European LeukemiaNet criteria for failure or suboptimal response reliably identify patients with CML in early chronic phase treated with imatinib whose eventual outcome is poor

How to treat CML patients in the tyrosine kinase inhibitors era? From imatinib standard dose to second generation drugs front-line: unmet needs, pitfalls and advantages

Imatinib has revolutionized treatment strategies for chronic myeloid leukemia patients: long-term overall survival was reported to be up to 80% at 8 years of follow-up in respondent patients. Despite the straightforward results obtained, it has been estimated a failure rate per year of 2-4%. Several attempts to improve response have been made with high-dose of imatinib and with combination of standard dose with interferon, but both failed to ameliorate cytogenetic and molecular responses and long-term event-free and overall survival and no advantages were reported in high-risk patients. The introduction of second generation tyrosine kinase inhibitors in clinical practice allowed to rescue more than 50% of patients resistant or intolerant to imatinib. Both dasatinib and nilotinib were tested as single agent in first-line and then tested against imatinib standard dose: the results of phases II and III trials showed early and maintained complete cytogenetic response, rapid reduction of molecular burden and significant reduction of progression rate. At the present time, after FDA approval of both agents in first-line, several points of discussion are still unresolved.

Evolution of definitions of response, progression-free survival and event-free survival in front-line studies of chronic myeloid leukemia

Standardized definitions of response and outcome are useful to evaluate study data, facilitate treatment guideline adherence and aid clinical decision-making. Although definitions of response in chronic myeloid leukemia (CML) have been standardized, definitions of disease progression have not been standardized, despite widespread adoption of the term to reflect development of advanced disease. This article reviews definitions of response and disease progression used for progression-free survival and event-free survival in key CML studies and implications for interpreting patient response. It is proposed that adherence to definitions of progression from the European LeukmiaNet may aid future research and therapeutic decision-making.

Dasatinib or imatinib in newly diagnosed chronic-phase chronic myeloid leukemia: 2-year follow-up from a randomized phase 3 trial (DASISION)

Dasatinib is a highly potent BCR-ABL inhibitor with established efficacy and safety in imatinib-resistant/-intolerant patients with chronic myeloid leukemia (CML). In the phase 3 DASISION trial, patients with newly diagnosed chronic-phase (CP) CML were randomized to receive dasatinib 100 mg (n = 259) or imatinib 400 mg (n = 260) once daily. Primary data showed superior efficacy for dasatinib compared with imatinib after 12 months, including significantly higher rates of complete cytogenetic response (CCyR), confirmed CCyR (primary end point), and major molecular response (MMR). Here, 24-month data are presented. Cumulative response rates by 24 months in dasatinib and imatinib arms were: CCyR in 86% versus 82%, MMR in 64% versus 46%, and BCR-ABL reduction to ≤ 0.0032% (4.5-log reduction) in 17% versus 8%. Transformation to accelerated-/ blast-phase CML on study occurred in 2.3% with dasatinib versus 5.0% with imatinib. BCR-ABL mutations, assessed after discontinuation, were detected in 10 patients in each arm. In safety analyses, fluid retention, superficial edema, myalgia, vomiting, and rash were less frequent with dasatinib compared with imatinib, whereas pleural effusion and grade 3/4 thrombocytopenia were more frequent with dasatinib. Overall, dasatinib continues to show faster and deeper responses compared with imatinib, supporting first-line use of dasatinib in patients with newly diagnosed CML-CP. This study was registered at ClinicalTrials.gov: NCT00481247.

Front-line therapy with second-generation tyrosine kinase inhibitors in patients with early chronic phase chronic myeloid leukemia: what is the optimal response?

PURPOSE

The response definitions proposed by the European LeukemiaNet (ELN) are defined on the basis of imatinib front-line therapy. It is unknown whether these definitions apply to patients treated with second-generation tyrosine kinase inhibitors (TKIs).

PATIENTS AND METHODS

One hundred sixty-seven patients with newly diagnosed chronic myelogenous leukemia (CML) in chronic phase were treated with second-generation TKIs in phase II trials (nilotinib, 81; dasatinib, 86). Median follow-up was 33 months. Event-free survival (EFS) was measured from the start of treatment to the date of loss of complete hematologic response, loss of complete or major cytogenetic response, discontinuation of therapy for toxicity or lack of efficacy, progression to accelerated or blastic phases, or death at any time.

RESULTS

Overall, 155 patients (93%) achieved complete cytogenetic response (CCyR), including 146 (87%) with major molecular response (MMR; complete in 46 patients [28%]). According to the ELN definitions, the rates of suboptimal response were 0%, 2%, 1%, and 12% at 3, 6, 12, and 18 months of therapy, respectively. There was no difference in EFS and CCyR duration between patients who achieved CCyR with and without MMR across all the landmark times of 3, 6, 12, and 18 months.

CONCLUSION

The use of second-generation TKIs as initial therapy in CML induces high rates of CCyR at early time points. The ELN definitions of response proposed for imatinib therapy are not applicable in this setting. We propose that achievement of CCyR and partial cytogenetic response at 3 months should be considered optimal and suboptimal responses, respectively. The achievement of MMR offered no advantage over CCyR in defining long-term outcome in patients with newly diagnosed CML treated with second-generation TKIs.

Assessment of BCR-ABL1 transcript levels at 3 months is the only requirement for predicting outcome for patients with chronic myeloid leukemia treated with tyrosine kinase inhibitors

PURPOSE

We studied BCR-ABL1 transcript levels in patients with chronic myeloid leukemia in chronic phase (CML-CP) at 3, 6, and 12 months after starting imatinib to identify molecular milestones that would predict for overall survival (OS) and other outcomes more reliably than serial marrow cytogenetics.

PATIENTS AND METHODS

We analyzed 282 patients with CML-CP who received imatinib 400 mg/d as first-line therapy followed by dasatinib or nilotinib if treatment with imatinib failed. We used a receiver operating characteristic curve to identify the cutoffs in transcript levels at 3, 6, and 12 months that would best predict patient outcome. We validated our findings in an independent cohort of 95 patients treated elsewhere.

RESULTS

Patients with transcript levels of more than 9.84% (n = 68) at 3 months had significantly lower 8-year probabilities of OS (56.9% v 93.3%; P < .001), progression-free survival, cumulative incidence of complete cytogenetic response, and complete molecular response than those with higher transcript levels. Similarly, transcript levels of more than 1.67% (n = 87) at 6 months and more than 0.53% (n = 93) at 12 months identified high-risk patients. However, transcript levels at 3 months were the most strongly predictive for the various outcomes. When we compared OS for the groups defined molecularly at 6 and 12 months with the usual cytogenetic milestones, categorization by transcript numbers was the only independent predictor for OS (relative risk, 0.207; P < .001 and relative risk, 0.158; P < .001, respectively).

CONCLUSION

A single measurement of BCR-ABL1 transcripts performed at 3 months is the best way to identify patients destined to fare poorly, thereby allowing early clinical intervention.

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.

Harmonization of molecular monitoring of chronic myeloid leukemia therapy in Japan

BACKGROUND

Real-time quantitative polymerase chain reaction (RQ-PCR) has been widely used for molecular monitoring for patients with chronic myeloid leukemia (CML). Currently, RQ-PCR is not based on the concept of international scale (IS) in Japan; mainly because none of the domestic laboratories have obtained their own conversion factor (CF) which makes it possible to convert locally scaled BCR-ABL (BCR-ABL (L)) value to the IS (BCR-ABL (IS)). To join the global trend of molecular assessment of BCR-ABL in CML patients, we have tried to obtain a CF in Japan.

METHODS

Samples from 55 patients were exchanged between the Japanese laboratory and the reference laboratory in Adelaide, and BCR-ABL and internal control gene transcripts of the samples were measured using RQ-PCR. The patient bias conversion method was used to determine the CF for the IS using the Bland and Altman method.

RESULTS

The local CF in the Japanese laboratory was determined to be 0.87. Based on this CF, 0.1% BCR-ABL (IS), defined as major molecular response, becomes equivalent to 731 copy/μg RNA BCR-ABL (L).

CONCLUSION

This study is the first to introduce a laboratory-specific CF for harmonizing RQ-PCR methodology for detecting BCR-ABL transcripts to Japan, which may open new windows for molecular assessment of CML patients in Japan.

Predicting the response of CML patients to tyrosine kinase inhibitor therapy

As of 2011, the choice of tyrosine kinase inhibitor (TKI) for the patient with newly diagnosed chronic-phase chronic myelogenous leukemia (CP-CML) is no longer limited to imatinib but can be expanded to include nilotinib and dasatinib. Since 2000, imatinib has demonstrated remarkable efficacy in the majority of chronic-phase patients. Nilotinib and dasatinib, both more potent TKIs, are likely to produce quicker and deeper molecular responses, but there are no established criteria for choosing the best inhibitor for each patient. We now need to establish clearly defined recommendations to address this new stage, in which individualized therapy in the front-line should become a reality. Likely to be paramount in this setting are assays that directly assess the efficacy of the protein-drug and drug-transporter interactions, taking into account factors intrinsic to the patient, factors related to disease stage, and the amount of drug freely available in the plasma.

Evolving treatment strategies for patients newly diagnosed with chronic myeloid leukemia: the role of second-generation BCR-ABL inhibitors as first-line therapy

In patients with chronic myeloid leukemia (CML), disease in the initial chronic phase (CP) and subsequent progression are driven by the oncogenic activity of the BCR-ABL fusion kinase. Imatinib, a tyrosine kinase inhibitor of BCR-ABL, has been the mainstay of first-line therapy for CML for 10 years. Although patients with CML-CP respond well to imatinib, those who have delayed reductions in leukemic burden during imatinib therapy, such as not achieving a complete cytogenetic response (CCyR) by 12 months, have an increased risk of disease progression. It has been recognized, with 8 years of observation, that patients who achieve an early major molecular response (MMR) on imatinib have a very low probability of disease progression. Recent randomized phase 3 trials have shown that first-line treatment with dasatinib or nilotinib-more potent BCR-ABL inhibitors-results in significantly higher rates and more rapid achievement of CCyR and MMR in comparison with standard-dose imatinib. These trials suggest that CML treatment can be improved with more potent BCR-ABL inhibition during initial therapy, but further follow-up is needed to confirm that the improved response rates with dasatinib and nilotinib are maintained long term.

The achievement of an early complete cytogenetic response is a major determinant for outcome in patients with early chronic phase chronic myeloid leukemia treated with tyrosine kinase inhibitors

We analyzed the association between achievement of early complete cytogenetic response (CCyR) and event-free survival (EFS) and overall survival (OS) in patients with newly diagnosed chronic myeloid leukemia in chronic phase treated with imatinib 400 mg (n = 73), or imatinib 800 mg daily (n = 208), or second- generation tyrosine kinase inhibitors (n = 154). The overall CCyR rates were 87%, 91%, and 96%, respectively (P = .06); and major molecular response (MMR) rates were 77%, 87%, and 89%, respectively (P = .05). Their 3-year EFS rates were 85%, 92%, and 97% (P = .01), and OS rates were 93%, 97%, and 100% (P = .18), respectively. By landmark analysis, patients with 3-, 6-, and 12-month CCyR had significantly better outcome: 3-year EFS rates of 98%, 97%, and 98% and OS rates of 99%, 99%, and 99%, respectively, compared with 83%, 72%, and 67% and 95%, 90%, and 94%, in patients who did not achieve a CCyR. Among patients achieving CCyR at 12 months, the depth of molecular response was not associated with differences in OS or EFS. In conclusion, second tyrosine kinase inhibitors induced higher rates of CCyR and MMR than imatinib. The achievement of early CCyR remains a major determinant of chronic myeloid leukemia outcome regardless of whether MMR is achieved or not.

Measuring response to BCR-ABL inhibitors in chronic myeloid leukemia

In patients with chronic myeloid leukemia (CML), the hallmark Philadelphia chromosome is the marker of disease that can be detected by conventional metaphase cytogenetics, fluorescence in situ hybridization, or polymerase chain reaction. The current "gold standard" of treatment response is cytogenetic response. Cytogenetic response to imatinib is strongly associated with disease progression and survival. Various strategies aimed at improving cytogenetic response have been explored, such as escalation of imatinib and switching to the newer breakpoint cluster region/v-abl Abelson murine leukemia viral oncogene (BCR-ABL) inhibitors dasatinib and nilotinib. Data from recent randomized trials of dasatinib and nilotinib as first-line therapy of newly diagnosed chronic-phase CML suggest that these agents are more effective than imatinib in achieving 6-month and 12-month complete cytogenetic responses. However, it is still too early to know whether or not this early response will translate into a long-term survival advantage. In addition, more sensitive assays to detect residual disease also may be associated with improved long-term outcomes. The deepest measure of response-a complete molecular response-may help identify patients who can stop taking imatinib for the short term, although the long-term consequences of this strategy remain unknown.

Imatinib is effective in children with previously untreated chronic myelogenous leukemia in early chronic phase: results of the French national phase IV trial

PURPOSE

Imatinib is the standard of care in adults with chronic myeloid leukemia (CML) in chronic phase (CP). Only a few studies to assess efficacy in children have been performed. We report on the results of the French prospective trial (ClinicalTrials.gov identifier NCT00845221) conducted in children and adolescents with newly diagnosed CML in CP.

PATIENTS AND METHODS

A total of 44 patients from age 10 months to 17 years with newly diagnosed CML in CP received daily imatinib 260 mg/m(2). Progression-free survival, responses, and tolerance were evaluated.

RESULTS

With a median follow-up times of 31 months (range, 11 to 64 months), the estimated progression-free survival rate at 36 months was 98% (95% CI, 85% to 100%). A complete hematologic response was achieved in 98% of the patients. The rates of complete cytogenetic response (CCyR) and major molecular response (MMR) were 61% and 31% at 12 months, respectively. During follow-up, CCyR and MMR were achieved in 36 children (77%) and 25 children (57%), respectively. Overall, 30% of the patients discontinued imatinib, mainly because of unsatisfactory response. The most common adverse events were neutropenia and musculoskeletal events.

CONCLUSION

Imatinib is effective in children with CML in CP with response rates similar to rates reported in adults. The adverse effects are acceptable, but longer follow-up studies are required to fully assess the long-term impact.

Molecular monitoring of imatinib in chronic myeloid leukemia patients in complete cytogenetic remission: does achievement of a stable major molecular response at any time point identify a privileged group of patients? A multicenter experience in Argentina and Uruguay

BACKGROUND

Monitoring minimal residual disease (MRD) by real-time quantitative polymerase chain reaction (RT-PCR) in chronic myeloid leukemia (CML) patients is mandatory in the era of tyrosine kinase inhibitors. Achieving a major molecular response (MMR) at 12 and 18 months predicts a better progression and event-free survival.

PATIENTS AND METHODS

The objective of this prospective, multicentric study was to evaluate MRD by standardized RT-PCR in 178 patients with chronic-phase CML who were treated with imatinib at different institutions in Argentina and Uruguay and to determine if achievement of a stable MMR (BCR-ABL transcript levels < 0.1%) identifies a low-risk cytogenetic relapse group. The median age of the patients was 50 years, and 55% of them had received imatinib as first-line therapy. BCR-ABL transcript levels were measured after achievement of complete cytogenetic remission (CCyR) and at 6-month intervals.

RESULTS

MMR was detected in 44% patients at the start of the study. This value increased to 79% at month 36 of evaluation. Complete molecular response (CMR) also increased from 24% to 52% of patients. Not achieving a stable MMR determined a higher risk of cytogenetic relapse (9% of MMR patients not achieving an MMR vs. 1% of patients who achieved MMR). Patients with sustained MMR had a significantly better cytogenetic relapse-free survival at 48 months (97% vs. 87%; P = .008) but showed no differences in overall survival. Patients who did not remain in CCyR changed treatment.

CONCLUSIONS

A stable MMR is a strong predictor for a durable CCyR. Standardized molecular monitoring could replace cytogenetic analysis once CCyR is obtained. These results emphasize the validity and feasibility of molecular monitoring in all standardized medical centers of the world.

Outcome of treatment of chronic myeloid leukemia with second-generation tyrosine kinase inhibitors after imatinib failure

Although imatinib revolutionized the management of chronic myeloid leukemia (CML), recent data indicate a transformation in the treatment approach likely in the near future. For patients whose CML does not respond to standard-dose imatinib therapy, increasing the imatinib dose is a second-line option. However, high-dose imatinib is not an appropriate approach for patients experiencing drug toxicity, and there remain questions concerning the durability of responses achieved with this strategy. Alternative second-line options include the newer tyrosine kinase inhibitors (TKIs) such as dasatinib and nilotinib. A substantial amount of long-term data for these agents is available. Although both are potent and specific BCR-ABL TKIs, dasatinib and nilotinib exhibit unique pharmacological profiles and response patterns relative to different patient characteristics, such as disease stage and BCR-ABL mutational status. The superiority of second-generation TKIs over imatinib in newly diagnosed disease has been recognized as well. They induce high and rapid rates of cytogenetic and molecular response, with less progression to advanced forms of disease in comparison with imatinib. Several investigational agents specific for those patients with the T315I mutation remain under evaluation. The future of CML therapy may include early use of these potent agents to help more patients achieve molecular remission and potentially be a path to a CML cure.

Frontline imatinib treatment of chronic myeloid leukemia: no impact of age on outcome, a survey by the GIMEMA CML Working Party

The median age of chronic myeloid leukemia (CML) patients is ∼ 60 years, and age is still considered an important prognostic factor, included in Sokal and EURO risk scores. However, few data are available about the long-term outcome of older patients treated with imatinib (IM) frontline. We analyzed the relationship between age and outcome in 559 early chronic-phase CML patients enrolled in 3 prospective clinical trials of Gruppo Italiano Malattie Ematologiche dell'Adulto CML Working Party, treated frontline with IM, with a median follow-up of 60 months. There were 115 older patients (≥ 65 years; 21%). The complete cytogenetic and major molecular response rates were similar in the 2 age groups. In older patients, event-free survival (55% vs 67%), failure-free survival (78% vs 92%), progression-free survival (62% vs 78%), and overall survival (75% vs 89%) were significantly inferior (all P < .01) because of a higher proportion of deaths that occurred in complete hematologic response, therefore unrelated to CML progression (15% vs 3%, P < .0001). The outcome was similar once those deaths were censored. These data show that response to IM was not affected by age and that the mortality rate linked to CML is similar in both age groups. This trial was registered at www.clinicaltrials.gov as #NCT00514488 and #NCT00510926.

Early cytogenetic and molecular response during first-line treatment of chronic myeloid leukemia in chronic phase: long-term implications

Chronic myeloid leukemia (CML) depends on the kinase activity of the BCR-ABL1 fusion protein. This dependency has led to the development of BCR-ABL1 inhibitors, such as imatinib, dasatinib, and nilotinib, which have proved to be highly efficacious treatments for CML. The European LeukemiaNet guidelines have established the importance of achieving a certain depth of response at different time points during imatinib therapy for patients with newly diagnosed CML in chronic phase. Patients who achieve a complete cytogenetic response by 12 months or a major molecular response by 18 months are classified as optimal responders and deemed to have excellent long-term outcomes. Conversely, failing to achieve such milestones is associated with an increased risk of worse long-term outcomes, such as loss of response, disease progression, or death. With ongoing treatment, patients not in complete cytogenetic response face a decreasing probability of ever achieving a complete cytogenetic response or major molecular response and increasing risk of disease progression. Available data therefore support treatment recommendations based on achieving defined levels of response within a specified duration of treatment. Recent data have shown that dasatinib and nilotinib used as frontline CML therapy result in higher response rates that are achieved at earlier time points compared with standard-dose imatinib therapy. Future analyses will need to determine whether these higher rates of deep and fast responses translate into improved long-term survival.

BCR-ABL kinase domain mutation analysis in chronic myeloid leukemia patients treated with tyrosine kinase inhibitors: recommendations from an expert panel on behalf of European LeukemiaNet

Mutations in the Bcr-Abl kinase domain may cause, or contribute to, resistance to tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia patients. Recommendations aimed to rationalize the use of BCR-ABL mutation testing in chronic myeloid leukemia have been compiled by a panel of experts appointed by the European LeukemiaNet (ELN) and European Treatment and Outcome Study and are here reported. Based on a critical review of the literature and, whenever necessary, on panelists' experience, key issues were identified and discussed concerning: (1) when to perform mutation analysis, (2) how to perform it, and (3) how to translate results into clinical practice. In chronic phase patients receiving imatinib first-line, mutation analysis is recommended only in case of failure or suboptimal response according to the ELN criteria. In imatinib-resistant patients receiving an alternative TKI, mutation analysis is recommended in case of hematologic or cytogenetic failure as provisionally defined by the ELN. The recommended methodology is direct sequencing, although it may be preceded by screening with other techniques, such as denaturing-high performance liquid chromatography. In all the cases outlined within this abstract, a positive result is an indication for therapeutic change. Some specific mutations weigh on TKI selection.

Interpretation of cytogenetic and molecular results in patients treated for CML

The International Randomized Study of Interferon vs. STI571 (IRIS) trial that investigated the use of the tyrosine kinase inhibitor (TKI) imatinib (versus interferon) changed the treatment and outcome of chronic myeloid leukemia (CML). Long-term follow-up of IRIS patients has defined response parameters and methods of tracking residual disease with cytogenetic testing of bone marrow metaphases and molecular monitoring of BCR-ABL transcripts using quantitative reverse-transcriptase polymerase chain reaction. Cytogenetic and molecular responses are now considered useful surrogates for long-term outcome. Early and robust response to imatinib predicts positive long-term outcomes. However, 15-25% of patients fail initial treatment or become intolerant of imatinib and need increased doses or alternate treatment. Second-line treatment with the second-generation TKIs nilotinib and dasatinib have resulted in favorable rates of progression-free survival (PFS) and overall survival. Data from the ENESTnd (nilotinib) and DASISION (dasatinib) trials in newly diagnosed chronic-phase CML patients demonstrated more robust and rapid complete cytogenetic (77-80%) and major molecular responses (43-46%) at 12 months compared with imatinib (65-66% and 22-28%). The relationship between a complete cytogenetic response at 12 months and long-term PFS supports a role for second-generation TKIs as first-line treatment of newly diagnosed chronic-phase CML.

Suboptimal responses in chronic myeloid leukemia: milestones and mechanisms

Patients with chronic myeloid leukemia who fail to achieve timely treatment responses have a worse prognosis. Although many patients respond well to first-line treatment with imatinib, a significant proportion relapse or experience an inadequate response. Since effective alternative Bcr-Abl inhibitors are available (i.e., dasatinib or nilotinib), several regional groups have proposed milestones for imatinib failure or suboptimal response based on the achievement of specified levels of response within a defined treatment duration. A suboptimal response indicates that, although patients may continue to receive a benefit from continuing imatinib treatment at the assigned dose, long-term outcome may be better with an alternative strategy. The underlying mechanisms behind suboptimal responses are multifactorial and may differ from those causing relapse.

Monitoring response and resistance to treatment in chronic myeloid leukemia

Chronic myeloid leukemia (cml) results from expression of the constitutive tyrosine kinase activity of the Bcr-Abl oncoprotein. Imatinib, a tyrosine kinase inhibitor (tki), is highly effective in the treatment of cml. However, some patients treated with imatinib will fail to respond, will respond suboptimally, or will relapse because of primary or acquired resistance or intolerance. Research activities focusing on the mechanisms that underlie imatinib resistance have identified mutations in the BCR-ABL gene, clonal evolution, and amplification of the BCR-ABL gene as common causes. Cytogenetic and molecular techniques are currently used to monitor cml therapy for both response and relapse. With multiple and more potent therapeutic options now available, monitoring techniques can permit treatment to be tailored to the individual patient based on disease characteristics-for example, according to BCR-ABL mutation profile or to patient characteristics such as certain comorbid conditions. This approach should benefit patients by increasing the potential for better long-term outcomes.

Prognostic Significance of Treatment Response in CML in View of Current Recommendations for Treatment and Monitoring

The use of small-molecule kinase inhibitors has redefined the management of cancer. Chronic myelogenous leukaemia (CML) has become the paradigm for targeted cancer treatment. Imatinib has become the gold standard in the treatment of CML with excellent and durable responses and minimal side effects. Molecular diagnostics constitute an integral part of the routine monitoring. Results of cytogenetic analysis and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) indicate suboptimal response or treatment failure and guide treatment. New Abl kinase inhibitors such as nilotinib or dasatinib are options after the failure of or intolerance to imatinib, and both are available for first-line treatment of newly diagnosed CML. This review focuses on the prognostic significance of achieving a response at specific time points in patients with CML treated with imatinib, nilotinib or dasatinib in view of available data and current treatment recommendations.

Navigating the road toward optimal initial therapy for chronic myeloid leukemia

PURPOSE OF REVIEW

Tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of chronic myeloid leukemia (CML) and are now widely accepted as the initial therapy of choice in this disease, supplanting interferon and allogeneic stem cell transplantation. There are currently three drugs approved by the US Food and Drug Administration (FDA) for front-line treatment of CML: imatinib, nilotinib, and dasatinib. A fourth drug, bosutinib, may also win FDA approval in 2011. The goal of this review is to summarize the most recent information on initial treatment of CML and to aid clinicians in managing newly diagnosed CML patients.

RECENT FINDINGS

Phase III studies comparing imatinib with nilotinib or dasatinib in newly diagnosed CML were published in June 2010, leading to accelerated FDA approval for both of these 'second-generation' TKIs for initial therapy of CML. There are significant differences between the agents in terms of frequency and rate of responses, progression-free survival, and side-effects. However, the follow-up period on these trials is short, and there are as yet no significant differences in overall survival. Guidelines for monitoring CML patients on TKI therapy have been recently revised.

SUMMARY

Management of newly diagnosed CML patients in the coming decade will begin to resemble antibiotic treatment of infection, with therapy individualized based on patient risk factors, co-morbidities, and tolerability. In addition, the cost of therapy will emerge as an important consideration as generic imatinib becomes available in 2015. In this context, clinical trials to guide decision-making in newly diagnosed CML patients are needed.

Poor adherence is the main reason for loss of CCyR and imatinib failure for chronic myeloid leukemia patients on long-term therapy

We studied the relation between adherence to imatinib measured with microelectronic monitoring systems and the probabilities of losing a complete cytogenetic response (CCyR) and of imatinib failure in 87 CCyR chronic myeloid leukemia patients receiving long-term therapy. We included in our analysis the most relevant prognostic factors described to date. On multivariate analysis, the adherence rate and having failed to achieve a major molecular response were the only independent predictors for loss of CCyR and discontinuation of imatinib therapy. The 23 patients with an adherence rate less than or equal to 85% had a higher probability of losing their CCyR at 2 years (26.8% vs 1.5%, P = .0002) and a lower probability of remaining on imatinib (64.5% vs 90.6%, P = .006) than the 64 patients with an adherence rate more than 85%. In summary, we have shown that poor adherence is the principal factor contributing to the loss of cytogenetic responses and treatment failure in patients on long-term therapy.

Current status of imatinib as frontline therapy for chronic myeloid leukemia

Imatinib is remarkably effective in treating newly diagnosed patients with chronic myeloid leukemia (CML) in chronic phase. However, at 5 years more than one third of the patients have abandoned the medication on account of side effects, lack of efficacy, or progression. Here we review the current results with imatinib, the prognostic factors for response, and issues associated with long-term treatment with imatinib such as pregnancy, adherence to therapy, and complete molecular responses.

Front-line and salvage therapies with tyrosine kinase inhibitors and other treatments in chronic myeloid leukemia

Chronic myeloid leukemia (CML) has been a model disease in the development of targeted therapies. After nearly 40 years of the recognition of the chromosomal abnormality that defines CML, specific therapy was developed, initially with imatinib mesylate, which has transformed our treatment algorithms and has changed the natural history of the disease. Today, most patients have the expectation of a favorable outcome when treated with standard-dose imatinib. However, a significant proportion of patients do not achieve the optimal desirable outcome. Effective salvage therapy followed the recognition of some of the most common mechanisms of resistance. More recently, the focus has turned to new areas of research and medical need, such as improving the front-line therapy to minimize the risk of resistance, to fight the most resistant mutant forms of BCR-ABL, and to eliminate minimal residual disease with the goal of achieving total elimination of the disease and treatment discontinuation. In this review, we analyze the current status of therapy of CML, and we discuss some of the most relevant clinical questions that we face today.

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.

Improved outcome following allogeneic stem cell transplantation in chronic myeloid leukemia is associated with higher expression of BMI-1 and immune responses to BMI-1 protein

BMI-1 and EZH2 are polycomb group (PcG) proteins which maintain self-renewal of stem cells, and are overexpressed in leukemia. To investigate the potential of PcG proteins as leukemia-associated antigens, and targets for graft-versus-leukemia (GVL) effects, we studied cells from 86 chronic myeloid leukemia (CML) patients and 25 HLA-A*0201⁺ sibling donors collected prior to allogeneic stem cell transplantation (SCT). Although BMI-1 overexpression in CD34⁺ cells of CML patients treated with pharmacotherapy is associated with poor prognosis, we found, conversely, that in CML patients treated with SCT, a higher expression of BMI-1, and correspondingly lower expression of its target for repression, CDKN2A, is associated with improved leukemia-free survival. Cytotoxic T lymphocyte (CTL) responses to BMI-1 peptide were detected in 5 of 25 (20%) donors, and 8 of 19 (42%) HLA-A*0201⁺ CML patients. BMI-1 generated more total and high avidity immune responses, and was more immunogenic than EZH2. PcG-specific CTLs had memory phenotype, were readily expanded in short-term cultures, and were detected post-SCT in recipients of PcG-specific CTL-positive donors. A higher BMI-1 expression in CML CD34⁺ progenitors was associated with native BMI-1 immune responses. These immune responses to PcG proteins may target leukemia stem cells and have relevance for disease control by GVL.

Importance of monitoring and early switch to second generation tyrosine kinase inhibitors for the prognosis of patients with chronic myeloid leukemia with imatinib resistance or intolerance

Imatinib mesylate was the first BCR-ABL-target agent approved for the treatment of chronic myeloid leukemia. Although most patients respond well to imatinib therapy, the literature shows that one third develops resistance or intolerance. The timing of second-line treatment after failure of initial treatment may have a significant impact on long-term outcome. Thus, appropriate monitoring to identify resistance and/or intolerance is crucial to early intervention with second generation tyrosine kinase inhibitors and attainment of better results

Seeking the causes and solutions to imatinib-resistance in chronic myeloid leukemia

Although only 5000 new cases of chronic myeloid leukemia (CML) were seen in the United States in 2009, this neoplasm continues to make scientific headlines year-after-year. Advances in understanding the molecular pathogenesis coupled with exciting developments in both drug design and development, targeting the initiating tyrosine kinase, have kept CML in the scientific limelight for more than a decade. Indeed, imatinib, a small-molecule inhibitor of the leukemia-initiating Bcr-Abl tyrosine kinase, has quickly become the therapeutic standard for newly diagnosed chronic phase-CML (CP-CML) patients. Yet, nearly one-third of patients will still have an inferior response to imatinib, either failing to respond to primary therapy or demonstrating progression after an initial response. Significant efforts geared toward understanding the molecular mechanisms of imatinib resistance have yielded valuable insights into the cellular biology of drug trafficking, enzyme structure and function, and the rational design of novel small molecule enzyme inhibitors. Indeed, new classes of kinase inhibitors have recently been investigated in imatinib-resistant CML. Understanding the pathogenesis of tyrosine kinase inhibitor resistance and the molecular rationale for the development of second and now third generation therapies for patients with CML will be keys to further disease control over the next 10 years.

Molecular measurement of BCR-ABL transcript variations in chronic myeloid leukemia patients in cytogenetic remission

Background

The monitoring of BCR-ABL transcript levels by real-time quantitative polymerase chain reaction (RT-qPCR) has become important to assess minimal residual disease (MRD) and standard of care in the treatment of chronic myeloid leukemia (CML). In this study, we performed a prospective, sequential analysis using RT-qPCR monitoring of BCR-ABL gene rearrangements in blood samples from 91 CML patients in chronic phase (CP) who achieved complete cytogenetic remission (CCyR) and major molecular remission (MMR) throughout imatinib treatment.

Methods

The absolute level of BCR-ABL transcript from peripheral blood was serially measured every 4 to 12 weeks by RT-qPCR. Only level variations > 0.5%, according to the international scale, was considered positive. Sequential cytogenetic analysis was also performed in bone marrow samples from all patients using standard protocols.

Results

Based on sequential analysis of BCR-ABL transcripts, the 91 patients were divided into three categories: (A) 57 (62.6%) had no variation on sequential analysis; (B) 30 (32.9%) had a single positive variation result obtained in a single sample; and (C) 4 (4.39%) had variations of BCR-ABL transcripts in at least two consecutive samples. Of the 34 patients who had elevated levels of transcripts (group B and C), 19 (55.8%) had a < 1% of BCR-ABL/BCR ratio, 13 (38.2%) patients had a 1% to 10% increase and 2 patients had a >10% increase of RT-qPCR. The last two patients had lost a CCyR, and none of them showed mutations in the ABL gene. Transient cytogenetic alterations in Ph-negative cells were observed in five (5.5%) patients, and none of whom lost CCyR.

Conclusions

Despite an increase levels of BCR-ABL/BCR ratio variations by RT-qPCR, the majority of CML patients with MMR remained in CCyR. Thus, such single variations should neither be considered predictive of subsequent failure and nor an indication for altering imatinib dose or switching to second generation therapy. Changing of imatinib on the basis of BCR-ABL/BCR% sustained increase and mutational studies is a prudent approach for preserving other therapeutic options in imatinib-resistant patients.

The European LeukemiaNet: achievements and perspectives

The only way to cure leukemia is by cooperative research. To optimize research, the European LeukemiaNet integrates 105 national leukemia trial groups and networks, 105 interdisciplinary partner groups and about 1,000 leukemia specialists from 175 institutions. They care for tens of thousands of leukemia patients in 33 countries across Europe. Their ultimate goal is to cure leukemia. Since its inception in 2002, the European LeukemiaNet has steadily expanded and has unified leukemia research across Europe. The European LeukemiaNet grew from two major roots: 1) the German Competence Network on Acute and Chronic Leukemias; and 2) the collaboration of European Investigators on Chronic Myeloid Leukemia. The European LeukemiaNet has improved leukemia research and management across Europe. Its concept has led to funding by the European Commission as a network of excellence. Other sources (European Science Foundation; European LeukemiaNet-Foundation) will take over when the support of the European Commission ends.

OCT-1 function varies with cell lineage but is not influenced by BCR-ABL

BACKGROUND

Despite the excellent responses to imatinib therapy observed in patients with chronic phase chronic myeloid leukemia, approximately 25% of patients display primary resistance or suboptimal response. The OCT-1 activity in mononuclear cells reflects the efficiency of active influx of imatinib. OCT-1 activity in mononuclear cells is highly variable between patients and significantly correlates with a patient's molecular response to imatinib treatment and overall survival. The present study examined whether cell lineage and BCR-ABL expression influenced OCT-1 activity.

DESIGN AND METHODS

The OCT-1 activity and OCT-1 mRNA expression was assessed in pure populations of neutrophils, monocytes and lymphocytes recovered from chronic myeloid leukemia patients at diagnosis, in cytogenetic remission and normal individuals. The role of BCR-ABL on OCT-1 activity and differentiation was examined in a cell line model of ectopic BCR-ABL expression.

RESULTS

The OCT-1 activity and OCT-1 mRNA expression was highest in the neutrophil population and lowest in lymphocytes (P<0.05). This was observed for patients at diagnosis, in cytogenetic remission and normal individuals. Interestingly, neutrophil OCT-1 activity was not significantly different between patients at diagnosis, in remission and normal donors. This was also observed for monocytes and lymphocytes. Furthermore, OCT-1 activity in mononuclear cells was significantly correlated with the OCT-1 activity in neutrophils (P=0.001). In a cell line model in which BCR-ABL was ectopically expressed, we found no evidence that BCR-ABL directly affected OCT-1 expression and function. However, BCR-ABL stimulated granulocyte differentiation which, in turn, led to significantly increased OCT-1 activity (P=0.024).

CONCLUSIONS

These studies suggest that the predictive OCT-1 activity in patient mononuclear cells is strongly related to cell lineage, particularly the presence of neutrophils in the peripheral blood. Furthermore, BCR-ABL expression is unlikely to directly influence OCT-1 activity but may have an indirect role by enhancing granulocyte differentiation.

Three decades of transplantation for chronic myeloid leukemia: what have we learned?

Last year marked 30 years of hematopoietic stem cell transplantation as a curative treatment of chronic myeloid leukemia (CML). Initially studies used stem cells from identical twins but techniques rapidly developed to use cells first from HLA-identical siblings and later unrelated donors. During the 1990s CML became the most frequent indication for allogeneic transplantation worldwide. This, together with the relative biologic homogeneity of CML in chronic phase, its responsiveness to graft-versus-leukemia effect and the ability to monitor low level residual disease placed CML at the forefront of research into different strategies of stem cell transplantation. The introduction of BCR-ABL1 tyrosine kinase inhibitors during the last decade resulted in long-term disease control in the majority of patients with CML. In those who fail to respond and/or develop intolerance to these agents, transplantation remains an effective therapeutic solution. The combination of tyrosine kinase inhibitors with transplantation is an exciting new strategy and it provides inspiration for similar approaches in other malignancies.

Monitoring molecular response in chronic myeloid leukemia

Before the advent of tyrosine kinase inhibitor (TKI) therapy, the evaluation of hematologic and cytogenetic responses was sufficient to gauge treatment efficacy in patients with chronic myeloid leukemia. However, with more potent TKI therapies, the majority of patients achieve complete cytogenetic response. Furthermore, deeper molecular responses are now commonly achieved, necessitating a reliance on molecular monitoring to assess residual leukemic disease. The prognostic significance between molecular responses and duration of complete cytogenetic response, progression-free survival, and event-free survival is described herein. A discussion of the concept of complete molecular response is also provided, and the potential for imatinib treatment discontinuation is evaluated. The implications of rising BCR-ABL1 transcript levels and caveats of molecular monitoring are also described.

Chronic myeloid leukemia and second-generation tyrosine kinase inhibitors: when, how, and which one?

Chronic myeloid leukemia (CML) is a progressive and often fatal myeloproliferative disorder. The introduction of imatinib, a tyrosine kinase inhibitor (TKI) specific for BCR-ABL, was a major breakthrough in CML therapy. Although most patients respond to first-line imatinib therapy, some experience a loss of response (resistance) or require treatment discontinuation due to toxicity (intolerance). For patients who fail with standard-dose imatinib therapy, imatinib dose escalation is a second-line option. However, high-dose imatinib is not an appropriate approach for patients experiencing drug toxicity, and there remain questions over the durability of responses achieved with this strategy. Alternative second-line options include the newer TKIs dasatinib and nilotinib. A substantial amount of long-term data for these agents is available. Although both are potent and specific BCR-ABL TKIs, dasatinib and nilotinib exhibit unique pharmacological profiles and response patterns relative to different patient characteristics, such as disease stage and BCR-ABL mutational status. To optimize therapeutic benefit, clinicians should select treatment based on each patient's historical response, adverse-event tolerance level, and risk factors.

"Real-life" results of front-line treatment with Imatinib in older patients (≥ 65 years) with newly diagnosed chronic myelogenous leukemia

The age role was evaluated in 117 consecutive patients with newly diagnosed CML at our Institution treated with front-line Imatinib from 9/02 to 3/08. Forty patients (34.1%) aged ≥ 65 years and 77 (65.9%) <65 years. Thirty-four older patients (85%) had at least 1 comorbidity versus 39 younger patients (50.6%) (p<0.001). Complete cytogenetic response (CCyR) was achieved in 34/40 older patients (85%) as compared to 69/77 younger patients (89.6%), without statistically significant differences. Severe (grades 3-4 WHO) hematological and extra-hematological toxicities were more common in older patients (p=0.02 and p=0.017, respectively). Rates of permanent Imatinib discontinuation and dose reduction to 300 mg or less were significantly higher in older patients (p=0.009 and p=0.001, respectively). In conclusion, Imatinib in older patients with newly diagnosed CML seems to have the same efficacy as in younger patients, but tends to be more toxic, leading to higher rates of discontinuation and dose reduction. To overcome this problem, future trials concerning best dosage in this subset of patients could be useful.

Long-term prognostic significance of early molecular response to imatinib in newly diagnosed chronic myeloid leukemia: an analysis from the International Randomized Study of Interferon and STI571 (IRIS)

This study examines the prognostic significance of early molecular response using an expanded dataset in chronic myeloid leukemia patients enrolled in the International Randomized Study of Interferon and STI571 (IRIS). Serial molecular studies demonstrate decreases in BCR-ABL transcripts over time. Analyses of event-free survival (EFS) and time to progression to accelerated phase/blast crisis (AP/BC) at 7 years were based on molecular responses using the international scale (IS) at 6-, 12-, and 18-month landmarks. Patients with BCR-ABL transcripts > 10% at 6 months and > 1% at 12 months had inferior EFS and higher rate of progression to AP/BC compared with all other molecular response groups. Conversely, patients who achieved major molecular response [MMR: BCR-ABL (IS) ≤ 0.1%] by 18 months enjoyed remarkably durable responses, with no progression to AP/BC and 95% EFS at 7 years. The probability of loss of complete cytogenetic response by 7 years was only 3% for patients in MMR at 18 months versus 26% for patients with complete cytogenetic response but not MMR (P < .001). This study shows a strong association between the degree to which BCR-ABL transcript numbers are reduced by therapy and long-term clinical outcome, supporting the use of time-dependent molecular measures to determine optimal response to therapy. This study is registered at www.clinicaltrials.gov as NCT00006343.

The poor response to imatinib observed in CML patients with low OCT-1 activity is not attributable to lower uptake of imatinib into their CD34+ cells

The functional activity of the organic cation transporter 1 (OCT-1) protein in chronic myeloid leukemia (CML) mononuclear cells (MNCs) is highly predictive of molecular response in imatinib treated patients. Here we investigate whether the MNC OCT-1 activity (OA) provides a surrogate indicator of effective targeting of the more immature CD34(+) cells. While confirming our previous findings that high MNC OA is significantly associated with the achievement of major molecular response (MMR; P = .017), the present studies found no relationship between high CD34(+) OA and the achievement of MMR. Furthermore, no correlation was found between the MNC OA and the CD34(+) OA in matched CML samples. These results suggest that the predictive value of the MNC OA may primarily reflect the effective targeting and subsequent reduction of mature CML cells. Therefore kinase inhibition in these mature cells, and not the CD34(+) cells, may be the key determinant of response in CML.