Detection of sub-microscopic levels of disease (minimal residual disease; MRD) in childhood acute lymphoblastic leukaemia (ALL) during treatment is an important prognostic factor. Currently, stratification of therapy for the new frontline trial in childhood ALL (UKALL 2011) is provided by MRD analysis using real time quantitative PCR (RQ-PCR) to identify and quantitate the patient specific rearrangements of the immunoglobulin (Ig) and T-cell receptor (TCR) genes. The current methodology is expensive, time-consuming and complex to perform. Although MRD has proven to be a powerful and essential tool in stratification of ALL patients, 8% of individuals in the current UKALL 2011 trial do not have an informative MRD result. Recently, Next Generation Sequencing (NGS) has led to the opportunity to improve the sensitivity and specificity of Ig/TCR based MRD analysis.
Having established NGS for identifying clonal targets in ALL, we are currently assessing the ability of the method and pipeline to quantify disease levels in end of induction and relapse samples, previously analysed by RQ-PCR, to determine the concordance between the methodologies. Indeed, logarithmic dilution series of patient DNA in a normal background revealed that stratification based on a clinical threshold of 1 in 1,000,000 is possible using this methodology. Further investigation into the clinical utility of NGS for MRD analysis will focus on analysing earlier time points in treatment and studying the potential use of blood rather than bone marrow. Altogether, this will further improve the predictive value and specificity of MRD testing.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.