Molecular monitoring of response to imatinib (Glivec) in CML patients pretreated with interferon alpha. Low levels of residual disease are associated with continuous remission

Assessment of molecular response to tyrosine kinase inhibitors in Tunisian Patients with Chronic Myeloid Leukemia

AIM

This study was carried out to assess the minimal residual disease in Tunisian patients with chronic myeloid leukemia (CML) treated with tyrosine kinase inhibitors in routine clinical practice, to recognize potentially eligible carrier for treatment discontinuation, based on a molecular response (MR).

PATIENTS AND METHODS

A retrospective study was carried out in the Hospital University of Sfax, south of Tunisia from January 2016 to October 2020, including all CML patients in the chronic phase at diagnosis, treated with TKI (tyrosine kinase inhibitors) for a minimum duration of 6 months. Quantitative assessment of the BCR-ABL transcript was performed using the Cepheid Xpert BCR-ABL ultra-assay. Molecular response and outcome were evaluated, according to the European Leukemia Net guidelines.

RESULTS

A total of 162 CML patients were carried out. The median age was 50 years, the sex ratio M/F was 1.62. The rate of cumulative EMR; MMR and DMR was 80.8%; 73.8% and 55.9% respectively. According to the ELN criteria, 141 CML patients were evaluable. Optimal, suboptimal response and failure were noted in 81 (57.4%), 33(23.4%), and 27(19.1%) patients, respectively. Overall survival (OS) and progression-free survival (PFS) were 96.3% and 85%. Risk factors for an event (death/progression) were lack of EMR, MMR, and DMR (P < 0.05). Among 149 patients with sustained DMR; 14 (8.6%) CML patients have discontinued TKI therapy.

CONCLUSION

Despite the limit of our study (duration and size), the available real-life molecular responses with TKI therapy should be considered to identify potentially CML patients eligible for discontinuation of TKI therapy.

Overexpression of Hes1 is involved in sensitization of K562 cells to Imatinib

Tyrosine kinase inhibitor (TKI)-based therapy has created promising results among much chronic myeloid leukemia (CML) patients. Imatinib as a relatively specific inhibitor of Bcr-Abl is at present one of the undisputed therapeutic agent for newlydiagnosed patients with CML. However, the occurrence of imatinib-resistance enlightens the urgent need to identify other therapeutic agents against CML. Juglone (5-hydroxy-2-methyl-1, 4-naphthoquinone) exerts cytotoxic effects against various human cancer cell lines. However, the mechanisms through which Juglone induces anticancer effects in CML especially in comparison with imatinib treatment remain unknown. Our results revealed that Juglone-inhibited K562 cells growth through inducing apoptosis. Based on our Western blot analyses, Juglone significantly reduced p-Akt levels and increased the expression level of Forkhead box O1 (FoxO1) and FoxO3a proteins. Moreover, hairy/enhancer of split-1 (Hes1) protein, overexpressed under the influence of Juglone, is apparently involved in Juglone-induced apoptosis among K562 cells. Conversely, treatment with imatinib attenuated Hes1 protein expression. Considering the different functional mechanism of Juglone compared with imatinib, it seems that Juglone treatment could be a useful alternative strategy for the treatment of patients with imatinib-resistance.

Evaluating measurable residual disease in acute myeloid leukemia

Mounting evidence indicates that the presence of measurable ("minimal") residual disease (MRD), defined as posttherapy persistence of leukemic cells at levels below morphologic detection, is a strong, independent prognostic marker of increased risk of relapse and shorter survival in patients with acute myeloid leukemia (AML) and can be used to refine risk-stratification and treatment response assessment. Because of the association between MRD and relapse risk, it has been postulated that testing for MRD posttreatment may help guide postremission treatment strategies by identifying high-risk patients who might benefit from preemptive treatment. This strategy, which remains to be formally tested, may be particularly attractive with availability of agents that could be used to specifically eradicate MRD. This review examines current methods of MRD detection, challenges to adopting MRD testing in routine clinical practice, and recent recommendations for MRD testing in AML issued by the European LeukemiaNet MRD Working Party. Inclusion of MRD as an end point in future randomized clinical trials will provide the data needed to move toward standardizing MRD assays and may provide a more accurate assessment of therapeutic efficacy than current morphologic measures.

Measurable residual disease testing in acute myeloid leukaemia

There is considerable interest in developing techniques to detect and/or quantify remaining leukaemia cells termed measurable or, less precisely, minimal residual disease (MRD) in persons with acute myeloid leukaemia (AML) in complete remission defined by cytomorphological criteria. An important reason for AML MRD-testing is the possibility of estimating the likelihood (and timing) of leukaemia relapse. A perfect MRD-test would precisely quantify leukaemia cells biologically able and likely to cause leukaemia relapse within a defined interval. AML is genetically diverse and there is currently no uniform approach to detecting such cells. Several technologies focused on immune phenotype or cytogenetic and/or molecular abnormalities have been developed, each with advantages and disadvantages. Many studies report a positive MRD-test at diverse time points during AML therapy identifies persons with a higher risk of leukaemia relapse compared with those with a negative MRD-test even after adjusting for other prognostic and predictive variables. No MRD-test in AML has perfect sensitivity and specificity for relapse prediction at the cohort- or subject levels and there are substantial rates of false-positive and -negative tests. Despite these limitations, correlations between MRD-test results and relapse risk have generated interest in MRD-test result-directed therapy interventions. However, convincing proof that a specific intervention will reduce relapse risk in persons with a positive MRD-test is lacking and needs testing in randomized trials. Routine clinical use of MRD-testing requires further refinements and standardization/harmonization of assay platforms and results reporting. Such data are needed to determine whether results of MRD-testing can be used as a surrogate end point in AML therapy trials. This could make drug-testing more efficient and accelerate regulatory approvals. Although MRD-testing in AML has advanced substantially, much remains to be done.

Exploratory study on the impact of switching to nilotinib in 18 patients with chronic myeloid leukemia in chronic phase with suboptimal response to imatinib

BACKGROUND

The phase II, exploratory, open-label Exploring Nilotinib BCR-ABL Effects (ENABL) study [ClinicalTrials.gov identifier: NCT00644878] assessed the impact of switching to nilotinib therapy in patients with chronic myeloid leukemia in chronic phase (CML-CP) who had a suboptimal molecular response with imatinib.

METHODS

Patients with CML-CP who had previously achieved a complete cytogenetic response (CCyR), but had a suboptimal molecular response, with frontline imatinib therapy (N = 18) were assigned to receive nilotinib 300 mg twice daily. The primary endpoint was the change in BCR-ABL1 transcript levels from baseline after 12 months; rates of major molecular response (MMR) and safety were also assessed.

RESULTS

At 3 months after switching to nilotinib, 10 of 17 (59%) evaluable patients had achieved MMR. At 12 months, 9 of 12 (75%) evaluable patients had achieved MMR, and the median BCR-ABL1 level among all patients remaining in the study was 0.020% on the International Scale (IS), equivalent to a 3.7-log reduction from the standardized IS baseline (primary endpoint). Adverse events (AEs) were typically grade 1/2 and manageable with dose interruptions. A total of three patients experienced serious study drug-related AEs, including pancreatitis, bradycardia, and vertigo. No deaths were reported.

CONCLUSIONS

Overall, results from this exploratory study suggest that switching to nilotinib due to suboptimal molecular response with imatinib can result in improved molecular response for patients with CML-CP.

Significance of deeper molecular responses in patients with chronic myeloid leukemia in early chronic phase treated with tyrosine kinase inhibitors

Most patients with chronic myeloid leukemia (CML) in chronic phase (CP) treated with tyrosine kinase inhibitors (TKI) achieve complete cytogenetic response (CCyR). An increasing number of patients also achieve deep molecular responses (MR). We determined the frequency and significance of deep MR after TKI therapy for CML in CP. MR included: major molecular response (MMR), MR4, MR4.5, and undetectable transcripts (UND), i.e., BCR-ABL/ABL of ≤0.1, ≤0.01, ≤0.0032%, and undetectable transcripts, respectively. Four hundred eighty-three patients received imatinib 400 mg/day (IM400, 71, July 2000 to April 2001), imatinib 800 mg/day (IM800, 204, June 2001 to July 2005), nilotinib (106, July 2005 to date), or dasatinib (102, November 2005 to date). UND rates at 36 months were 18.1, 30.6, 29.2, and 28.6%, respectively. Patients achieving UND have superior transformation-free survival (TFS) and overall survival (OS) versus those obtaining ≤MMR, but not other MR levels. At the 18- and 24-month landmark analysis, patients achieving UND have no advantage in TFS and OS compared to those achieving a lesser degree of MR. Among patients achieving MR4.5, those who maintain it for ≥2 years (susMR4·5) have no additional benefit in TFS or OS. Most patients with early CP CML receiving TKI achieve MMR. BCR-ABL transcripts become undetectable in a significant fraction of them. Deeper MR at 18 or 24 months are not associated with a benefit in TFS or OS. Furthermore, achieving susMR4·5 does not appear to further reduce the risk of transformation or death.

Aclacinomycin A sensitizes K562 chronic myeloid leukemia cells to imatinib through p38MAPK-mediated erythroid differentiation

Expression of oncogenic Bcr-Abl inhibits cell differentiation of hematopoietic stem/progenitor cells in chronic myeloid leukemia (CML). Differentiation therapy is considered to be a new strategy for treating this type of leukemia. Aclacinomycin A (ACM) is an antitumor antibiotic. Previous studies have shown that ACM induced erythroid differentiation of CML cells. In this study, we investigate the effect of ACM on the sensitivity of human CML cell line K562 to Bcr-Abl specific inhibitor imatinib (STI571, Gleevec). We first determined the optimal concentration of ACM for erythroid differentiation but not growth inhibition and apoptosis in K562 cells. Then, pretreatment with this optimal concentration of ACM followed by a minimally toxic concentration of imatinib strongly induced growth inhibition and apoptosis compared to that with simultaneous co-treatment, indicating that ACM-induced erythroid differentiation sensitizes K562 cells to imatinib. Sequential treatment with ACM and imatinib induced Bcr-Abl down-regulation, cytochrome c release into the cytosol, and caspase-3 activation, as well as decreased Mcl-1 and Bcl-xL expressions, but did not affect Fas ligand/Fas death receptor and procaspase-8 expressions. ACM/imatinib sequential treatment-induced apoptosis was suppressed by a caspase-9 inhibitor and a caspase-3 inhibitor, indicating that the caspase cascade is involved in this apoptosis. Furthermore, we demonstrated that ACM induced erythroid differentiation through the p38 mitogen-activated protein kinase (MAPK) pathway. The inhibition of erythroid differentiation by p38MAPK inhibitor SB202190, p38MAPK dominant negative mutant or p38MAPK shRNA knockdown, reduced the ACM/imatinib sequential treatment-mediated growth inhibition and apoptosis. These results suggest that differentiated K562 cells induced by ACM-mediated p38MAPK pathway become more sensitive to imatinib and result in down-regulations of Bcr-Abl and anti-apoptotic proteins, growth inhibition and apoptosis. These results provided a potential management by which ACM might have a crucial impact on increasing sensitivity of CML cells to imatinib in the differentiation therapeutic approaches.

Evaluation of 5-year imatinib treatment of 458 patients with CP-CML in routine clinical practice and prognostic impact of different BCR-ABL cutoff levels

We evaluated responses to the treatment and long-term outcomes of chronic myeloid leukemia patients treated with imatinib as first-line treatment in routine clinical setting from two countries with centralized tyrosine kinase inhibitors (TKIs) treatment. We assessed prognostic significance of European LeukemiaNet (ELN) 2006- and 2009-defined responses and the prognostic value of molecular responses at defined time points on 5-year survivals. Among the cumulative rates of incidence of hematologic, cytogenetic, and molecular responses and all important survival parameters, we evaluated the prognostic significance of different BCR-ABL transcript-level ratios (≤1%; >1%–≤10%; >10%) at 3, 6, 12, and 18 months (n = 199). The ELN optimal response criteria and their predictive role were significantly beneficial for event-free survival at all given time points. We found significant improvement in survivals of patients with BCR-ABL lower than 10% in the 6th and 12th months. Significantly better outcome was found in patients who achieved major molecular response (MMR) in the 12th month. The cumulative incidences of complete cytogenetic response (CCyR) and MMR were significantly associated with the molecular response in the 3rd month. The ELN response criteria and their predictive role were helpful at given time points; however, the 2009 definition did not significantly alter the prognostic accuracy compared with that of the 2006 definition. The significant value was observed for cytogenetic responses at the 6th and 12th month. Moreover, progression-free and event-free survivals were improved with MMR at the 12th month.

Current practices in the management of chronic myeloid leukemia

BACKGROUND

A previous survey of physician self-reported practice patterns in the management of CML was conducted in 2005. The National Comprehensive Cancer Network and European LeukemiaNet guidelines now include nilotinib and dasatinib in their treatment algorithms for CML. To assess these new guidelines, a cross-sectional survey of US hematologists and/or oncologists was conducted in December 2010 through an online survey.

MATERIALS AND METHODS

The survey had 43 questions consisting of items updated from the 2005 survey to reflect changes in clinical practice, tyrosine kinase inhibitor therapy, and current guidelines.

RESULTS

Analysis of the responses from 507 board certified medical oncologists/hematologists suggests that the use of imatinib 400 mg as an initial treatment option had decreased from 62% in 2005 to 52% in the 2010 survey. Currently, nearly 40% of physicians would choose either nilotinib or dasatinib as first-line treatment. From the surveyed physicians, achievement of at least a major molecular response (MMR) is the predominant treatment goal in chronic phase CML.

CONCLUSION

This survey emphasizes the need for continued updates and education regarding optimal therapy, monitoring practices, and therapeutic end points in CML.

Initial molecular response at 3 months may predict both response and event-free survival at 24 months in imatinib-resistant or -intolerant patients with Philadelphia chromosome-positive chronic myeloid leukemia in chronic phase treated with nilotinib

PURPOSE

The association between initial molecular response and longer-term outcomes with nilotinib was examined.

PATIENTS AND METHODS

Patients with imatinib-resistant or -intolerant chronic myeloid leukemia in chronic phase from the phase II nilotinib registration study with available postbaseline BCR-ABL1 transcript assessments were included (N = 237).

RESULTS

BCR-ABL1 transcript levels (International Scale [IS]) at 3 months correlated with complete cytogenetic response (CCyR) by 24 months. Patients with BCR-ABL1 (IS) of > 1% to ≤ 10% at 3 months with nilotinib had higher cumulative incidence of CCyR by 24 months than patients with BCR-ABL1 (IS) of > 10% (53% v 16%). BCR-ABL1 (IS) at 3 months predicted major molecular response (MMR) by 24 months. Cumulative incidence of MMR by 24 months for patients with BCR-ABL1 (IS) of > 0.1% to ≤ 1%, > 1% to ≤ 10%, and > 10% was 65%, 27%, and 9%, respectively. These differences were observed for patients with or without baseline BCR-ABL1 mutations and for those with imatinib resistance or intolerance. Estimated event-free survival (EFS) rates at 24 months decreased with higher transcript levels at 3 months; patients with BCR-ABL1 (IS) of ≤ 1% had an estimated 24-month EFS rate of 82%, compared with 70% for patients with BCR-ABL1 (IS) of > 1% to ≤ 10% and 48% for patients with BCR-ABL1 (IS) of > 10%.

CONCLUSION

Patients with BCR-ABL1 (IS) of > 10% at 3 months had a lower cumulative incidence of CCyR and MMR and lower rates of EFS versus patients with BCR-ABL1 (IS) of ≤ 10%. Prospective studies may determine whether close monitoring or alternative therapies are warranted for patients with minimal initial molecular response.

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.

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.

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.

Comprehensive evaluation of time-to-response parameter as a predictor of treatment failure following imatinib therapy in chronic phase chronic myeloid leukemia: which parameter at which time-point does matter?

Early recognition of high-risk patient is important to improve long-term outcomes following imatinib therapy for chronic myeloid leukemia (CML). Some controversy surrounds the question, which of short-term response parameters at which time-point, including complete cytogenetic response (CCyR) or major molecular response (MMR) at 6 or 12 months, is the best predictor for treatment outcomes. In this comprehensive analysis, we adopted landmark analysis method, time-dependent Cox's proportional hazard model, and receiver-operating characteristics (ROC) method to analyze time-to-response parameter as predictor of long-term outcomes in 187 chronic phase (CP) CML patients. Regardless of the methods of analysis, earlier achievement of short-term response such as CCyR or MMR could predict the higher probability of achieving better interim outcome (such as treatment failure or loss of response [LOR]). Similar to the findings from other studies, our ROC analysis provided cutoff time points for MMR (18-36 months) and CCyR (6-12 months) that were the best predictors for LOR or treatment failure, which can be an indirect evidence supporting the ELN recommendation. The patient who achieves short-term response rapidly will have a lower risk of losing response or failing after imatinib therapy in CML patients.

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.

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.

Peripheral blood vs. bone marrow for molecular monitoring of BCR-ABL1 levels in chronic myelogenous leukemia, a retrospective analysis in allogeneic bone marrow recipients

Molecular monitoring of the BCR-ABL1 transcript in chronic myelogenous leukemia (CML) using quantitative real-time PCR (RQ-PCR) can be performed using either bone marrow (BM) or peripheral blood (PB). However, a recent report by Stock et al. [International Journal of Oncology 28 (2006) 1099] questioned the reliability of PB samples for BCR-ABL1 detection as performed by RQ-PCR. We report a study on 114 CML patients who received allogeneic stem cell transplantation (ASCT), and who were monitored by RQ-PCR using paired samples of BM and PB: the total number of determinations was 428, with a median follow-up after transplant of 8 years. BCR-ABL1 transcript was undetectable or <0.1%, in 106 (49.57%) and 62 (29%) paired determinations, respectively. BCR-ABL1 was >0.1% in 36 (16.8%) paired determinations and was discordant in 10 (4.7%). Agreement between PB and BM results was quantified by the kappa test (k = 0.85; 95% CI 0.76-0.94). This study shows that BCR-ABL1 RQ-PCR monitoring of CML patients after ASCT with PB is concordant with BM in 95.3% of cases, and thus may be used to monitor the disease. This may be relevant when discussing both quality of life issues and the need for post-transplant monitoring with the patient.

Dasatinib versus imatinib in newly diagnosed chronic-phase chronic myeloid leukemia

BACKGROUND

Treatment with dasatinib, a highly potent BCR-ABL kinase inhibitor, has resulted in high rates of complete cytogenetic response and progression-free survival among patients with chronic myeloid leukemia (CML) in the chronic phase, after failure of imatinib treatment. We assessed the efficacy and safety of dasatinib, as compared with imatinib, for the first-line treatment of chronic-phase CML.

METHODS

In a multinational study, 519 patients with newly diagnosed chronic-phase CML were randomly assigned to receive dasatinib at a dose of 100 mg once daily (259 patients) or imatinib at a dose of 400 mg once daily (260 patients). The primary end point was complete cytogenetic response by 12 months, confirmed on two consecutive assessments at least 28 days apart. Secondary end points, including major molecular response, were tested at a significance level of 0.0001 to adjust for multiple comparisons.

RESULTS

After a minimum follow-up of 12 months, the rate of confirmed complete cytogenetic response was higher with dasatinib than with imatinib (77% vs. 66%, P=0.007), as was the rate of complete cytogenetic response observed on at least one assessment (83% vs. 72%, P=0.001). The rate of major molecular response was higher with dasatinib than with imatinib (46% vs. 28%, P<0.0001), and responses were achieved in a shorter time with dasatinib (P<0.0001). Progression to the accelerated or blastic phase of CML occurred in 5 patients who were receiving dasatinib (1.9%) and in 9 patients who were receiving imatinib (3.5%). The safety profiles of the two treatments were similar.

CONCLUSIONS

Dasatinib, administered once daily, as compared with imatinib, administered once daily, induced significantly higher and faster rates of complete cytogenetic response and major molecular response. Since achieving complete cytogenetic response within 12 months has been associated with better long-term, progression-free survival, dasatinib may improve the long-term outcomes among patients with newly diagnosed chronic-phase CML. (ClinicalTrials.gov number, NCT00481247.)

Positive response to imatinib mesylate therapy for childhood chronic myeloid leukemia

Chronic myeloid leukemia (CML) is rare in the pediatric population, accounting for 2-3% of childhood leukemia cases, with an annual incidence of one case per million children. The low toxicity profile of imatinib mesylate has led to its approval as a front-line therapy in children for whom interferon treatment has failed or who have relapsed after allogeneic transplantation. We describe the positive responses of 2 children (case 1 - from a 7-year-old male since May 2005; case 2 - from a 5-year-old female since June 2006) with Philadelphia-positive chromosome CML treated with imatinib (300 mg/day, orally) for up to 28 months, as evaluated by morphological, cytogenetic, and molecular approaches. Our patients are alive, are in the chronic phase, and are in continuous morphological complete remission.

Genomic and proteomic biomarkers for cancer: a multitude of opportunities

Biomarkers are molecular indicators of a biological status, and as biochemical species can be assayed to evaluate the presence of cancer and therapeutic interventions. Through a variety of mechanisms cancer cells provide the biomarker material for their own detection. Biomarkers may be detectable in the blood, other body fluids, or tissues. The expectation is that the level of an informative biomarker is related to the specific type of disease present in the body. Biomarkers have potential both as diagnostic indicators and monitors of the effectiveness of clinical interventions. Biomarkers are also able to stratify cancer patients to the most appropriate treatment. Effective biomarkers for the early detection of cancer should provide a patient with a better outcome which in turn will translate into more efficient delivery of healthcare. Technologies for the early detection of cancer have resulted in reductions in disease-associated mortalities from cancers that are otherwise deadly if allowed to progress. Such screening technologies have proven that early detection will decrease the morbidity and mortality from cancer. An emerging theme in biomarker research is the expectation that panels of biomarker analytes rather than single markers will be needed to have sufficient sensitivity and specificity for the presymptomatic detection of cancer. Biomarkers may provide prognostic information of disease enabling interventions using targeted therapeutic agents as well as course-corrections in cancer treatment. Novel genomic, proteomic and metabolomic technologies are being used to discover and validate tumor biomarkers individually and in panels.

Dasatinib-associated major molecular responses in patients with chronic myeloid leukemia in chronic phase following imatinib failure: response dynamics and predictive value

Dasatinib is a highly potent BCR-ABL inhibitor that has shown durable efficacy in patients with chronic phase (CP) chronic myeloid leukemia (CML) after resistance, suboptimal response, or intolerance to prior imatinib. In patients with CML, BCR-ABL transcript measurement is the most sensitive method for assessing minimal residual disease. Here, molecular responses were analyzed in 1067 patients with CML-CP treated with dasatinib during phase II/III trials. After 3, 6, 12, and 24 months of follow-up, a major molecular response (MMR) was achieved by 12, 22, 35, and 40% of patients, respectively. The 24-month MMR rate was 34% in patients with resistance or suboptimal response to imatinib (n=829) and 63% in imatinib-intolerant patients (n=238). Among patients who had achieved a complete cytogenetic response (CCyR), 72% also achieved MMR. Responses with dasatinib 100 mg once daily were similar to other doses. In landmark analyses, 24-month progression-free survival was higher in patients who had achieved MMR or CCyR at 12 months than in those without MMR or CCyR at 12 months. MMR at 12 months was associated with a longer duration of CCyR. Overall, this analysis shows that dasatinib treatment results in high MMR rates in patients with CML-CP after imatinib failure.

Molecular monitoring in chronic myeloid leukemia: response to tyrosine kinase inhibitors and prognostic implications

The majority of patients with chronic-phase (CP) chronic myeloid leukemia (CML) who are treated with Bcr-Abl tyrosine kinase inhibitors such as imatinib and dasatinib achieve cytogenetic disease remission (ie, Philadelphia chromosome-positive cells undetectable by cytogenetic evaluation). However, more sensitive methods are required for monitoring residual disease (ie, molecular monitoring of BCR-ABL transcript levels). It is generally accepted that molecular responses have prognostic significance. Patients with CP CML who achieve early molecular responses are more likely to achieve durable cytogenetic responses and are less likely to experience disease progression. Rising BCR-ABL transcript levels also indicate loss of response, often as a consequence of developing BCR-ABL mutations. However, some studies have suggested that patients who achieve complete cytogenetic disease remission may not derive an additional prognostic benefit from achieving a major molecular response. Practical issues also exist for molecular monitoring with respect to restricted access and variability in methodologies and data reporting. Although molecular monitoring has a clear role in assessing residual disease and determining the risk of disease progression in patients with CML, the importance of cytogenetic monitoring should not be ignored.

Imatinib mesylate therapy in chronic myeloid leukemia patients in stable complete cytogenic response after interferon-alpha results in a very high complete molecular response rate

To determine the impact on minimal residual disease by switching to imatinib chronic phase chronic myeloid leukaemia (CP-CML) patients responsive to interferon-alpha (IFNalpha), in stable complete cytogenetic response (CCR) but with persistent PCR positivity. Twenty-six Philadelphia positive (Ph+) CML patients in stable CCR after IFNalpha but persistently positive at PCR analysis during this treatment, were given imatinib mesylate at standard dose. At enrolment into the study, median IFN treatment and CCR duration were 88 months (range 15-202) and 73 months (range 10-148), respectively. Imatinib treatment resulted in a progressive and consistent decline of the residual disease as measured by quantitative PCR (RQ-PCR) in all but one of the 26 patients; at the end of follow-up, after a median of 32 months (range 21-49) of treatment, a major molecular response (BCR/ABL levels <0.1) was reached in 20 patients (77%), and BCR/ABL transcripts were undetectable in 13 (50%). The achievement of molecular response was significantly correlated with post-IFN baseline transcript level (mean 1.194 for patients achieving complete molecular response versus 18.97 for those who did not; p<0.001), but not with other clinical/biological disease characteristics. These results indicate that patients induced into CCR by IFN treatment represent a subset with very favourable prognosis, which can significantly improve molecular response with imatinib and further support investigative treatment schedules combining these two drugs.

Diagnosis and management of chronic myeloid leukemia

BACKGROUND

The success of imatinib therapy for chronic myeloid leukemia (CML) has brought new challenges; these include optimizing disease monitoring, imatinib resistance, and use of novel, more potent tyrosine kinase inhibitors. Thus, there is a need to establish new best practices for CML management in the post-imatinib era.

METHODS

An internet-based questionnaire, consisting of 26 multiple choice questions, was developed to assess hematologists' and oncologists' self-reported treatment strategies for CML.

RESULTS

Between November 2005 and January 2006, 956 eligible physicians responded to the survey; 727 from the US and 229 from Europe. Most US respondents (60%) practiced in the community setting, whereas European respondents were primarily academic (44%) and hospital-based (40%). Physicians' responses were generally in line with current recommendations, although differences were identified. Confusion existed among respondents over optimal timing of treatment decisions, with a notable proportion of physicians focusing on a single timepoint rather than consistent monitoring, as currently advocated. Some respondents were unaware of new molecular monitoring techniques, when to monitor for BCR-ABL mutations (and the impact on treatment decisions), and the benefit of new tyrosine kinase inhibitors.

CONCLUSIONS

Responses to the survey suggest that treatment practices in some areas of CML management are not in line with current recommendations. Identified areas of need should be targeted in future educational activities for the CML community.

Dose modification of imatinib by monitoring the level of BCR-ABL transcript in chronic myelogenous leukemia

Chronic myelogenous leukemia (CML) is a hematological malignancy that is characterized by the chromosome anomaly, t(9;22)(q34;q11). By this chromosomal translocation, a novel activated tyrosine kinase, BCR-ABL chimeric protein, is generated, and the protein is causative of the disease. Recently, Imatinib mesylate targeting to a BCR-ABL chimeric protein has been developed, and shown to achieve complete remission at a high rate. Patients are currently required to receive a fixed dose, 400 mg daily; however, it is possible that some of patients can maintain their remission with reduced doses of imatinib. In this study, we determined levels of BCR-ABL transcript in CML patients by real-time quantitative polymerase chain reaction analysis, and explored the possibility of individualization of therapeutic doses of imatinib. Thirty-five CML patients, including 17 newly diagnosed patients, 16 patients pre-treated with interferon-alpha, and 2 relapsed patients after allogeneic transplantation, were treated with imatinib. Complete cytogenetic response was achieved in 31 (89%) patients. Major molecular response (MMR) was achieved in 21 (60%). Complete molecular response (CMR) was achieved in 7 (20%). Imatinib was discontinued in 2 patients, one patient with MMR due to noncompliance and other patient sustaining CMR, but both patients relapsed 7 and 13 months later, respectively. The doses of imatinib were reduced in 7 patients due to its side effects, but 4 out of the 7 patients have sustained MMR, and 2 of them have sustained CMR for more than 23 months. These results indicate that some patients are able to maintain MMR with low-dose imatinib.

Molecular monitoring of chronic myelogenous leukemia: identification of the most suitable internal control gene for real-time quantification of BCR-ABL transcripts

Monitoring breakpoint cluster region-Abelson kinase (BCR-ABL) levels in patients treated for chronic myelogenous leukemia (CML) has become an integral part of patient management. Real-time reverse transcriptase-polymerase chain reaction is the method of choice for this purpose because of its high analytical sensitivity and reproducibility. Given the variation of RNA quality and quantity in clinical specimens, accurate quantitative assessment of BCR-ABL depends on normalization of the BCR-ABL signal to an appropriate internal reference. However, the controls used by different laboratories vary, and there is no clear consensus on an ideal reference due to limited investigations. In this study, we compared nine commonly used control genes for three criteria: mRNA abundance, levels in CML and non-CML cells, and their degradation kinetics in comparison with BCR-ABL. We found that beta-glucuronidase (GUSB) is the most suitable among the nine genes tested. Although ABL is most widely used, our data suggest that the amount of ABL is different in CML and non-CML cells. Moreover, ABL levels are regulated by cellular stress. These findings have a direct impact on current clinical laboratory practice and patient care because the use of a proper control gene affects the reported levels of BCR-ABL transcripts used for patient management decisions.

BCR-ABL mRNA levels at and after the time of a complete cytogenetic response (CCR) predict the duration of CCR in imatinib mesylate-treated patients with CML

Although most patients with chronic myeloid leukemia (CML) treated with imatinib mesylate achieve a complete cytogenetic response (CCR), some patients will relapse. To determine the potential of real-time quantitative BCR-ABL reverse transcriptase-polymerase chain reaction (RT-PCR) to predict the duration of continued CCR, we monitored 85 patients treated with imatinib mesylate who achieved a CCR. With a median follow-up of 13 months after CCR (29 months after imatinib mesylate; median 6 RQ-PCR assays), 23 patients (27%) had disease progression (predominantly loss of CCR). Compared with the median baseline level of BCR-ABL mRNA, 42% of patients achieved at least a 2-log molecular response at the time of first reaching CCR. Failure to achieve a 2-log response at the time of CCR was an independent predictive marker of subsequent progression-free survival (hazard ratio = 5.8; 95% CI, 1.7-20; P = .005). After CCR, BCR-ABL mRNA levels progressively declined for at least the next 15 months, and 42 patients (49%) ultimately achieved at least a 3-log reduction in BCR-ABL mRNA. Patients failing to achieve this 3-log response, at any time during therapy, had significantly shorter progression-free survival (hazard ratio = 8.1; 95% CI, 3.1-22; P < .001). The achievement of either a 2-log molecular response at the time of CCR or a 3-log response anytime thereafter is a significant and independent prognostic marker of subsequent progression-free survival.

Cytogenetic response to prior treatment with interferon-α is predictive for survival after allogeneic hematopoietic stem cell transplantation in chronic myeloid leukemia

We investigated the impact of a cytogenetic response (CyR) to IFN prior to and at the time of allogeneic hematopoietic stem cell transplantation (HSCT) on transplant-related mortality (TRM), relapse rate and survival probability after HSCT in 162 transplanted patients with chronic myeloid leukemia. One-hundred-one patients (62.3%) achieved a CyR prior to HSCT. Survival probabilities were higher in patients, who achieved any CyR prior to HSCT than in patients without CyR (63.6 vs 49.2%: P = 0.019). Survival probabilities in patients, who achieved a major CyR were better than in patients with minimal and minor CyR or in patients with no CyR (69.4 vs 58.8% vs 49.2%: P = 0.040). TRM and survival of chronic phase patients without CyR at the time of HSCT were similar to that of patients transplanted in advanced phase. Both groups combined had an outcome inferior to patients with at least minimal CyR (TRM, Gray test: P = 0.016, survival, log-rank test: P = 0.002). Univariate and multivariate analyses identified CyR prior to or at HSCT as a strong and independently favorable prognostic factor. We therefore conclude that allogeneic HSCT in CyR should be investigated prospectively as an alternative treatment option in defined patient groups.

Continuous complete hematological and cytogenetic remission with molecular minimal residual disease 9 years after discontinuation of interferon-alpha in a patient with Philadelphia chromosome-positive chronic myeloid leukemia

Interferon-alpha has been used as standard therapy for patients with Philadelphia-positive chronic myeloid leukemia (CML) for more than 20 years. Recently randomized trials have shown a superiority of the tyrosine kinase inhibitor imatinib in respect to its efficacy to induce complete hematological and cytogenetic remissions and more importantly in overall survival. Although follow-up is much shorter for imatinib than for interferon-alpha, this data changed the treatment algorithms in this disease. At the end of the era of interferon-alpha as a single-drug first-line treatment for most patients we present a case report which exemplifies a rare but exciting property of interferon-alpha in CML: the induction of complete hematological and cytogenetic remissions which can persist over years after discontinuation of the drug. Hence, the enrollment of CML patients in clinical trials which explore a combination treatment of imatinib and interferon-alpha is warranted.

Automated fluorescent in situ hybridization (FISH) analysis of t(9;22)(q34;q11) in interphase nuclei

BACKGROUND

For chronic myeloid leukemia, the FISH detection of t(9;22)(q34;q11) in interphase nuclei of peripheral leukocytes is an alternative method to bone marrow karyotyping for monitoring treatment. With automation, several drawbacks of manual analysis may be circumvented. In this article, the capabilities of a commercially available automated image acquisition and analysis system were determined by detecting t(9;22)(q34;q11) in interphase nuclei of peripheral leukocytes.

METHODS

Three peripheral blood samples of normal adults, 21 samples of CML patients, and one sample of a t(9;22)(q34;q11) positive cell-line were used.

RESULTS

Single nuclei with correctly detected signals amounted to 99.6% of nuclei analyzed after exclusion of overlapping nuclei and nuclei with incorrect signal detection. A cut-off value of 0.84 mum was defined to discriminate between translocation positive and negative nuclei based on the shortest distance between signals. Using this value, the false positive rate of the automated analysis for negative samples was 7.0%, whereas that of the manual analysis was 5.8%. Automated and manual results showed strong correlation (R(2) = 0.985), the mean difference of results was only 3.7%.

CONCLUSIONS

A reliable and objective automated analysis of large numbers of cells is possible, avoiding interobserver variability and producing statistically more accurate results than manual evaluation.

Sustained complete molecular remissions after treatment with imatinib-mesylate in patients with failure after allogeneic stem cell transplantation for chronic myelogenous leukemia: results of a prospective phase II open-label multicenter study

PURPOSE

In the era of molecular therapy of chronic myelogenous leukemia (CML) applying BCR-ABL tyrosine kinase inhibitors, the usefulness of molecular end points, in particular, quantitative polymerase chain reaction (PCR) for BCR-ABL in monitoring responses has been broadly accepted. Therefore, we have designed a prospective phase II trial in CML, which, for the first time, evaluated the feasibility and safety of molecular end points as surrogate markers to guide through a stratified treatment algorithm within a multicenter trial.

PATIENTS AND METHODS

As a clinical model, we adopted minimal residual disease (MRD) found in relapse after allogeneic stem cell transplantation (SCT) in CML. Forty-four patients were enrolled and received the BCR-ABL tyrosine kinase inhibitor imatinib (IM) at a starting dose of 400 mg/d. The quality of molecular responses achieved then decided on discontinuation of IM or dose escalation up to 800 mg/d, and finally, on application of donor lymphocyte infusions. Results Seventy percent of patients achieved a complete molecular response (CMR), defined as nested PCR-negativity for BCR-ABL in three consecutive samples. Interestingly, in four out of 10 patients who discontinued IM, CMR was durable even after cessation of IM with a median follow-up of 494 days. This suggests the possibility of long-term tumor control in a subset of patients.

CONCLUSION

The treatment strategy showed that IM treatment was well-tolerated and highly efficacious in MRD after allogeneic SCT. Moreover, this study demonstrated that evaluation of a molecular end point within a multicenter trial can be a safe and effective tool for clinical decision making.

Survival benefit with imatinib mesylate therapy in patients with accelerated-phase chronic myelogenous leukemia--comparison with historic experience

BACKGROUND

The effect of imatinib mesylate on survival in the accelerated phase of chronic myelogenous leukemia (CML) is unknown. The objectives of this study were to update the long-term experience with imatinib in patients who had accelerated-phase CML and to compare outcomes with historic experience.

METHODS

The outcomes of 176 patients who received treatment with imatinib were reviewed and compared with the outcomes of 213 historic control patients with accelerated-phase CML who received treatment with interferon-alpha or with other modalities.

RESULTS

With imatinib, the complete hematologic response rate was 82% versus a rate < or = 50% for others, and the complete cytogenetic response rate was 43% versus rates of 0-6% for others. The estimated 4-year survival rates were 53% with imatinib, 42% with interferon-alpha, and 0-21% for others. A multivariate analysis of the total population of 389 patients indicated that imatinib therapy (vs. other therapies) was an independent, favorable prognostic factor for survival (P < 0.0001; hazard rate, 0.62). A subset analysis that included only patients who were treated with imatinib and interferon-alpha (276 patients) also identified imatinib as an independent favorable prognostic factor (P < 0.0001; hazard rate, 0.65). The 3-month cytogenetic response to imatinib was associated with significantly different survival outcomes (P < 0.0001). A multivariate analysis that included pretreatment characteristics and 3-month cytogenetic response among 150 patients who received imatinib and were alive at 3 months identified only 2 adverse independent prognostic factors: lack of a cytogenetic response at 3 months (P < 0.001) and anemia (hemoglobin < 10 g/dL; P = 0.003). Patients who had neither factor (41%) had an estimated 4-year survival rate of 88%; in the other patients, the 4-year survival rate was < or = 60%. This may have implications in relation to subsequent therapy, because, according to the outcomes of patients who underwent allogeneic transplantation in accelerated phase at the authors' institution and from literature reports, the estimates of 5-year survival were 25-30%.

CONCLUSIONS

The current results suggest that imatinib improved survival compared with other therapies in patients with accelerated-phase CML.

Molecular genetic analysis of haematological malignancies: I. Acute leukaemias and myeloproliferative disorders

Molecular genetic techniques are now routinely applied to haematological malignancies within a clinical laboratory setting. The detection of genetic rearrangements not only assists with diagnosis and treatment decisions, but also adds important prognostic information. In addition, genetic rearrangements associated with leukaemia can be used as molecular markers allowing the detection of low levels of residual disease. This review will concentrate on the application of molecular genetic techniques to the acute leukaemias and myeloprolferative disorders.

Response and resistance in 300 patients with BCR-ABL-positive leukemias treated with imatinib in a single center: a 4.5-year follow-up

BACKGROUND

The advent of imatinib has considerably changed the treatment of chronic myeloid leukemia (CML). Early studies demonstrated high rates of hematologic and cytogenetic responses in all phases of the disease after limited observation periods.

METHODS

The authors evaluated long-term outcome, rates of response, and resistance in 300 patients with BCR-ABL-positive leukemias (CML in chronic phase after failure to respond to interferon-alpha [CP], n = 139; accelerated phase [AP], n = 80; myeloid blast crisis [BC], n = 76; lymphoid BC and Philadelphia chromosome-positive acute lymphoblastic leukemia, n = 5) who entered clinical trials with imatinib in a single center after an observation time of 4.5 years.

RESULTS

In CP, hematologic remission was achieved in 97% and major (MCR) and complete cytogenetic remission (CCR) in 61% and 49% of patients, respectively. The chance to achieve MCR was higher in patients commencing imatinib earlier in the course of CML. In AP, the median survival period after the start of imatinib was 44 months, and MCR and CCR were observed in 31% and 26% of patients, respectively. In myeloid BC, the median survival period after the start of imatinib and after diagnosis of BC was 6 and 9 months, respectively. Hematologic resistance occurred in 25%, 41%, and 92% of patients in CP, AP, and myeloid BC, respectively, and was associated with BCR-ABL mutations in 45% of patients and with clonal evolution in 58% of patients.

CONCLUSIONS

The data emphasized the need for a prolonged follow-up of patients treated with imatinib to define the clinical potential of the drug and to establish methods to optimize therapy.

Personalized medical treatment strategies for patients with chronic myeloid leukemia

Management of patients with chronic myeloid leukemia has become increasingly difficult over the last few years since there are a variety of treatment options available. The ultimate challenge is to decide the most appropriate treatment strategy for an individual patient. To facilitate this, assessment of an individual patient's disease in terms of status, tempo and response to initial treatment needs to be determined. This review article discusses the current treatment options in the management of chronic myeloid leukemia, the factors that influence management decisions and suggests how treatment for the individual patient may be tailored whilst involving the patient in the decision-making process.

Post-transplantation dynamics of the immune response to chronic myelogenous leukemia

We model the immune dynamics between T cells and cancer cells in leukemia patients after bone marrow transplants, using a system of six delay differential equations to track the various cell-populations. Our approach incorporates time delays and accounts for the progression of cells through different modes of behavior. We explore possible mechanisms behind a successful cure, whether mediated by a blood-restricted immune response or a cancer-specific graft-versus-leukemia (GVL) effect. Characteristic features of this model include sustained proliferation of T cells after initial stimulation, saturated T cell proliferation rate, and the possible elimination of cancer cells, independent of fixed-point stability. In addition, we use numerical simulations to examine the effects of varying initial cell concentrations on the likelihood of a successful transplant. Among the observed trends, we note that higher initial concentrations of donor-derived, anti-host T cells slightly favor the chance of success, while higher initial concentrations of general host blood cells more significantly favor the chance of success. These observations lead to the hypothesis that anti-host T cells benefit from stimulation by general host blood cells, which induce them to proliferate to sufficient levels to eliminate cancer.

Early prediction of molecular remission by monitoring BCR-ABL transcript levels in patients achieving a complete cytogenetic response after imatinib therapy for posttransplantation chronic myelogenous leukemia relapse

Imatinib induces a high complete cytogenetic response (CCR) rate in relapsed chronic myelogenous leukemia. By analyzing minimal residual disease (MRD) under the levels of CCR, we tried to assess the molecular response after imatinib therapy. By using real-time quantitative reverse transcriptase-polymerase chain reaction (Q-RT-PCR), MRD was evaluated in 23 patients (3 in cytogenetic relapse, 6 in chronic phase, 9 in accelerated phase, and 5 in blast crisis) who were treated with standard-dose imatinib for relapsed chronic myelogenous leukemia after allogeneic stem cell transplantation. With a median therapy time of 399 days (range, 35-817 days), 19 (83%) patients achieved a CCR. Meanwhile, 11 (58%) of them achieved a molecular remission (MR), which was associated with improved survival. The Q-RT-PCR data were compared according to the best response (MR, n = 11; CCR, n = 8) in the patients achieving a CCR. The BCR-ABL/ABL ratios were similar in 2 groups at 3 months but were significantly different at 6 months (median, 0.0000012 for MR and 0.00022 for CCR; P =.003). The probability of a subsequent MR was significantly higher in patients with a lower BCR-ABL/ABL ratio at 6 months (100% for <0.0001 versus 33% for >/=0.0001; P =.006) or a greater reduction in the level between 3 and 6 months (log-reduction >/=1.0;, 100%; <1.0, 17%; P =.003). Q-RT-PCR is a reliable method for monitoring MRD: the early trends in the BCR-ABL/ABL ratio may be clinically useful in discriminating patients who will achieve an MR from those who will remain in CCR.

Molecular monitoring of BCR-ABL as a guide to clinical management in chronic myeloid leukaemia

Molecular monitoring of BCR-ABL transcript levels by real-time quantitative PCR is increasingly used to assess treatment response in patients with chronic myeloid leukaemia (CML). This has become particularly relevant in the era of imatinib therapy when residual levels of leukaemia usually fall below the level of detection by bone marrow cytogenetic analysis. Studies of imatinib-treated patients have determined that BCR-ABL levels measured early in therapy can predict subsequent response and the probability of acquired resistance. The defining of a molecular level of response that indicates a high probability of progression-free survival highlights the relevance of molecular analysis for clinical management. Small increases in the BCR-ABL level can identify patients with kinase domain mutations that lead to imatinib resistance. Therefore, these assays can be used as a screening strategy for mutation analysis. As second generation kinase inhibitors commence clinical trials, the molecular response will be a primary end-point that determines efficacy.

Chronic myeloid leukemia: current application of cytogenetics and molecular testing for diagnosis and treatment

Chronic myeloid leukemia provides an illustrative disease model for both molecular pathogenesis of cancer and rational drug therapy. Chronic myeloid leukemia is a clonal stem cell disease caused by an acquired somatic mutation that fuses, through chromosomal translocation, the abl and bcr genes on chromosomes 9 and 22, respectively. The bcr/abl gene product is an oncogenic protein that localizes to the cytoskeleton and displays an up-regulated tyrosine kinase activity that leads to the recruitment of downstream effectors of cell proliferation and cell survival and consequently cell transformation. Such molecular information on pathogenesis has facilitated accurate diagnosis, the development of pathogenesis-targeted drug therapy, and most recently the application of molecular techniques for monitoring minimal residual disease after successful therapy. These issues are discussed within the context of clinical practice.

Management of early stage disease

More than 80% of newly diagnosed patients with chronic myeloid leukemia in chronic phase will achieve a complete cytogenetic response (CCR) with the standard dose of 400 mg imatinib daily. The probability of progression free survival is tightly correlated with the level of response, approaching 100% in those patients who achieve a reduction of BCR-ABL mRNA by at least 3-log at 12 months. High Sokal risk predicts poorer outcome, but on-treatment response parameters generally override pretherapeutic prognostic variables. Standard disease monitoring includes full blood counts, cytogenetics and quantitative RT-PCR for BCR-ABL mRNA but must be tailored to the level of response attained by a given patient. Conservative therapeutic milestones include a complete hematologic response at 3 months, a minor cytogenetic response at 6, a major cytogenetic response at 12 and CCR at 18, but a more aggressive approach may be justified in specific circumstances. Failure to achieve any of these milestones should trigger a re-assessment of the therapeutic strategy. Most patients with CCR remain positive by RT-PCR, and discontinuation of drug is usually followed by relapse, suggesting that imatinib fails to eradicate leukemic stem cells. The mechanisms underlying disease persistence are not well understood. Evidence is accumulating that early therapy intensification using high doses of imatinib (800 mg daily) or imatinib in combination with cytarabine or interferon-alpha may induce higher rates of RT-PCR negativity. Large studies will be required to determine whether this translates into improved progression free and overall survival.