Optimizing timing of secondary tyrosine kinase therapy in chronic myeloid leukemia

The tyrosine kinase inhibitor (TKI) imatinb has radically changed the treatment of chronic myeloid leukemia (CML). Most patients treated in chronic phase can be expected to achieve a complete cytogenetic remission (CCyR). However, primary imatinib therapy fails in a number of patients initially, or relapse occurs later after a good cytogenetic response. Treatment of accelerated phase and blast crisis yields disappointing results and is rarely associated with long-term disease control. Imatinib failures can now be potentially salvaged with new TKIs or, if a donor exists, by a hematopoetic stem cell transplantation. Given these multiple effective treatment options, tight monitoring of cytogenetic and molecular response is essential in deciding when imatinib therapy should be abandoned for alternative therapy. This review will define the types of tests used to monitor the disease, provide clinically relevant endpoints, and outline guidelines for monitoring patients with CML on imatinib therapy.