PB1939 ACCURACY AND SPEED OF REPORTING MOLECULAR RESPONSE IN PATIENTS ON TYROSINE KINASE INHIBITORS THERAPY WITH GENEXPERT CARTRIDGE‐BASED BCR‐ABL1 QUANTITATION

Abstract

Background:Monitoring of minimal residual disease (MRD) in chronic myeloid leukemia (CML) patients who are on tyrosine kinase inhibitors (TKI) is one of the best standardized molecular methods. Guidelines for treating these patients include the evaluation of molecular response (MR) based on % BCR‐ABL1 on the International Scale (IS) in defined time points. Achieving timely MR is necessary for determining the status of the disease and the use of appropriate therapy.Aims:The aim of this study was to introduce the GeneXpert cartridge‐based BCR‐ABL1 detection into routine molecular monitoring of CML Slovenian patients from north‐eastern region and compare the MR results with those obtained from a standard laboratory method.Methods:BCR‐ABL1 transcript quantification was performed in 40 peripheral blood samples from CML patients at different stages of the disease in two different laboratories. First one used automated GeneXpert BCR‐ABL Ultra Assay (Cepheid, USA) and the second one used standardized laboratory protocol. The results for both analyzes were expressed as % IS and were estimated by MR according to Laboratory recommendations for scoring deep molecular responses following treatment for chronic myeloid leukemia.Results:The analysis of the results showed that there were no statistically significant differences in the results expressed in % IS (p = 0, 272). Samples according to the estimated MR were divided into 3 groups (8 MR3 samples, 3 MR4 samples and 27 ≥ MR4.5 samples). 27/40 samples had a completely identical MR with both methods. Furthermore, 11/40 samples had higher MR obtained with GeneXpert, while 0/40 samples had lower MR compared to SP. In 2/40 cases, GeneXpert gave MR5 for sample with SP MR3 and MR4 for sample with SP MR3. None of the results obtained with GeneXpert had any effect on a different clinical decision on treatment with TKI as obtained under the SP. When the major molecular response (MMR) was analyzed, 78% agreement was achieved.Summary/Conclusion:GeneXpert BCR‐ABL Ultra Assay provides reproducible results and doesn’t show significant differences compared with the standardized laboratory protocol. From clinical aspect, GeneXpert BCR‐ABL Ultra Assay correctly classified the patients in MR and can be considered as a useful and very fast clinical tool for the molecular follow up of patients on tyrosine kinase inhibitors.