Minimal residual disease analysis in children with t(12;21)-positive acute lymphoblastic leukemia: comparison of Ig/TCR rearrangements and the genomic fusion gene.

Quantification of minimal residual disease (MRD) based on clonotypic immunoglobulin/ T-cell receptor (Ig/TCR) gene rearrangements is widely used as an independent prognostic parameter in childhood acute lymphoblastic leukemia (ALL). In this study we compared MRD by quantification of Ig/TCR targets and genomic ETV6-RUNX1 specific sequences. In ten of twelve patients with t(12;21)+ ALL we observed concordance with rapid blast reduction in nine, and high-level persistence in one case. The two remaining patients showed low-level persistence of the genomic breakpoint specific sequence. These patients have remained in complete remission for 38 and 41 months, so far, indicating that a small ETV6-RUNX1-positive clone is not detrimental to the short-term prognosis of affected children.