To assess the engraftment of hematopoietic stem cells following reduced-intensity conditioning in children presenting with solid tumors or hematological malignancy by evaluating post-transplantation chimerism and hematological reconstitution.

To study acute and/or chronic graft-versus-host reaction (incidence and severity) and immune reconstitution, post-transplantation To study the effectiveness of the protocol on tumor response.

To study overall survival.

Primary criterion

• Hematological reconstitution and chimerism post-transplantation

Secondary criteria

• Adverse effects, graft-related mortality at D90 and at 12 months, incidence and severity of acute and/or chronic GVH reactions
• Analysis of variations in post-transplantation immunological function profiles
• Median duration of response in therapy-responsive patients and median duration of stability in stabilized patients

Inclusion Criteria:

• Patients aged less than 20 years old

• Lansky score > 60%

• Life expectancy greater than 2 months

• Diagnoses:

  3- Solid tumor or hematological malignancy remaining unresponsive to the reference strategies according to French best practices in pediatrics.

  4- Malignancies for which allografting is the recognized indication but is contraindicated with myeloablative conditioning.

• Usual criteria for allogeneic grafting (pre-graft profile)

• Having a HLA-identical sibling donor for HLA-A, HLA-B and HLA-DR antigens or a HLA mismatch on only one antigen, or having a 10/10 pheno-identical donor, or compatible cord blood.

• Signed informed consent

Exclusion Criteria:

• Patient presenting rapidly-progressive malignancy
• In cases where the potential donor is related, sibling presenting contraindication against hematopoietic stem cell donation
• Unable to sufficiently understand the treatment and its consequences, even after explanation