Haema 2012; 3(1): 57-64
by Tassoula Touloumenidou, Apostolia Papalexandri, Kostas Stamatopoulos
Hematology Department and HCT Unit, G. Papanicolaou Hospital, Thessaloniki, Greece
Abstract
The advent of therapies with a curative potential for patients with hematological malig- nancies created the need for better assessment of response. Hence, sensitive and accurate detection of minimal residual disease (MRD) is considered as a pre-requisite for therapeutic success. MRD assessment in chronic myeloid leukemia (CML) is based on the detection of the chimeric BCR-ABL mRNA transcripts which serve as a “molecular signature” which can be used for the discrimination of residual malignant cells from normal hematopoietic cells. Modern PCR protocols for the detection of BCR- ABL transcripts fulfil some important criteria: in particular, (i) they provide specificity for malignancy and, (ii) they are characterized by satisfactory sensitivity. However, limitations persist: thus, standardization is suboptimal or not fully implemented, while the precise quantification of MRD levels is still an open issue. Today, the molecular monitoring of BCR-ABL transcripts in CML is performed by real-time quantitative PCR (RQ-PCR) protocols. Thanks to international multi-institutional initiatives, recommendations for harmonizing the differing RQ-PCR methodologies with the objective of maximizing reliability of analysis for clinical decision making now exist: all aspects of the analysis are covered, from source and number of cells to validation of PCR amplification efficiencies, ensuring the comparability of the results from different trials and/or medical centers. A cornerstone of the follow-up of CML patients treated with tyrosine kinase inhibitors relates to the accurate detection of somatic mutations with- in the BCR-ABL kinase domain, which represent the major mechanism of acquired resistance. Several approaches are available for mutation detection; however, presently the most widely used method is direct sequencing. More sensitive approaches may be beneficial, but are yet to prove their clinical utility.