Recent advances in the path toward the cure for chronic myeloid leukemia

ABSTRACT

Through the phase 3 International Randomized Study of Interferon vs. STI571 (IRIS) trial, imatinib emerged as the standard treatment for chronic myeloid leukemia (CML) and has successfully prolonged the duration of both the chronic phase (CP) and the disease-free state. The majority of newly diagnosed patients treated for CP-CML achieve a complete cytogenetic response (CCyR), and over time, most of these eventually achieve major molecular responses (MMRs) and even complete molecular responses (CMRs). In ongoing phase 3 randomized trials of second-generation tyrosine kinase inhibitors (TKIs), nilotinib and dasatinib have been found to have superior efficacies in helping achieve cytogenetic and molecular responses, including MMRs and CMRs. However, only the MMR rate was significantly higher in bosutinib compared with the imatinib control, but not in CCyR rate. Current reports of imatinib discontinuation suggested that achieving CMR is an important prerequisite for CML to be cured. Recent data from the STIM (Stop Imatinib) trial showed that imatinib can be successfully discontinued in patients who achieve a certain level of CMR. Standardized real-time quantitative reverse transcriptase-polymerase chain reaction (RQ-PCR) assays have been available in routine clinical practice, and efforts are being focused on achieving higher sensitivity and optimizing the time of imatinib discontinuation. Although very few patients are cured by administration of only Bcr-Abl TKIs, including imatinib and second-generation TKIs, current advances may eventually make this possible. This report summarizes the detailed clinical data obtained in the DASISION, ENESTnd, and BELA studies and discusses high-sensitivity detection methods and future therapeutic strategies.