when appropriate, will be obtained per institutional guidelines

• ≥ 60 years. Note: Patients ≥ 18 years and < 60 years with HCT-comorbidity index (CI) ≥ 2 are also included

• Karnofsky performance status ≥ 70

• Eligible patients will have a histopathological confirmed diagnosis of hematologic malignancy in one of the following categories :

  • Acute myelogenous leukemia:

    • Patients with de novo or secondary disease in unfavorable risk group including poor risk cytogenetics according to National Comprehensive Cancer Network (NCCN) guidelines for AML i.e., monosomal karyotype, -5,5q-,-7,7q-,11q23-non t(9;11), inv (3), t(3;3), t(6;9), t(9;22) and complex karyotypes (≥ 3 unrelated abnormalities), or all patient in intermediate risk groups accept patients with FLT3-NPM1+ disease, OR
    • Patients with a complete morphological remission (CR) with minimal residual disease (MRD)-positive status by flow cytometry (≥ 0.1% by flow cytometry) or cytogenetic after at least 2 prior induction therapies, OR
    • Patients with chemosensitive active disease defined as at least 50% reduction in their blast count after last treatment

  • Myelodysplastic syndrome in high-intermediate (int-2) and high-risk categories per Revised International Prognostic Scoring System- (IPSS-R)

  • Acute lymphocytic leukemia

    • Patients with de novo or secondary disease according to NCCN guidelines for ALL hypoploidy (< 44 chromosomes); t(v;11q23): MLL rearranged; t(9;22) (q34;q11.2); complex cytogenetics (5 or more chromosomal abnormalities); high white blood cell (WBC) at diagnosis (≥ 30,000 for B lineage or ≥ 50,000 for T lineage); iAMP21loss of 13q, and abnormal 17p, OR
    • Patients with a complete response (CR) with MRD-positive status by flow cytometry (≥ 0.1% by flow cytometry) or cytogenetics after at least 2 prior induction therapies, OR
    • Patients with chemosensitive active disease defined as at least 50% reduction in their blast count after last treatment

• A pretreatment measured creatinine clearance (absolute value) of ≥ 60 ml/minute (To be performed within 30 days prior to day 1 of protocol therapy unless otherwise stated)

• Patients must have a serum bilirubin ≤ 2.0 mg/dl (To be performed within 30 days prior to day 1 of protocol therapy unless otherwise stated)

• Patients must have a serum glutamic oxaloacetic transaminase (SGOT) ≤ 2.5 times the institutional upper limits of normal (To be performed within 30 days prior to day 1 of protocol therapy unless otherwise stated)

• Patients must have a serum glutamic pyruvic transaminase (SGPT) ≤ 2.5 times the institutional upper limits of normal (To be performed within 30 days prior to day 1 of protocol therapy unless otherwise stated)

• Ejection fraction measured by echocardiogram or multigated acquisition scan (MUGA) ≥ 50% (To be performed within 30 days prior to day 1 of protocol therapy unless otherwise stated)

• Diffusion capacity of the lung for carbon monoxide (DLCO) > 50% predicted (To be performed within 30 days prior to day 1 of protocol therapy unless otherwise stated)

• Forced expiratory volume in 1 second (FEV1) > 50% predicted (To be performed within 30 days prior to day 1 of protocol therapy unless otherwise stated)

• Agreement by females and males of childbearing potential to use an effective method of birth control or abstain from heterosexual activity for the course of the study through at least 6 months after the last dose of protocol therapy

  • Childbearing potential defined as not being surgically sterilized (men and women) or have not been free from menses for > 1 year (women only)

• DONOR SPECIFIC CRITERIA: All candidates for this study must have an human leukocyte antigen (HLA) (A, B, C, and DR) identical sibling who is willing to donate mobilized peripheral blood stem cells (preferred) or bone marrow, or have a 10/10 (A, B, C, DR and DQ) allele matched unrelated donor. DQ or DP mismatch is allowed per discretion of the principal investigator. City of Hope (COH) standards of practice (SOP) (B.001.11) will be used for allogeneic donor evaluation, selection, and consent. Donor screening will be in compliance with all requirements of Food and Drug Administration (FDA) regulation 21 CFR Part 1271 including donor screening for COVID-19 exposure or infection

Exclusion Criteria:

• Patients who had a prior allogeneic transplant
• All patients with prior radiation treatment to the lung, liver, and kidney
• Patients who have received prior radiopharmaceutical therapy
• Inclusion of other patients with previous radiation exposure will be determined based on the radiation oncologist medical doctor (MD) principal investigator (PI) evaluation and judgement
• For patients with leukemia or MDS: Patients may not have received more than 3 prior regimens, where the regimen intent was to induce remission
• Receiving any other investigational agents or concurrent biological, intensive chemotherapy or radiation therapy for the previous 2 weeks from conditioning
• Patients should have discontinued all previous intensive therapy, chemotherapy, or radiotherapy for 2 weeks prior to commencing therapy on this study. Note: Low dose chemotherapy or maintenance chemotherapy given within 7 days of planned study enrollment is permitted. These include hydroxyurea, 6-meraptopurine, oral methotrexate, vincristine, oral etoposide, and tyrosine kinase inhibitors (TKIs). FLT-3 inhibitors can also be given up to 3 days before conditioning regimen
• History of allergic reactions attributed to compounds of similar chemical or biologic composition to study agent
• Patients with other active malignancies are ineligible for this study, other than non-melanoma skin cancers
• Patients should not have any uncontrolled illness including ongoing or active bacterial, viral or fungal infection
• The recipient has a medical problem or neurologic/psychiatric dysfunction which would impair his/her ability to be compliant with the medical regimen and to tolerate transplantation or would prolong hematologic recovery which in the opinion of the investigator (treating physician) would place the recipient at unacceptable risk
• Females only: Pregnant or breastfeeding
• Any other condition that would, in the Investigator's judgment, contraindicate the patient's participation in the clinical study due to safety concerns with clinical study procedures
• Prospective participants who, in the opinion of the investigator, may not be able to comply with all study procedures (including compliance issues related to feasibility/logistics)