The impact of molecular biology techniques on the management of newly diagnosed chronic myeloid leukemia patients in chronic phase. A review.

Since the introduction of tyrosine kinase inhibitors (TKI) in chronic myeloid leukemia (CML), the management of this disease has completely changed. The aim has been first to bring to the patient a maximal response and to identify at different time-points what could be considered an optimal response (which is to render the progression free survival as important as possible). To achieve this, new molecular tools were needed, the most important being the real time quantitative PCR (RT-qPCR), to measure the number of remaining transcripts after several period of treatment. The second important tool was the sequencing of the BCR-ABL kinase domain to identify potential mutations giving rise to resistance to imatinib first and next to second generation TKIs. This technique, much more sensitive than cytogenetics, has allowed the definition of important levels of transcripts (the major molecular response i.e. a three log reduction and the complete molecular response i.e. a 4.5 log reduction) the first ensuring a long term PFS on treatment, the second allowing the birth of studies looking at whether it would be possible to discontinue the treatment in this group of patients.