Minimal residual disease monitoring in childhood B lymphoblastic leukemia with t(12;21)(p13;q22); ETV6–RUNX1: concordant results using quantitation of fusion transcript and flow cytometry

Summary Introduction The translocation t(12;21)(p13;q22) resulting in the fusion gene ETV 6– RUNX 1 , is the most frequent gene fusion in childhood B lymphoblastic leukemia. In the Nordic Society of Paediatric Haematology and Oncology ALL ‐2008 treatment protocol, treatment stratification in B‐lineage ALL is based on results of minimal residual disease ( MRD ) analysis with fluorescence‐activated cell sorting ( FACS ). In this study, we determined whether RT ‐ qPCR of the ETV 6– RUNX 1 fusion transcript can be a reliable alternative for MRD analysis. Methods Seventy‐eight bone marrow samples from 29 children at diagnosis and day 15, 29, and 78 during treatment were analyzed for MRD with FACS and with quantitative reverse transcription polymerase chain reaction ( RT ‐ qPCR ). Fusion transcript MRD was defined as the ETV 6– RUNX 1/ GUSB ratio at the follow‐up time point (day 15/29/78) divided with the ETV 6– RUNX 1/ GUSB ratio at diagnosis (%). Results MRD analysis with FACS and with RT ‐ qPCR of ETV 6– RUNX 1 fusion transcript showed strong correlation. All cases showed concordant results at the treatment stratifying time points day 29 and day 78, when comparing the two methods with a cutoff set to 0.1%. Conclusion RT ‐ qPCR is a valuable addition and could also be an alternative to FACS in cases where FACS is not achievable for MRD analysis.