Long-Term Outcomes of Imatinib Treatment for Chronic Myeloid Leukemia.

BACKGROUND: Imatinib, a selective BCR-ABL1 kinase inhibitor, improved the prognosis for patients with chronic myeloid leukemia (CML). We conducted efficacy and safety analyses on the basis of more than 10 years of follow-up in patients with CML who were treated with imatinib as initial therapy. METHODS: In this open-label, multicenter trial with crossover design, we randomly assigned patients with newly diagnosed CML in the chronic phase to receive either imatinib or interferon alfa plus cytarabine. Long-term analyses included overall survival, response to treatment, and serious adverse events. RESULTS: The median follow-up was 10.9 years. Given the high rate of crossover among patients who had been randomly assigned to receive interferon alfa plus cytarabine (65.6%) and the short duration of therapy before crossover in these patients (median, 0.8 years), the current analyses focused on patients who had been randomly assigned to receive imatinib. Among the patients in the imatinib group, the estimated overall survival rate at 10 years was 83.3%. Approximately half the patients (48.3%) who had been randomly assigned to imatinib completed study treatment with imatinib, and 82.8% had a complete cytogenetic response. Serious adverse events that were considered by the investigators to be related to imatinib were uncommon and most frequently occurred during the first year of treatment. CONCLUSIONS: Almost 11 years of follow-up showed that the efficacy of imatinib persisted over time and that long-term administration of imatinib was not associated with unacceptable cumulative or late toxic effects. (Funded by Novartis Pharmaceuticals; IRIS ClinicalTrials.gov numbers, NCT00006343 and NCT00333840 .).

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.

A gene expression signature of CD34+ cells to predict major cytogenetic response in chronic-phase chronic myeloid leukemia patients treated with imatinib.

In chronic-phase chronic myeloid leukemia (CML) patients, the lack of a major cytogenetic response (< 36% Ph(+) metaphases) to imatinib within 12 months indicates failure and mandates a change of therapy. To identify biomarkers predictive of imatinib failure, we performed gene expression array profiling of CD34(+) cells from 2 independent cohorts of imatinib-naive chronic-phase CML patients. The learning set consisted of retrospectively selected patients with a complete cytogenetic response or more than 65% Ph(+) metaphases within 12 months of imatinib therapy. Based on analysis of variance P less than .1 and fold difference 1.5 or more, we identified 885 probe sets with differential expression between responders and nonresponders, from which we extracted a 75-probe set minimal signature (classifier) that separated the 2 groups. On application to a prospectively accrued validation set, the classifier correctly predicted 88% of responders and 83% of nonresponders. Bioinformatics analysis and comparison with published studies revealed overlap of classifier genes with CML progression signatures and implicated beta-catenin in their regulation, suggesting that chronic-phase CML patients destined to fail imatinib have more advanced disease than evident by morphologic criteria. Our classifier may allow directing more aggressive therapy upfront to the patients most likely to benefit while sparing good-risk patients from unnecessary toxicity.

Impact of genomic risk factors on outcome after hematopoietic stem cell transplantation for patients with chronic myeloid leukemia.

BACKGROUND: Non-HLA gene polymorphisms have been shown to influence outcome after allogeneic hematopoietic stem cell transplantation. Results were derived from heterogeneous, small populations and their value remains a matter of debate. DESIGN AND METHODS: In this study, we assessed the effect of single nucleotide polymorphisms in genes for interleukin 1 receptor antagonist (IL1RN), interleukin 4 (IL4), interleukin 6 (IL6), interleukin 10 (IL10), interferon (IFNG), tumor necrosis factor (TNF) and the cell surface receptors tumor necrosis factor receptor II (TNFRSFIB), vitamin D receptor (VDR) and estrogen receptor alpha (ESR1) in a homogeneous cohort of 228 HLA identical sibling transplants for chronic myeloid leukemia. Three good predictors of overall survival, identified via statistical methods including Cox regression analysis, were investigated for their effects on transplant-related mortality and relapse. Predictive power was assessed after integration into the established European Group for Blood and Marrow Transplantation (EBMT) risk score. RESULTS: Absence of patient TNFRSFIB 196R, absence of donor IL10 ATA/ACC and presence of donor IL1RN allele 2 genotypes were associated with increased transplantation-related mortality and decreased survival. Application of prediction error and concordance index statistics gave evidence that integration improved the EBMT risk score. CONCLUSIONS: Non-HLA genotypes were associated with survival after allogeneic hematopoietic stem cell transplantation. When three genetic polymorphisms were added into the EBMT risk model they improved the goodness of fit. Non-HLA genotyping could, therefore, be used to improve donor selection algorithms and risk assessment prior to allogeneic hematopoietic stem cell transplantation.

Five-year follow-up of patients receiving imatinib for chronic myeloid leukemia.

BACKGROUND: The cause of chronic myeloid leukemia (CML) is a constitutively active BCR-ABL tyrosine kinase. Imatinib inhibits this kinase, and in a short-term study was superior to interferon alfa plus cytarabine for newly diagnosed CML in the chronic phase. For 5 years, we followed patients with CML who received imatinib as initial therapy. METHODS: We randomly assigned 553 patients to receive imatinib and 553 to receive interferon alfa plus cytarabine and then evaluated them for overall and event-free survival; progression to accelerated-phase CML or blast crisis; hematologic, cytogenetic, and molecular responses; and adverse events. RESULTS: The median follow-up was 60 months. Kaplan-Meier estimates of cumulative best rates of complete cytogenetic response among patients receiving imatinib were 69% by 12 months and 87% by 60 months. An estimated 7% of patients progressed to accelerated-phase CML or blast crisis, and the estimated overall survival of patients who received imatinib as initial therapy was 89% at 60 months. Patients who had a complete cytogenetic response or in whom levels of BCR-ABL transcripts had fallen by at least 3 log had a significantly lower risk of disease progression than did patients without a complete cytogenetic response (P<0.001). Grade 3 or 4 adverse events diminished over time, and there was no clinically significant change in the profile of adverse events. CONCLUSIONS: After 5 years of follow-up, continuous treatment of chronic-phase CML with imatinib as initial therapy was found to induce durable responses in a high proportion of patients. (ClinicalTrials.gov number, NCT00006343 [ClinicalTrials.gov].)

High rates of durable response are achieved with imatinib after treatment with interferon alpha plus cytarabine: results from the International Randomized Study of Interferon and STI571 (IRIS) trial.

BACKGROUND: Imatinib is the standard of care for newly diagnosed chronic-phase chronic myeloid leukemia. The largest randomized clinical trial of imatinib was the multinational IRIS trial in which 1106 patients were randomized to receive either imatinib 400 mg/day or a standard regimen of interferon-alpha plus cytarabine. DESIGN AND METHODS: Patients were allowed to cross over to the opposite treatment for intolerance, lack of response, disease progression, and, following release of the initial efficacy data, reluctance to remain on therapy with interferon-alpha plus cytarabine. The safety and efficacy of imatinib in patients who crossed over from interferon-alpha plus cytarabine to imatinib is reported here. RESULTS: Of 553 patients originally assigned to interferon-alpha plus cytarabine, 65% crossed over to imatinib, of whom 67% continue to receive treatment. After a median of 54 months of imatinib treatment on study, 93% achieved complete hematologic remission, 86% achieved major cytogenetic remission, and 81% achieved a complete cytogenetic remission as the best observed response. Estimated rates of freedom from progression to accelerated or blast phase and overall survival were 91% and 89%, respectively, at 48 months after starting imatinib. CONCLUSIONS: This is the largest analysis to date describing the efficacy of imatinib in patients who have received prior therapies for chronic myeloid leukemia and it demonstrates excellent responses to this treatment. (ClinicalTrials.gov identifier: NCT00006343).

De-escalation of tyrosine kinase inhibitor therapy before complete treatment discontinuation in patients with chronic myeloid leukaemia (DESTINY): a non-randomised, phase 2 trial.

BACKGROUND: All studies of treatment-free remission (TFR) in patients with chronic myeloid leukaemia have discontinued tyrosine kinase inhibitor (TKI) treatment abruptly and have focussed on patients with stable MR4 (BCR-ABL to ABL ratio ≤0·01%). We aimed to examine the effects of gradual treatment withdrawal and whether TFR is feasible for patients with less deep but stable remission. METHODS: The De-Escalation and Stopping Treatment with Imatinib, Nilotinib, or sprYcel (DESTINY) study is a non-randomised, phase 2 trial undertaken at 20 UK hospitals. We recruited patients (aged ≥18 years) with chronic myeloid leukaemia in first chronic phase, who had received TKI therapy for 3 years or more, with three or more BCR-ABL quantitative PCR transcript measurements (BCR-ABL to ABL1 ratio) less than 0·1% (major molecular response [MMR]) in the 12 months before entry. Patients with all PCR measurements less than 0·01% were assigned to the MR4 group. Patients with results between 0·1% and 0·01% were allocated to the MMR group. TKI treatment was de-escalated to half the standard dose for 12 months, then stopped for a further 24 months, with frequent PCR monitoring. Recurrence was defined as the first of two consecutive samples with PCR measurement greater than 0·1%, which required treatment recommencement at full dose. The primary endpoint was the proportion of patients who could first de-escalate their treatment for 12 months, and then stop treatment completely for a further 2 years, without losing MMR. Analysis was by intention to treat. This study is registered with ClinicalTrials.gov, number NCT01804985. FINDINGS: Treatment at entry was imatinib (n=148), nilotinib (n=16), or dasatinib (n=10), for a median of 6·9 years (IQR 4·8-10·2). Between Dec 16, 2013, and May 6, 2015, we enrolled 49 patients into the MMR group and 125 into the MR4 group. In the MR4 group, 84 (67%) patients reached the 36-month trial completion point and recurrence-free survival was 72% (95% CI 64-80). In the MMR group, 16 (33%) entrants completed the study and recurrence-free survival was 36% (25-53). No disease progression was seen and two deaths occurred due to unrelated causes. All recurrences regained MMR within 5 months of treatment resumption. INTERPRETATION: Initial de-escalation before discontinuation might improve the success of TFR protocols, although the mechanism of its benefit is not yet clear. The findings also suggest that TFR merits further study in patients with stable MMR. FUNDING: Newcastle University and Bloodwise.

Pharmacokinetic investigation of imatinib using accelerator mass spectrometry in patients with chronic myeloid leukemia.

PURPOSE: To investigate the potential use of accelerator mass spectrometry (AMS) in the study of the clinical pharmacology of imatinib. EXPERIMENTAL DESIGN: Six patients who were receiving imatinib (400 mg/d) as part of their ongoing treatment for chronic myeloid leukemia (CML) received a dose containing a trace quantity (13.6 kBq) of (14)C-imatinib. Blood samples were collected from patients before and at various times up to 72 h after administration of the test dose and were processed to provide samples of plasma and peripheral blood lymphocytes (PBL). Samples were analyzed by AMS, with chromatographic separation of parent compound from metabolites. In addition, plasma samples were analyzed by liquid chromatography/mass spectrometry (LCMS). RESULTS: Analysis of the AMS data indicated that imatinib was rapidly absorbed and could be detected in plasma up to 72 h after administration. Imatinib was also detectable in PBL at 24 h after administration of the (14)C-labeled dose. Comparison of plasma concentrations determined by AMS with those derived by LCMS analysis gave similar average estimates of area under plasma concentration time curve (26 +/- 3 versus 27 +/- 11 microg/mL.h), but with some variation within each individual. CONCLUSIONS: Using this technique, data were obtained in a small number of patients on the pharmacokinetics of a single dose of imatinib in the context of chronic dosing, which could shed light on possible pharmacologic causes of resistance to imatinib in CML.

Imatinib compared with interferon and low-dose cytarabine for newly diagnosed chronic-phase chronic myeloid leukemia.

BACKGROUND: Imatinib, a selective inhibitor of the BCR-ABL tyrosine kinase, produces high response rates in patients with chronic-phase chronic myeloid leukemia (CML) who have had no response to interferon alfa. We compared the efficacy of imatinib with that of interferon alfa combined with low-dose cytarabine in newly diagnosed chronic-phase CML. METHODS: We randomly assigned 1106 patients to receive imatinib (553 patients) or interferon alfa plus low-dose cytarabine (553 patients). Crossover to the alternative group was allowed if stringent criteria defining treatment failure or intolerance were met. Patients were evaluated for hematologic and cytogenetic responses, toxic effects, and rates of progression. RESULTS: After a median follow-up of 19 months, the estimated rate of a major cytogenetic response (0 to 35 percent of cells in metaphase positive for the Philadelphia chromosome) at 18 months was 87.1 percent (95 percent confidence interval, 84.1 to 90.0) in the imatinib group and 34.7 percent (95 percent confidence interval, 29.3 to 40.0) in the group given interferon alfa plus cytarabine (P<0.001). The estimated rates of complete cytogenetic response were 76.2 percent (95 percent confidence interval, 72.5 to 79.9) and 14.5 percent (95 percent confidence interval, 10.5 to 18.5), respectively (P<0.001). At 18 months, the estimated rate of freedom from progression to accelerated-phase or blast-crisis CML was 96.7 percent in the imatinib group and 91.5 percent in the combination-therapy group (P<0.001). Imatinib was better tolerated than combination therapy. CONCLUSIONS: In terms of hematologic and cytogenetic responses, tolerability, and the likelihood of progression to accelerated-phase or blast-crisis CML, imatinib was superior to interferon alfa plus low-dose cytarabine as first-line therapy in newly diagnosed chronic-phase CML.

Hematologic and cytogenetic responses to imatinib mesylate in chronic myelogenous leukemia.

BACKGROUND: Chronic myelogenous leukemia (CML) is caused by the BCR-ABL tyrosine kinase, the product of the Philadelphia chromosome. Imatinib mesylate, formerly STI571, is a selective inhibitor of this kinase. METHODS: A total of 532 patients with late--chronic-phase CML in whom previous therapy with interferon alfa had failed were treated with 400 mg of oral imatinib daily. Patients were evaluated for cytogenetic and hematologic responses. Time to progression, survival, and toxic effects were also evaluated. RESULTS: Imatinib induced major cytogenetic responses in 60 percent of the 454 patients with confirmed chronic-phase CML and complete hematologic responses in 95 percent. After a median follow-up of 18 months, CML had not progressed to the accelerated or blast phases in an estimated 89 percent of patients, and 95 percent of the patients were alive. Grade 3 or 4 nonhematologic toxic effects were infrequent, and hematologic toxic effects were manageable. Only 2 percent of patients discontinued treatment because of drug-related adverse events, and no treatment-related deaths occurred. CONCLUSIONS: Imatinib induced high rates of cytogenetic and hematologic responses in patients with chronic-phase CML in whom previous interferon therapy had failed.

De-escalation of tyrosine kinase inhibitor dose in patients with chronic myeloid leukaemia with stable major molecular response (DESTINY): an interim analysis of a non-randomised, phase 2 trial.

BACKGROUND: Discontinuation of tyrosine kinase inhibitor (TKI) therapy is feasible for some patients with chronic myeloid leukaemia with deep molecular responses; however, patients with stable major molecular response (MMR), but not MR4, have not been studied, nor has the effect of treatment de-escalation rather than outright cessation. We aimed to examine the effects of treatment de-escalation as a prelude to complete cessation, not only in patients with MR4 or greater, but also in those with MMR but not MR4. METHODS: We did this interim analysis of a non-randomised, phase 2 trial at 20 hospitals in the UK. We recruited patients (aged ≥18 years) with chronic myeloid leukaemia in first chronic phase who had received TKI for 3 years or more and were either in stable MR4 (BCR-ABL1:ABL1 ratio <0·01%; MR4 cohort) or in stable MMR (BCR-ABL1:ABL1 ratio consistently <0·1%) but not MR4 (MMR cohort) for 12 months or longer. Participants received half their standard TKI dose (imatinib 200 mg daily, dasatinib 50 mg daily, or nilotinib 200 mg twice daily) for 12 months. Molecular recurrence was defined as loss of MMR (BCR-ABL1:ABL1 ratio >0·1%) on two consecutive samples. The primary endpoint of this interim analysis was the proportion of patients who lost MMR on de-escalation and regained MMR on TKI resumption. Analyses were by intention to treat. This study is registered with ClinicalTrials.gov, number NCT01804985. FINDINGS: Between Dec 16, 2013 and April 10, 2015, we enrolled 174 patients into the MMR cohort (n=49) or the MR4 cohort (n=125). During the 12 months of half-dose therapy, 12 patients (7%) had molecular recurrence, all of whom regained MMR within 4 months of full-dose TKI resumption (median time to recovery 77 days). Recurrence was significantly lower in the MR4 cohort (three [2%; 90% CI 0·2-4·8] of 121 evaluable patients) than in the MMR cohort (nine [19%; 90% CI 9·5-28·0] of 48 evaluable patients; hazard ratio 0·12, 90% CI 0·04-0·37; p=0·0007), but was unrelated to previous TKI or TKI therapy duration. Adverse events (eg, lethargy, diarrhoea, rash, and nausea) improved during the first 3 months of de-escalation, though not thereafter. 16 serious adverse events were reported, including one fatality due to worsening pre-existing peripheral arterial occlusive disease in a patient who had received only imatinib. INTERPRETATION: TKI de-escalation is safe for most patients with excellent responses to TKI therapy, and is associated with improvement in symptoms. These findings show that lower TKI doses might maintain responses in these patients, implying that such patients could be unnecessarily overtreated. Studies of more ambitious de-escalation are warranted. FUNDING: Newcastle University and Bloodwise.

Practical management of patients with chronic myeloid leukemia receiving imatinib.

The introduction of imatinib, a specific inhibitor of the Bcr-Abl tyrosine kinase, has dramatically changed the management of chronic myeloid leukemia (CML). More than 10,000 patients worldwide have been treated with imatinib in clinical trials, and a large body of information has accumulated about the use of this drug. The purpose of this article is to review practical guidelines in regard to optimal dosing, monitoring, managing common side effects such as myelosuppression, and potential drug interactions. The treatment recommendations are intended to optimize therapy with imatinib while taking into account a patient's specific circumstances.

Quality of life in patients with newly diagnosed chronic phase chronic myeloid leukemia on imatinib versus interferon alfa plus low-dose cytarabine: results from the IRIS Study.

PURPOSE: Quality of life (QOL) outcomes in patients with chronic myeloid leukemia (CML) were evaluated in an international phase III study. PATIENTS AND METHODS: Newly diagnosed patients with chronic phase CML were randomly assigned to imatinib or interferon alfa plus subcutaneous low-dose cytarabine (IFN+LDAC). Cross-over to the other treatment was permitted because of intolerance or lack of efficacy. Patients completed cancer-specific QOL (Functional Assessment of Cancer Therapy-Biologic Response Modifiers) and utility (Euro QoL-5D) questionnaires at baseline and during treatment (n = 1,049). The primary QOL end point was the Trial Outcome Index (TOI; a measure of physical function and well-being). Secondary end points included social and family well-being (SFWB), emotional well-being (EWB), and the utility score. Primary analyses were intention to treat with secondary analyses accounting for cross-over. RESULTS: Patients receiving IFN+LDAC experienced a large decline in the TOI, whereas those receiving imatinib maintained their baseline level. Treatment differences at each visit were significant (P <.001) and clinically relevant in favor of imatinib. Mean SFWB, EWB, and utility scores were also significantly better for those patients taking imatinib. Patients who crossed over to imatinib experienced a large increase in TOI; significant (P <.001) differences were observed between patients who did and did not cross over in favor of imatinib. CONCLUSION: Imatinib offers clear QOL advantages compared with IFN+LDAC as first-line treatment of chronic phase CML. In addition, patients who cross over to imatinib from IFN+LDAC experience a significant improvement in QOL compared with patients who continue to take IFN+LDAC.

Imatinib in patients with newly diagnosed chronic-phase chronic myeloid leukemia.

The International Randomized Study of Interferon and STI571 (IRIS) study prospectively compared imatinib with interferon-alpha/low-dose cytarabine (IFN/LDAC) in 1,106 newly diagnosed patients with Philadelphia chromosome-positive chronic myeloid leukemia (CML). Patients not responding to or intolerant of their assigned treatment were allowed to cross over. At 18 months, the projected probability of achieving a complete cytogenetic response was 76.2% for imatinib and 14.5% for IFN/LDAC, respectively (P <.01). Freedom from progression to accelerated phase or blast crisis was 96.7% for imatinib versus 91.5% for IFN/LDAC (P <.01). At the time of the analysis, 85.7% of imatinib-treated patients continued on first-line therapy, but only 10.8% of patients continued with IFN/LDAC. Most cross-overs to imatinib were due to interferon-intolerance. Overall survival was not different in the two groups at 19 months, reflecting efficient rescue of IFN/LDAC failures with imatinib. Imatinib should now be considered the standard therapy for newly diagnosed patients with CML.

Imatinib therapy in chronic myeloid leukemia.

This article briefly recaps the key clinical trials that involve imatinib and focuses on the ongoing results and implications of these studies for future research in imatinib-based therapy in chronic myeloid leukemia (CML). Imatinib by no means has replaced allografting in the treatment of CML, although clearly, there has been a radical shift in thinking in considering which patients should undergo transplant. The route to cure with minimal toxicity may involve creative use of drug and transplant technologies.

Efficacy of imatinib dose escalation in patients with chronic myeloid leukemia in chronic phase.

BACKGROUND: Imatinib mesylate given orally at a daily dose of 400 mg is the standard of care as initial therapy for patients with chronic myeloid leukemia (CML) in chronic phase (CML-CP). Treatment guidelines propose dose escalation based on clinical assessments of disease response. METHODS: Response and survival were analyzed in a cohort of patients (n = 106) with newly diagnosed CML-CP who were enrolled on the International Randomized Study of Interferon and STI571 (IRIS) trial, who began treatment with imatinib at a dose of 400 mg daily, and who subsequently underwent dose escalation to either 600 mg or 800 mg daily. Reasons for dose escalation were evaluated retrospectively based on 2 sets of criteria: the IRIS protocol-defined criteria (n = 39 patients) and the European LeukemiaNet (ELN) recommendations (n = 48 patients). RESULTS: Among all 106 patients who underwent dose escalation, the rates of freedom from progression to accelerated phase or blast phase and overall survival were 89% and 84% at 3 years after dose increase, respectively. A cytogenetic response was obtained in 42% of patients who had their dose escalated based on protocol criteria and in 38% of patients who had their dose escalated according to the ELN recommendations. CONCLUSIONS: The results from this retrospective analysis supported imatinib dose escalation as an appropriate initial option for patients with CML-CP who were experiencing suboptimal cytogenetic response or resistance.

Imatinib pharmacokinetics and its correlation with response and safety in chronic-phase chronic myeloid leukemia: a subanalysis of the IRIS study.

Imatinib at 400 mg daily is standard treatment for chronic myeloid leukemia in chronic phase. We here describe the correlation of imatinib trough plasma concentrations (C(mins)) with clinical responses, event-free survival (EFS), and adverse events (AEs). Trough level plasma samples were obtained on day 29 (steady state, n = 351). Plasma concentrations of imatinib and its metabolite CGP74588 were determined by liquid chromatography/mass spectrometry. The overall mean (+/- SD, CV%) steady-state C(min) for imatinib and CGP74588 were 979 ng/mL (+/- 530 ng/mL, 54.1%) and 242 ng/mL (+/- 106 ng/mL, 43.6%), respectively. Cumulative estimated complete cytogenetic response (CCyR) and major molecular response (MMR) rates differed among the quartiles of imatinib trough levels (P = .01 for CCyR, P = .02 for MMR). C(min) of imatinib was significantly higher in patients who achieved CCyR (1009 +/- 544 ng/mL vs 812 +/- 409 ng/mL, P = .01). Patients with high imatinib exposure had better rates of CCyR and MMR and EFS. An exploratory analysis demonstrated that imatinib trough levels were predictive of higher CCyR independently of Sokal risk group. AE rates were similar among the imatinib quartile categories except fluid retention, rash, myalgia, and anemia, which were more common at higher imatinib concentrations. These results suggest that an adequate plasma concentration of imatinib is important for a good clinical response. This study is registered at http://clinicaltrials.gov as NCT00333840.

Favorable long-term follow-up results over 6 years for response, survival, and safety with imatinib mesylate therapy in chronic-phase chronic myeloid leukemia after failure of interferon-alpha treatment.

Imatinib mesylate, a targeted inhibitor of BCR-ABL tyrosine kinase, is the standard of care for chronic myeloid leukemia (CML). A phase 2 trial of imatinib in late chronic-phase (CP) CML after interferon-alpha (IFNalpha) failure enrolled 532 patients, 454 with a confirmed diagnosis of CP CML. Median time from diagnosis was 34 months; median duration of imatinib treatment was 65 months. Cumulative best rates of major cytogenetic response (MCyR) and complete cytogenetic response (CCyR) were 67% and 57%, respectively. At the 5-year landmark, 184 (41%) of the 454 patients are in CCyR. At more than 6 years, 199 (44%) of the 454 patients remain on imatinib. Most responses occurred within 12 months of starting imatinib; however, some patients achieved initial MCyR and CCyR more than 5 years after imatinib initiation. Estimated rates of freedom from progression to accelerated phase (AP) and blastic phase (BP) and overall survival at 6 years were 61% and 76%, respectively. Both freedom from progression to AP/BP and overall survival (OS) were associated with cytogenetic response level at 12 months. No increase in rates of serious adverse events was observed with continuous use of imatinib for up to 6.5 years, compared with earlier time points. Imatinib continues to be an effective and safe therapy for patients with CP CML after failure of IFN.