Monitoring minimal residual disease and controlling drug resistance in chronicmyeloid leukaemia patients in treatment with imatinib as a guide to clinicalmanagement.

Imatinib mesylate, binding to the inactive conformation of Bcr-Abl tyrosine kinase and suppressing the Ph chromosome positive clone, has revolutionized the treatment of chronic myeloid leukaemia (CML) patients. Given the high rates of clinical and cytogenetic remission achieved, the molecular monitoring of BCR-ABL transcript levels by RT-qPCR has become always more important to assess minimal residual disease. Recently, recommendations for harmonizing current methodologies for detecting and measuring BCR-ABL transcripts in CML patients have been suggested. Studies of imatinib-treated patients have determined that the BCR-ABL levels measured early in therapy may predict durable cytogenetic remission and in turn prolonged progression free-survival or acquisition of resistance. The major mechanism of imatinib resistance is clonal expansion of leukaemia cells with mutations in the Bcr-Abl fusion tyrosine kinase. The early reduction of such mutations may allow timely treatment intervention to prevent or overcome resistance. We review current trends in the management of chronic myeloid leukaemia patients undergoing treatment with tyrosine kinase inhibitors.