Proton-Based Total Marrow Irradiation for Allogeneic Transplantation in High-Risk AML/MDS

Summary

This is an open-label, single-center, non-randomized phase I/II pilot study evaluating proton-based Total Marrow Irradiation (TMI) as part of the conditioning regimen prior to allogeneic hematopoietic stem cell transplantation (allo-HSCT) in adult patients with high-risk or relapsed/refractory acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). These patients have an unfavorable prognosis with standard conditioning approaches. Participants will receive a standard conditioning regimen consisting of either myeloablative or reduced-intensity chemotherapy, selected according to age and comorbidities, combined with proton TMI delivered at a total dose of 12 Gy in three fractions. Graft-versus-host disease (GvHD) prophylaxis will be administered according to institutional standards, preferentially using post-transplant cyclophosphamide. Patients will subsequently undergo standard allo-HSCT and will be followed for at least 24 months after transplantation. The primary objective of the study is to assess the safety and tolerability of proton TMI added to standard conditioning, as measured by non-relapse mortality and treatment-related toxicity within the first 100 days after transplantation. Secondary objectives include evaluation of engraftment kinetics, incidence of relapse, overall and relapse-free survival, GvHD outcomes, and quality of life. Study outcomes will be analyzed descriptively and compared with a matched historical cohort.

Eligibility

Inclusion Criteria:

1. Underlying diagnosis of acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS),

   A) Acute Myeloid Leukemia (AML), meeting at least one of the following criteria:

   i. Relapsed disease after a prior complete remission (CR) or

   ii. Disease refractory to at least two cycles of intensive chemotherapy or

   iii. High-risk AML in complete remission (CR), defined by at least one of the following:

   iii a) Adverse molecular or cytogenetic risk according to ELN 2022 classification or

   iii b) Presence of measurable/minimal residual disease (MRD).

   B) Myelodysplastic Syndrome (MDS), meeting at least one of the following criteria:

   i. Relapsed MDS with increased blasts (MDS-IB) or

   ii. MDS-IB2 without reduction of bone marrow blasts below 10% after induction chemotherapy or after at least two cycles of azacitidine or

   iii. IPSS-M score \> 0.5 (high-risk or very high-risk disease).
2. Eligibility confirmed by the institutionalal Transplant Indication Committee according to standard criteria.
3. Age ≥ 18 years and ≤ 65 years
4. Ability to understand and voluntarily sign written informed consent

Exclusion Criteria:

Severe comorbidity, defined as the presence of one or more of the following conditions:

1. Left ventricular ejection fraction (LVEF) \< 40%
2. Creatinine clearance \< 0.5 mL/s
3. Total bilirubin \> 40 µmol/L (unless attributable to Gilbert's syndrome or hemolysis) and alanine aminotransferase (ALT) or aspartate aminotransferase (AST) \> 5 × upper limit of normal (ULN)
4. Pulmonary function impairment defined as forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) \< 50% of predicted value, or diffusing capacity of the lung for carbon monoxide (DLCO) \< 50% of predicted value after correction for anemia
5. Karnofsky Performance Status \< 70%
6. Active viral hepatitis or human immunodeficiency virus (HIV) infection
7. Presence of liver cirrhosis
8. Pregnancy

Conditions6

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