Prospective use of molecular minimal residual disease for risk stratification in children and adolescents with acute lymphoblastic leukemia : Long-term results of the AIEOP-BFM ALL 2000 trial in Austria.

Since 1979 Austrian children and adolescents with acute lymphoblastic leukemia (ALL) have been treated according to protocols of the Berlin-Frankfurt-Münster (BFM) study group. The Associazione Italiana di Ematologia e Oncologia Pediatrica and BFM (AIEOP-BFM) ALL 2000 study was designed to prospectively study patient stratification into three risk groups using minimal residual disease (MRD) on two time points during the patient's early disease course. The MRD levels were monitored by detection of clone-specific rearrangements of the immunoglobulin and T‑cell receptor genes applying a quantitative polymerase chain reaction-based technique. The 7‑year event-free survival (EFS) and overall survival rates for all 608 Austrian patients treated between June 1999 and December 2009 within the AIEOP-BFM 2000 study were 84 ± 2% and 91 ± 1%, respectively, with a median observation time of 6.58 years. Event-free survival for patients with precursor B‑cell and T‑cell ALL were 84 ± 2% (n = 521) and 84 ± 4% (n = 87; p = 0.460), respectively. The MRD assessment was feasible in 94% of the patients and allowed the definition of precursor B‑cell ALL patients with a low, intermediate or high risk of relapse even on top of clinically relevant subgroups. A similar finding with respect to MRD relevance in T‑ALL patients was not possible due to the small number of patients and events. Since this pivotal international AIEOP-BFM ALL 2000 trial, molecular response to treatment has been continuously used with additional refinements to stratify patients into different risk groups in all successive trials of the AIEOP-BFM ALL study group.