Phase IV study evaluating efficacy of escalated dose of imatinib in chronic myeloid leukemia patients showing suboptimal response to standard dose imatinib

Comparative analyses of nilotinib versus high-dose imatinib versus sustained standard-dose imatinib in patients with chronic phase chronic myeloid leukemia following suboptimal molecular response to first-line imatinib

The aim of this study was to investigate the efficacy of nilotinib (NIL) versus high-dose imatinib (IM) versus sustained standard-dose IM for patients with chronic myeloid leukemia (CML) with suboptimal molecular response to first-line IM therapy. Patients with CML who achieved complete cytogenetic response (CCyR) but not major molecular response (MMR) after 18-24 months on first-line IM therapy were enrolled and divided into three treatment cohorts: NIL 800 mg/day (Cohort 1, n = 28) and IM 800 mg/day (Cohort 2, n = 28) in the RE-NICE study, and sustained IM 400 mg/day (Cohort 3, n = 52) in clinical practice. The primary efficacy variable of cumulative rate of MMR by 12 months was not different among the three cohorts. However, the cumulative incidence of MMR by 36 months was significantly higher in Cohort 1 than Cohort 3 (83.1% vs. 57.1%, P = 0.021), but there were no significant differences in Cohort 1 vs. 2 (P = 0.195) and Cohort 2 vs. 3 (P = 0.297). Different profile for adverse events was observed between NIL and high-dose IM therapy. In conclusion, our data suggested that switching to NIL may provide more effective long-term response than sustaining standard-dose IM for patients with suboptimal molecular response to first-line IM.

Safety and efficacy of switching to nilotinib 400 mg twice daily for patients with chronic myeloid leukemia in chronic phase with suboptimal response or failure on front-line imatinib or nilotinib 300 mg twice daily

In a randomized, phase III trial of nilotinib versus imatinib in patients with newly diagnosed Philadelphia chromosome positive chronic myeloid leukemia in chronic phase, more patients had suboptimal response or treatment failure on front-line imatinib than on nilotinib. Patients with suboptimal response/treatment failure on imatinib 400 mg once or twice daily or nilotinib 300 mg twice daily could enter an extension study to receive nilotinib 400 mg twice daily. After a 19-month median follow up, the safety profile of nilotinib 400 mg twice daily in patients switching from imatinib (n=35) was consistent with previous reports, and few new adverse events occurred in patients escalating from nilotinib 300 mg twice daily (n=19). Of patients previously treated with imatinib or nilotinib 300 mg twice daily, respectively, 15 of 26 (58%) and 2 of 6 (33%) without complete cytogenetic response at extension study entry, and 11 of 34 (32%) and 7 of 18 (39%) without major molecular response at extension study entry, achieved these responses at any time on nilotinib 400 mg twice daily. Estimated 18-month rates of freedom from progression and overall survival after entering the extension study were lower for patients switched from imatinib (85% and 87%, respectively) versus nilotinib 300 mg twice daily (95% and 94%, respectively). Nilotinib dose escalation was generally well tolerated and improved responses in about one-third of patients with suboptimal response/treatment failure. Switch to nilotinib improved responses in some patients with suboptimal response/treatment failure on imatinib, but many did not achieve complete cytogenetic response (clinicaltrials.gov identifiers: 00718263, 00471497 - extension).

Application of array comparative genomic hybridization in chronic myeloid leukemia

Chromosomal alteration is one of the hallmarks of chronic myeloid leukemia (CML), and the Philadelphia chromosome is the most important and key example of the chromosomal changes in this disease. Indeed, the BCR-ABL1 fusion product is a target against which many tyrosine kinase inhibitors (TKIs) have been proven to be effective in the treatment of CML. However, the reality is that CML patients show resistance to TKIs both in an acquired and de novo manner, and the mechanism of TKI resistance is still largely unknown. This phenomenon suggests that in addition to the BCR-ABL mutation, further genetic alterations such as copy number aberration may be involved in unexplained TKI resistance. Although the recent array comparative genomic hybridization analyses (array-CGH) across the whole genome have detected multiple genetic aberrations in CML, the detailed feature of chromosomal alterations involved in different clinical phases of CML, such as chronic phase, accelerated phase, and blast crisis, remains unclear. Here we review the methodological aspects of array-CGH analysis for studying CML and its related data analysis.

Suboptimal responses in chronic myeloid leukemia: implications and management strategies

The high response rates and increased survival associated with imatinib therapy prompted a paradigm shift in the management of chronic myeloid leukemia. However, 25% to 30% of imatinib-treated patients develop drug resistance or intolerance, increasing the risk of disease progression and poor prognosis. In 2006, the European LeukemiaNet proposed criteria to identify patients with a suboptimal response to, or failure associated with, imatinib; these recommendations were updated in 2009. Suboptimal responders represent a unique treatment challenge. Although they may respond to continued imatinib therapy, their long-term outcomes may not be as favorable as those for optimally responding patients. Validation studies demonstrated that suboptimal responders are a heterogeneous group, and that the prognostic implications of suboptimal response vary by time point. There are few data derived from clinical trials to guide therapeutic decisions for these patients. Clinical trials are currently underway to assess the efficacy of newer tyrosine kinase inhibitors in this setting. Identification of suboptimal responders or patients failing treatment using hematologic, cytogenetic, and molecular techniques allows physicians to alter therapy earlier in the treatment course to improve long-term outcomes.

Dose escalation of imatinib in chronic-phase chronic myeloid leukemia patients: is it still reasonable?

Suboptimal response or treatment failure to standard-dose imatinib are relevant problems in chronic-phase chronic myeloid leukemia patients. Insufficient adherence is one of the main causes of insufficient response but biological reasons also have to be considered. Various mechanisms of resistance have been described in the past, some of them mediating absolute resistance and others, relative resistance, to imatinib. The latter can be overcome by dose intensification of imatinib. However, the availability of second-generation tyrosine kinase inhibitors means these patients can be switched to these novel agents. Thus, which strategy is most appropriate for the individual patient with insufficient response to standard-dose imatinib remains elusive. Moreover, it remains unclear whether dose intensification of imatinib in the first-line setting might allow a more rapid and deeper response rate. This article will summarize data on imatinib dose intensification and will make recommendations about which patients imatinib dose intensification is most appropriate for.

NCCN Task Force report: tyrosine kinase inhibitor therapy selection in the management of patients with chronic myelogenous leukemia

The advent of imatinib has dramatically improved outcomes in patients with chronic myelogenous leukemia (CML). It has become the standard of care for all patients with newly diagnosed chronic-phase CML based on its successful induction of durable responses in most patients. However, its use is complicated by the development of resistance in some patients. Dose escalation might overcome this resistance if detected early. The second-generation tyrosine kinase inhibitors (TKIs) dasatinib and nilotinib provide effective therapeutic options for managing patients resistant or intolerant to imatinib. Recent studies have shown that dasatinib and nilotinib provide quicker and potentially better responses than standard-dose imatinib when used as a first-line treatment. The goal of therapy for patients with CML is the achievement of a complete cytogenetic response, and eventually a major molecular response, to prevent disease progression to accelerated or blast phase. Selecting the appropriate TKI depends on many factors, including disease phase, primary or secondary resistance to TKI, the agent's side effect profile and its relative effectiveness against BCR-ABL mutations, and the patient's tolerance to therapy. In October 2010, NCCN organized a task force consisting of a panel of experts from NCCN Member Institutions with expertise in the management of patients with CML to discuss these issues. This report provides recommendations regarding the selection of TKI therapy for the management of patients with CML based on the evaluation of available published clinical data and expert opinion among the task force members.

Increased BCR promoter DNA methylation status strongly correlates with favorable response to imatinib in chronic myeloid leukemia patients

To define the correlation between BCR promoter DNA methylation and response to imatinib in chronic myeloid leukemia (CML), we investigated BCR promoter DNA methylation in three groups of subjects. The first group included chronic phase patients enrolled in an imatinib dose escalation trial. In the trial, patients who failed to achieve optimal response with 400 mg/day (suboptimal responders) received an escalated imatinib dose. The level of BCR promoter DNA methylation was quantitated at baseline six months after dose escalation. The second group included patients who achieved complete cytogenetic remission after receiving 400 mg/day of imatinib (optimal responders), and the third group were the healthy controls. In the suboptimal responders, an increased BCR promoter DNA methylation at six months compared with the baseline was related to a rapid reduction in the BCR-ABL/ABL transcript level following dose escalation (p=0.001) and a longer time to treatment failure (TTFx) of the dose-escalated imatinib (p=0.008). When multivariate analysis was performed with regard to the baseline BCR-ABL transcript level, baseline BCR promoter DNA methylation, and a change in the BCR promoter DNA methylation following dose escalation, the increase in the BCR promoter DNA methylation following dose escalation was an independent predictive factor for TTFx of dose-escalated imatinib (hazard ratio, 0.294; p=0.015). The baseline BCR promoter DNA methylation level in the suboptimal responders was lower than that in BCR promoter DNA methylation in the optimal responders (p=0.001) and healthy controls (p<0.001). In both the optimal and suboptimal responders, BCR promoter DNA methylation had an inverse correlation with the duration of the 400 mg/day imatinib use. In conclusion, increased BCR promoter DNA methylation strongly correlates with a more favorable imatinib response in CML patients.