Chimeric antigen-receptor (CAR) engineered natural killer cells in a chronic myeloid leukemia (CML) blast crisis model

During the last two decades, the introduction of tyrosine kinase inhibitors (TKIs) to the therapy has changed the natural history of CML but progression into accelerated and blast phase (AP/BP) occurs in 3-5% of cases, especially in patients resistant to several lines of TKIs. In TKI-refractory patients in advanced phases, the only curative option is hematopoietic stem cell transplantation. We and others have shown the relevance of the expression of the Interleukin-2-Receptor α subunit (IL2RA/CD25) as a biomarker of CML progression, suggesting its potential use as a therapeutic target for CAR-based therapies. Here we show the development of a CAR-NK therapy model able to target efficiently a blast crisis cell line (K562). The design of the CAR was based on the scFv of the clinically approved anti-CD25 monoclonal antibody (Basiliximab). The CAR construct was integrated into NK92 cells resulting in the generation of CD25 CAR-NK92 cells. Target K562 cells were engineered by lentiviral gene transfer of CD25. In vitro functionality experiments and in vivo leukemogenicity experiments in NSG mice transplanted by K562-CD25 cells showed the efficacy and specificity of this strategy. These proof-of-concept studies could represent a first step for further development of this technology in refractory/relapsed (R/R) CML patients in BP as well as in R/R acute myeloblastic leukemias (AML).

Accelerated-phase CML: de novo and transformed

Despite the dramatic improvements in outcomes for the majority of chronic myeloid leukemia (CML) patients over the past 2 decades, a similar improvement has not been observed in the more advanced stages of the disease. Blast phase CML (BP-CML), although infrequent, remains poorly understood and inadequately treated. Consequently, the key initial goal of therapy in a newly diagnosed patient with chronic phase CML continues to be prevention of disease progression. Advances in genomic investigation in CML, specifically related to BP-CML, clearly demonstrate we have only scratched the surface in our understanding of the disease biology, a prerequisite to devising more targeted and effective therapeutic approaches to prevention and treatment. Importantly, the introduction of the concept of "CML-like" acute lymphoblastic leukemia (ALL) has the potential to simplify the differentiation between BCR::ABL1-positive ALL from de novo lymphoid BP-CML, optimizing monitoring and therapeutics. The development of novel treatment strategies such as the MATCHPOINT approach for BP-CML, utilizing combination chemotherapy with fludarabine, cytarabine, and idarubicin in addition to dose-modified ponatinib, may also be an important step in improving treatment outcomes. However, identifying patients who are high risk of transformation remains a challenge, and the recent 2022 updates to the international guidelines may add further confusion to this area. Further work is required to clarify the identification and treatment strategy for the patients who require a more aggressive approach than standard chronic phase CML management.

A Case Report of Chronic Myelogenous Leukemia Presenting as Blastic Crisis with a T-Cell Acute Lymphoblastic Leukemia Phenotype: Awareness of a Rare Entity

Chronic myelogenous leukemia at blast crisis with a T-cell phenotype (T-ALL CML-BC) at diagnosis, without any prior history of CML is extremely rare. After the introduction of tyrosine kinase inhibitors (TKIs), CML patients have a median survival comparable to general population and accelerated/blast crisis are rarely encountered. Most CML patients (80%) transform into acute myeloid leukemia and the rest into B-ALL. Anecdotal cases of Ph+ T-ALL, either de novo or in the context of CML-BC have been reported. Left shift in the blood, the presence of splenomegaly/extramedullary infiltration and the occurrence of BCR::ABL1 rearrangement in both the blastic population, as well as in the myeloid cell compartment are key points in differentiating de novo Ph+ T-ALL from T-ALL CML-BC. The latter is a rare entity, characterized by extramedullary disease, p210 transcript and clonal evolution. Lack of preceding CML does not rule out the diagnosis of T-ALL CML-BC. Prompt TKI treatment with ALL-directed therapy followed by allogeneic stem cell transplantation may offer long-term survival in this otherwise poor prognosis entity. In this paper, we describe a patient with T-ALL CML-BC at presentation, still alive 51 months after diagnosis and we offer a review of the literature on this rare subject. All clinical and laboratory features are provided in order to distinguish de novo Ph+ T-ALL from T-ALL CML-BC, underscoring the prognostic and therapeutic significance of such a differentiation.

Blast phase myeloproliferative neoplasm: contemporary review and 2024 treatment algorithm

Leukemic transformation in myeloproliferative neoplasms (MPN), also referred to as "blast-phase MPN", is the most feared disease complication, with incidence estimates of 1-4% for essential thrombocythemia, 3-7% for polycythemia vera, and 9-13% for primary myelofibrosis. Diagnosis of MPN-BP requires the presence of ≥20% circulating or bone marrow blasts; a lower level of excess blasts (10-19%) constitutes "accelerated phase" disease (MPN-AP). Neither "intensive" nor "less intensive" chemotherapy, by itself, secures long-term survival in MPN-BP. Large-scale retrospective series have consistently shown a dismal prognosis in MPN-BP, with 1- and 3-year survival estimates of <20% and <5%, respectively. Allogeneic hematopoietic stem cell transplant (AHSCT) offers the possibility of a >30% 3-year survival rate and should be pursued, ideally, while the patient is still in chronic phase disease. The value of pre-transplant bridging chemotherapy is uncertain in MPN-AP while it is advised in MPN-BP; in this regard, we currently favor combination chemotherapy with venetoclax (Ven) and hypomethylating agent (HMA); response is more likely in the absence of complex/monosomal karyotype and presence of TET2 mutation. Furthermore, in the presence of an IDH mutation, the use of IDH inhibitors, either alone or in combination with Ven-HMA, can be considered. Pre-transplant clearance of excess blasts is desired but not mandated; in this regard, additional salvage chemotherapy is more likely to compromise transplant eligibility rather than improve post-transplant survival. Controlled studies are needed to determine the optimal pre- and post-transplant measures that target transplant-associated morbidity and post-transplant relapse.

Outcomes after allogeneic hematopoietic cell transplant in patients diagnosed with blast phase of myeloproliferative neoplasms: A retrospective study from the Chronic Malignancies Working Party of the European Society for Blood and Marrow Transplantation

Allogeneic hematopoietic cell transplant (allo-HCT) provides the only potential route to long-term remission in patients diagnosed with blast phase transformation of myeloproliferative neoplasm (BP-MPN). We report on a large, retrospective European Society for Blood and Marrow Transplantation registry-based study of BP-MPN patients undergoing allo-HCT. BP-MPN patients undergoing first allo-HCT between 2005 and 2019 were included. A total of 663 patients were included. With a median follow-up of 62 months, the estimated 3-year overall survival (OS) was 36% (95% confidence interval [CI], 32-36). Factors associated with lower OS were Karnofsky Performance Score (KPS) <90 (hazard ratio [HR] 1.65, p < .001) and active disease at allo-HCT (HR 1.45, p < .001), whereas patients undergoing allo-HCT more recently associated with a higher OS (HR 0.96, p = .008). In a selected patient's population, the 3-year OS of patients undergoing allo-HCT in complete response (CR) and with a KPS ≥90 was 60%. KPS < 90 (HR 1.4, p = .001) and active disease (HR 1.44, p = .0004) were associated with a lower progression-free survival (PFS). Conversely, most recent allo-HCT associated with a higher PFS (HR 0.96, p = .008). Active disease at allo-HCT (HR 1.34, p = .03) was associated with a higher cumulative incidence of relapse (RI) and allo-HCT in earlier calendar years (HR 0.96, p = .02) associated with a lower RI. Last, KPS < 90 (HR 1.91, p < .001), active disease (HR 1.74, p = .003) and allo-HCT from mismatched related donors were associated with a higher non-relapse mortality (HR 2.66, p = .003). In this large series of BP-MPN patients, about one third were alive at 3 years after transplantation. Patients undergoing allo-HCT in the more recent era, with a KPS ≥90 and in CR at transplant had a better prognosis.

Comparison of Different Treatment Strategies for Blast-Phase Myeloproliferative Neoplasms

INTRODUCTION

Up to 20% of patients with myeloproliferative neoplasms (MPN) will progress to blast phase (MPN-BP). Outcomes are dismal, with intensive chemotherapy providing little benefit. Low-intensity therapy is preferred due to better tolerability, but the prognosis remains poor. Allogeneic stem cell transplant (AHSCT) is still the only potential for long term survival.

PATIENTS AND METHODS

To better evaluate the initial treatment approach in MPN-BP, we performed a single-institution retrospective analysis of 75 patients with MPN-BP treated at Moffitt Cancer Center between 2001 and 2021. Patients were stratified by initial treatment: best supportive care (BSC), hypomethylating agent (HMA)-based therapy or intensive chemotherapy (IC).

RESULTS

Median overall survival (mOS) for the entire cohort was 4.8 months (BSC 0.8 months, HMA 4.7 months, and IC 11.4 months). Among IC patients, improved survival was evident in those that received AHSCT (mOS 40.8 months vs. 4.9 months, p < .01). Most patients that underwent AHSCT were initially treated with IC (p < .01). All patients that underwent AHSCT had achieved complete response (CR) or CR with incomplete hematological recovery (CRi). On multivariate analysis, factors associated with improved survival were receipt of therapy (HMA or IC) (P = .017), CR/CRi (P = .037) and receipt of AHSCT (p < .001).

CONCLUSION

We show that active treatment with IC improves survival, but it is mostly tied to receipt of AHSCT. IC is a reasonable approach in appropriate patients as it can provide an effective bridge to AHSCT. Other treatment strategies such as molecularly targeted therapy and novel agents are desperately needed.

Blast and accelerated phase CML: room for improvement

Tyrosine kinase inhibitors (TKIs) revolutionized the treatment of chronic myeloid leukemia (CML). With TKI therapy, the percentage of patients who progress to accelerated phase (AP) or blast phase (BP) CML has decreased from more than 20% to 1% to 1.5% per year. Although AP- and BP-CML occur in a minority of patients, outcomes in these patients are significantly worse compared with chronic phase CML, with decreased response rates and duration of response to TKI. Despite this, TKIs have improved outcomes in advanced phase CML, particularly in de novo AP patients, but are often inadequate for lasting remissions. The goal of initial therapy in advanced CML is a return to a chronic phase followed by consideration for bone marrow transplantation. The addition of induction chemotherapy with TKI is often necessary for achievement of a second chronic phase. Given the small population of patients with advanced CML, development of novel treatment strategies and investigational agents is challenging, although clinical trial participation is encouraged in AP and BP patients, whenever possible. We review the overall management approach to advanced CML, including TKI selection, combination therapy, consideration of transplant, and novel agents.

Accelerated Phase of Myeloproliferative Neoplasms

BACKGROUND

Myeloproliferative neoplasms (MPNs) can transform into blast phase MPN (leukemic transformation; MPN-BP), typically via accelerated phase MPN (MPN-AP), in ∼20-25% of the cases. MPN-AP and MPN-BP are characterized by 10-19% and ≥20% blasts, respectively. MPN-AP/BP portend a dismal prognosis with no established conventional treatment. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the sole modality associated with long-term survival.

SUMMARY

MPN-AP/BP has a markedly different mutational profile from de novo acute myeloid leukemia (AML). In MPN-AP/BP, TP53 and IDH1/2 are more frequent, whereas FLT3 and DNMT3A are rare. Higher incidence of leukemic transformation has been associated with the most aggressive MPN subtype, myelofibrosis (MF); other risk factors for leukemic transformation include rising blast counts above 3-5%, advanced age, severe anemia, thrombocytopenia, leukocytosis, increasing bone marrow fibrosis, type 1 CALR-unmutated status, lack of driver mutations (negative for JAK2, CALR, or MPL genes), adverse cytogenetics, and acquisition of ≥2 high-molecular risk mutations (ASXL1, EZH2, IDH1/2, SRSF2, and U2AF1Q157). The aforementioned factors have been incorporated in several novel prognostic scoring systems for MF. Currently, elderly/unfit patients with MPN-AP/BP are treated with hypomethylating agents with/without ruxolitinib; these regimens appear to confer comparable benefit to intensive chemotherapy but with lower toxicity. Retrospective studies in patients who acquired actionable mutations during MPN-AP/BP showed positive outcomes with targeted AML treatments, such as IDH1/2 inhibitors, and require further evaluation in clinical trials. Key Messages: Therapy for MPN-AP patients represents an unmet medical need. MF patients, in particular, should be appropriately stratified regarding their prognosis and the risk for transformation. Higher-risk patients should be monitored regularly and treated prior to progression to MPN-BP. MPN-AP patients may be treated with hypomethylating agents alone or in combination with ruxolitinib; also, patients can be provided with the option to enroll in rationally designed clinical trials exploring combination regimens, including novel targeted drugs, with an ultimate goal to transition to transplant.

A stem cell reporter based platform to identify and target drug resistant stem cells in myeloid leukemia

Intratumoral heterogeneity is a common feature of many myeloid leukemias and a significant reason for treatment failure and relapse. Thus, identifying the cells responsible for residual disease and leukemia re-growth is critical to better understanding how they are regulated. Here, we show that a knock-in reporter mouse for the stem cell gene Musashi 2 (Msi2) allows identification of leukemia stem cells in aggressive myeloid malignancies, and provides a strategy for defining their core dependencies. Specifically, we carry out a high throughput screen using Msi2-reporter blast crisis chronic myeloid leukemia (bcCML) and identify several adhesion molecules that are preferentially expressed in therapy resistant bcCML cells and play a key role in bcCML. In particular, we focus on syndecan-1, whose deletion triggers defects in bcCML growth and propagation and markedly improves survival of transplanted mice. Further, live imaging reveals that the spatiotemporal dynamics of leukemia cells are critically dependent on syndecan signaling, as loss of this signal impairs their localization, migration and dissemination to distant sites. Finally, at a molecular level, syndecan loss directly impairs integrin β7 function, suggesting that syndecan exerts its influence, at least in part, by coordinating integrin activity in bcCML. These data present a platform for delineating the biological underpinnings of leukemia stem cell function, and highlight the Sdc1-Itgβ7 signaling axis as a key regulatory control point for bcCML growth and dissemination.

Rapid Fire: Acute Blast Crisis/Hyperviscosity Syndrome

Emergency providers are likely to encounter patients with acute and chronic leukemias. In some cases, the first presentation to the emergency department may be for symptoms related to blast crisis and leukostasis. Making a timely diagnosis and consulting a hematologist can be life saving. Presenting symptoms are caused by complications of bone marrow infiltration and hyperleukocytosis with white blood cell counts over 100,000. Presentations may include fatigue (anemia), bleeding (thrombocytopenia), shortness of breath, and/or neurologic symptoms owing to hyperleukocytosis and subsequent leukostasis. Treatment of symptomatic cases involves induction chemotherapy and/or leukapheresis. Asymptomatic hyperleukocytosis can be treated with hydroxyurea.

Evaluation of healthcare resource utilization and incremental economic burden of patients with chronic myeloid leukemia after disease progression to blast phase

AIMS

To evaluate healthcare resource utilization and economic burden of patients with chronic myeloid leukemia (CML) progression to the blast phase.

METHODS

Patients (≥ 18 years) with ≥1 inpatient or ≥2 outpatient CML diagnoses were identified from the MarketScan Commercial and Medicare databases (January 1, 2007-June 30, 2015). CML patients were grouped into two study cohorts, those with evidence of disease progression to the blast phase and those without. Patients were required to have continuous medical and prescription coverage during a 12-month baseline period, in which demographics and clinical characteristics were evaluated. All-cause healthcare resource utilization and costs were evaluated during the baseline period, and a variable follow-up period, lasting ≥1 day and up to 1 year. Generalized linear models (GLM) were used to compare the incremental costs of CML patients with vs without progression.

RESULTS

Of the overall study population, 587 (7%) experienced disease progression and 7,504 (93%) did not. On the index date, of patients with progression, ∼ 31% were treated with allogeneic hematopoietic cell transplant and 69% with chemotherapy. During the baseline period, mean total healthcare costs, including costs for hospitalizations and outpatient costs, were significantly greater for CML patients with progression as compared to those without progression ($143,778 vs $53,143, p < .001). During the follow-up, mean total healthcare costs, costs for hospitalizations, and outpatient medical service costs were substantially greater for patients with progression as compared to those without progression; however, costs for outpatient prescriptions were less for patients who progressed. When patient characteristics were controlled for, mean incremental 1-year cost for CML patients with vs without progression was $270,925 (confidence interval = $235,290-$311,958, p < .001).

CONCLUSIONS

The healthcare burden, in terms of healthcare resource utilization and costs, of patients with CML progression is substantial. Healthcare providers and payers should consider various strategies to minimize the rate of CML progression.

T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is biologically distinct from its B lymphoblastic (B-ALL) counterpart and shows different kinetic patterns of disease response. Although very similar regimens are used to treat T-ALL and B-ALL, distinctions in response to different elements of therapy have been observed. Similar to B-ALL, the key prognostic determinant in T-ALL is minimal residual disease (MRD) response. Unlike B-ALL, other factors including age, white blood cell count at diagnosis, and genetics of the ALL blasts are not independently prognostic when MRD response is included. Recent insights into T-ALL biology, using modern genomic techniques, have identified a number of recurrent lesions that can be grouped into several targetable pathways, including Notch, Jak/Stat, PI3K/Akt/mTOR, and MAPK. With contemporary chemotherapy, outcomes for de novo T-ALL have steadily improved and now approach those observed in B-ALL, with approximately 85% 5-year event-free survival. Unfortunately, salvage has remained poor, with less than 25% event-free and overall survival rates for relapsed disease. Thus, current efforts are focused on preventing relapse by augmenting therapy for high-risk patients, sparing toxicity in favorable subsets and developing new approaches for the treatment of recurrent disease.

Potential mechanisms of disease progression and management of advanced-phase chronic myeloid leukemia

Despite vast improvements in the treatment of Philadelphia chromosome-positive chronic myeloid leukemia (CML) in chronic phase (CP), advanced stages of CML, accelerated phase or blast crisis, remain notoriously difficult to treat. Treatments that are highly effective against CML-CP produce disappointing results against advanced disease. Therefore, a primary goal of therapy should be to maintain patients in CP for as long as possible, by (1) striving for deep, early molecular response to treatment; (2) using tyrosine kinase inhibitors that lower risk of disease progression; and (3) more closely observing patients who demonstrate cytogenetic risk factors at diagnosis or during treatment.

[Sudden blast crisis of chronic myeloid leukemia after a 13-year durable remission following allogeneic bone marrow transplantation and donor lymphocyte infusion]

We describe a rare case of sudden blast crisis of chronic myeloid leukemia that occurred after a 13-year durable remission, following allogeneic bone marrow transplantation and donor lymphocyte infusion. A 55-year-old Japanese man was diagnosed with chronic-phase chronic myeloid leukemia 24 years previously. He underwent allogeneic bone marrow transplantation 2 years after diagnosis. Although the disease recurred 6 years after transplantation, the patient achieved remission again by a donor lymphocyte infusion. Despite a 13-year durable remission, the disease later relapsed into a sudden blast crisis. Prednisolone and vincristine combined with imatinib mesylate effectively achieved a major molecular response. However, the disease relapsed repeatedly with central nervous system infiltration. Dasatinib and intrathecal methotrexate, cytarabine, and dexamethasone administration via the Ommaya reservoir controlled disease progression. Nevertheless, the disease became refractory to treatment with the emergence of a T315I Bcr-Abl gene mutation. The patient eventually died 43 months post crisis.

Chronic myelomonocytic leukemia: myelodysplastic or myeloproliferative?

Chronic myelomonocytic leukemia (CMML) is a clonal disease of the hematopoietic stem cell that provokes a stable increase in peripheral blood monocyte count. The World Health Organisation classification appropriately underlines that the disease combines dysplastic and proliferative features. The percentage of blast cells in the blood and bone marrow distinguishes CMML-1 from CMML-2. The disease is usually diagnosed after the age of 50, with a strong male predominance. Inconstant and non-specific cytogenetic aberrations have a negative prognostic impact. Recurrent gene mutations affect mainly the TET2, SRSF2, and ASXL1 genes. Median survival is 3 years, with patients dying from progression to AML (20-30%) or from cytopenias. ASXL1 is the only gene whose mutation predicts outcome and can be included within a prognostic score. Allogeneic stem cell transplantation is possibly curative but rarely feasible. Hydroxyurea, which is the conventional cytoreductive agent, is used in myeloproliferative forms, and demethylating agents could be efficient in the most aggressive forms of the disease.

Dasatinib maintenance therapy after allogeneic hematopoietic stem cell transplantation for an isolated central nervous system blast crisis in chronic myelogenous leukemia

A 22-year-old male with Ph-positive chronic myelogenous leukemia (CML) was started on treatment with imatinib. After 12 months of therapy, he achieved a complete cytogenetic response (CCyR). Although the CCyR persisted in his bone marrow, he developed an isolated CML blast crisis in his central nervous system (CNS) after 29 months of therapy. He underwent allogeneic hematopoietic stem cell transplantation (HSCT) following combination therapy with dasatinib, intrathecal chemotherapy and cranial irradiation. Subsequently, 168 days after allogeneic HSCT, he was started on dasatinib maintenance therapy to prevent a CNS relapse. Thirty-eight months after allogeneic HSCT, he has sustained a complete molecular response in both bone marrow and CNS. We believe dasatinib has the potential to prevent CNS relapse if used for maintenance therapy after allogeneic HSCT.

Proposed criteria for response assessment in patients treated in clinical trials for myeloproliferative neoplasms in blast phase (MPN-BP): formal recommendations from the post-myeloproliferative neoplasm acute myeloid leukemia consortium

Leukemic transformation (LT) of a myeloproliferative neoplasm (MPN) is associated with a dismal prognosis and no medical therapies have shown a survival improvement in patients with MPN in blast phase (MPN-BP). Effective therapies for the treatment of MPN-BP are a serious unmet need. Consensus response criteria do not exist for the treatment of patients with MPN-BP and this is necessary for the uniformed reporting of treatment response in clinical trials. We have identified relevant MPN and MPN-BP features in order to define treatment response categories that reflect hematological, clinical, pathological, cytogenetic and molecular changes after therapeutic intervention. We plan to validate these proposed response criteria within multi-centered clinical trials.

Day 15 bone marrow driven double induction in young adult patients with acute myeloid leukemia: feasibility, toxicity, and therapeutic results

The strategy named double induction (DI) in acute myeloid leukemia (AML) consists of two courses of chemotherapy irrespective of the degree of cytoreduction in the bone marrow (BM) after the first course, unless severe complications prohibit its application. We describe treatment results from a series of 33 patients in whom DI was adopted only after demonstration of persistence of more than 10% blast cells at day 15 (D15) examination of BM. All patients received as induction idarubicin, cytarabine, and etoposide. As second induction, we administered the combination of fludarabine, intermediate dose cytarabine, and Granulocyte colony stimulating factor (G-CSF). The median blast count at D15 was 30 (15-90). Overall, 30 of 33 patients were judged as eligible to receive DI, reasons for exclusion being in all cases active infection in the context of severe pancytopenia. Nineteen patients (63%) had unfavorable karyotype and 11 (37%) normal karyotype; seven of these had Fms-like tyrosine kinase gene internal tandem duplication (FLT3/ITD) mutation. Overall, complete remission (CR) was achieved in 20/30 patients (67%), while eight patients (27%) were refractory and two died of infectious complications. All refractory patients had unfavorable cytogenetics. All patients achieving CR were programmed to receive allogeneic stem cell transplantation (allo-SCT), which was actually performed in 11 patients. Our study suggest that D15 driven DI represents a feasible and effective therapeutic strategy in young adult AML patients, improving therapeutic results and not compromising feasibility of allo-SCT. When compared with conventional DI, it offers the potential to avoid unnecessary toxicity in a consistent proportion of patients.

Prognostic implication of N-RAS gene mutations in Egyptian adult acute myeloid leukemia

The pathogenesis of acute myeloid leukemia (AML) involves the cooperation of mutations promoting proliferation/survival and those impairing differentiation. Point mutations of the N-RAS gene are the most frequent somatic mutations causing aberrant signal-transduction in acute myeloid leukemia (AML). The aim of the present work is to study the frequency and prognostic significance of N-RAS gene mutations (N-RASmut) in de novo Egyptian adult AML. Bone marrow specimens from 150 patients with de novo acute myeloid leukemia and controls were analyzed by genomic PCR-SSCP at codons 12, 13 (exon 1), and 61 (exon 2) for N-RAS mutations. In 12.7% (19/150) AML cases, N-RAS gene mutations were found and were observed more frequently in the FAB subtype M4eo (P = 0.028) and with codon 12, 13 (14 of 19; 73.7%). Patients with N-RAS mutation had a significant lower peripheral and marrow blasts (P = 0.004, P = 0.03) and clinical outcome did not improve more than in patients without mutation. In patients with N-RAS gene mutation vs. those without, complete remission rate was (63.2% vs. 56.5%; P = 0.46), resistant disease (15.8% vs. 23.6%; P = 0.51), three years overall survival (44% vs 42%; P= 0.85) and disease free survival (42.1% vs. 38.9%, P = 0.74). Multivariate analysis showed that age was the strongest unfavorable factor for overall survival (relative risk [RR], 1.9; P = 0.002), followed by cytogenetics (P = 0.004). FAB types, N-RAS mutation and leukocytosis were the least important. In conclusion, the frequency and spectrum of N-RAS gene mutation differ between biologically distinct subtypes of AML but do not significantly influence prognosis and clinical outcome in patients with AML.

Sacroiliitis as an initial manifestation of acute myelogenous leukemia

Sacroiliitis is the most pathognomonic and earliest manifestation of ankylosing spondylitis. We herein report a 28-year-old female patient who presented with sacroiliitis as an initial manifestation of acute myelogenous leukemia (AML). She had a 3-month history of anemia and walking difficulty. Bone marrow findings revealed an increase of blasts with trilineage dysplasia. Although she was initially diagnosed with myelodysplastic syndrome (MDS), blasts rapidly increased and AML developed 1 month after the diagnosis of MDS with Sacroiliitis. Induction chemotherapy failed to induce a complete remission of AML, but it did effectively treat the sacroiliitis. However, the sacroiliitis relapsed when the leukemia cells progressed thereafter. Oral corticosteroids helped ameliorate the sacroiliitis. She underwent bone marrow transplantation (BMT) from an HLA-identical sister during a nonremission period; however, the leukemic cells began to rapidly increase from day 30 after BMT. The close relationship between the occurrence of sacroiliitis and AML suggested that autoimmune sacroiliitis was a paraneoplastic phenomenon of AML in this patient. Although autoimmune disorders develop in a substantial number of MDS patients, they are rarely observed in de novo AML. No previous report has described sacroiliitis as the initial manifestation of de novo AML.

Temporary blast reduction after immunoglobulin administration for congenital cytomegalovirus infection masking infant leukemia with cryptic MLL rearrangement

Differentiation between reactive bone marrow suppression due to viral infection and early stages of leukemia can be difficult particularly in young infants. We report on a 2-month-old girl presenting with pancytopenia and positive markers for congenital cytomegalovirus (CMV) infection. Definitive diagnosis of coexisting pro-B cell infant leukemia with cryptic MLL rearrangement was delayed by the transient regeneration of normal hematopoiesis and reduction of abnormal blastoid cells in the bone marrow following immunoglobulin administration. Molecular diagnosis could only be established using interphase fluorescence in situ hybridization (FISH) analysis which may be considered as a valuable additional diagnostic tool in similar cases.

Allogeneic stem cell transplantation for patients with chronic myeloid leukemia and acute lymphocytic leukemia after Bcr-Abl kinase mutation-related imatinib failure

Resistance to imatinib mesylate is an emerging problem in the treatment of chronic myeloid leukemia (CML), often associated with point mutations in the Bcr-Abl kinase domain. Outcome of patients with such mutations after allogeneic stem cell transplantation (Allo-SCT) is unknown. Ten imatinib-resistant patients with Bcr-Abl kinase mutations received a transplant: 9 had CML (3 in chronic phase, 4 in accelerated phase, and 2 in blast phase) and 1 had Philadelphia-positive acute lymphocytic leukemia (ALL). Patients harbored 9 different protein kinase mutations (T315I mutation, n = 2). Preparative regimens were ablative (n = 7) and nonablative (n = 3). All patients engrafted; there were no treatment-related deaths. Disease response was complete molecular (CMR; n = 7), major molecular (n = 2), and no response (n = 1). Three patients (mutations Q252H, E255K, and T315I) died of relapse after Allo-SCT. Seven patients are alive (6 in CMR) for a median of 19 months. Allo-SCT remains an important salvage option for patients who develop resistance to imatinib through Bcr-Abl mutations.

Expression of MAC-1 (CD11b) in acute myeloid leukemia (AML) is associated with an unfavorable prognosis

There is evidence to suggest, that cellular adhesion molecules and receptors could play a role in leukemia, e.g., through altered adhesive qualities of leukemic blasts. We have studied the expression of the beta2-integrin Mac-1 (CD11b) on mononuclear cells in 48 patients with AML at first diagnosis by flow cytometry using a direct fluorescein-conjugated antibody. A case was defined as positive if more than 20% of the cells expressed Mac-1. Within the FAB types, we observed a high expression rate in cases with M5 (100% MAC-1+ cases, 73% MAC-1+ cells), M4 (75% MAC-1+ cases, 48% MAC-1+ cells) and in cases with FAB-M1 with 71% MAC-1+ cases and 29% MAC-1+ cells. Separating our patients' cohort in cytogenetic risk groups, we could detect significant higher proportions of MAC-1+, cases (88% vs. 27%, P = 0.005) and cells (51% vs. 16%, P = 0.015) with poor cytogenetic risk compared to the favorable risk group. For clinical evaluations only patients treated according to the protocols of the German AML Cooperative Group (AML-CG) were included (n = 29, cases with AML-M3 were excluded). More MAC-1+ cases and cells were found in the "non-responders" group (n = 8) compared to the "responders" group (n = 24). We can conclude that AML cases with high MAC-1 expression are characterized by a worse prognosis. Evaluation of MAC-1 expression in AML might therefore contribute clinically important data with respect to develop new therapies that influence the interactions between integrins like MAC-1 on leukemic cells and endothelial or immunoreactive cells.

Sudden blastic transformation in patients with chronic myeloid leukemia treated with imatinib mesylate

Sudden blastic transformation (SBT) has been reported in 0.5% to 2.5% of patients treated with interferon-α (IFN-α) during the first 3 years of therapy. Imatinib is now standard therapy for patients with chronic myeloid leukemia in chronic phase. We investigated the occurrence of SBT among patients treated with imatinib. Among 541 patients treated with imatinib in chronic phase, 23 developed blast phase, which was of sudden onset (ie, occurring in patients previously in complete cytogenetic remission) in 4 patients (17%; 0.7% of the total), 2 lymphoid and 2 myeloid. Patients with SBT were found to have low-risk features more often at the time of presentation and had achieved optimal response with imatinib. Three of the 4 patients underwent allogeneic stem cell transplantation and achieved a molecular remission. SBT is still a rare event, probably less common than that observed with IFN-α therapy. Continuous monitoring of patients treated with imatinib is mandatory.

Inherited pericentric inversion of chromosome 16 in chronic phase of chronic myeloid leukaemia

The simultaneous occurrence of two specific acquired chromosomal abnormalities in chronic or acute leukaemias is rare. Inherited chromosomal abnormalities are also rare events in the general population. In chronic myeloid leukaemia (CML), characterised by the t(9;22)(q34;q11), the inv(16)(p13q22) has been described associated with the acceleration of disease or onset of blast crisis. We report on a patient with chronic phase of CML and both acquired t(9;22)(q34;q11) and inherited inv(16)(p13q22), who obtained a complete remission of the disease after bone marrow transplant. Therefore, it is worth to comment that an additional chromosomal abnormality in disease does not obligatory mean transformation of the disease to a more aggressive form, since chromosomal abnormalities are also seen in normal individuals.

Allogeneic stem-cell transplantation in patients with refractory acute leukemia: a long-term follow-up

We examined retrospectively 44 patients with refractory acute leukemia (acute myeloid leukemia (AML)/acute lymphoblastic leukemia=25/19) who underwent allogeneic transplantation at our center between 11/1990 and 04/2004. The median leukemic blasts was 25% and age 28 years (range, 3-56). Twenty-one patients had untreated relapse, 13 failed reinduction, eight in partial remission and two aplastic. Conditioning was myeloablative using cyclophosphamide, busulfan, total-body irradiation and etoposide (Bu/Cy/VP, n=22; TBI/Cy/VP, n=17; others, n=5) followed by marrow or peripheral blood transplant (n=23/21) from unrelated or related donors (n=28/16). All patients had graft-versus-host disease (GVHD) prophylaxis with cyclosporin and methotrexate. One patient experienced late graft failure. Severe acute-GVHD and chronic-GVHD appeared in eight and 14 patients, respectively. Thirteen patients (30%) remain alive after a median of 25.3 months (range, 2.4-134.1); with 31 deaths, mostly from relapse (n=15) and infections (n=12). Overall survival (OS) and progression-free survival (PFS) at 5 years was 28 and 26%, respectively. OS and PFS were significantly better with blasts < or =20% and time to transplant < or =1 year while transplant-related mortality was less with the use of TBI. We conclude that patients with refractory leukemia can benefit from allogeneic BMT, especially with < or =20% marrow blast.

Activated natural killer cells from patients with acute myeloid leukemia are cytotoxic against autologous leukemic blasts in NOD/SCID mice

Natural killer (NK) cells are implicated in the surveillance of hematological malignancies. They participate in the immune response against residual acute myeloid leukemia (AML) after hematopoietic stem cell transplantation with partial HLA class I disparity. However, the role of NK cells in autologous leukemia-specific immunity remains poorly understood. We studied the function of NK cells in AML patients at diagnosis. Following isolation, CD56+CD3- cells exhibited a high proliferative potential in vitro in response to interleukin (IL)-2. The polyclonal population of activated AML-NK cells expressed normal levels of the activating receptor NKG2D and the major natural cytotoxicity receptor NKp46. AML-NK cells were highly effective with respect to interferon-gamma production, cytotoxicity against HLA class I-deficient K562 erythroleukemia cells in vitro and retardation of tumor growth in vivo in K562-bearing NOD/SCID mice. Importantly, when AML blasts were injected into NOD/SCID mice, a single dose of adoptively transferred autologous AML-NK cells significantly reduced the AML load by 8-77%. Recognition of AML blasts may be related to the observed upregulation of ligands for NKG2D and natural cytotoxicity receptors in vivo. We conclude that AML patient-derived NK cells are fully functional, in support of exploring the benefit of AML immunotherapy with IL-2-stimulated autologous NK cells.

Blastic phase of chronic myelogenous leukemia

Chronic myeloid leukemia (CML), a clonal stem cell disorder, inevitably evolves into a blastic phase that is very resistant to treatment. Recent developments of a better understanding of molecular changes in CML have led to highly effective targeted therapy that can induce molecular remissions, many of which are long-lasting. It is expected that these approaches will eventually improve treatment of the blastic phase of this disease, the molecular changes during its evolution to blastic phase, and the potential for therapeutic interventions. We review the molecular biology and evolution of treatment of the blastic phase of CML.

Therapie der chronischen myeloischen Leukämie 2004

Chronic myelogenous leukemia constitutes a clinical model for other neoplastic diseases. The cytogenetic hallmark of CML, the Ph chromosome with the molecular juxtaposition of BCR and ABL genes and the multistep pathogenesis with the stable chronic phase, the accelerated phase and the terminal blast crisis provide the background for the translation of molecular-cytogenetic findings into clinical practice. The systematic development of the selective BCR-ABL inhibitor imatinib was based on the discovery of the molecular pathogenesis of CML. Promising preclinical data were confirmed in phase I-III trials. Concerning hematologic and cytogenetic response and adverse effects imatinib is superior to interferon alpha. Open questions are treatment duration in patients with good response, long term side effects, persistence of minimal residual disease in almost all patients, development of resistance after long term therapy, and the efficacy of combination treatments. Prospective clinical trials, e. g. CML study IV of the German CML Study Group, should answer these questions. The impact of the various treatment modalities (imatinib, interferon alpha, ara-C, allogeneic stem cell transplantation) will be elucidated. The recruitment of newly diagnosed CML patients into CML-study IV is recommended.

Allogeneic bone marrow transplantation from an unrelated donor for the treatment of chronic myelogenous leukemia in blast crisis in a patient with Kleinfelter's syndrome

We describe the first reported Klinefelter's syndrome (KS) in which allogeneic bone marrow transplantation from an unrelated donor (UR-BMT) was performed for treatment of chronic myelogenous leukemia in blast crisis (CML-BC). A 31-year-old male patient was diagnosed as having CML-BC with KS in April 2001. The result of a bone marrow chromosomal examination were 47, XXY, t(9;22)(q34;q11). After he had been treated with chemotherapy and imatinib mesylate, he underwent UR-BMT in February 2002. After the UR-BMT, his bone marrow chromosome changed from 47, XXY, t(9;22)(q34;q11) to 46,XY and 100% donor-type chimerism was obtained. However, he relapsed on day 83 after UR-BMT. After treatment with imatinib mesylate and tapering of immunosuppressive agents, skin and liver GVHD developed and then donor-type chimerism was increased with decreased blast cells. However, the patient died due to progression of disease in October 2002.

Early blastic transformation following complete cytogenetic response in a pediatric chronic myeloid leukemia patient treated with imatinib mesylate

This article reports early blastic transformation of chronic myeloid leukemia (CML) in a child following a complete cytogenetic response induced by imatinib mesylate. A 14-year-old Japanese boy was diagnosed with t(9;22) cryptic CML in the chronic phase and treated with imatinib. His response to treatment was slow, but a major cytogenetic response was obtained at 142 days of therapy. However, he developed lymphoid blastic transformation at 9 months. He attained remission with acute lymphoblastic leukemia-type chemotherapy and then successfully received a non-T-cell-depleted allogeneic stem cell transplantation (allo-SCT) with his mother's two loci-mismatched donor cells. A sudden blastic transformation may occur even with a complete cytogenetic response induced by imatinib. CML patients who respond slowly to imatinib may still be candidates for allo-SCT, even when a major cytogenetic response is obtained.

Bilateral renal infarction in chronic myelomonocytic leukemia on blast crisis

The major complications of myelodysplastic syndromes are related to cytopenia and evolution to acute myeloid leukemia. Bleeding episodes in MDS, although relatively uncommon, are often related to thrombocytopenia. Bleeding may be exacerbated by platelet dysfunction, which is also found frequently. Furthermore, the major hemostatic problem underlying hyperleukocytosis, as evident in patients with MDS on blast crisis, appears to be hemorrhage rather than thrombosis. Acute thromboembolism, which causes occlusion of blood supply and organ infarction, has rarely been observed in patients with MDS. Recently, we encountered an elderly female patient, who had chronic myelomonocytic leukemia with marked myelodysplasia, terminating in blast crisis and bilateral renal infarction. This complication rapidly led to oliguric acute renal failure and mortality.

Durable molecular response to imatinib mesylate following nonmyeloablative allogeneic stem-cell transplantation for persisting myeloid blast crisis in chronic myeloid leukemia

We report a chronic myeloid leukemia (CML) patient in chronic phase (CP) who developed blast crisis (BC) under imatinib mesylate administered in a dose reduced and non-continuous fashion because of hematologic intolerance. The patient underwent nonmyeloablative stem-cell transplant from a matched unrelated donor, but failed to achieve full donor chimerism and antileukemic response resulting in persistence of advanced disease. Complete hematologic, cytogenetic and molecular responses were attained 5 weeks after readministration of regularly dosed imatinib and two-step nested RT-PCR confirmed molecular remission throughout a 6 month follow-up period. This is the first case demonstrating that imatinib mesylate is a highly effective and safe treatment option to induce durable molecular remission in patients with CML who remain in myeloid blast crisis after nonmyeloablative allogeneic stem-cell transplantation.

[Successful induction of complete cytogenetic response with high-dose imatinib mesylate and subsequent allogeneic stem cell transplantation for CML blastic crisis]

A 29-year-old man was referred to our hospital with leukocytosis on March 7th, 2002. The white blood cell count was 132.9 x 10(3)/microliter with 42.0% blast cells. We diagnosed Philadelphia chromosome-positive chronic myelogenous leukemia (CML) in a blast crisis and started imatinib mesylate therapy at a dose of 800 mg/day on March 9th, 2002. The patient's peripheral blood blasts had disappeared by March 22nd, 2002, and the percentage of blasts in the bone marrow was 0.6% on May 2nd, 2002. The patient achieved a complete cytogenetic response on May 13th, 2002, and underwent allogeneic peripheral blood stem cell transplantation from his HLA-identical sibling donor on May 30th, 2002. Although adverse reactions such as grade 3/4 of hematological events (leukopenia, anemia, thrombocytopenia and neutropenia) and grade 1/2 of non-hematological events (hyperbilirubinemia, dermatitis and edema) were observed, these adverse reactions were clinically managed. This case suggested the usefulness of imatinib mesylate in the management of the CML-associated blast crisis.

Generation of cytotoxic responses in mice and human individuals against hematological malignancies using survivin-RNA-transfected dendritic cells

Survivin is a member of the inhibitors of apoptosis family and is overexpressed in many types of human cancers, making it an attractive target for T cell-based immunotherapeutic strategies. Recently, HLA-A2-binding peptides derived from the survivin protein were identified as capable of inducing specific T cell responses in cancer patients. Here we demonstrate that human survivin-specific CTLs generated from PBMC by stimulation with autologous dendritic cells transfected with survivin-RNA were cytotoxic for a range of hemopoietic malignant cell lines and primary tumor cells isolated from patients with acute myeloid leukemia. We also show that vaccination of mice with survivin-RNA-transfected dendritic cells leads to long term resistance to challenge by a survivin-expressing lymphoma, demonstrating the potential of survivin as a tumor rejection Ag. Our data provide evidence for the use of survivin as a target structure for immunotherapeutic strategies against hematological neoplasms.

Perspectives on the treatment of chronic phase and advanced phase CML and Philadelphia chromosome positive ALL(1)

Chronic myeloid leukaemia (CML) is a malignant disease of the bone marrow characterised by the presence of the Philadelphia (Ph) chromosome. About 20% of acute lymphoblastic leukaemia (ALL) patients also show this genetic abnormality. A new drug, imatinib (Glivec, Novartis Pharma AG, Basel, Switzerland, and formerly STI571) is having a profound effect on the treatment and management of all stages of CML and Philadelphia chromosome positive (Ph+) ALL. New treatment algorithms are being developed. Should imatinib replace or be combined with existing therapies? To address this question, we review the pros and cons of therapy with interferon-alpha (IFN-alpha), allogeneic transplantation, autologous transplantation, imatinib, and in the case of Ph+ ALL, chemotherapy and experimental approaches. Conservative and aggressive treatments will be discussed and new molecular methods of monitoring cytogenetic response and their significance will also be reviewed.

Factors predicting response and graft-versus-host disease after donor lymphocyte infusions: a study on 593 infusions

In the present study, we analyze factors predicting graft-versus-host disease (GvHD) and response after donor lymphocyte infusions (DLI). A total of 100 patients received 593 DLI between June 1990 and December 2000 in a bulk dose (n=14) or in escalating dose infusions (n=86). Patients were analyzed after stratification for type of relapse: (1). molecular relapse (n=6), (2). cytogenetic relapse (n=20), (3). chronic phase of chronic myeloid leukemia (CML) or complete remission of other disease post chemotherapy (n=24), (4). CML in accelerated/blastic phase (n=14), (5). resistant disease not responding to chemotherapy (n=36). The proportion of responders to DLI in these five groups was 100, 90, 75, 36 and 0% (P<0.0001). Factors predicting response by multivariate analysis were type of relapse (P<0.0001), post-DLI GvHD (P=0.005), pancytopenia (P=0.008), and a diagnosis of CML (P=0.04). Acute GvHD (grades II-IV) occurred in 21 patients (21%), and correlated in multivariate analysis with pancytopenia and less than four DLI. Other predictors of GvHD were the number of CD3+cells/infusion and serum levels of gamma-glutamyl transferase (gammaGT). The actuarial probability of treatment-related mortality was 9% for HLA identical siblings and 44% for alternative donor transplants (P=0.006). Response to DLI is predicted by tumor burden and is associated with GvHD and pancytopenia.

The usefulness of monitoring WT1 gene transcripts for the prediction and management of relapse following allogeneic stem cell transplantation in acute type leukemia

In acute-type leukemia, no method for the prediction of relapse following allogeneic stem cell transplantation based on minimal residual disease (MRD) levels is established yet. In the present study, MRD in 72 cases of allogeneic transplantation for acute myeloid leukemia, acute lymphoid leukemia, and chronic myeloid leukemia (accelerated phase or blast crisis) was monitored frequently by quantitating the transcript of WT1 gene, a "panleukemic MRD marker," using reverse transcriptase-polymerase chain reaction. Based on the negativity of expression of chimeric genes, the background level of WT1 transcripts in bone marrow following allogeneic transplantation was significantly decreased compared with the level in healthy volunteers. The probability of relapse occurring within 40 days significantly increased step-by-step according to the increase in WT1 expression level (100% for 1.0 x 10(-2)-5.0 x 10(-2), 44.4% for 4.0 x 10(-3)-1.0 x 10(-2), 10.2% for 4.0 x 10(-4)-4.0 x 10(-3), and 0.8% for < 4.0 x 10(-4)) when WT1 level in K562 was defined as 1.0). WT1 levels in patients having relapse increased exponentially with a constant doubling time. The doubling time of the WT1 level in patients for whom the discontinuation of immunosuppressive agents or donor leukocyte infusion was effective was significantly longer than that for patients in whom it was not (P <.05). No patients with a short doubling time of WT1 transcripts (< 13 days) responded to these immunomodulation therapies. These findings strongly suggest that the WT1 assay is very useful for the prediction and management of relapse following allogeneic stem cell transplantation regardless of the presence of chimeric gene markers.

Imatinib mesylate (STI-571) given concurrently with nonmyeloablative stem cell transplantation did not compromise engraftment and resulted in cytogenetic remission in a patient with chronic myeloid leukemia in blast crisis

The main obstacles to successful hematopoietic stem cell transplantation for patients with chronic myeloid leukemia (CML) in blast crisis (BC) are increased post-transplant relapse and high treatment-related mortality. We report a patient with CML in BC who was treated initially with imatinib mesylate and was then concurrently treated with a nonmyeloablative stem cell transplant. Successful engraftment of donor cells followed by complete cytogenetic remission was achieved in the absence of severe therapy-related toxicities. This case demonstrates that imatinib mesylate given through nonmyeloablative transplant is a minimally toxic therapeutic approach, which does not compromise engraftment and may result in a favorable outcome in patients with CML in BC.

Management decisions in chronic myeloid leukemia

Until recently, interferon-alfa or interferon plus cytarabine was considered the best initial treatment for newly diagnosed chronic myeloid leukemia (CML) patients not eligible for allogeneic stem cell transplantation. The remarkably rapid and apparently durable control of hematologic features and the high rate of cytogenetic response achieved with imatinib used as a single agent suggest that this drug could prolong life substantially. However, response to the drug is variable between patients and here criteria are tentatively suggested for defining response and nonresponse or response failure. It is likely that patients who fail to respond to imatinib may benefit from alternative therapy initiated as early as possible. The issue of whether to offer allogeneic stem cell transplant to any newly diagnosed patient is addressed and a possible strategy is suggested. Undoubtedly, the suggestions made here will require revision as we acquire further information on the utility of imatinib.

Salvage chemotherapy with donor lymphocyte infusion and STI 571 in a patient relapsing with B-lymphoblastic phase chronic myeloid leukemia after allogeneic bone marrow transplantation

Relapse is the main cause of treatment failure following hematopoietic stem cell transplantation for blastic phase chronic myeloid leukemia. Treatment options including donor lymphocyte infusion, second transplantation, interferon- and re-induction chemotherapy are often unsuccessful. We report a patient with blastic phase chronic myeloid leukemia relapsing after allogeneic stem cell transplantation. The post-transplant leukemia was characterized with B-lymphoid markers and multiple genetic abnormalities including double Ph-chromosomes. The disease was treated with three courses of salvage chemotherapy combined with donor lymphocyte infusion and bcr-abl tyrosine kinase inhibitor. The leukemia proved to be non-responsive both to immune therapy and STI 571. The presented case demonstrates the need for combination approaches in post-transplant relapsed leukemia and discusses the possible contributing mechanisms of STI-571 resistance.

Practical aspects of the treatment of chronic myelogenous leukemia with imatinib mesylate

Imatinib mesylate (Gleeve; formerly known as STI-571; Novartis Pharmaceuticals, Basel, Switzerland) is a protein tyrosine kinase inhibitor that has been approved by the US Food and Drug Administration for chronic-phase chronic myeloid leukemia (CML) that is refractory to or intolerant of interferon-alpha, and with accelerated and blast-phase CML. Imatinib is remarkably effective as treatment for chronic-phase and accelerated-phase CML at doses of 400 mg and 600 mg daily, respectively. Although dramatic responses are noted in patients with myeloid blast crisis, lymphoid blast crisis, and Philadelphia chromosome-positive acute lymphoblastic leukemia, the responses are usually incomplete and of short duration. The role of imatinib in relation to allogeneic stem cell transplantation is discussed, recognizing that the data on which any decisions can be made are relatively immature. At this time, it remains to be seen whether the chronic phase of CML can be extended sufficiently long in some patients so that they are functionally "cured," and whether doses of imatinib higher than 400 mg daily will improve response rates in chronic-phase CML. The feasibility of combining imatinib with other agents also needs to be examined, as does the utility of molecular monitoring of response. Finally, developing methods to overcome resistance to imatinib is a looming challenge.