EUTOS Molecular Monitoring Objectives  · 

Objectives of Molecular Monitoring

The main objectives will be

• Strengthen the registry and provide quality controlled outcome data
• Distribute internationally standardized RQ PCR analyses for BCR-ABL quantification and for detection of BCR-ABL mutations
• Determinate prognostic significance of sensitive detection of BCR-ABL mutations

International distribution of standardized RQ PCR analyses for BCR-ABL quantification and assessment of resistance in CML and BCR-ABL positive ALL

This objective will allow the use of standardized molecular monitoring of residual disease and the international comparison and harmonization of the assessment of resistance.
Real-time Quantitative PCR (RQ PCR), sequencing, D-HPLC or allele specific PCR methods will be used. Protein based assays will be optimized to analyze the inhibition or reactivation of BCR-ABL by determination of the phosphorylation status of BCR-ABL substrates. The project will be carried out across Europe and beyond. A task force has started to compare results between laboratories by control rounds of samples collected in the course of treatment. Cooperation has already been established within the diagnostic work packages of the European LeukemiaNet. This objective provides an excellent opportunity for laboratories offering monitoring service for large clinical trials throughout Europe, to confirm, refute or evaluate their respective techniques. The project will link data originating from clinical institutions and molecular laboratories across Europe. The tested population will provide a base from which scientific questions can be addressed on a larger scale than is currently possible within individual studies. Such questions are i) determination of the proportion of patients achieving complete cytogenetic or molecular remission over time, ii) the effect of time to remission on survival, iii) the potential prognostic significance of the rate of reduction of BCR-ABL transcript levels on survival, iv) the analysis of mechanisms of acquired resistance including clonal evolution, ABL kinase domain mutations, and BCR-ABL amplification.

Determination of prognostic significance of sensitive detection of BCR-ABL mutations

In 50% to 90% of patients with acquired resistance to imatinib, mutations in the kinase domain (KD) of BCR-ABL have been detected. Although mutations have been identified in more than 20 different amino acids, the eight most common mutations account for greater than 70% of cases. In some patients who relapsed with KD mutations, analysis of archived material stored prior to therapy revealed identical nucleotide exchanges. In most of these cases the proportion of mutant allele was very small, and detection required sensitive techniques, such as polymerase chain reaction with allele specific oligonucleotides (ASOPCR). Overall, these data are consistent with selection of resistant clones in the presence of imatinib. The available data from imatinib-naïve samples are at the moment limited to patients in whom mutations were detected at the time of relapse, and the incidence of mutations prior to therapy in unselected patients has not been established. Furthermore, it is not known whether KD mutant clones that are detectable prior to therapy are regularly selected in the presence of imatinib, and whether they may predict for an adverse outcome on therapy.

Created by: A. Hellenbrecht , generated 2007/12/19 , last changed: 2008/01/08