Suboptimal Response to or Failure of Imatinib Treatment for Chronic Myeloid Leukemia: What is the Optimal Strategy?

Treatment responses to imatinib vary among patients with chronic myeloid leukemia (CML), and definitions of treatment failure and suboptimal response have been published. This article discusses monitoring and treatment of patients with CML after failure of or suboptimal response to imatinib therapy. We reviewed articles listed on PubMed from January 1, 2002, to July 31, 2008, and abstracts from the 2007 Annual Meeting of the American Society of Hematology. Search terms used were chronic myeloid/myelogenous leukemia, imatinib, and BCR-ABL. To enable early recognition of suboptimal responses, patients should be frequently monitored according to published guidelines, including cytogenetic analysis every 6 months until a complete response is achieved and molecular monitoring every 3 months from the start of therapy or monthly if an increasing BCR-ABL1 transcript level is detected. Mutational analysis of BCR-ABL1 may assist with treatment selection. A recent survey suggests that a notable proportion of physicians do not follow treatment guidelines and that broader communication is required. Recent recommendations state that, in patients whose response to imatinib at 400 mg/d is suboptimal, the dose should be increased, whereas alternative therapies, such as dasatinib, nilotinib, and allogeneic stem cell transplant (in eligible patients), and imatinib dose escalation should be considered after imatinib failure. However, clinical data are lacking to confirm this sequence of treatments, and introducing alternative therapies at an earlier stage of treatment, for example, after a suboptimal response, may produce better long-term outcomes in a higher proportion of patients. Patient and disease characteristics should be carefully considered to optimize treatment strategy for CML.