Early landmark analysis of imatinib treatment in CML chronic phase: less than 10% BCR-ABL by FISH at 3 months associated with improved long-term clinical outcome

Distribution of BCR::ABL1 Transcripts in the Different Clinical Phases of Chronic Myeloid Leukemia: Effect on Hematological Parameters and Patient Survival

Chronic myeloid leukemia (CML) is a hematopoietic stem cell disorder characterized by the presence of the Philadelphia chromosome, a product of the reciprocal translocation t(9;22)(q34;q11), in the BCR and ABL genes. These rearrangements in both genes lead to the formation of various fusion mRNA products, with preferential expression of b2a2, b3a2, and other BCR::ABL1 mRNA variants, combined with additional chromosomal abnormalities. Notably, the distribution and frequency of different mRNA variants vary in different populations. However, studies concerning this in Mexico are limited, and the results have been inconclusive. This study therefore aimed to determine the distribution of BCR::ABL1 mRNA variants in different clinical phases of CML and their effect on hematological parameters and patient survival. This study included 33 patients, whose demographic, clinical, and molecular data on BCR::ABL1 mRNA variants and hematological parameters were collected to identify potential associations. A total of 84.8% (n = 28) of patients had BCR::ABL1 translocation and increased platelet and basophil counts. The most frequent mRNA variant was b3a2 (64.3%), followed by b2a2 (28.6%) and e1a2 (3.6%). Concerning the clinical phases of CML, 75.8% (n = 25), 21.2% (n = 7), and 3% (n = 1) of patients were in the chronic, blast, and accelerated phases, respectively. Moreover, the b3a2 mRNA variant was more commonly identified in patients in the chronic phase. No correlation was observed between mRNA variant expression and patient survival. However, b2a2 was indicative of patients with longer survival as well as those treated with imatinib or nilotinib. Additionally, platelet count could be a marker of BCR::ABL1 translocation.

Droplet digital PCR for BCR/ABL(P210) detection of chronic myeloid leukemia: A high sensitive method of the minimal residual disease and disease progression

OBJECTIVE

This study intended to establish a droplet digital PCR (dd-PCR) for monitoring minimal residual disease (MRD) in patients with BCR/ABL (P210)-positive chronic myeloid leukemia (CML), thereby achieving deep-level monitoring of tumor load and determining the efficacy for guided clinically individualized treatment.

METHODS

Using dd-PCR and RT-qPCR, two cell suspensions were obtained from K562 cells and normal peripheral blood mononuclear cells by gradient dilution and were measured at the cellular level. At peripheral blood (PB) level, 61 cases with CML-chronic phase (CML-CP) were obtained after tyrosine kinase inhibitor (TKI) treatment and regular follow-ups. By RT-qPCR, BCR/ABL (P210) fusion gene was undetectable in PB after three successive analyses, which were performed once every 3 months. At the same time, dd-PCR was performed simultaneously with the last equal amount of cDNA. Ten CML patients with MR4.5 were followed up by the two methods.

RESULTS

At the cellular level, consistency of results of dd-PCR and RT-qPCR reached R²  ≥ 0.99, with conversion equation of Y = 33.148X^1.222 (Y: dd-PCR results; X: RT-qPCR results). In the dd-PCR test, 11 of the 61 patients with CML (18.03%) tested positive and showed statistically significant difference (P < .01). In the follow-up of 10 CML patients who were in MR4.5. All patients were loss of MR4.0, and 4 were tested positive by dd-PCR 3 months earlier than by RT-qPCR.

CONCLUSION

In contrast with RT-qPCR, dd-PCR is more sensitive, thus enabling accurate conversion of dd-PCR results into internationally standard RT-qPCR results by conversion equation, to achieve a deeper molecular biology-based stratification of BCR/ABL(P210) MRD. It has some reference value to monitor disease progression in clinic.

Present and future of molecular monitoring in chronic myeloid leukaemia

Currently, physicians treating chronic myeloid leukaemia (CML) patients can rely on a wide spectrum of therapeutic options: the best use of such options is essential to achieve excellent clinical outcomes and, possibly, treatment-free remission (TFR). To accomplish this, proper integration of expert clinical and laboratory monitoring of CML patients is fundamental. Molecular response (MR) monitoring of patients at defined time points has emerged as an important success factor for optimal disease management and BCR-ABL1 kinase domain mutation screening is useful to guide therapeutic reassessment in patients who do not achieve optimal responses to tyrosine kinase inhibitor therapy. Deeper MRs might be associated with improved long-term survival outcomes. More importantly, they are considered a gateway to TFR. In molecular biology, novel procedures and technologies are continually being developed. More sophisticated molecular tools and automated analytical solutions are emerging as CML treatment endpoints and expectations become more and more ambitious. Here we provide a critical overview of current and novel methodologies, present their strengths and pitfalls and discuss what their present and future role might be.

Analysis of 2013 European LeukaemiaNet (ELN) responses in chronic phase CML across four frontline TKI modalities and impact on clinical outcomes

This study assessed the relevance of 2013 European LeukaemiaNet (ELN) response categories on patients treated with common frontline tyrosine kinase inhibitors (TKI) in chronic myeloid leukaemia in chronic phase (CML-CP). Four hundred and eighty-seven patients treated with imatinib (400 mg; IM 400, n = 70; 800 mg; IM800, n = 201), dasatinib (n = 107) or nilotinib (n = 109) were analysed. Intention to treat (ITT) analysis indicated that the proportion of patients falling into optimal, warning and failure ELN categories were 89%, 6%, 6% at 3 months, 78%, 17% and 6% at 6 months, and 75%, 13% and 13% at 12 months, respectively. Rates of optimal response at 3 months were 75% for IM400, 90% for IM800, 89% for dasatinib and 97% for nilotinib; 41%, 80%, 86% and 89% at 6 months; and 47%, 77%, 76% and 87% at 12 months, respectively. Patients achieving optimal response had longer eventfree (EFS), failurefree (FFS), transformationfree (TFS) and overall survival (OS) compared to warning and failure responses at all-time points. Treatment with imatinib 800, dasatinib or nilotinib predicted for achieving an optimal response. Optimal response predicted for significantly longer EFS, FFS, TFS and OS at 3, 6 and 12 months, irrespective of the TKI modality used. ELN response categories reliably predicted outcomes in CML patients receiving commonly used TKIs.

Response-related predictors of survival in CML

The assessment of response to tyrosine kinase inhibitor (TKI) treatment in chronic myeloid leukemia (CML) does not only reflect tumor burden at a given time but has been shown to be linked to long-term survival outcomes as well. Therefore, the quantification of molecular or cytogenetic response as early as 3 months on treatment allows a prognostic stratification of a patient's individual risk. With competing TKI regimens available, a timely switch of treatment can be considered if unfavorable outcome has to be expected due to early response failure. Numerous studies have demonstrated the association of long-term outcome with early response for first-line treatment with imatinib, with second-generation TKI and for second-line TKI treatment as well.

Long-term molecular and cytogenetic response and survival outcomes with imatinib 400 mg, imatinib 800 mg, dasatinib, and nilotinib in patients with chronic-phase chronic myeloid leukaemia: retrospective analysis of patient data from five clinical trials

BACKGROUND

Several tyrosine kinase inhibitors (TKIs) are available for treatment of patients with chronic myeloid leukaemia in chronic phase (CML-CP). We analysed long-term molecular and cytogenetic response and survival outcomes for four TKI modalities used as frontline therapy for CML-CP.

METHODS

In a retrospective cohort analysis, we included data from patients with CML-CP treated in prospective clinical trials with frontline TKI modalities at a single institution between July 31, 2000, and Sept 10, 2013. The main aim of the study was to determine whether achievement of complete cytogenetic response or major molecular response had similar prognostic implications irrespective of the frontline TKI modality used. We analysed each TKI modality for response assessment and analysed survival endpoints (event-free, failure-free, transformation-free, and overall survival) with the Kaplan-Meier method. Univariate and multivariate analyses were done with Cox proportional hazard regression.

FINDINGS

Our analysis included 482 patients who were treated with imatinib 400 mg daily (n=68), imatinib 800 mg daily (n=200), dasatinib 50 mg twice daily or 100 mg daily (n=106), or nilotinib 400 mg twice daily (n=108). More patients receiving imatinib 800 mg or second-generation TKIs (ie, dasatinib or nilotinib) achieved complete cytogenetic response (58 [87%] of 67 for imatinib 400 mg vs 180 [90%] of 199 for imatinib 800 mg, vs 100 [96%] of 104 for dasatinib vs 99 [93%] of 107 for nilotinib), major molecular response (51 [76%] vs 171 [86%] vs 93 [90%] vs 97 [91%]), and 4·5 log or higher reduction in BCR-ABL transcripts (MR(4·5) response 38 [57%] vs 148 [74%] vs 76 [71%] vs 76 [71%]). This finding was consistent over time (3-60 months). 5-year event free survival significantly differed between the imatinib 400 mg group and the other TKI groups (imatinib 800 mg p=0·029, dasatinib p=0·003, nilotinib p=0·031). There was no significant difference in 5-year failure-free survival (p=0·32, p=0·075, p=0·332), transformation-free survival (p=0·053, p=0·038, p=0·493), or overall survival (p=0·563, p=0·162, p=0·981). Multivariate analysis showed that therapy with imatinib 800 mg (HR 0·51, 95% CI 0·29-0·88, p=0·016), dasatinib (0·28, 0·12-0·66, p=0·004), or nilotinib (0·42, 0·20-0·89, p=0·024) predicted for better event-free survival compared with imatinib 400 mg, but that failure-free, transformation-free, and overall survival were similar irrespective of the TKI used. 28 (41%) patients receiving imatinib 400 mg, 85 (43%) receiving imatinib 800 mg, 23 (21%) receiving dasatinib, and 27 (25%) receiving nilotinib discontinued treatment for any reason.

INTERPRETATION

Treatment with imatinib 800 mg or the second-generation TKIs dasatinib or nilotinib resulted in superior and deeper responses than did standard-dose imatinib, which were maintained after 5 years of follow-up. Results with imatinib 800 mg were similar to those with second-generation TKIs, although more patients discontinued therapy.

FUNDING

MD Anderson Cancer Center, National Cancer Institute.

Importance of early and deeper responses to long-term survival in CML patients: Implications of BCR-ABL testing in management of CML in Indian setting

The prognosis of patients with chronic myeloid leukemia (CML) has changed radically since the advent of imatinib mesylate, a selective inhibitor of BCR-ABL tyrosine kinase. Shortly thereafter, more potent BCR-ABL inhibitors (dasatinib and nilotinib) were introduced for use in patients resistant to or intolerant of imatinib. All three drugs are now approved for initial therapy for chronic phase CML. Response to tyrosine kinase inhibitor (TKI) treatment is assessed with standardized quantitative reverse transcriptase polymerase chain reaction (Q-RTPCR) and/or cytogenetics at 3, 6 and 12 months. Clinical trials have clearly demonstrated that early and deeper cytogenetic and molecular response to TKI therapy is associated with lower rate of disease progression and improved long-term outcomes. In recent times, molecular response as determined by BCR-ABL transcript levels at defined time points is rapidly gaining popularity as a predictive marker for subsequent outcomes in CML. Optimal response is defined as BCR-ABL transcript levels of ≤10% at 3 months, <1% at 6 months, and ≤0.1% from 12 months onward while >10% at 6 months and >1% from 12 months onward define failure. Patients who do not achieve molecular milestones at 3 or 6 months with 3 months being highly predictive are less likely to achieve cytogenetic responses eventually; early identification of such patients who have a low probability of achieving an adequate response are thus candidates for alternative treatment. Review of literature by electronic search of MEDline, Google Scholar was done using keywords and data was identified and systematically evaluated.

Evaluation of response to first-line treatment for chronic myeloid leukemia: has imatinib been outperformed?

SUMMARY 

Achievement of deep, early response to first-line tyrosine kinase inhibitor (TKI) therapy significantly predicts favorable long-term outcome in chronic myeloid leukemia (CML). Although imatinib is an effective first-line treatment, nilotinib and dasatinib, more potent TKIs, are more effective in eliciting deep, rapid response to therapy and preventing disease progression, and may represent superior first-line treatment options in CML. Although many patients who are resistant to, or intolerant of first-line imatinib can be rescued by second-line TKIs, the clinical outlook for these patients is inferior, particularly if there is disease progression. Therefore, clinicians should strive to minimize the occurrence of disease progression, and optimize the depth of response early in the treatment course in patients with chronic-phase CML.

Long-term outcome with dasatinib after imatinib failure in chronic-phase chronic myeloid leukemia: follow-up of a phase 3 study

We present long-term follow-up of a dasatinib phase 3 study of patients with imatinib-resistant/-intolerant chronic myeloid leukemia (CML). In the CA180-034 study, 670 patients with imatinib-resistant/-intolerant CML in chronic phase (CML-CP) received dasatinib 100 mg once daily, 50 mg twice daily, 140 mg once daily, or 70 mg twice daily. At 6 years, 188 (28%) of 670 patients remained on study treatment. Estimated 6-year protocol-defined progression-free survival (PFS) rates were 49%, 51%, 40%, and 47%, respectively, and estimated 6-year overall survival (OS) rates were 71%, 74%, 77%, and 70%, respectively (intent-to-treat population, including protocol-defined progression or death after discontinuation). Estimated 6-year rates of survival without transformation on study treatment were 76%, 80%, 83%, and 74%, respectively. Major molecular response was achieved in 43% (100 mg once daily) and 40% (all other arms) of patients by 6 years. Molecular and cytogenetic responses at 3 and 6 months were highly predictive of PFS and OS. Notably, estimated 6-year PFS rates based on ≤1%, >1% to 10%, and >10% BCR-ABL transcripts at 3 months were 68%, 58%, and 26%, respectively. Most adverse events occurred by 2 years. Imatinib-resistant/-intolerant patients with CML-CP can experience long-term benefit with dasatinib therapy, particularly if achieving BCR-ABL ≤10% at 3 months. This study was registered at ClinicalTrials.gov: NCT00123474.

Considerations for early switch to nilotinib or dasatinib in patients with chronic myeloid leukemia with inadequate response to first-line imatinib

Clinical evidence in chronic myeloid leukemia demonstrates a significant link between optimal response to tyrosine kinase inhibitor (TKI) therapy and favorable clinical outcome. For patients with suboptimal response to first-line TKI, clinical data show that a considerable proportion can be rescued by second-line TKI. Practice guidelines now recommend that clinicians consider a switch in TKI for patients with suboptimal response as early as 3 months after first-line TKI initiation, thus allowing clinicians to intervene in a timely manner and consider the potential benefit of a switch in TKI therapy.

Early responses predict better outcomes in patients with newly diagnosed chronic myeloid leukemia: results with four tyrosine kinase inhibitor modalities

Early responses to tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia (CML)-chronic phase (CP) are associated with improved outcome. We analyzed the impact of such a response on outcomes among patients treated with 4 TKI modalities as frontline therapy in CML-CP. A total of 483 patients who received 400 or 800 mg imatinib, nilotinib, or dasatinib were analyzed. The median follow-up was 72 mo. Landmark analysis at 3 mo by molecular response showed that the cumulative proportions of 3-y event-free survival (EFS) for 3-mo BCR-ABL levels was 95% for those with ≤1%, 98% for >1% to 10%, and 61% for those with >10% (P = .001). The corresponding values by cytogenetic responses were 97% if Ph+ = 0%, 89% if Ph+ = 1% to 35%, and 81% if Ph+ >35% (P = .001). Cytogenetic response at 3 mo significantly discriminated for 3-y overall survival (OS): 98%, 96%, and 92%, respectively (P = .01). In multivariate analysis, young patients, high Sokal index, and treatment with imatinib 400 significantly predicted for poor (>35%) cytogenetic response at 3 mo. Early responses are predictive for EFS and failure-free survival and to a lesser extent OS, regardless of the treatment modality, although therapies other than standard-dose imatinib result in higher rates of deep early responses.

Genome Fusion Detection: a novel method to detect fusion genes from SNP-array data

MOTIVATION

Fusion genes result from genomic rearrangements, such as deletions, amplifications and translocations. Such rearrangements can also frequently be observed in cancer and have been postulated as driving event in cancer development. to detect them, one needs to analyze the transition region of two segments with different copy number, the location where fusions are known to occur. Finding fusion genes is essential to understanding cancer development and may lead to new therapeutic approaches.

RESULTS

Here we present a novel method, the Genomic Fusion Detection algorithm, to predict fusion genes on a genomic level based on SNP-array data. This algorithm detects genes at the transition region of segments with copy number variation. With the application of defined constraints, certain properties of the detected genes are evaluated to predict whether they may be fused. We evaluated our prediction by calculating the observed frequency of known fusions in both primary cancers and cell lines. We tested a set of cell lines positive for the BCR-ABL1 fusion and prostate cancers positive for the TMPRSS2-ERG fusion. We could detect the fusions in all positive cell lines, but not in the negative controls.