Chronic myelogenous leukemia: monitoring response to therapy.

Molecular monitoring is a key component of the management of patients with chronic myeloid leukemia. The current recommendation is that molecular monitoring be performed in place of cytogenetic assessment when a major molecular response (MMR) is achieved. With the more potent kinase inhibitors nilotinib and dasatinib now approved as front-line therapy, more patients will achieve an MMR and will benefit from molecular monitoring. There is a strong correlation between certain BCR-ABL1 levels and the cytogenetic response, which means that molecular monitoring may act as a surrogate for cytogenetic response, but only if the BCR-ABL1 values are converted to the international reporting scale. Furthermore, improvements in the limit of BCR-ABL1 detection and reduction of intra-assay variability are ongoing issues of importance for molecular monitoring. Standardization of molecular methods to accurately assess the patient response also remains a challenge, despite the recent certification of international scale reference materials.