Multiple conditioning regimens have been used for the HSCT, some of which include radiotherapy. Total body irradiation (TBI) has demonstrated to be superior to chemotherapy alone in the phase III FORUM trial. However, concerns for long-term toxicity have made TBI less used. Total marrow and lymphoid irradiation (TMLI) has emerged as a new alternative that can potentially keep the benefits of radiation but reducing toxicity to healthy tissues.

The primary objective of this trial is to evaluate the feasibility and safety of TMLI as part of conditioning schemes with or without etoposide for HSCT in patients between age 16 and 45 years with ALL in first line or relapsed disease. As secondary endpoint the efficacy will be assessed by minimal residual disease at 60 days post-transplant, as well as other outcome measures such as non-relapse mortality (NRM), relapse free survival (RFS) and overall survival (OS).

TMLI will be administered as part of the conventional reduced intensity conditioning scheme of our institution:

Fludarabine 25 mg/m2 + cyclophosphamide 350 mg/m2 on days -6 to -3, for patients with positive measurable residual disease TMLI will be added in doses of 12 Gy on days -3 to -1 divided into 6 fractions of 2 Gy every 12 hours for 3 days, which will be administered through a computed tomography tomotherapy system.

Infusion of peripheral blood hematopoietic stem cells will be performed on day 0 and after this, prophylaxis for GVHD with post-transplant cyclophosphamide 50 mg/kg will be administered on days +3 and +4, followed by tacrolimus or cyclosporine A plus mycophenolate mofetil regardless of HLA matching.

The procedure for the donation of hematopoietic cells will be done through a peripheral blood apheresis with previous stimulation with filgrastim at 10 mcg/kg for 4 days according to the standardized procedures of our institution.

The leukocyte and platelet count will be monitored by serial complete blood count, and a bone marrow aspiration (BMA) and minimal residual disease (MRD) will be performed on day 60 after transplantation.

Inclusion Criteria:

• Diagnosis of ALL confirmed by flow cytometry.
• Patients between age 16 and 45 years with ALL in first remission, refractory, or relapsing
• Patients who have an identical or haploidentical allogeneic donor by high resolution HLA

Exclusion Criteria:

• Patients who do not meet the age previously mentioned.
• Patient with comorbidities that rule them out for HSCT, with a Hematopoietic cell transplantation-specific comorbidity index (HCT-CI) greater than 2.
• Poor performance status or Karnofsky less than 70%
• Transthoracic echocardiogram with alteration in myocardial function with left ventricular ejection fraction (LVEF) less than 50%
• Patients who previously and for another reason have already received radiotherapy or who refuse to receive it