Non-myeloablative conditioning with allogeneic hematopoietic cell transplantation for the treatment of high-risk acute lymphoblastic leukemia

Tyrosine Kinase Inhibitor Post-Allogeneic Stem Cell Transplantation in Adult Philadelphia-Positive B-Acute Lymphoblastic Leukemia: State of the Art and Future Directions

In a scenario characterized by continuous improvement in outcomes, Philadelphia chromosome-positive (Ph+) ALL, once considered a biologically defined subtype with one of the poorest prognoses, now includes patients achieving long-term survival even without allogeneic stem cell transplantation. First-line therapy is increasingly adopting a chemo-free approach, combining tyrosine kinase inhibitors (TKIs) with immunotherapy-specifically blinatumomab-which has resulted in high rates of complete molecular responses and improved survival outcomes. Within this paradigm shift, the allocation to transplantation is becoming increasingly selective and genomically oriented, focusing on patients with particularly unfavorable prognostic and predictive factors. For patients undergoing transplantation, maintenance therapy with TKIs has emerged as one of the most important strategies to reduce the risk of relapse. However, there remains considerable uncertainty regarding which patients benefit most from this approach, the optimal TKI agents, dosing strategies, and the duration of maintenance therapy. In this review, we aim to consolidate the available evidence on this topic, analyzing it in the context of the most recent clinical experiences.

Toxicities associated with tyrosine kinase inhibitor maintenance following allogeneic hematopoietic cell transplantation in Philadelphia chromosome-positive acute lymphoblastic leukemia

Allogeneic hematopoietic cell transplantation (HCT) offers a potential cure in Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL); nonetheless, relapses are common and the major cause of mortality. One strategy to prevent relapse is tyrosine kinase inhibitor (TKI) maintenance post-HCT, but published clinical experience is primarily with the first-generation TKI imatinib while data with newer generation TKIs are limited. We conducted a retrospective analysis of 185 Ph+ ALL patients who underwent HCT followed by TKI maintenance from 2003 to 2021 at City of Hope. Initially, 50 (27.0%) received imatinib, 118 (63.8%) received a second-generation TKI (2G-TKI), and 17 (9.2%) received ponatinib. A total of 77 patients (41.6%) required a dose reduction of their initial TKI due to toxicity. Sixty-six patients (35.7%) did not complete maintenance due to toxicity; 69 patients (37.3%) discontinued 1 TKI, and 11 (5.9%) discontinued 2 TKIs due to toxicity. Initial imatinib versus 2G-TKI versus ponatinib maintenance was discontinued in 19 (38.0%) versus 68 (57.6%) versus 3 (17.6%) patients due to toxicity (p = .003), respectively. Patients on ponatinib as their initial TKI had a longer duration of TKI maintenance versus 2G-TKI: 576.0 days (range, 72-921) versus 254.5 days (range, 3-2740; p = .02). The most common reasons for initial TKI discontinuation include gastrointestinal (GI) intolerance (15.1%), cytopenia (8.6%), and fluid retention (3.8%). The 5-year overall survival and progression-free survival for the total population were 78% and 71%, respectively. Our findings demonstrate the challenges of delivering post-HCT TKI maintenance in a large real-world cohort as toxicities leading to TKI interruptions, discontinuation, and dose reduction were common.

Leveraging CD19CAR T cells early in the treatment of older patients with B-ALL: are we there yet?

Older adults (≥55 years old) with B-cell acute lymphoblastic leukemia (B-ALL) have dismal outcomes with standard chemotherapy as the result of low treatment efficacy and considerable risks for treatment-related morbidity and mortality. There has been a recent success with the introduction of novel therapies, such as blinatumomab and inotuzumab, in the frontline therapeutic paradigm in older adults with B-ALL. However, these agents have their own challenges including the limited durability of remission, the need for additional concurrent chemotherapy and the prolonged course of treatment, and limited efficacy in the setting of extramedullary disease. Here, we hypothesize that the incorporation of chimeric antigen receptor (CAR) T cell therapy as a consolidation treatment in older adults with B-cell ALL in their first complete remission is the ideal setting to advance treatment outcomes by reducing treatment toxicity, enhancing remission durability, and expanding the use of this effective therapy in this age population.

Total body irradiation versus busulfan based intermediate intensity conditioning for stem cell transplantation in ALL patients >45 years-a registry-based study by the Acute Leukemia Working Party of the EBMT

Allogeneic hematopoietic cell transplantation is a potentially curative treatment in high-risk acute lymphoblastic leukemia (ALL). Conditioning regimens based on ≥12 Gray total body irradiation (TBI) represent the current standard in patients ≤45 years, whereas elderly patients frequently receive intermediate intensity conditioning (IIC) to reduce toxicity. To evaluate the role of TBI as a backbone of IIC in ALL, a retrospective, registry-based study included patients >45 years transplanted from matched donors in first complete remission, who had received either fludarabine/TBI 8 Gy (FluTBI8, n = 262), or the most popular, irradiation-free alternative fludarabine/busulfan, comprising busulfan 6.4 mg/kg (FluBu6.4, n = 188) or 9.6 mg/kg (FluBu9.6, n = 51). At two years, overall survival (OS) was 68.5%, 57%, and 62.2%, leukemia-free survival (LFS) was 58%, 42.7%, and 45%, relapse incidence (RI) was 27.2%, 40%, and 30.9%, and non-relapse-mortality (NRM) was 23.1%, 20.7%, and 26.8% for patients receiving FluTBI8Gy, FluBu6.4, and FluBu9.6, respectively. In multivariate analysis, the risk of NRM, acute and chronic graft-versus-host disease was not influenced by conditioning. However, RI was higher after FluBu6.4 (hazard ratio [HR] [95% CI]: 1.85 [1.16-2.95]), and LFS was lower after both FluBu6.4 (HR: 1.56 [1.09-2.23]) and FluBu9.6 (HR: 1.63 [1.02-2.58]) as compared to FluTBI8. Although only resulting in a non-significant advantage in OS, this observation indicates a stronger anti-leukemic efficacy of TBI-based intermediate intensity conditioning.

Allogeneic stem cell transplant outcomes between TBI-containing reduced intensity and myeloablative conditioning regimens for ALL in complete remission

Total-body irradiation (TBI)-based conditioning regimen is preferred in acute lymphoblastic leukemia (ALL). We retrospectively evaluated allogeneic stem cell transplant (alloSCT) outcomes of 86 adult ALL patients in complete remission (CR) who received TBI-containing reduced intensity (RIC) (Flu/Mel/TBI = 31) and myeloablative conditioning (MAC) (VP16/TBI = 47; CY/TBI = 8) between January 2005 and December 2019. All patients received peripheral blood allografts. Patients in the RIC group were older than the MAC group (61 years old versus 36 years, p < .001). Donor was 8/8 HLA-matched in 83% and unrelated in 65% of patients. Three-year survival was 56.04% for RIC and 69.9% for MAC (HR 0.64; p = .19). Propensity score-based multivariable Cox analyses (PSCA) did not demonstrate any difference in grade III-IV acute graft versus host disease (GVHD) (SHR 1.23, p = .91), chronic GVHD (SHR 0.92, p = .88), survival (HR 0.94, p = .92), and relapse-free survival (HR 0.66, p = .47) between both groups, while relapse rate was lower (SHR 0.21, p = .02) for MAC compared to RIC. Our study did not demonstrate any difference in survival for TBI-containing RIC and MAC alloSCT for adult ALL in CR.

Hematopoietic cell transplants in resource-poor countries: challenges and opportunities

INTRODUCTION

Numbers of hematopoietic cell transplants continue to increase globally but most of this activity is in resource-rich countries. Limitations to increasing transplant activity in resource-poor countries include lack of sophisticated personnel and infrastructure, complexity in identifying and accessing donors, unavailability of some new drugs and high cost.

AREAS COVERED

We searched the biomedical literature for hematopoietic cell transplants and resource-rich and resource-poor countries. Recent advances which potentially make transplants more accessible in resource-poor countries include: (1) outpatient transplants; (2) grafts stored at 4°C; (3) less intensive pretransplant conditioning; (4) use of generic drugs; (5) less complex and costly donor access; and (6) increased collaboration with transplant centers in resource-rich countries.

EXPERT OPINION

We reviewed publications on the limitations and solutions discussed above. Paradoxically, most data we analyzed originate from resource-rich countries. We found no convincing epidemiological data to support a recent increased transplant rate in resource-poor countries yet but hope to see increases soon.

Prophylactic or preemptive tyrosine kinase inhibitor therapy after allogeneic hematopoietic cell transplantation for Philadelphia chromosome-positive acute lymphoblastic leukemia

Prevention of disease relapse after allogeneic hematopoietic cell transplantation (allo-HCT) in patients with Philadelphia chromosome-positive acute lymphoblastic leukemia remains a major concern. Maintenance therapy with tyrosine kinase inhibitors (TKIs) after allo-HCT has been used to reduce the incidence of relapse. Two main strategies are employed for using TKIs after allo-HCT: prophylactic TKI therapy, which is given before measurable residual disease (MRD) detection, and preemptive TKI therapy, which is given after MRD detection. These strategies both have advantages and disadvantages in terms of treatment efficacy, adverse events, adherence, and socioeconomic factors. In addition, many issues remain to be resolved because of the lack of large prospective studies on how to use TKIs after allo-HCT. These include indications for prophylactic and preemptive TKI therapy, timing of initiation, frequency of MRD monitoring, TKI selection, dose, and treatment duration. While the current available evidence is extremely limited, this article will discuss these issues after summarizing some representative and recent studies. It will also share a novel indicator that can be used to visualize the reversible transition between molecular relapse and remission by TKI therapy.

Treatment of Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia in Adults

Simple Summary

Outcome of patients with Philadelphia-chromosome positive acute lymphoblastic leukemia (Ph+ ALL) dramatically improved during the past 20 years with the advent of tyrosine kinase inhibitors and monoclonal antibodies. Their great efficacy in young and fit patients led to question our reliance on chemotherapy and allogeneic hematopoietic stem cell transplantation. Moreover, these well-tolerated treatments can be safely administrated even in the elderly that represent the majority of Ph+ ALL patient. This review will focus on the recent changes of paradigm in the management of Ph+ ALL patients and the development of novel therapeutic strategies.

Abstract

Philadelphia-chromosome positive acute lymphoblastic leukemia (Ph+ ALL) is the most common subtype of B-ALL in adults and its incidence increases with age. It is characterized by the presence of BCR-ABL oncoprotein that plays a central role in the leukemogenesis of Ph+ ALL. Ph+ ALL patients traditionally had dismal prognosis and long-term survivors were only observed among patients who underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT) in first complete remission (CR1). However, feasibility of allo-HSCT is limited in this elderly population. Fortunately, development of increasingly powerful tyrosine kinase inhibitors (TKIs) from the beginning of the 2000′s dramatically improved the prognosis of Ph+ ALL patients with complete response rates above 90%, deep molecular responses and prolonged survival, altogether with good tolerance. TKIs became the keystone of Ph+ ALL management and their great efficacy led to develop reduced-intensity chemotherapy backbones. Subsequent introduction of blinatumomab allowed going further with development of chemo free strategies. This review will focus on these amazing recent advances as well as novel therapeutic strategies in adult Ph+ ALL.

Real-world outcomes in elderly ALL patients with and without allogeneic hematopoietic stem cell transplantation: a single-center evaluation over 10 years

Elderly patients (EP) of 60 years and above with acute lymphoblastic leukemia (ALL) have a dismal prognosis, but pediatric-inspired chemotherapy and allogeneic stem cell transplantation (allo HCT) are used reluctantly due to limited data and historical reports of high treatment-related mortality in EP. We analyzed 130 adult ALL patients treated at our center between 2009 and 2019, of which 26 were EP (range 60-76 years). Induction with pediatric-inspired protocols was feasible in 65.2% of EP and resulted in complete remission in 86.7% compared to 88.0% in younger patients (YP) of less than 60 years. Early death occurred in 6.7% of EP. Three-year overall survival (OS) for Ph - B-ALL was significantly worse for EP (n = 16) than YP (n = 64) with 30.0% vs 78.1% (p ≤ 0.001). Forty-nine patients received allo HCT including 8 EP, for which improved 3-year OS of 87.5% was observed, whereas EP without allo HCT died after a median of 9.5 months. In Ph + B-ALL, 3-year OS did not differ between EP (60.0%, n = 7) and YP (70.8%, n = 19). Non-relapse mortality and infection rate were low in EP (14.3% and 12.5%, respectively). Our data indicate that selected EP can be treated effectively and safely with pediatric regimens and might benefit from intensified therapy including allo HCT.

Conditioning Regimens for Frail Patients with Acute Leukemia Undergoing Allogeneic Stem Cell Transplant: How to Strike Gently

Despite the recent dramatic progress in acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) therapy, allogeneic transplant remains a mainstay of treatment for patients with acute leukemia. The availability of novel compounds and low intensity chemotherapy regimens made it possible for a significant proportion of elderly and comorbid patients with AML or ALL to undergo curative treatment protocols. In addition, the expansion of donor availability and the recent dramatic progress in haploidentical stem cell transplant, allow the identification of an available donor for nearly every patient. Therefore, an increasing number of transplants are currently performed in elderly and frail patients with AML or ALL. However, allo-Hematopoietic stem cell transplant (HSCT) in this delicate setting represents an important challenge, especially regarding the selection of the conditioning protocol. Ideally, conditioning intensity should be reduced as much as possible; however, in patients with acute leukemia relapse remains the major cause of transplant failure. In this article we present modern tools to assess the patient health status before transplant, review the available data on the outcome of frail AML an ALL patients undergoing allo-HSCT, and discuss how preparatory regimens can be optimized in this setting.

Dasatinib-based Two-step Induction for Adults with Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia

Dasatinib-based 2-step induction resulted in a 100% CR rate with minimal toxicities and 53% MRD negativity.

This protocol treatment increased the number of HSCTs in CR1, thereby improving 3-year EFS.

The standard treatment for adults with Philadelphia chromosome–positive (Ph⁺) acute lymphoblastic leukemia (ALL) in Japan is imatinib-based chemotherapy followed by allogeneic hematopoietic stem cell transplantation (HSCT). However, ∼40% of patients cannot undergo HSCT in their first complete remission (CR1) because of chemotherapy-related toxicities or relapse before HSCT or older age. In this study, we evaluated dasatinib-based 2-step induction with the primary end point of 3-year event-free survival (EFS). The first induction (IND1) was dasatinib plus prednisolone to achieve CR, and IND2 was dasatinib plus intensive chemotherapy to achieve minimal residual disease (MRD) negativity. For patients who achieved CR and had an appropriate donor, HSCT during a consolidation phase later than the first consolidation, which included high-dose methotrexate, was recommended. Patients with pretransplantation MRD positivity were assigned to receive prophylactic dasatinib after HSCT. All 78 eligible patients achieved CR or incomplete CR after IND1, and 52.6% achieved MRD negativity after IND2. Nonrelapse mortality (NRM) was not reported. T315I mutation was detected in all 4 hematological relapses before HSCT. Fifty-eight patients (74.4%) underwent HSCT in CR1, and 44 (75.9%) had negative pretransplantation MRD. At a median follow-up of 4.0 years, 3-year EFS and overall survival were 66.2% (95% confidence interval [CI], 54.4-75.5) and 80.5% (95% CI, 69.7-87.7), respectively. The cumulative incidence of relapse and NRM at 3 years from enrollment were 26.1% and 7.8%, respectively. Dasatinib-based 2-step induction was demonstrated to improve 3-year EFS in Ph⁺ ALL. This study was registered in the UMIN Clinical Trial Registry as #UMIN000012173.

A risk score system for stratifying the risk of relapse in B cell acute lymphocytic leukemia patients after allogenic stem cell transplantation

BACKGROUND

For patients with B cell acute lymphocytic leukemia (B-ALL) who underwent allogeneic stem cell transplantation (allo-SCT), many variables have been demonstrated to be associated with leukemia relapse. In this study, we attempted to establish a risk score system to predict transplant outcomes more precisely in patients with B-ALL after allo-SCT.

METHODS

A total of 477 patients with B-ALL who underwent allo-SCT at Peking University People's Hospital from December 2010 to December 2015 were enrolled in this retrospective study. We aimed to evaluate the factors associated with transplant outcomes after allo-SCT, and establish a risk score to identify patients with different probabilities of relapse. The univariate and multivariate analyses were performed with the Cox proportional hazards model with time-dependent variables.

RESULTS

All patients achieved neutrophil engraftment, and 95.4% of patients achieved platelet engraftment. The 5-year cumulative incidence of relapse (CIR), overall survival (OS), leukemia-free survival (LFS), and non-relapse mortality were 20.7%, 70.4%, 65.6%, and 13.9%, respectively. Multivariate analysis showed that patients with positive post-transplantation minimal residual disease (MRD), transplanted beyond the first complete remission (≥CR2), and without chronic graft-versus-host disease (cGVHD) had higher CIR (P  < 0.001, P = 0.004, and P  < 0.001, respectively) and worse LFS (P  < 0.001, P = 0.017, and P  < 0.001, respectively), and OS (P  < 0.001, P = 0.009, and P  < 0.001, respectively) than patients without MRD after transplantation, transplanted in CR1, and with cGVHD. A risk score for predicting relapse was formulated with the three above variables. The 5-year relapse rates were 6.3%, 16.6%, 55.9%, and 81.8% for patients with scores of 0, 1, 2, and 3 (P  < 0.001), respectively, while the 5-year LFS and OS values decreased with increasing risk score.

CONCLUSION

This new risk score system might stratify patients with different risks of relapse, which could guide treatment.

Maintenance Strategies After Hematopoietic Cell Transplantation

Hematopoietic cell transplantation (HCT) is an essential component of potentially curative therapy for patients with hematologic malignancies. High-dose chemotherapy with autologous (auto) stem cell rescue is used to overcome chemoresistance in multiple myeloma, non-Hodgkin lymphoma, and Hodgkin lymphoma. Alternatively, poor-risk acute leukemias rely on the graft versus leukemia effect of allogeneic (allo) products. Long-term remissions are feasible with both auto- and allo-HCT; however, disease relapse is the leading cause of death after HCT for many patients. In recognition of this, novel therapies are being investigated in the upfront, relapsed/refractory, and post-HCT maintenance settings to deepen response and maintain disease control. To date, the most robust data to support this approach are in multiple myeloma, where post-transplant maintenance therapy has improved clinical outcomes. In Hodgkin lymphoma, patients with high-risk features may benefit from post-auto-HCT vedotin (BV) regardless of pre-HCT BV exposure. Apart from mantle cell lymphoma, where rituximab maintenance is generally accepted, post-auto-HCT maintenance in other forms of NHL is less established. In patients who undergo allo-HCT, the utilization of maintenance therapy is an important component of improving post-HCT outcomes, however, an individualized approach that considers patient factors such as residual toxicity from HCT, an immature graft with poor graft function, infection, and graft-versus-host disease create a complex environment for aggressive interventions. Initiation of directed agents in patients with identified mutations prior to allo-HCT, including FLT3 in acute myeloid leukemia and Philadelphia chromosome in acute lymphoid leukemia have generally improved post-HCT outcomes. Ongoing studies are exploring the safety and efficacy of additional maintenance strategies post-allo-HCT in an effort to further improve post-HCT outcomes.

Hematopoietic Cell Transplantation in the Treatment of Adult Acute Lymphoblastic Leukemia: Updated 2019 Evidence-Based Review from the American Society for Transplantation and Cellular Therapy

The role of hematopoietic cell transplantation (HCT) in adults with acute lymphoblastic leukemia (ALL) is reviewed and critically evaluated in this systematic evidence-based review. Specific criteria were used for searching the published literature and for grading the quality and strength of the evidence and the strength of the recommendations. A panel of ALL experts developed consensus on the treatment recommendations based on the evidence. Allogeneic HCT offers a survival benefit in selected patients with ALL, and this review summarizes the standard indications as well as the areas of controversy. There is now greater experience with pediatric-inspired chemotherapy regimens that has transformed upfront therapy for adult ALL, resulting in higher remission rates and overall survival. This in turn has increased the equipoise around decision making for ALL in first complete remission (CR1) when there is no measurable residual disease (MRD) at the end of induction and/or consolidation. Randomized studies are needed for adults with ALL to compare allogeneic HCT in CR1 with pediatric-inspired chemotherapy alone. Indications for transplantation in the evolving landscape of MRD assessments and novel targeted and immune therapeutics remain important areas of investigation.

Minimal residual disease-based long-term efficacy of reduced-intensity conditioning versus myeloablative conditioning for adult Philadelphia-positive acute lymphoblastic leukemia

BACKGROUND

The sensitivity of Philadelphia chromosome (Ph)-positive acute lymphoblastic leukemia (ALL) to reduced-intensity conditioning (RIC) allogeneic hematopoietic cell transplantation (HCT) versus myeloablative conditioning (MAC) allogeneic HCT by minimal residual disease (MRD) kinetics is not well established.

METHODS

This study compared long-term outcomes based on MRD kinetics for 79 patients with RIC transplants and 116 patients with MAC transplants in first complete remission (CR1) after tyrosine kinase inhibitor-based chemotherapy (median follow-up, 67.1 months). MRD monitoring was centrally evaluated by real-time quantitative polymerase chain reaction for all patients.

RESULTS

RIC showed a cumulative incidence of relapse (CIR; 30.6% vs 31.7%), nonrelapse mortality (17.5% vs 14.9%), disease-free survival (DFS; 51.9% vs 53.4%), and overall survival (61.1% vs 61.4%) comparable to those associated with MAC. In all MRD kinetics-based subgroups, no differences in CIR (early complete molecular response [CMR], 19.3% vs 4.8%; early major molecular response [MMR], 17.0% vs 26.8%; late CMR, 20.0% vs 14.3%; late MMR, 28.3% vs 31.0%; poor molecular response [PMR], 57.9% vs 62.4%) or DFS (early CMR, 71.6% vs 76.2%; early MMR, 66.9% vs 52.1%; late CMR, 50.0% vs 64.3%; late MMR, 50.7% vs 53.7%; PMR, 31.6% vs 34.1%) were observed between RIC and MAC. In a multivariate analysis, the conditioning intensity had no significant impact on transplantation outcomes.

CONCLUSIONS

RIC is a valid alternative choice for long-term disease control and is worthy of further investigation in prospective trials for adult Ph-positive ALL in CR1.

Reduced Intensity Conditioning Allogeneic Hematopoietic Stem Cell Transplantation for Acute Lymphoblastic Leukemia; Current Evidence, and Improving Outcomes Going Forward

PURPOSE OF REVIEW

Outcomes for older adults with acute lymphoblastic leukemia (ALL) remain poor, and allogeneic hematopoietic stem cell transplant (HSCT) remains a potentially curative modality. However, benefits are offset by high rates of non-relapse mortality (NRM) in patients undergoing myeloablative conditioning (MAC) regimens. Reduced intensity conditioning (RIC) regimens can extend this therapy to adults who are unfit for MAC, although at the cost of higher relapse rates. In this review, we discuss evidence to support the usage of RIC regimens, controversies, and potential strategies to improve transplant outcomes going forward.

RECENT FINDINGS

Several novel therapies have recently been approved for the treatment of relapsed ALL and may play an important role in bridging adults with residual disease to RIC transplant. Assessing response to initial therapy via minimal residual disease (MRD) monitoring may determine which patients will derive the most benefit from allogeneic HSCT. Reduced intensity allogeneic HSCT remains a potentially curative therapy that can be offered to older adults however challenges remain. Going forward, MRD testing and novel therapies may help better select which patients should proceed to transplant and assist in getting those patients to transplant with optimally controlled disease.

Allogeneic stem cell transplantation in acute lymphoblastic leukemia patients older than 60 years: a survey from the acute leukemia working party of EBMT

Hematopoietic stem cell transplantation (HSCT) is being increasingly explored as a treatment modality for older patients with acute lymphoblastic leukemia (ALL). Yet, concerns regarding the long term outcome of transplantation in older patients limit the wide spread applicability of this approach. In this analysis we set out to determine the outcome of ALL patients over the age of 60 who underwent reduced intensity HSCT. Herein, we present the experience of the acute leukemia working party (ALWP) of the EBMT in this age group. We analyzed a cohort of 142 patients transplanted in first remission with a median age of 62 (range 60–76 years) and a median follow-up period of 36 months post-transplant. At 3 years, overall survival (OS) and leukemia-free survival were 42% and 35%, respectively. Multivariate analyses identified cytomegalovirus (CMV) donor-recipient matching (CMV D+/R+) to be significantly associated with inferior OS. Patients transplanted from unrelated donors experienced increased grade II-IV acute graft versus host disease compared to those receiving grafts from matched related donors [Hazard ratio (HR) of 3.7, 95% confidence interval (CI), 1.75–7.8; p = 0.0005). Outcome was not impacted by Philadelphia chromosome status. A select subset of older ALL patients will benefit from extended survival and a disease free state following HSCT.

Nonmyeloablative allogeneic hematopoietic cell transplantation

Most hematological malignancies occur in older patients. Until recently these patients and those with comorbidities were not candidates for treatment with allogeneic hematopoietic transplantation because they were unable to tolerate the heretofore used high-dose conditioning regimens. The finding that many of the cures achieved with allogeneic hematopoietic transplantation were due to graft-versus-tumor effects led to the development of less toxic and well-tolerated reduced intensity and nonmyeloablative regimens. These regimens enabled allogeneic engraftment, thereby setting the stage for graft-versus-tumor effects. This review summarizes the encouraging early results seen with the new regimens and discusses the two hurdles that need to be overcome for achieving even greater success, disease relapse and graft-versus-host disease.

Diagnostic and treatment of adult Philadelphia chromosome-positive acute lymphoblastic leukemia

The outcome of adult patients with Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL) has improved substantially with the introduction of tyrosine kinase inhibitors (TKIs). TKIs are now integral components of therapy for Ph+ ALL. The current consensus is that they improve patient outcomes compared with historical control patients treated with chemotherapy alone, and increase the number of patients able to receive stem cell transplant. New challenges have emerged with respect to induction of resistance mainly via Abelson tyrosine kinase mutations. Several novel kinase inhibitors with significantly more potent antileukemic activity are currently being developed. Furthermore novel immune therapies, which recruit or modify patient's own T cells to fight leukemic cells, are being developed and could find an important place in Ph+ ALL therapy by few years. In this article, we reviewed treatment approaches in adults with Ph+ ALL with a focus on TKIs and combined chemotherapy regimens.

The development of agents targeting the BCR-ABL tyrosine kinase as Philadelphia chromosome-positive acute lymphoblastic leukemia treatment

INTRODUCTION

In Philadelphia chromosome-positive (Ph⁺) acute lymphoblastic leukemia (ALL), the BCR-ABL translocation is the main transforming event; consequently, it is targeted by ABL-tyrosine kinase inhibitors (TKIs), the first of which to be identified was imatinib mesylate. There are now four newer TKIs, three so-called second-generation inhibitors and one third generation inhibitor, all of which are more potent than imatinib in in vitro assays. Areas covered: This paper reviews the current knowledge on the function of BCR-ABL. Furthermore, this paper highlights the impact of this knowledge on the development of a targeted therapy approach in Ph⁺ ALL and the obstacles for the successful treatment with these drugs. Expert opinion: Identifying key components involved in disease pathogenesis may lead to new approaches that might overcome resistance mediated to the BCR-ABL TKIs. In a near future, the authors believe that monoclonal antibodies and immunotherapy should also be combined with TKIs and up-front chemotherapy for the successful treatment of ALL.

Refining the Role of Hematopoietic Cell Transplantation for Acute Lymphoblastic Leukemia as Novel Therapies Emerge

Acute lymphoblastic leukemia (ALL) is a rare adult neoplasm. The disorder consists of precursor B or T phenotypes. In the pediatric population, ALL was a success story in that 80% of children with ALL enjoy long-term survival. In adults, similar complete remission rates are achieved with current induction regimens; however, less than 50% of patients are alive at 5 years, with most deaths due to relapsed disease. Accordingly, optimizing post remission consolidation therapy might improve in outcomes. Such strategies may include chemotherapy and autologous or allogeneic transplant. Moreover, the ability to modify such therapy based on better disease risk stratification while taking into account patient characteristics such as performance status and presence of comorbidities is necessary to tailor treatment accordingly. Here, we review available medical literature on the use of hematopoietic cell transplantation as a consolidation modality in the treatment of adult ALL.

Idarubicin-intensified BUCY2 conditioning regimen improved survival in high-risk acute myeloid, but not lymphocytic leukemia patients undergoing allogeneic hematopoietic stem cell transplantation: A retrospective comparative study

The intensity of conditioning regimen is highly correlated with outcomes of allogeneic hematopoietic stem cell transplantation (allo-HSCT). We have previously reported that idarubicin (IDA) intensified BUCY2 regimen could reduce relapse and improve survival for high-risk hematological malignancies undergoing allo-HSCT. However, there is no published study comparing the efficacy of IDA-BUCY2 regimen for high-risk acute myeloid leukemia (AML) versus acute lymphocytic leukemia (ALL). We further retrospectively compared therapeutic outcomes of intensified conditioning regimen on 140 high-risk AML and ALL patients in the data analyses. IDA 15mg/m(2)/d was administered by continuous infusion from day -11 to -9, followed by intravenous injection of busulfan (BU) (3.2mg/kg/d) from day -6 to -4, and intravenous injection of cyclophosphamide (CY) (1.8g/m(2)/d) from day -3 to -2 in IDA-BUCY2 regimen. For high-risk AML, cumulative probabilities of 3-year relapse rates in IDA-BUCY2 and traditional BUCY2 regimens were 16.9%, 43.3% (P=0.016). Cumulative probabilities of 3-year overall survival (OS) and disease-free survival (DFS) were 69.2% vs 44.0% (P=0.024), and 66.9% vs 38.2% (P=0.01). However, two regimens showed no significant differences for high-risk ALL. Multivariate analysis also indicated that IDA intensified BUCY2 conditioning was the favorable variable to reduce relapse and elevate survival for high-risk AML patients. In conclusion, IDA-BUCY2 regimen reduces relapse and improves survival for high-risk AML undergoing allo-HSCT, but not presenting uniform therapeutic effects for high-risk ALL.

Evaluation of allogeneic transplantation in first or later minimal residual disease - negative remission following adult-inspired therapy for acute lymphoblastic leukemia

Comparisons without hematopoietic cell transplantation (HCT) to myeloablative (MAC) or reduced-intensity HCT (RIC) for adults with acute lymphoblastic leukemia (ALL) in first minimal-residual-disease negative remission (MRD(Neg) CR1) are limited. Further, the importance of MRD(Neg) following salvage therapy (MRD(Neg) CR2+) is unknown. We evaluated 89 patients in MRD(Neg) CR1 after adult-inspired treatment: 33 received MAC (12 Philadelphia chromosome [Ph]+), 17 received RIC (13 Ph+), and 39 Deferred HCT (3 Ph+). Three-year overall survival (OS) estimates for MAC, RIC, and Deferred HCT were 71%, 69%, and 68%, while 3-year event-free survival (EFS) estimates were 65%, 54%, and 28%, respectively. Further, HCT in MRD(Neg) CR1 performed similarly to MRD(Neg) CR2+: 3-year OS estimates were 70% and 69%, and 3-year EFS estimates were 62% and 62%, respectively. In conclusion, adults with ALL in MRD(Neg) CR1 following adult-inspired therapy had similar OS with or without HCT, and HCT in MRD(Neg) CR2 + can yield long-term survival.

Treatment of Philadelphia chromosome-positive acute lymphoblastic leukemia in adults: a broader range of options, improved outcomes, and more therapeutic dilemmas

The article addresses selected key areas of flux in the management of Philadelphia chromosome-positive acute lymphoblastic leukemia. There is no doubt that tyrosine kinase inhibitors (TKIs) have made a major contribution to higher rates of complete remission and that more patients are now surviving long term. Many patients tolerate TKIs well, and remission can be achieved with minimal toxicity. Because remissions can include a proportion of patients who become BCR-ABL1 transcript negative, the question of whether allogeneic hematopoietic stem cell transplantation can be avoided requires discussion. Despite the major progress that has been made and the relative profusion of therapeutic choice compared with 10 years ago, evidence is still lacking for many of the major possible interventions, and how to combine them is unclear. Because of the rarity of the condition and the enticing possibility of increasing traction to therapy, clinical trials and international cooperation remain paramount.

Marrow damage and hematopoietic recovery following allogeneic bone marrow transplantation for acute leukemias: Effect of radiation dose and conditioning regimen

BACKGROUND AND PURPOSE

Total body irradiation (TBI) is a common component of hematopoietic cell transplantation (HCT) conditioning regimens. Preclinical studies suggest prolonged bone marrow (BM) injury after TBI could contribute to impaired engraftment and poor hematopoietic function.

MATERIALS AND METHODS

We studied the longitudinal changes in the marrow environment in patients receiving allogeneic HCT with myeloablative (MA, n=42) and reduced intensity (RIC, n=56) doses of TBI from 2003-2013, including BM cellularity, histologic features of injury and repair, hematologic and immunologic recovery.

RESULTS

Following MA conditioning, a 30% decrease in the marrow cellularity persisted at 1 year post-transplant (p=0.03). RIC HCT marrow cellularity transiently decreased but returned to baseline by 6 months even though the RIC group received mostly umbilical cord blood (UCB) grafts (82%, vs. 17% in the MA cohort, p<0.01). There was no evidence of persistent marrow vascular damage or inflammation. Recipients of more intensive conditioning did not show more persistent cytopenias with the exception of a tendency for minimal thrombocytopenia. Immune recovery was similar between MA and RIC.

CONCLUSIONS

These findings suggest that TBI associated with MA conditioning leads to prolonged reductions in marrow cellularity, but does not show additional histological evidence of long-term injury, which is further supported by similar peripheral counts and immunologic recovery.

Pushing the envelope-nonmyeloablative and reduced intensity preparative regimens for allogeneic hematopoietic transplantation

Allogeneic hematopoietic cell transplantation (HCT) was originally developed to allow delivery of myeloablative doses of chemotherapy and radiotherapy. With better understanding of disease pathophysiology, the graft vs malignancy (GVM) effect of allogeneic hematopoietic transplantation and toxicities associated with myeloablative conditioning (MAC) regimens, the focus shifted to developing less toxic conditioning regimens to reduce treatment-related morbidity without compromising survival. Although HCT with MAC is preferred to reduced intensity conditioning (RIC) for most patients ⩽60 years with AML/myelodysplastic syndrome and ALL, RIC and nonmyeloablative (NMA) regimens allow HCT for many otherwise ineligible patients. Reduced intensity preparative regimens have produced high rates of PFS for diagnoses, which are highly sensitive to GVM. Relapse of the malignancy is the major cause of treatment failure with RIC/NMA HCT. Incorporation of novel agents like bortezomib or lenalidomide, addition of cellular immunotherapy and use of targeted radiation therapies could further improve outcome. In this review, we discuss commonly used RIC/NMA regimens and promising novel regimens.

Comparison of outcomes of idarubicin intensified TBI-CY and traditional TBI-CY conditioning regimen for high-risk acute lymphoblastic leukemia undergoing allogeneic hematopoietic stem cell transplantation: A single center experience

High-risk acute lymphoblastic leukemia (ALL) carries a very poor prognosis, even after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Exploring novel conditioning regimen to more effectively eliminate leukemic clone while not alter transplant-related mortality (TRM) has become focus of attention. We retrospectively evaluated outcomes of 87 high-risk ALL patients undergoing allo-HSCT: 47 patients received idarubicin (IDA) intensified TBI-CY and 40 patients received traditional TBI-CY regimen. In IDA intensified group, patients received TBI (8Gy) on day-8, IDA of 15mg/m2/d from day-6 to -5, followed by CY (60mg/kg/d) on day-3 to -2. The cumulative incidence of relapse was significantly lower in IDA intensified group compared with TBI-CY group (P=0.018). Oropharyngeal mucositis was observed more frequent in IDA intensified group (P=0.013), while not followed by increased TRM. Very high-risk ALL patients benefit from IDA intensified regimen with only two of eight patients in no remission (NR) pre-transplantation and two of twelve ph+ALL patients relapsed after transplantation. After a median follow-up for all survivors of 21 months (range, 12-53 months), 2-year estimated OS and DFS was 66.2% vs 45.3% (P=0.031) and 62.5% vs 43.5% (P=0.044), respectively. In conclusion, IDA intensified TBI-CY regimen may reduce relapse while not increasing TRM, providing better survival for high-risk ALL patients undergoing allo-HSCT.

Tyrosine kinase inhibitors improve long-term outcome of allogeneic hematopoietic stem cell transplantation for adult patients with Philadelphia chromosome positive acute lymphoblastic leukemia

This study aimed to determine the impact of tyrosine kinase inhibitors given pre- and post-allogeneic stem cell transplantation on long-term outcome of patients allografted for Philadelphia chromosome-positive acute lymphoblastic leukemia. This retrospective analysis from the EBMT Acute Leukemia Working Party included 473 de novo Philadelphia chromosome-positive acute lymphoblastic leukemia patients in first complete remission who underwent an allogeneic stem cell transplantation using a human leukocyte antigen-identical sibling or human leukocyte antigen-matched unrelated donor between 2000 and 2010. Three hundred and ninety patients received tyrosine kinase inhibitors before transplant, 329 at induction and 274 at consolidation. Kaplan-Meier estimates of leukemia-free survival, overall survival, cumulative incidences of relapse incidence, and non-relapse mortality at five years were 38%, 46%, 36% and 26%, respectively. In multivariate analysis, tyrosine-kinase inhibitors given before allogeneic stem cell transplantation was associated with a better overall survival (HR=0.68; P=0.04) and was associated with lower relapse incidence (HR=0.5; P=0.01). In the post-transplant period, multivariate analysis identified prophylactic tyrosine-kinase inhibitor administration to be a significant factor for improved leukemia-free survival (HR=0.44; P=0.002) and overall survival (HR=0.42; P=0.004), and a lower relapse incidence (HR=0.40; P=0.01). Over the past decade, administration of tyrosine kinase inhibitors before allogeneic stem cell transplantation has significantly improved the long-term allogeneic stem cell transplantation outcome of adult Philadelphia chromosome-positive acute lymphoblastic leukemia. Prospective studies will be of great interest to further confirm the potential benefit of the prophylactic use of tyrosine kinase inhibitors in the post-transplant setting.

Role of allogeneic hematopoietic stem cell transplantation in adult patients with acute lymphoblastic leukemia

Adult acute lymphoblastic leukemia (ALL) is a heterogeneous disease, due to the expression of different biological and clinical risk factors, for which allogeneic stem cell transplantation (alloHSCT) is an effective consolidation therapy. The non-relapse mortality of alloHSCT remains significantly higher compared with that of conventional chemotherapy. Therefore, one of the main challenges in the care of ALL is to establish a more precise prognostic definition to select patients who could take advantage from an alloHSCT. Currently, the use of minimal residual disease following induction and early consolidation therapy has improved the prognostic accuracy in defining ALL risk class. In Philadelphia-positive ALL, the introduction of tyrosine kinase inhibitors pre and post alloHSCT appears to improve outcomes significantly and, in the absence of specially designed clinical trials, alloHSCT remains the most effective post-remission therapy. Nowadays, alloHSCT can be performed according to various modalities encompassing the use of different conditioning regimens, as well as distinct donors and stem cell source, with a significant accessibility to transplant.

Patients with Philadelphia-positive leukemia with BCR-ABL kinase mutations before allogeneic transplantation predominantly relapse with the same mutation

Despite the successes of tyrosine kinase inhibitors (TKIs) in improving outcomes in patients with chronic myeloid leukemia (CML) and Philadelphia-positive acute lymphoblastic leukemia (Ph + ALL), allogeneic hematopoietic stem cell transplantation (HSCT) continues to be an important and potentially curative option for selected patients with either disease. After HSCT, TKIs are increasingly being used to treat or prevent disease relapse, and practice patterns suggest that these TKIs are often chosen empirically without regard to pre-HSCT mutation status. We investigated whether ABL kinase domain mutations persist after transplantation and, thus, whether pre-HSCT mutation status should inform the selection of post-HSCT TKIs in these patients. We retrospectively analyzed adults who underwent allogeneic HSCT for CML and Ph + ALL at our institution between 2000 and 2010, and we identified subjects who had detectable BCR-ABL transcripts by polymerase chain reaction (PCR), as well as available RNA for Sanger sequencing of the ABL kinase domain, in both the pre- and post-HSCT settings. In total, 95 CML and 20 Ph + ALL patients with positive PCR transcripts were identified, of which 10 (10.5%) and 4 (20.0%), respectively, were found to have pre-HSCT ABL kinase mutations known to confer TKI resistance. In 9 (64.2%) of these 14 patients, the same kinase mutation was also detectable at an average time of 191 days after HSCT. Seven (50.0%) of the 14 harboring mutations had relapsed/refractory disease by last follow-up, of which, in retrospect, 6 had received a predictably ineffective TKI within the first 100 days after transplantation based on our mutation analysis. These data support the idea that pre-existing mutations in the ABL kinase domain, frequently associated with resistance to TKIs and prevalent in a transplantation population, are persistently detectable in the majority of patients after transplantation. We propose that such resistance patterns should be considered when selecting TKIs in the post-HSCT setting, including clinical trials of post-HSCT TKI prophylaxis.

Hematopoietic stem cell transplantation in adolescents and young adults

BACKGROUND

Adolescents and young adults (AYAs) are a very unique subset of our population journeying through a dynamic stage of their lives. This age group often remains understudied as a separate entity because they are commonly lumped into either pediatric or adult subgroups.

METHODS

Here we review acute and chronic issues surrounding hematopoietic stem cell transplantation (HSCT) with a focus on the AYA age group.

RESULTS

HSCT is a commonly used treatment modality for patients with certain types of cancers. AYA patients undergoing HSCT present a very unique perspective, circumstances, medical, psychological and social issues requiring a diligent workup, care and follow-up.

CONCLUSION

The medical care of these patients should be approached in a multidisciplinary method involving the patient, caregivers, physicians, psychologists and social workers.

Results from a clofarabine-busulfan-containing, reduced-toxicity conditioning regimen prior to allogeneic stem cell transplantation: the phase 2 prospective CLORIC trial

We prospectively evaluated the safety and efficacy of a clofarabine, intravenous busulfan and antithymocyte globulin-based reduced-toxicity conditioning (CloB2A2) regimen before allogeneic stem cell transplantation. Thirty high-risk patients (median age: 59 years; acute myeloid leukemia n=11, acute lymphoblastic leukemia n=13; myelodysplastic syndrome n=5, bi-phenotypic leukemia n=1) were included in this phase 2 study. At time of their transplant, 20 and seven patients were in first and second complete remission, respectively, while three patients with myelodysplastic syndrome were responding to chemotherapy or who had not been previously treated. The CloB2A2 regimen consisted of clofarabine 30 mg/m(2)/day for 4 days, busulfan 3.2 mg/kg/day for 2 days and antithymocyte globulin 2.5 mg/kg/day for 2 days. The median follow-up was 23 months. Engraftment occurred in all patients. The 1-year overall survival, leukemia-free survival, relapse incidence and non-relapse mortality rates were 63±9%, 57±9%, 40±9%, and 3.3±3%, respectively. Comparing patients with acute myeloid leukemia/myelodysplastic syndrome versus those with acute lymphoblastic leukemia/bi-phenotypic leukemia, the 1-year overall and leukemia-free survival rates were 75±10% versus 50±13%, respectively (P=0.07) and 69±12% versus 43±13%, respectively (P=0.08), while the 1-year relapse incidence was 25±11% versus 57±14%, respectively (P=0.05). The CloB2A2 regimen prior to allogeneic stem cell transplantation is feasible, allowing for full engraftment and low toxicity. Disease control appears to be satisfactory, especially in patients with acute myeloid leukemia/myelodysplastic syndrome. The trial was registered at www.clinicaltrials.gov no. NCT00863148.

Impact of minimal residual disease on outcomes after umbilical cord blood transplantation for adults with Philadelphia-positive acute lymphoblastic leukaemia: an analysis on behalf of Eurocord, Cord Blood Committee and the Acute Leukaemia working party of the European group for Blood and Marrow Transplantation

The status of umbilical cord blood transplantation (UCBT) in adults with Philadelphia-positive acute lymphoblastic leukaemia (Ph+ALL) and the impact of minimal residual disease (MRD) before transplant are not well established. We analysed 98 patients receiving UCBT for Ph+ALL in first (CR1) or second (CR2) complete remission (CR1, n = 79; CR2, n = 19) with MRD available before UCBT (92% analysed by reverse transcription polymerase chain reaction). Median age was 38 years and median follow-up was 36 months; 63% of patients received myeloablative conditioning and 42% received double-unit UCBT. Eighty-three patients were treated with at least one tyrosine kinase inhibitor before UCBT. MRD was negative (-) in 39 and positive (+) in 59 patients. Three-year cumulative incidence of relapse was 34%; 45% in MRD+ and 16% in MRD- patients (P =0·013). Three-year cumulative incidence of non-relapse mortality was 31%; it was increased in patients older than 35 years (P = 0·02). Leukaemia-free survival (LFS) at 3 years was 36%; 27% in MRD+ and 49% in MRD- patients (P = 0·05), and 41% for CR1 and 14% for CR2 (P = 0·008). Multivariate analysis identified only CR1 as being associated with improved LFS. In conclusion, MRD+ before UCBT is associated with increased relapse. Strategies to decrease relapse in UCBT recipients with Ph+ALL and MRD+ are needed.

Conditioning regimens for hematopoietic cell transplantation: one size does not fit all

An essential component of allogeneic and autologous hematopoietic cell transplantation (HCT) is the conditioning regimen administered before the hematopoietic cell infusion. Early regimens relied on dose intensity, assuming that high-dose chemoradiotherapy would eliminate malignant disease and reinfusion of the graft would then restore hematopoiesis. However, as the contribution of graft-versus-tumor effects to the success of allogeneic HCT was recognized over time, in an effort to exploit these, many investigators lowered the dose of radiation and chemotherapeutic agents in the preparative regimen. This resulted in a major paradigm shift, and consequently, the pool of eligible patients underwent a remarkable expansion. In this article, we provide a review of the definition of high-dose, reduced-intensity, and nonmyeloablative conditioning regimens, the most commonly used agents and combinations, and the evolution of some early regimens. We also provide a brief review of the toxicities associated with these regimens.

Current and future management of Ph/BCR-ABL positive ALL

Following the introduction of targeted therapy with tyrosine kinase inhibitors (TKI) at the beginning of the past decade, the outcome of patients with Philadelphia-chromosome positive acute lymphoblastic leukemia (Ph+ ALL) has dramatically improved. Presently, the use of refined programs with first/second generation TKI's and chemotherapy together with allogeneic stem cell transplantation allow up to 50% of all patients to be cured. Further progress is expected with the new TKI ponatinib, overcoming resistance caused by T315I point mutation, other targeted therapies, autologous transplantation in molecularly negative patients, therapeutic monoclonal antibodies like inotuzumab ozogamicin and blinatumomab, and chimeric antigen receptor-modified T cells. Ph+ ALL could become curable in the near future even without allogeneic stem cell transplantation, minimizing the risk of therapy-related death and improving greatly the quality of patients' life.

Ph+ ALL patients in first complete remission have similar survival after reduced intensity and myeloablative allogeneic transplantation: impact of tyrosine kinase inhibitor and minimal residual disease

The efficacy of reduced intensity conditioning (RIC) allogeneic hematopoietic cell transplantation (HCT) for Philadelphia chromosome positive (Ph+) acute lymphoblastic leukemia (ALL) is uncertain. We analyzed 197 adults with Ph+ ALL in first complete remission; 67 patients receiving RIC were matched with 130 receiving myeloablative conditioning (MAC) for age, donor type and HCT year. Over 75% received pre-HCT tyrosine kinase inhibitors (TKIs), mostly imatinib; 39% (RIC) and 49% (MAC) were minimal residual disease (MRD)(neg) pre-HCT. At a median 4.5 years follow-up, 1-year transplant-related mortality (TRM) was lower in RIC (13%) than MAC (36%; P=0.001) while the 3-year relapse rate was 49% in RIC and 28% in MAC (P=0.058). Overall survival (OS) was similar (RIC 39% (95% confidence interval (CI) 27-52) vs 35% (95% CI 27-44); P=0.62). Patients MRD(pos) pre-HCT had higher risk of relapse with RIC vs MAC (hazard ratio (HR) 1.97; P=0.026). However, patients receiving pre-HCT TKI in combination with MRD negativity pre-RIC HCT had superior OS (55%) compared with a similar MRD population after MAC (33%; P=0.0042). In multivariate analysis, RIC lowered TRM (HR 0.6; P=0.057), but absence of pre-HCT TKI (HR 1.88; P=0.018), RIC (HR 1.891; P=0.054) and pre-HCT MRD(pos) (HR 1.6; P=0.070) increased relapse risk. RIC is a valid alternative strategy for Ph+ ALL patients ineligible for MAC and MRD(neg) status is preferred pre-HCT.

Treatment of Philadelphia-positive acute lymphoid leukemia

SUMMARY Philadelphia-positive (Ph+) acute lymphoblastic leukemia (ALL) represents approximately 15–30% of ALL in adults and is characterized by the expression of the fusion protein BCR–ABL with oncogenic activity. Remission and survival rates were lower whereas relapse risk was increased in Ph+ compared with Philadelphia-negative ALL, until remarkable improvements in the management of Ph+ ALL were achieved through the introduction of tyrosine kinase inhibitors that reduce the activity of the BCR–ABL protein. However, in patients achieving complete remission, allogeneic hematopoietic stem cell transplantation is in most cases a mandatory therapeutic step because rate of relapses are still high. This review will illustrate the current therapeutic options for the management of Ph+ ALL and indicate how better curative options may stem from appropriate implementation of tyrosine kinase inhibitors and novel antitumoral agents.

UKALLXII/ECOG2993: addition of imatinib to a standard treatment regimen enhances long-term outcomes in Philadelphia positive acute lymphoblastic leukemia

The Philadelphia chromosome positive arm of the UKALLXII/ECOG2993 study for adult acute lymphoblastic leukemia (ALL) enrolled 266 patients between 1993 and 2003 (pre-imatinib cohort). In 2003 imatinib was introduced as a single-agent course following induction (N = 86, late imatinib). In 2005 imatinib was added to the second phase of induction (N = 89, early imatinib). The complete remission (CR) rate was 92% in the imatinib cohort vs 82% in the preimatinib cohort (P = .004). At 4 years, the overall survival (OS) of all patients in the imatinib cohort was 38% vs 22% in the preimatinib cohort (P = .003). The magnitude of the difference between the preimatinib and imatinib cohorts in event-free survival (EFS), OS, and relapse-free survival (RFS) seen in univariate analysis was even greater in the multivariate analysis. In the preimatinib cohort, 31% of those starting treatment achieved hematopoietic stem cell transplant (alloHSCT) compared with 46% in the imatinib cohort. A Cox multivariate analysis taking alloHSCT into account showed a modest additional benefit to imatinib (hazard ratio for EFS = 0.64, 95% confidence interval 0.44-0.93, P = .02), but no significant benefit for OS and RFS. Adding imatinib to standard therapy improves CR rate and long-term OS for adults with ALL. A proportion of the OS benefit derives from the fact that imatinib facilitates alloHSCT. This trial was registered at clinicaltrials.gov as NCT00002514.

Pharmacokinetically-targeted BU and fludarabine as conditioning before allogeneic hematopoietic cell transplantation for adults with ALL in first remission

Allogeneic hematopoietic cell transplantation offers improved survival in patients with ALL, but with regimens containing TBI, the nonrelapse mortality is 20-40%. Efforts to lessen transplant toxicities by reducing conditioning regimen intensity have led to increased relapse risk. Therefore, there is a need for less toxic regimens that maintain an anti-leukemia effect. We report here a retrospective review of 65 patients with ALL in first remission receiving grafts from allogeneic donors after fludarabine 40 mg/m(2)/day for 4 days and i.v. BU targeted to a median daily area under the concentration-time curve below 6000 μmoles min/L. At 2 years after transplantation, OS was 65% (95% confidence interval (CI): 52-77%), relapse-free survival was 61% (95% CI: 48-73%), cumulative incidence of relapse was 26% (95% CI: 17-39%) and cumulative incidence of nonrelapse mortality was 14% (95% CI: 8-26%). Age over 35 years, Ph chromosome positivity and minimal residual disease at transplant did not adversely affect outcomes. Pharmacokinetically targeted BU and fludarabine can provide intensive pre-transplant conditioning for adults with ALL in first remission, with promising relapse-free and OS rates.