Responses to second-line tyrosine kinase inhibitors are durable: an intention-to-treat analysis in chronic myeloid leukemia patients

CFL1 is Implicated in Chronic Myeloid Leukemia Response during Imatinib Therapy

Cofilin (CFL1) is one critical member of the actin deploy family (ADF). Overexpression of CFL1 is associated with aggressive features and poor prognosis in malignancies. We evaluated the expression of CFL1 in patients with chronic myeloid leukemia in the chronic phase (CML-CP), acute myelocytic leukemia (AML) and healthy controls. The role of CFL1 in imatinib therapy was also investigated using cell line. We found that the expression of CFL1 was lower in CML patients than that in healthy controls, and was significantly upregulated after imatinib therapy (p<0.05). CML patients with lower CFL1 achieved higher Major molecular response (MMR) rate after 6 months of imatinib therapy (p<0.05). Cofilin, P-cofilin and F-actin, especially branched F-actin were all upregulated after imatinib therapy. The lower CFL1 expression before treatment may predicts a better response to imatinib. Imatinib affects F-actin remodeling in CML patients by regulating CFL1 expression and activity.

Prognosis in Chronic Myeloid Leukemia: Baseline Factors, Dynamic Risk Assessment and Novel Insights

The introduction of tyrosine kinase inhibitors (TKIs) has changed the treatment paradigm of chronic myeloid leukemia (CML), leading to a dramatic improvement of the outcome of CML patients, who now have a nearly normal life expectancy and, in some selected cases, the possibility of aiming for the more ambitious goal of treatment-free remission (TFR). However, the minority of patients who fail treatment and progress from chronic phase (CP) to accelerated phase (AP) and blast phase (BP) still have a relatively poor prognosis. The identification of predictive elements enabling a prompt recognition of patients at higher risk of progression still remains among the priorities in the field of CML management. Currently, the baseline risk is assessed using simple clinical and hematologic parameters, other than evaluating the presence of additional chromosomal abnormalities (ACAs), especially those at "high-risk". Beyond the onset, a re-evaluation of the risk status is mandatory, monitoring the response to TKI treatment. Moreover, novel critical insights are emerging into the role of genomic factors, present at diagnosis or evolving on therapy. This review presents the current knowledge regarding prognostic factors in CML and their potential role for an improved risk classification and a subsequent enhancement of therapeutic decisions and disease management.

Transplantation in CML in the TKI era: who, when, and how?

Molecular therapy with tyrosine kinase inhibitors (TKIs) has significantly reduced the indication for allogeneic hematopoietic stem cell transplantation (allo-HSCT) in chronic myeloid leukemia (CML). Treatment-free remission can be obtained in about 50% of patients with an optimal response. However, cure rates up to 90% are restricted to patients receiving HSCT. Timing is essential since HSCT in the early stages of the disease has the best outcome. Patients in a more advanced phase (AdP) than chronic-phase (chP) CML undergo HSCT with suboptimal outcomes, and the gap between chP and AdP disease is widening. First-line therapy should start with first- or second-generation (G) TKIs. Patients failing treatment (BCR-ABL1 transcripts of greater than 10% at 3 and 6 months and greater than 1% at 12 months) should be switched to second-line TKIs, and HSCT should be considered. Patients not responding to 2G-TKI therapy as well as patients in an accelerated phase (AP) or blast crisis (BC) are candidates for HSCT. Therapy resistant BCR-ABL1 mutations, high-risk additional cytogenetic abnormalities, and molecular signs of leukemia progression should trigger the indication for HSCT. Patients who, despite dose adjustments, do not tolerate or develop severe adverse events, including vascular events, to multiple TKIs are also candidates for HSCT. In AdP CML, TKIs do not show long-lasting results, and the outcome of HSCT is less optimal without pretransplant therapy. In these patients the induction of chP2 with TKIs, either alone (AP) or in combination with intensive chemotherapy (BC), followed by HSCT should be pursued.

Precision Medicine in Low- and Middle-Income Countries

Most cancer cases occur in low- and middle-income countries (LMICs). The sophisticated technical and human infrastructure needed for optimal diagnosis, treatment, and monitoring of cancers is difficult enough in affluent countries; it is especially challenging in LMICs. In Western, educated, industrial, rich, democratic countries, there is a growing emphasis on and success with precision medicine, whereby targeted therapy is directed at cancers based on the specific genetic lesions in the cancer. Can such precision approaches be delivered in LMICs? We offer some examples of novel partnerships and creative solutions that suggest that precision medicine may be possible in LMICs given heavy doses of will, creativity, and persistence and a little luck.

Molecular testing of chronic myeloid leukaemia in low resource areas

Most cancer cases occur in areas of low resources. The diagnosis, treatment and monitoring of cancers is especially challenging in these locations. Unique partnerships exist between non-profit organisations and pharmaceutical companies to provide free drugs to CML patients throughout the world if the diagnosis can be rigorously and unambiguously established. But there lies the rub: How do you perform molecular diagnostics in areas where even electricity is unreliable? Here we describe the evolution of testing patients from low resource areas, which, when merged with a remarkable effort to bring tyrosine kinase inhibitors to patients across the globe, have led to survival outcomes similar to cases in industrialised countries.

New approaches to molecular monitoring in CML (and other diseases)

Chronic myeloid leukemia (CML) is the model cancer, demonstrating the clinical benefits of targeted therapy and the power of molecular diagnostics and monitoring. In CML, the BCR-ABL1 fusion gene and its companion messenger RNA offers a unique target differentiating cancer from the normal cell, affording the potential for very sensitive and specific assays. Because CML is such an ideal model, new methods are arising that should make testing in CML faster, more reliable, and reach a greater sensitivity. New ultrasensitive sequencing approaches, coupled with single-cell genomic approaches, further the study of measurable residual disease, clonal heterogeneity, and promise to make clinical trials more innovative and informative. These methods should be able to be transferred to other hematological and solid malignancies.

Responses to Dasatinib as a Second- and Third-Line Tyrosine Kinase Inhibitor in Chronic Phase Chronic Myeloid Leukaemia Patients

We retrospectively evaluated the efficacy and safety of dasatinib among 48 Chinese patients with chronic phase chronic myeloid leukaemia. The proportions of patients achieving the optimal molecular responses at 3, 6, and 12 months, a major molecular response (MMR) rate and a complete cytogenetic response (CCyR) rate were 87.0, 87.0, 72.2, 45.8, and 72.7% for patients with dasatinib as second-line therapy, and 34.8, 34.8, 33.3, 20.8, and 46.2% as third-line therapy, respectively. A BCR-ABL1 transcript level on the International Scale (BCR-ABL1IS) of ≤10% at the initiation of -dasatinib treatment was found to be associated with a higher probability of achieving MMR. Among patients with a -BCR-ABL1IS higher than 10% at initiation of dasatinib treatment, dasatinib showed better performance as a second-line therapy than as a third-line therapy. The patients who achieved an optimal molecular response at 3 months had a superior cumulative incidence of MMR and CCyR compared with patients who failed to achieve such a response. Dasatinib induced considerable responses as a second-line treatment, especially in patients with a BCR-ABL1IS ≤10% at initiation of treatment, whereas the efficacy was limited in patients receiving third-line therapy with a BCR-ABL1IS >10% at the initiation of treatment.

We do still transplant CML, don't we?

The remarkable clinical activity of tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia (CML) has transformed patient outcome. Consequently, allogeneic stem cell transplantation (allo-SCT) is no longer the only treatment modality with the ability to deliver long-term survival. In contrast to the central position it held in the treatment algorithm 20 years ago, allografting is now largely reserved for patients with either chronic-phase disease resistant to TKI therapy or advanced-phase disease. Over the same period, progress in transplant technology, principally the introduction of reduced intensity conditioning regimens coupled with increased donor availability, has extended transplant options in patients with CML whose outcome can be predicted to be poor if they are treated with TKIs alone. Consequently, transplantation is still a vitally important, potentially curative therapeutic modality in selected patients with either chronic- or advanced-phase CML. The major causes of transplant failure in patients allografted for CML are transplant toxicity and disease relapse. A greater understanding of the distinct contributions made by various factors such as patient fitness, patient-donor HLA disparity, conditioning regimen intensity, and transplant toxicity increasingly permits personalized transplant decision making. At the same time, advances in the design of conditioning regimens coupled with the use of adjunctive posttransplant cellular and pharmacologic therapies provide opportunities for reducing the risk of disease relapse. The role of SCT in the management of CML will grow in the future because of an increase in disease prevalence and because of continued improvements in transplant outcome.

New Methodologies in the Molecular Monitoring of CML

In chronic myeloid leukemia (CML), the BCR-ABL fusion gene is both the therapeutic target of tyrosine kinase inhibitors and the indisputable direct marker of disease burden. Thus, sensitive assays for BCR-ABL now drive therapeutic options and are good surrogates for short- and long-term outcomes. Because CML is such an ideal model, new methods are arising that should make testing in CML faster, more reliable, and reach a greater sensitivity. These methods should be able to be transferred to other hematological malignancies that have mutation markers.

Treating the chronic-phase chronic myeloid leukemia patient: which TKI, when to switch and when to stop?

INTRODUCTION

With the discovery of imatinib mesylate nearly 20 years ago, tyrosine kinase inhibitors (TKIs) were found to be effective in chronic myeloid leukemia (CML). TKI therapy has since revolutionized the treatment of CML and has served as a paradigm of success for targeted drug therapy in cancer. Several new TKIs for CML have been approved over the last two decades that exhibit improved potency over imatinib and have different off-target profiles, providing options for individualized therapy selection. Areas covered: Current management of chronic phase CML, including guidance on the sequential use of imatinib and newer-generation TKIs and evolving treatment strategies such as TKI discontinuation. Relevant literature was identified by searching biomedical databases (i.e. PubMed) for primary research material. Expert commentary: Although survival outcomes have drastically improved for CML patients, treatment for CML has grown more complex with the introduction of next-generation TKIs and the advent of treatment-free remissions (TFR). Goals of therapy have shifted accordingly, with increased focus on improving quality of life, managing patient expectations and optimizing patient adherence.

Predictive parameters for imatinib failure in patients with chronic myeloid leukemia

OBJECTIVE

Until recently, imatinib was the standard first-line treatment in chronic myeloid leukemia (CML). The inclusion of nilotinib and dasatinib as first-line options in CML raised a debate on treatment selection. The aim of our study was to analyze predictive parameters for imatinib response as the first-line treatment of CML patients.

METHODS

The study included 168 consecutive patients with chronic phase Philadelphia-positive CML who were diagnosed and treated with Imatinib 400 mg once daily at a single university hospital. Numerous parameters were analyzed in terms of imatinib response including comorbidities as well as occurrence of second malignancies.

RESULTS

After the median follow-up of 87 months in 61 patients (36.3%), the imatinib failure was verified. Cox regression analysis identified hepatomegaly (p = 0.001), leukocytosis ≥ 100 × 109/l (p = 0.001), blood blasts ≥ 1% (p = 0.002), and the presence of additional cytogenetic aberrations (p = 0.002) as predictors of Imatinib failure. Based on these findings, a new prognostic model was developed according to which imatinib failure had 17% (8/47) of patients in low risk, 34.9% (30/86) of patients in intermediate risk, and 76.7% (23/30) of patients in high-risk group (HR = 3.973, 95% CI for HR 2.237-7.053, p < 0.001).

CONCLUSION

The new score allows better selection of patients who are suitable for treatment with imatinib and may guideline the clinical decision for front-line treatment of CML.

Molecular monitoring of chronic myeloid leukemia: present and future

INTRODUCTION

Fusion of BCR-ABL1 genes causes chronic myeloid leukemia (CML). As a reliable marker of disease burden, it also serves as the target of tyrosine kinase inhibitors (TKIs). New more sensitive molecular diagnostic tools for BCR-ABL1 can contribute to therapeutic decision-making, especially in considering drug discontinuation for patients enjoying prolonged deep molecular response. Areas covered: Several novel platforms are transforming CML molecular diagnostics to enable faster point-of-care devices, better understanding of clonal diversity and resistance mutations. Here, we review these molecular platforms, knowing implementation in other hematological malignancies will ensue. Expert commentary: Treatment with TKI in CML is the first example of a highly effective targeted therapy. Monitoring of BCR-ABL1 mRNA is standard in assessing disease burden being highly predictive of outcomes recommended by both European LeukemiaNet (ELN) and National Comprehensive Cancer Network (NCCN); however, studies has demonstrated poor adherence to these recommendations. In both clinical practice and assay performance, further optimizing of BCR-ABL1 monitoring can be envisioned including point-of-care methods for increased availability of rapid, standardized testing and increasingly sensitive molecular assays that allow for quantification of MRD and detecting resistance mutations.

Monitoring disease burden in chronic myeloid leukemia: Past, present, and future

Tyrosine kinase inhibitor (TKI) therapy yields sustained cytogenetic remissions in most patients with chronic-phase chronic myeloid leukemia (CML). Peripheral blood quantitative reverse transcription polymerase chain reaction (qRT-PCR) monitoring of the chimeric BCR-ABL1 mRNA transcript levels is a very sensitive method to measure disease burden in patients with cytogenetic remission. qRT-PCR allows identification of patients (1) at high risk of progression early (3-6 months) after treatment initiation, (2) with no response to TKI therapy, (3) with undetectable disease who could be eligible for TKI discontinuation trials. Molecular monitoring is a minimally invasive method to optimize treatment and outcomes in CML. Am. J. Hematol. 91:742-746, 2016. © 2016 Wiley Periodicals, Inc.

Chronic myeloid leukemia: reminiscences and dreams

With the deaths of Janet Rowley and John Goldman in December 2013, the world lost two pioneers in the field of chronic myeloid leukemia. In 1973, Janet Rowley, unraveled the cytogenetic anatomy of the Philadelphia chromosome, which subsequently led to the identification of the BCR-ABL1 fusion gene and its principal pathogenetic role in the development of chronic myeloid leukemia. This work was also of major importance to support the idea that cytogenetic changes were drivers of leukemogenesis. John Goldman originally made seminal contributions to the use of autologous and allogeneic stem cell transplantation from the late 1970s onwards. Then, in collaboration with Brian Druker, he led efforts to develop ABL1 tyrosine kinase inhibitors for the treatment of patients with chronic myeloid leukemia in the late 1990s. He also led the global efforts to develop and harmonize methodology for molecular monitoring, and was an indefatigable organizer of international conferences. These conferences brought together clinicians and scientists, and accelerated the adoption of new therapies. The abundance of praise, tributes and testimonies expressed by many serve to illustrate the indelible impressions these two passionate and affable scholars made on so many people's lives. This tribute provides an outline of the remarkable story of chronic myeloid leukemia, and in writing it, it is clear that the historical triumph of biomedical science over this leukemia cannot be considered without appreciating the work of both Janet Rowley and John Goldman.

BCR-ABL1 Transcript Levels at 3 and 6 Months Are Better for Identifying Chronic Myeloid Leukemia Patients with Poor Outcome in Response to Second-Line Second-Generation Tyrosine Kinase Inhibitors after Imatinib Failure: A Report from a Single Institution

Early reduction of BCR-ABL1 transcript levels has been associated with improved outcome in chronic myeloid leukemia (CML) treatment. We evaluated 54 chronic-phase CML patients treated with imatinib who switched therapy to dasatinib (n = 33) or nilotinib (n = 21). BCR-ABL1 transcript levels were measured in peripheral blood using real-time quantitative PCR (RQ-PCR) every 3 months from the start of second-line treatment. Patients with BCR-ABL transcript levels >10% at 3 months and >1% at 6 months had significantly inferior progression-free (PFS) and event-free survival (EFS) than patients with RQ-PCR <10% at 3 months and <1% at 6 months (66 vs. 100%, p = 0.01, and 33 vs. 73%, p = 0.02, respectively). Patients with RQ-PCR <10% at 3 months and >1% at 6 months also had inferior PFS and EFS than patients with RQ-PCR <10% at 3 months and <1% at 6 months (48 vs. 100%, p = 0.002, and 25 vs. 73%, p < 0.0001, respectively). Two measurements of BCR-ABL levels were better than a single one to stratify chronic-phase CML patients as failure after second-line therapy.

Bosutinib Therapy in Patients With Chronic Myeloid Leukemia: Practical Considerations for Management of Side Effects

The past decade has witnessed great advances in the treatment of chronic myeloid leukemia (CML), brought about in large part by the development of BCR-ABL tyrosine kinase inhibitors (TKIs). Bosutinib joins the armamentarium of approved TKIs for the treatment of chronic phase (CP), accelerated phase (AP), and blast phase (BP) Philadelphia chromosome (Ph)-positive CML resistant to or intolerant of prior therapy. Bosutinib has an adverse-event (AE) profile distinct from that of other TKIs. Diarrhea is the predominant toxicity associated with bosutinib treatment; other commonly reported nonhematologic AEs include rash and liver enzyme elevations. Cardiac events, fluid retention, and electrolyte abnormalities are infrequent. Optimal response to bosutinib requires adherence, which depends, in part, upon optimal management of associated toxicities. The oncology clinician can facilitate this process by providing patient education, timely patient follow-up, and close monitoring to promptly identify and manage AEs. Thus, optimal patient management requires a thorough and current understanding of toxicity profiles and AE management paradigms. This review provides an overview of bosutinib safety data derived from ongoing clinical trials and offers practical clinical strategies currently used to manage toxicities associated with bosutinib treatment in patients with Ph-positive CP, AP, and BP CML.

Treatment with dasatinib or nilotinib in chronic myeloid leukemia patients who failed to respond to two previously administered tyrosine kinase inhibitors--a single center experience

OBJECTIVE

To evaluate hematological, cytogenetic and molecular responses as well as the overall, progression-free and event-free survivals of chronic myeloid leukemia patients treated with a third tyrosine kinase inhibitor after failing to respond to imatinib and nilotinib/dasatinib.

METHODS

Bone marrow karyotyping and real-time quantitative polymerase chain reaction were performed at baseline and at 3, 6, 12 and 18 months after the initiation of treatment with a third tyrosine kinase inhibitor. Hematologic, cytogenetic and molecular responses were defined according to the European LeukemiaNet recommendations. BCR-ABL1 mutations were analyzed by Sanger sequencing.

RESULTS

We evaluated 25 chronic myeloid leukemia patients who had been previously treated with imatinib and a second tyrosine kinase inhibitor. Nine patients were switched to dasatinib, and 16 patients were switched to nilotinib as a third-line therapy. Of the chronic phase patients (n=18), 89% achieved a complete hematologic response, 13% achieved a complete cytogenetic response and 24% achieved a major molecular response. The following BCR-ABL1 mutations were detected in 6/14 (43%) chronic phase patients: E255V, Y253H, M244V, F317L (2) and F359V. M351T mutation was found in one patient in the accelerated phase of the disease. The five-year overall, progression-free and event-free survivals were 86, 54 and 22% (p<0.0001), respectively, for chronic phase patients and 66%, 66% and 0% (p<0.0001), respectively, for accelerated phase patients. All blast crisis patients died within 6 months of treatment. Fifty-six percent of the chronic phase patients lost their hematologic response within a median of 23 months.

CONCLUSIONS

Although the responses achieved by the third tyrosine kinase inhibitor were not sustainable, a third tyrosine kinase inhibitor may be an option for improving patient status until a donor becomes available for transplant. Because the long-term outcome for these patients is poor, the development of new therapies for resistant chronic myeloid leukemia patients is necessary.

Chronic myeloid leukaemia

In less than 10 years, the prognosis of chronic myeloid leukaemia has changed from that of a fatal disease to a disorder amenable simply to lifelong oral medication and compatible with a normal lifespan. This change has been made possible by a deep understanding of the molecular pathogenesis and a determination to develop targeted and selective drugs. This Seminar summarises the presentation, pathophysiology, diagnosis and monitoring technology, treatment options, side-effects, and outcomes of chronic myeloid leukaemia, and discusses the possibility of cure-ie, stable undetectable or low level disease in the absence of medication. Chronic myeloid leukaemia continues to instruct us in the mechanisms of leukaemogenesis and provides hope not only for similar developments in management of other malignancies, but also for the remarkable speed with which these can move from bench to bedside.

Diagnosing and managing advanced chronic myeloid leukemia

Clinical staging of chronic myeloid leukemia (CML) distinguishes between chronic phase (CP-CML), accelerated phase (AP-CML), and blastic phase (BP-CML), reflecting its natural history in the absence of effective therapy. Morphologically, transformation from CP-CML to AP/BP-CML is characterized by a progressive or sudden loss of differentiation. Multiple different somatic mutations have been implicated in transformation from CP-CML to AP/BC-CML, but no characteristic mutation or combination of mutations have emerged. Gene expression profiles of AP-CML and BP-CML are similar, consistent with biphasic evolution at the molecular level. Gene expression of tyrosine kinase inhibitor (TKI)-resistant CP-CML and second CP-CML resemble AP/BP-CML, suggesting that morphology alone is a poor predictor of biologic behavior. At the clinical level, progression to AP/BP-CML or resistance to first-line TKI therapy distinguishes a good risk condition with survival close to the general population from a disease likely to reduce survival. Progression while receiving TKI therapy is frequently caused by mutations in the target kinase BCR-ABL1, but progression may occur in the absence of explanatory BCR-ABL1 mutations, suggesting involvement of alternative pathways. Identifying patients in whom milestones of TKI response fail to occur or whose disease progress while receiving therapy requires appropriate molecular monitoring. Selection of salvage TKI depends on prior TKI history, comorbidities, and BCR-ABL1 mutation status. Despite the introduction of novel TKIs, therapy of AP/BP-CML remains challenging and requires accepting modalities with substantial toxicity, such as hematopoietic stem cell transplantation (HSCT).

Current status of hematopoietic stem cell transplant in chronic myeloid leukemia

Indications for hematopoietic stem cell transplant (HSCT) in chronic myeloid leukemia (CML) have changed over time. This change has largely been influenced by the advent of tyrosine kinase inhibitors, increased understanding of the mechanisms underlying disease phase progression as well as drug resistance, refinement of transplant techniques and exploitation of graft versus leukemia effect in this disease. Here, we have discussed the status of HSCT in CML in the present era with regards to the current indications, factors determining outcome and management strategies for posttransplant relapse.

Definition and treatment of resistance to tyrosine kinase inhibitors in chronic myeloid leukemia

Resistance to tyrosine kinase inhibitors (TKIs) has many facets. The causes of resistance include low patient compliance, low plasma or intracellular drug concentration, BCR-ABL1 mutations, and clonal chromosome abnormalities in Ph+ cells, but in at least 50% of patients the causes are currently unknown. Primary resistance occurs when a predefined response level is not achieved within a prespecified period of time. Not achieving a complete hematologic response (CHR) within 3 months, not achieving a partial cytogenetic response and/or a BCR-ABL1 transcripts level ≤10% (international standard) within 6 months, and not achieving a complete cytogenetic response (CCyR) and/or a BCR-ABL1 transcripts level <1% within 12 months, define primary resistance. Secondary resistance is defined by a loss of CHR, or CCyR, or major molecular response. Resistance to imatinib calls without exceptions for a second-generation TKI. In case of resistance to two TKIs, an allogeneic stem cell transplantation should be considered.

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.

Deep molecular response in chronic myeloid leukemia: the new goal of therapy?

Chronic myeloid leukemia (CML) is caused by formation of the BCR-ABL1 fusion protein. Tyrosine kinase inhibitors (TKI) that target BCR-ABL1 are now the standard of care for patients with CML. Molecular monitoring of residual BCR-ABL1 mRNA transcripts, typically performed using real-time quantitative PCR, has improved treatment management, particularly for patients with CML in chronic phase. Major molecular response (MMR; i.e., a ≥3-log reduction in BCR-ABL1 transcript levels) is used in current treatment guidelines to assess prognosis. Recent evidence suggests that deeper molecular responses (≥4-log reductions in BCR-ABL1 transcript levels), particularly when attained early during treatment, may have even better correlation with long-term outcomes, including survival and disease progression. Furthermore, achieving deep molecular response is a requirement for entering trials evaluating treatment-free remission (TFR). In this review, we discuss the evolving definition of minimal residual disease and the various levels of molecular response under evaluation in current clinical studies. In addition, the available clinical data on achieving MMR and deeper levels of molecular response with TKI therapy, the prognostic value of deep molecular response, and factors that may predict a patient's ability to achieve and sustain a deep molecular response on TKI therapy are also discussed. Available data from TFR studies are addressed. We discuss current knowledge of the ideal conditions for attempting treatment discontinuation, factors predictive of molecular relapse, when TKI therapy should be restarted, and which therapeutic strategies (when administered in the first-line setting and beyond) are expected to best enable successful TFR.

Preclinical and clinical efficacy of XPO1/CRM1 inhibition by the karyopherin inhibitor KPT-330 in Ph+ leukemias

As tyrosine kinase inhibitors (TKIs) fail to induce long-term response in blast crisis chronic myelogenous leukemia (CML-BC) and Philadelphia chromosome-positive (Ph(+)) acute lymphoblastic leukemia (ALL), novel therapies targeting leukemia-dysregulated pathways are necessary. Exportin-1 (XPO1), also known as chromosome maintenance protein 1, regulates cell growth and differentiation by controlling the nucleocytoplasmic trafficking of proteins and RNAs, some of which are aberrantly modulated in BCR-ABL1(+) leukemias. Using CD34(+) progenitors from CML, B-ALL, and healthy individuals, we found that XPO1 expression was markedly increased, mostly in a TKI-sensitive manner, in CML-BC and Ph(+) B-ALL. Notably, XPO1 was also elevated in Ph(-) B-ALL. Moreover, the clinically relevant XPO1 inhibitor KPT-330 strongly triggered apoptosis and impaired the clonogenic potential of leukemic, but not normal, CD34(+) progenitors, and increased survival of BCR-ABL1(+) mice, 50% of which remained alive and, mostly, became BCR-ABL1 negative. Moreover, KPT-330 compassionate use in a patient with TKI-resistant CML undergoing disease progression significantly reduced white blood cell count, blast cells, splenomegaly, lactate dehydrogenase levels, and bone pain. Mechanistically, KPT-330 altered the subcellular localization of leukemia-regulated factors including RNA-binding heterogeneous nuclear ribonucleoprotein A1 and the oncogene SET, thereby inducing reactivation of protein phosphatase 2A tumor suppressor and inhibition of BCR-ABL1 in CML-BC cells. Because XPO1 is important for leukemic cell survival, KPT-330 may represent an alternative therapy for TKI-refractory Ph(+) leukemias.

[Current diagnostic requirements in chronic myeloid leukemia]

In patients with chronic myeloid leukemia, high-quality diagnostics is of paramount importance for the surveillance of treatment efficacy. The availability of new tyrosine kinase inhibitors providing more rapid and deeper responses requires the employment of standardized and highly sensitive diagnostic methods to ensure optimal monitoring of the patients. This review presents the current international diagnostic standards and the certified laboratories in Austria.

Current survival measures reliably reflect modern sequential treatment in CML: correlation with prognostic stratifications

Using the data of 723 chronic myeloid leukemia (CML) patients in the chronic phase, we analyzed the prognostic value of the Sokal, Euro, and EUTOS scores as well as the level of BCR-ABL1 and the achievement of complete cytogenetic response (CCgR) at 3 months of imatinib therapy in relation to the so-called current survival measures: the current cumulative incidence (CCI) reflecting the probability of being alive and in CCgR after starting imatinib therapy; the current leukemia-free survival (CLFS) reflecting the probability of being alive and in CCgR after achieving the first CCgR; and the overall survival. The greatest difference between the CCI curves at 5 years after initiating imatinib therapy was observed for the BCR-ABL1 transcripts at 3 months. The 5-year CCI was 94.3% in patients with BCR-ABL1 transcripts ≤ 10% and 57.1% in patients with BCR-ABL1 transcripts > 10% (P = 0.005). Therefore, the examination of BCR-ABL1 transcripts at 3 months may help in early identification of patients who are likely to perform poorly with imatinib. On the other hand, CLFS was not significantly affected by the considered stratifications. In conclusion, our results indicate that once the CCgR is achieved, the prognosis is good irrespective of the starting prognostic risks.

European LeukemiaNet recommendations for the management of chronic myeloid leukemia: 2013

Advances in chronic myeloid leukemia treatment, particularly regarding tyrosine kinase inhibitors, mandate regular updating of concepts and management. A European LeukemiaNet expert panel reviewed prior and new studies to update recommendations made in 2009. We recommend as initial treatment imatinib, nilotinib, or dasatinib. Response is assessed with standardized real quantitative polymerase chain reaction and/or cytogenetics at 3, 6, and 12 months. BCR-ABL1 transcript levels ≤10% at 3 months, <1% at 6 months, and ≤0.1% from 12 months onward define optimal response, whereas >10% at 6 months and >1% from 12 months onward define failure, mandating a change in treatment. Similarly, partial cytogenetic response (PCyR) at 3 months and complete cytogenetic response (CCyR) from 6 months onward define optimal response, whereas no CyR (Philadelphia chromosome-positive [Ph+] >95%) at 3 months, less than PCyR at 6 months, and less than CCyR from 12 months onward define failure. Between optimal and failure, there is an intermediate warning zone requiring more frequent monitoring. Similar definitions are provided for response to second-line therapy. Specific recommendations are made for patients in the accelerated and blastic phases, and for allogeneic stem cell transplantation. Optimal responders should continue therapy indefinitely, with careful surveillance, or they can be enrolled in controlled studies of treatment discontinuation once a deeper molecular response is achieved.

Allogeneic stem cell transplantation for chronic myeloid leukemia

In recent years new, more potent tyrosine-kinase inhibitors have been introduced to accompany imatinib for the treatment of chronic myeloid leukemia. Most patients in chronic phase obtain an optimal response to these oral agents with minimal toxicity. Allogeneic stem cell transplantation is therefore indicated only in a minority of patients who do not achieve an adequate response to first, second or third generation agents. Patients in accelerated phase have a lower chance of achieving an optimal response on these drugs. For patients in blast phase, transplantation remains the only therapy with curative potential, although now it is increasingly used in combination with tyrosine-kinase inhibitors. In this review we address the role of allogeneic stem cell transplantation in the treatment of this disease and how patients should be transplanted.

The next questions in chronic myeloid leukaemia and their answers

PURPOSE OF REVIEW

In this review, we analyze some of the topical issues in the clinical management of chronic myeloid leukaemia (CML).

RECENT FINDINGS

In recent years, the management of CML patients has increased in complexity as molecular monitoring has brought to the clinical scene new therapeutic targets and the second-generation tyrosine kinase inhibitors have been licensed for first-line use.

SUMMARY

In this article, we will try to answer some of the questions that a practising physician may face in clinical practice, such as: What should be the aim of therapy? What is the best front-line therapy? Which patients should receive an allogeneic stem cell transplant?

Bcl-xL anti-apoptotic network is dispensable for development and maintenance of CML but is required for disease progression where it represents a new therapeutic target

The dismal outcome of blast crisis chronic myelogenous leukemia (CML-BC) patients underscores the need for a better understanding of the mechanisms responsible for the development of drug resistance. Altered expression of the anti-apoptoticBcl-xL has been correlated with BCR-ABL leukemogenesis; however, its involvement in the pathogenesis and evolution of CML has not been formally demonstrated yet. Thus, we generated an inducible mouse model in which simultaneous expression of p210-BCR-ABL1 and deletion of bcl-x occurs within hematopoietic stem and progenitor cells. Absence of Bcl-xL did not affect development of the chronic phase-like myeloproliferative disease, but none of the deficient mice progressed to an advanced phenotype, suggesting the importance of Bcl-xL in survival of progressing early progenitor cells. Indeed, pharmacological antagonism of Bcl-xL, with ABT-263, combined with PP242-induced activation of BAD markedly augmented apoptosis of CML-BC cell lines and primary CD34(+) progenitors but not those from healthy donors, regardless of drug resistance induced by bone marrow stromal cell-generated signals. Moreover, studies in which BAD or Bcl-xL expression was molecularly altered strongly support their involvement in ABT-263/PP242-induced apoptosis of CML-BC progenitors. Thus, suppression of the antiapoptotic potential of Bcl-xL together with BAD activation represents an effective pharmacological approach for patients undergoing blastic transformation.

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.

Rapid initial decline in BCR-ABL1 is associated with superior responses to second-line nilotinib in patients with chronic-phase chronic myeloid leukemia

BACKGROUND

We evaluated BCR-ABL1 kinetics in patients treated with nilotinib and analyzed whether a dynamic model of changes in BCR-ABL1 levels over time could be used to predict long-term responses.

METHODS

Patients from the nilotinib registration trial (CAMN107A2101; registered at http://www.clinicaltrials.gov as NCT00109707) who had imatinib-resistant or -intolerant Philadelphia chromosome-positive (Ph+) chronic myeloid leukemia (CML) in chronic phase (CP) or accelerated phase with BCR-ABL1 > 10% (on the international scale [IS]) at baseline and, in the first 6 months, had at least three BCR-ABL1 transcript measurements and an average daily dose of at least 720 mg were included in this analysis (N = 123).

RESULTS

More than half of patients (65/123; 53%) had a slow monophasic response and the remainder (58/123; 47%) had a biphasic response, in which patients had a rapid initial decrease in BCR-ABL1 transcripts followed by a more gradual response. The biphasic response type strongly correlated with improved event-free survival (EFS). Data in the first 6 months of follow-up were sufficient to predict EFS at 24 months.

CONCLUSIONS

Unlike newly diagnosed patients with Ph+ CML-CP-in whom the majority had a biphasic response-approximately half of patients with imatinib-resistant or -intolerant CML had a slower, monophasic response. Second-line patients who did have a biphasic response had an EFS outlook similar to that of newly diagnosed patients treated with imatinib. Our model was comparable to using BCR-ABL1 (IS) ≤ 10% at 6 months as a threshold for predicting EFS.

The achievement of a 3-month complete cytogenetic response to second-generation tyrosine kinase inhibitors predicts survival in patients with chronic phase chronic myeloid leukemia after imatinib failure

BACKGROUND

We assessed whether the achievement of a 3-month complete cytogenetic response (CCyR) in 123 patients with chronic myeloid leukemia (CML) in the chronic phase, which was treated with second-generation tyrosine kinase inhibitors (2nd-TKI) after imatinib failure could predict for survival.

PATIENTS AND METHODS

In a multivariate analysis, the lack of a 3-month CCyR to 2nd-TKI therapy was selected as the only independent factor associated with poor event-free survival (hazard ratio [HR] 4.5; P < .001) and overall survival (5.4; P = .03).

RESULTS

The 3-year event-free survival and overall survival rates were 74% and 43%, respectively, for patients with 3-month CCyR, and were 98% and 79%, respectively, for patients without 3-month CCyR. In a multivariate analysis, high hemoglobin level, previous major cytogenetic response to imatinib therapy, and ≤90% Philadelphia-positive metaphases were associated with the achievement of a 3-month CCyR.

CONCLUSION

The achievement of a 3-month CCyR is the only predictor of outcome in patients treated with 2nd-TKI therapy after imatinib failure. Patients with <3-month CCyR may not obtain long-term benefit and should be followed-up closely.

Update on current monitoring recommendations in chronic myeloid leukemia: practical points for clinical practice

Excellent therapeutic options exist for the treatment of chronic-phase chronic myeloid leukemia (CML) patients. Therefore, managing CML patients has become a more common practice for many physicians. Most chronic-phase CML patients achieve durable cytogenetic and molecular responses on first-line tyrosine kinase inhibitor therapy. However, careful monitoring and assessment of adherence are essential for successful outcomes and to identify patients at risk for failing therapy. The European LeukemiaNet and National Comprehensive Cancer Network provide guidance and strategies for monitoring and managing patients treated with TKIs. These recommendations continue to evolve as approved treatment options expand to include second- and third-generation tyrosine kinase inhibitors. How measurements of response are defined and data supporting recent recommended changes to monitoring are reviewed here. These changes include increasing recognition of the importance of early response. The relevance of achieving deep molecular responses will also be addressed.

Initial choice of therapy among plenty for newly diagnosed chronic myeloid leukemia

Imatinib has been the preferred initial therapy for newly diagnosed chronic myeloid leukemia patients for the past 10 years. Recently, other, possibly better, tyrosine kinase inhibitors have been licensed for first-line use based on the early results of 2 large, randomized clinical trials. The pros and cons of the various alternatives to imatinib are analyzed herein, and I try to answer the question of are we ready to abandon imatinib and, if yes, then what treatment should a patient diagnosed today receive.

Nilotinib in imatinib-resistant or imatinib-intolerant patients with chronic myeloid leukemia in chronic phase: 48-month follow-up results of a phase II study

Nilotinib (Tasigna) is a BCR-ABL1 tyrosine kinase inhibitor approved for the treatment of patients with Philadelphia chromosome-positive chronic myeloid leukemia in chronic phase (CML-CP) who are newly diagnosed or intolerant of or resistant to imatinib. The 48-month follow-up data for patients with CML-CP treated with nilotinib after imatinib resistance or intolerance on an international phase II study were analyzed. Overall, 59% of patients achieved major cytogenetic response; 45% achieved complete cytogenetic response while on study. The estimated rate of overall survival (OS) and progression-free survival (PFS) at 48 months was 78% and 57%, respectively. Deeper levels of molecular responses at 3 and 6 months were highly positively correlated with long-term outcomes, including PFS and OS at 48 months. Of the 321 patients initially enrolled in the study, 98 (31%) were treated for at least 48 months. Discontinuations were primarily due to disease progression (30%) or adverse events (21%). Nilotinib is safe and effective for long-term use in responding patients with CML-CP who are intolerant of or resistant to imatinib. Further significant improvements in therapy are required for patients who are resistant or intolerant to imatinib.

Predictive value of early molecular response in patients with chronic myeloid leukemia treated with first-line dasatinib

Dasatinib is effective therapy for newly diagnosed patients with chronic myeloid leukemia, but not all patients respond well. We analyzed the outcome of patients treated with dasatinib as first-line therapy to identify patients who are more likely to fare poorly. The 8.6% of patients who at 3 months had a BCR-ABL1/ABL1 ratio > 10% had a significantly worse 2-year cumulative incidence of complete cytogenetic response (58.8% vs 96.6%, P < .001) and molecular responses than the remaining patients with a lower transcript levels. The predictive value of the 3-month transcript level could be improved using the dasatinib-specific transcript level cut-offs, namely, 2.2%, 0.92%, and 0.57% for complete cytogenetic response, 3 log and 4.5 log reductions in the transcript level, respectively. The study was registered at www.clinicaltrials.gov as #NCT01460693.

Definitions, methodological and statistical issues for phase 3 clinical trials in chronic myeloid leukemia: a proposal by the European LeukemiaNet

The treatment policy of chronic myeloid leukemia (CML), particularly with tyrosine kinase inhibitors, has been influenced by several recent studies that were well designed and rapidly performed, but their interpretation is of some concern because different end points and methodologies were used. To understand and compare the results of the previous and future studies and to translate their conclusion into clinical practice, there is a need for common definitions and methods for analyses of CML studies. A panel of experts was appointed by the European LeukemiaNet with the aim of developing a set of definitions and recommendations to be used in design, analyses, and reporting of phase 3 clinical trials in this disease. This paper summarizes the consensus of the panel on events and major end points of interest in CML. It also focuses on specific issues concerning the intention-to-treat principle and longitudinal data analyses in the context of long-term follow-up. The panel proposes that future clinical trials follow these recommendations.