Allogeneic Stem Cell Transplant for Children and Adolescents With Acute Lymoblastic Leukemia FORUM - Pharmacogenomic Study (add-on Study)

Note this is an add-on study to NCT 01949129, THE ALL SCTped FORUM study. Please refer to the main study for further details.

Busulfan (Bu) is a key compound in conditioning myeloablative regimens for patients undergoing hematopoietic stem cell transplantation (HSCT). Bu has been long used for the treatment of patients with leukemia and some congenital disorders; advantages and disadvantages of such treatment are well described. However, although Bu treatment has been shown to be effective, its use may be limited by related adverse events such as veno-occlusive disease (VOD), interstitial pneumonitis, acute Graft vs Host Disease (GVHD), and seizures. Thus, novel therapies are being investigated as well as the pharmacogenetics of these drugs. One of alternative drugs that may replace Bu due to its lower toxicity profile is Treosulfan (Treo). Fludarabine (Flu) is usually used in combination with Bu or Treo as an alternative to cyclophosphamide (Cy) also due to its lower toxicity. Thus, the Bu/Flu regimen is now being used more often than the previously more common Bu/Cy regimen. However, improvement to the regimen is still needed for reducing adverse drug effects. Pharmacogenomics (PG) offers the opportunity to individualize treatment according to patient genetic variations which influence activity of enzyme metabolizing or acting in the pathway of prescribed chemotherapy drugs.

This add-on research aims to prospectively investigate variations in several candidate genes (e.g GST, DCK and DNA repair pathway genes) related to all types of chemotherapeutic drugs (Bu/Flu/Thio; Treo/Flu/Thio and TBI/VP16) used in this protocol for their potential role as predictive biomarkers of pharmacokinetics (PK) variability and outcome of myeloablative therapy for pediatric patients receiving an allogeneic HSCT in acute lymphoblastic leukemia

For the busulfan arm countries: a cross-validation of busulfan quantification is performed. All Bu Therapeutic Drug Monitoring participating at the main ALL SCTped FORUM study will be assessed for the accuracy (%) and trueness (%) of 8 blinded Bu Quality Control samples. Criteria of acceptance are set according to FDA and ICH guidelines.

Blood samples will be collected prior to initiation of therapy for DNA banking and DNA analysis (for all patients), for DNA analysis (TBI/VP16, Bu/Flu/Thiotepa and Treo/Flu/Thiotepa groups) and PK analysis (only for the Bu group). PK and pharmacogenomic data will then be correlated with the studied outcomes (e.g.Veno-occlusive disease, Graft vs host disease, Treatment Related Mortality, Events Free Survival, Overall Survival).