Forecasting Relapse Outcomes With AlloHeme-based Risk Detection in Post-Allo-HCT AML/MDS Patients (FORWARD)

Inclusion Criteria: 1. Adults aged 18 years or above. 2. The participant must have one of the following diseases: AML or MDS (including CMML) and be eligible for allogeneic hematopoietic stem cell transplant. For participants with active disease (\> 5% blasts) before HCT, the treating physician must have the intent to perform a bone marrow examination at day 30 post-HCT as SOC patient management to confirm complete remission (\<5% blasts). 3. Participant must receive an allo-HCT from an HLA-matched related or unrelated donor, an HLA-mismatched donor, or a haploidentical donor. 4. Participant can be enrolled before, at, or up to 1-month post-allo-HCT as long as the participant is in complete remission (CR) at Day 30 and that a recipient pre-transplant or donor sample is available for baseline genotyping (reference). If the reference sample is unavailable or fails testing, the buccal swab collected at Day 30 may be used as the reference sample. 5. Myeloablative or reduced intensity/non-myeloablative conditioning except T-cell depleting therapies (Ex-vivo T cell depletion, CD34 selected graft, use of anti-thymocyte globulin or alemtuzumab). 6. Any graft versus host disease (GVHD) prophylaxis regimen. 7. Willing and able to provide written informed consent. 8. Willing and able to comply with study visits and procedures, including scheduled sample collections and clinical assessments Exclusion Criteria: 1. History of prior allo-HCT or any prior solid organ transplant. 2. Syngeneic donor (identical twin). 3. T cell depleted transplant (Ex-vivo T cell depletion, CD34 selected graft, use of antithymocyte globulin or alemtuzumab in the conditioning regimen) 4. Cord blood graft. 5. Pregnancy 6. Any condition that, in the investigator's opinion, would interfere with the participant's ability to comply with study procedures or jeopardize their safety. 7. Concurrent participation in an interventional or maintenance clinical trial for post allo-HCT relapse prevention; co-enrollment with other trials, such as those intended for GVHD / infection prevention or improving supportive care, is allowed.