Bcr-Abl kinase domain mutation analysis in chronic myeloid leukemia patients treated with tyrosine kinase inihibitors: recommendations from an expert panel on behalf of European LeukemiaNet

Simona Soverini1,*, Andreas Hochhaus2, Franck E Nicolini3, Franz Gruber4, Thoralf Lange5, Giuseppe Saglio6, Fabrizio Pane7, Martin C Müller8, Thomas Ernst2, Gianantonio Rosti1, Kimmo Porkka9, Michele Baccarani1, Nicholas CP Cross10, and Giovanni Martinelli1 Abstract: Mutations in the Bcr-Abl kinase domain (KD) may cause, or contribute to, resistance to tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia (CML) patients. Recommendations aimed to rationalize the use of BCR-ABL mutation testing in CML have been compiled by a panel of experts appointed by the European LeukemiaNet (ELN) and European Treatment and Outcome Study (EUTOS) and are here reported. Based on a critical review of the literature and, whenever necessary, on panelists' experience, key issues were identified and discussed concerning: i) when to perform mutation analysis; ii) how to perform it; iii) how to translate results into clinical practice. In chronic phase patients receiving imatinib first-line, mutation analysis is recommended only in case of failure or suboptimal response according to the ELN criteria. In imatinib-resistant patients receiving an alternative TKI, mutation analysis is recommended in case of hematologic or cytogenetic failure as provisionally defined by the ELN. The recommended methodology is direct sequencing, although it may be preceded by screening with other techniques like denaturing-high performance liquid chromatography. In all the cases outlined above, a positive result is an indication for therapeutic change. Some specific mutations weigh on TKI selection.