Clinical value of pre-transplant minimal residual disease in childhood lymphoblastic leukaemia: the results of the French minimal residual disease-guided protocol.

Minimal residual disease (MRD) is a major predictive factor of the cure rate of acute lymphoblastic leukaemia (ALL). Haematopoietic cell transplantation is a treatment option for patients at high risk of relapse. Between 2005 and 2008, we conducted a prospective study evaluating the feasibility and efficacy of the reduction of immunosuppressive medication shortly after a non-ex vivo T depleted myeloablative transplantation. Immunoglobulin (Ig)H/T-cell receptor MRD 30 d before transplant could be obtained in 122 of the 133 cases of high-risk paediatric ALL enrolled. There were no significant demographic differences except remission status (first or second complete remission) between the 95 children with MRD <10(-3) and the 27 with MRD ≥10(-3) . Multivariate analysis identified sex match and MRD as being significantly associated with 5-year survival. MRD ≥10(-3) compromised the 5-year cumulative incidence of relapse (43·6 vs. 16·7%). Complete remission status and stem cell source did not modify the relationship between MRD and prognosis. Thus, pre-transplant MRD is still a major predictor of outcome for ALL. The MRD-guided strategy resulted in survival for 72·3% of patients with MRD<10(-3) and 40·4% of those with MRD ≥10(-3).