Advanced CML: therapeutic options for patients in accelerated and blast phases

Tyrosine kinase inhibitor (TKI) therapy has impacted the natural course of chronic myelogenous leukemia (CML), because patients diagnosed as having chronic-phase disease can experience long-lasting responses. However, for patients with advanced CML (accelerated and blast phases), the efficacy of all current therapies is reduced. For these patients, allogeneic stem cell transplantation remains the preferred treatment if a donor is available, although TKIs play a valuable role as a bridging therapy. For patients with accelerated-phase CML, imatinib, dasatinib, and nilotinib have been shown to produce meaningful rates of hematologic and cytogenetic response. Imatinib and dasatinib are also approved for blast-phase CML. Studies with the newer agents have involved heavily pretreated patients; however, response rates have been at least comparable to those achieved with imatinib in previous studies. Therefore, these newer, more potent TKIs will probably be more likely to induce a deep response in previously untreated patients. Moreover, because fewer mechanisms appear to exist for secondary resistance to dasatinib and nilotinib, reducing the potential for disease to escape TKI therapy, these agents may result in improved longer-term outcomes. However, BCR-ABL-independent pathways may also become more important, indicating that other therapeutic targets may also have a future role in managing patients with advanced CML.