EUTOS Molecular Monitoring Work plan

Complete molecular response

Front line treatment of chronic phase CML with second generation TKIs has resulted in many patients achieving PCR negativity, i.e. undetectable BCR-ABL transcripts by real time quantitative reverse transcriptase polymerase chain reaction (RQ-PCR). However the degree to which disease can be excluded is often highly variable from sample to sample and from centre to centre. Different definitions of ‘complete molecular response’ (CMR) have been proposed but even in laboratories using the same basic definition (e.g. 4.5 log reduction) there is considerable variability in the precise way by which laboratories interpret individual samples. Furthermore, no systematic evaluation of laboratory performance with regard to sensitivity has been undertaken.
Standardisation of CMR is particularly challenging and will be piloted initially with the 15 laboratories being considered as candidates for monitoring centres in the ENEST1st trial. Following agreement of a consensus definition of CMR, labs will be evaluated for their ability to achieve the defined level of sensitivity using quality control samples prepared centrally in Mannheim and Salisbury. The results of this pilot will be used to inform how best to proceed with the remaining reference labs. Where the performance of individual laboratories is found to be suboptimal, appropriate investigations and training will be implemented in order to improve performance.

Rare variant BCR-ABL transcripts

Approximately 2-3% of CML patients have variant BCR-ABL fusions that cannot be monitored by RQ-PCR using standard methodologies. For the majority of these cases no molecular monitoring option is available. Most rare variants are accounted for by seven variant fusions (e1a2, e1a3, b2a3, b3a3, e6a2, e8a2, e19a2) and we will establish and validate robust RQ-PCR methods for each of these abnormalities. Different models for service provision will be explored but given the rarity of these fusions, establishment of just one or two laboratories in Europe to act as generally accessible rare variant reference laboratories may be preferable.

Conversion factors and molecular response

Laboratory-specific conversion factors are only valid for particular instruments and particular standard operating procedures; any change in laboratory protocols or upgrade of equipment will necessitate recalculation of the conversion factor. Furthermore, even without significant changes, it is unclear to what extent conversion factors are stable over time. We will continue therefore to provide the means to derive new conversion factors and will perform an annual validation process for established reference laboratories.

Resistance-associated mutations

A small number of reference laboratories were unable to participate in the initial performance evaluation round and, in addition, the results of the initial round may indicate the need for reassessment of some centres. We will therefore conduct an additional mutation detection performance evaluation and instigate remedial action for any suboptimally performing centres.

Created by: D.Goekbuget , generated 2007/12/19 , last changed: 2011/06/14