Long-term follow-up in childhood ALL patients, classified according to MRD measurements. (A) Disease-free survival of 129 ALL patients, classified according to 3 MRD-based risk groups in the International BFM study.1 Patients were classified as MRD-low-risk if no MRD was detected at day 33 (TP1) and at day 78 (TP2); patients with MRD ≥10−3 at TP2 were classified as MRD-high-risk; all other patients had MRD <10−3 at TP2 and were classified as MRD-intermediate-risk. (B) Disease-free survival of 54 infant ALL cases, treated according to the INTERFANT-99 treatment protocol.67 Patients were considered MRD-high-risk if the MRD level at TP3 was ≥10−4; patients were considered MRD-low-risk if MRD levels were <10−4 at both time points; all remaining patients were considered MRD-medium-risk. Only 3 of 24 MRD-low-risk patients relapsed, whereas all 14 MRD-high-risk patients relapsed. (C) Event-free survival of 3184 BCP-ALL patients of the AEIOP-BFM 2000 study (with kind permission by Dr V. Conter, Monza, Italy).63 Patients were classified as MRD-standard-risk (SR) if no MRD was detected at day 33 (TP1) and at day 78 (TP2) and as MRD-intermediate-risk (IR) when MRD was positive at 1 or both TPs but <10−3 at TP2. Patients with MRD ≥10−3 at TP2 were classified as MRD-high-risk (HR). (D) Event-free survival of 464 T-ALL patients of the AEIOP-BFM-ALL 2000 study (with kind permission by M. Schrappe, Kiel, Germany).64 The MRD-based classification is the same as for C.
