Analysis of minimal residual disease
Real-time quantitative polymerase chain reaction studies for MRD analysis were performed with immunoglobulin heavy chain (IGH) and T cell receptor (TCR) gene rearrangements as targets and interpreted according to the guidelines developed within the European Study Group for MRD detection in ALL . Ideally, two targets were used per patient, one with a quantitative range of 1 x 10-4 (0.01 %) and the second with a quantitative range of at least 5 x 10-4(0.05 %). A sample was evaluated as MRD negative, if no positive signal was detected in any of three patient deoxyribonucleic acid replicate samples (500 ng genomic DNA per sample) for a specific target with a quantitative range of 0.01 %. In two cases, MRD was determined by multiparametric flow cytometry according to EURO-Flow MRD guidelines since the IGH- or TCR- MRD marker could not be established. In patients with failure of remission induction the MRD response was measured by determination of MRD before and after the first and second CoALL-HR1 block as well as prior and subsequent to the application of AEP.