Response Dynamics in Chronic-Phase Chronic Myeloid Leukemia

Abstract

Cytogenetic response (CyR), especially complete CyR (CCyR), has historically and is currently associated with a significant survival advantage in patients with chronic-phase chronic myeloid leukemia (CP-CML). CCyR represents a critical level of disease reduction irrespective of treatment type, and timely achievement demonstrates treatment-sensitive disease. Guidelines from European LeukemiaNet and the National Comprehensive Cancer Network therefore state that alternative therapies should be considered for patients not achieving CCyR by 6 or 12 months. Data from clinical trials indicate that early CCyR affords the best benefit:risk ratio by minimizing the mounting risk of disease progression, and the duration of CCyR when achieved affects disease progression. Treatment options for patients who fail to achieve CCyR on standard-dose imatinib (400 mg/day) include imatinib dose escalation, dasatinib, nilotinib, stem-cell transplantation, or a clinical trial. While molecular testing gauges further risk reduction, disease stability, and often elimination of BCR-ABL transcripts below detection threshold, CCyR remains the most important surrogate for long-term survival and cytogenetic testing remains a key part of patient care in the management of CML, particularly early in response. Longerterm follow-up data will be required to confirm CCyR as a surrogate marker for survival in imatinib-resistant patients treated with the secondgeneration tyrosine kinase inhibitors, dasatinib and nilotinib.