Azacitidine salvage therapy for relapse of myeloid malignancies following allogeneic hematopoietic SCT

The graft versus leukemia effect: donor lymphocyte infusions and cellular therapy

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative therapy for many hematologic malignancies as well as non-malignant conditions. Part of the curative basis underlying HSCT for hematologic malignancies relies upon induction of the graft versus leukemia (GVL) effect in which donor immune cells recognize and eliminate residual malignant cells within the recipient, thereby maintaining remission. GVL is a clinically evident phenomenon; however, specific cell types responsible for inducing this effect and molecular mechanisms involved remain largely undefined. One of the best examples of GVL is observed after donor lymphocyte infusions (DLI), an established therapy for relapsed disease or incipient/anticipated relapse. DLI involves infusion of peripheral blood lymphocytes from the original HSCT donor into the recipient. Sustained remission can be observed in 20-80% of patients treated with DLI depending upon the underlying disease and the intrinsic burden of targeted cells. In this review, we will discuss current knowledge about mechanisms of GVL after DLI, experimental strategies for augmenting GVL by manipulation of DLI (e.g. neoantigen vaccination, specific cell type selection/depletion) and research outlook for improving DLI and cellular immunotherapies for hematologic malignancies through better molecular definition of the GVL effect.

Allogeneic stem cell transplantation for patients with myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are a heterogenous group of clonal hematopoietic stem cell neoplasms primarily affecting older persons, associated with dysplastic changes of bone marrow cells, peripheral cytopenias, and various risk of leukemic transformation. Although treatment with several drugs has shown improved disease control, allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the only curative treatment for MDS. The number of patients receiving a transplant, as well as survival, have increased past years because of the use of reduce-intensity conditioning regimens (RIC) as well as the use of haploidentical donors for transplantation. With treatment-related mortality as main limitation, pre-transplant evaluation is essential to assess risks for this older group of patients. In a recent randomized study, allo-HSCT with RIC for patients >50 years old with higher-risk MDS demonstrated superiority in survival compared with hypomethylating agents. Genetic mutations have been shown to significantly impact treatment outcomes including after transplant. Recently, a transplant-specific risk score (which includes age, donor type, performance status, cytogenetic category, recipient's cytomegalovirus status, percentage of blasts, and platelet count) has shown superiority in transplantation outcome prediction, compared with previous scoring systems. Survival remains low for most patients with TP53 mutations and novel treatment strategies are needed, such as administration of natural killer cells post-transplant, as there is no clear evidence that maintenance therapy after transplantation can improve outcomes.

How I treat high-risk acute myeloid leukemia using preemptive adoptive cellular immunotherapy

Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a potentially curative treatment for patients with high-risk acute leukemias, but unfortunately disease recurrence remains the major cause of death in these patients. Infusion of donor lymphocytes (DLI) has the potential to restore graft-versus-leukemia immunologic surveillance; however, efficacy varies across different hematologic entities. Although relapsed chronic myeloid leukemia, transplanted in chronic phase, has proven remarkably susceptible to DLI, response rates are more modest for relapsed acute myeloid leukemia and acute lymphoblastic leukemia. To prevent impending relapse, a number of groups have explored administering DLI preemptively on detection of measurable residual disease (MRD) or mixed chimerism. Evidence for the effectiveness of this strategy, although encouraging, comes from only a few, mostly single-center retrospective, nonrandomized studies. This article seeks to (1) discuss the available evidence supporting this approach while highlighting some of the inherent challenges of MRD-triggered treatment decisions post-transplant, (2) portray other forms of postremission cellular therapies, including the role of next-generation target-specific immunotherapies, and (3) provide a practical framework to support clinicians in their decision-making process when considering preemptive cellular therapy for this difficult-to-treat patient population.

Azacitidine and donor lymphocytes infusions in acute myeloid leukemia and myelodysplastic syndrome relapsed after allogeneic hematopoietic stem cell transplantation from alternative donors

Introduction

Azacitidine (AZA) either single-agent or with donor lymphocytes infusions (DLI) has been used as a salvage treatment for acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) relapsing after allogeneic hematopoietic stem cell transplantation (HSCT). To date, the majority of data come from patients relapsed after HSCT from full-matched donors.

Methods

We report a multicenter, collaborative, retrospective analysis of 71 patients with hematologic (n = 40, 56%) and molecular relapse (n = 31, 44%) of myeloid neoplasms after HSCT from alternative donors (mismatched unrelated, n = 39, 55%; haploidentical, n = 29, 41%) consecutively treated at three European centers with AZA ± DLI.

Results

Median time from HSCT to relapse was 9 months. Additional DLI were given to 33 patients (46%). After a median of four cycles, overall response rate (ORR) was 49% and complete response (CR) rate was 38%. CR lasted for a median of 17 months (range 5-89 months). Median follow-up in the entire cohort was 11 months (range 1-115 months). Event-free survival (EFS) and overall survival (OS) at 1 year were 26% and 53%, respectively. Treatment of molecular relapse granted higher CR rate (65% versus 15%; p = 0.0001), 1-year EFS (43% versus 13%; p = 0.006), and 1-year OS (79% versus 34%; p < 0.001) compared to hematologic relapses. Addition of DLI resulted in significantly higher responses and longer 1-year EFS and OS (Mantel-Byar test, p = 0.004 and p = 0.002, respectively). When applied to our cohort, the APSS-R score confirmed its ability to stratify patients into distinct prognostic groups with significantly different response rates (p = 0.0005) and survival (p < 0.0001). Treatment was well tolerated, with the incidence of late acute and chronic graft-versus-host disease of 27% and 18%, respectively.

Conclusion

AZA ± DLI proved feasible and effective in AML and MDS relapsing after HSCT from alternative donors. Despite modest efficacy among hematologic relapses, pre-emptive treatment with AZA ± DLI fared better in molecular relapse. Additional DLI contributed to improving efficacy and ensuring longer survival.

BMT for Myelodysplastic Syndrome: When and Where and How

Myelodysplastic syndromes (MDS) are a diverse group of hematological malignancies distinguished by a combination of dysplasia in the bone marrow, cytopenias and the risk of leukemic transformation. The hallmark of MDS is bone marrow failure which occurs due to selective growth of somatically mutated clonal hematopoietic stem cells. Multiple prognostic models have been developed to help predict survival and leukemic transformation, including the international prognostic scoring system (IPSS), revised international prognostic scoring system (IPSS-R), WHO prognostic scoring system (WPSS) and MD Anderson prognostic scoring system (MDAPSS). This risk stratification informs management as low risk (LR)-MDS treatment focuses on improving quality of life and cytopenias, while the treatment of high risk (HR)-MDS focuses on delaying disease progression and improving survival. While therapies such as erythropoiesis stimulating agents (ESAs), erythroid maturation agents (EMAs), immunomodulatory imide drugs (IMIDs), and hypomethylating agents (HMAs) may provide benefit, allogeneic blood or marrow transplant (alloBMT) is the only treatment that can offer cure for MDS. However, this therapy is marred, historically, by high rates of toxicity and transplant related mortality (TRM). Because of this, alloBMT is considered in a minority of MDS patients. With modern techniques, alloBMT has become a suitable option even for patients of advanced age or with significant comorbidities, many of whom who would not have been considered for transplant in prior years. Hence, a formal transplant evaluation to weigh the complex balance of patient and disease related factors and determine the potential benefit of transplant should be considered early in the disease course for most MDS patients. Once alloBMT is recommended, timing is a crucial consideration since delaying transplant can lead to disease progression and development of other comorbidities that may preclude transplant. Despite the success of alloBMT, relapse remains a major barrier to success and novel approaches are necessary to mitigate this risk and improve long term cure rates. This review describes various factors that should be considered when choosing patients with MDS who should pursue transplant, approaches and timing of transplant, and future directions of the field.

Prevention and Treatment of Acute Myeloid Leukemia Relapse after Hematopoietic Stem Cell Transplantation: The State of the Art and Future Perspectives

Allogeneic hematopoietic stem cell transplantation (HSCT) for high-risk acute myeloid leukemia (AML) represents the only curative option. Progress has been made in the last two decades in the pre-transplant induction therapies, supportive care, selection of donors and conditioning regimens that allowed to extend the HSCT to a larger number of patients, including those aged over 65 years and/or lacking an HLA-identical donor. Furthermore, improvements in the prophylaxis of the graft-versus-host disease and of infection have dramatically reduced transplant-related mortality. The relapse of AML remains the major reason for transplant failure affecting almost 40-50% of the patients. From 10 to 15 years ago to date, treatment options for AML relapsing after HSCT were limited to conventional cytotoxic chemotherapy and donor leukocyte infusions (DLI). Nowadays, novel agents and targeted therapies have enriched the therapeutic landscape. Moreover, very recently, the therapeutic landscape has been enriched by manipulated cellular products (CAR-T, CAR-CIK, CAR-NK). In light of these new perspectives, careful monitoring of minimal-residual disease (MRD) and prompt application of pre-emptive strategies in the post-transplant setting have become imperative. Herein, we review the current state of the art on monitoring, prevention and treatment of relapse of AML after HSCT with particular attention on novel agents and future directions.

Treatment of AML Relapse After Allo-HCT

With advances in allogeneic hematopoietic stem cell transplant (allo-HCT), disease relapse has replaced transplant-related mortality as the primary cause of treatment failure for patients with acute myeloid leukemia (AML). The efficacy of allo-HCT in AML is a consequence of a graft-versus-leukemia (GVL) effect that is mediated by T lymphocytes, and unique mechanisms of immune evasion underlying post-allo-HCT AML relapses have recently been characterized. Relapsed AML following allo-HCT presents a particularly vexing clinical challenge because transplant-related toxicities, such as graft-versus-host (GVHD) and infections, increase the risk of treatment-related morbidity and mortality. In general, the prognosis of relapsed AML following allo-HCT is poor with most patients failing to achieve a subsequent remission and 2-year survival consistently <15%. The two factors that have been found to predict a better prognosis are a longer duration of post-transplant remission prior to relapse and a lower disease burden at the time of relapse. When considered in combination with a patient's age; co-morbidities; and performance status, these factors can help to inform the appropriate therapy for the treatment of post-transplant relapse. This review discusses the options for the treatment of post-transplant AML relapse with a focus on the options to achieve a subsequent remission and consolidation with cellular immunotherapy, such as a second transplant or donor lymphocyte infusion (DLI). While intensive reinduction therapy and less intensive approaches with hypomethylating agents have long represented the two primary options for the initial treatment of post-transplant relapse, molecularly targeted therapies and immunotherapy are emerging as potential alternative options to achieve remission. Herein, we highlight response and survival outcomes achieved specifically in the post-transplant setting using each of these approaches and discuss how some therapies may overcome the immunologic mechanisms that have been implicated in post-transplant relapse. As long-term survival in post-transplant relapse necessarily involves consolidation with cellular immunotherapy, we present data on the efficacy and toxicity of both DLI and second allo-HCT including when such therapies are integrated with reinduction. Finally, we provide our general approach to the treatment of post-transplant relapse, integrating both novel therapies and our improved understanding of the mechanisms underlying post-transplant relapse.

Therapeutic Use of Valproic Acid and All-Trans Retinoic Acid in Acute Myeloid Leukemia-Literature Review and Discussion of Possible Use in Relapse after Allogeneic Stem Cell Transplantation

Even though allogeneic stem cell transplantation is the most intensive treatment for acute myeloid leukemia (AML), chemo-resistant leukemia relapse is still one of the most common causes of death for these patients, as is transplant-related mortality, i.e., graft versus host disease, infections, and organ damage. These relapse patients are not always candidates for additional intensive therapy or re-transplantation, and many of them have decreased quality of life and shortened expected survival. The efficiency of azacitidine for treatment of posttransplant AML relapse has been documented in several clinical trials. Valproic acid is an antiepileptic fatty acid that exerts antileukemic activity through histone deacetylase inhibition. The combination of valproic acid and all-trans retinoic acid (ATRA) is well tolerated even by unfit or elderly AML patients, and low-toxicity chemotherapy (e.g., azacitidine) can be added to this combination. The triple combination of azacitidine, valproic acid, and ATRA may therefore represent a low-intensity and low-toxicity alternative for these patients. In the present review, we review and discuss the general experience with valproic acid/ATRA in AML therapy and we discuss its possible use in low-intensity/toxicity treatment of post-allotransplant AML relapse. Our discussion is further illustrated by four case reports where combined treatments with sequential azacitidine/hydroxyurea, valproic acid, and ATRA were used.

Azacitidine for relapse of acute myeloid leukemia or myelodysplastic syndrome after allogeneic hematopoietic stem cell transplantation, multicenter PALG analysis

OBJECTIVES

Relapse of myelodysplastic syndromes (MDS) or acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) belongs to the major causes of treatment failure.

METHODS

Retrospective multicenter analysis of patients diagnosed with AML or MDS who had hematological relapse after allo-HSCT and were treated with azacitidine for this indication.

RESULTS

Twenty-three patients receiving azacitidine as the first treatment of relapse (Group_1) and 8 patients receiving azacitidine after other treatment of relapse (Group_2) were included. There were 68% males, median age at initiation of azacitidine was 53 years (15-66). Median time to relapse was 3.5 months and 6.3 months in Group_1 and Group_2, respectively; median time from relapse to azacitidine 0.2 and 2.3 months. Azacitidine 75 mg/m² , days 1-7, was administered in 78% and 75% of patients in Group_1 and Group_2, concomitant DLI in 48% and 50%. With median follow-up of 4.7 and 13.6 months, the median overall survival was 5.9 and 9.5 months. 17% and 37.5% patients proceeded to salvage allo-HSCT, with median OS of 11.6 months and not reached respectively.

CONCLUSIONS

Azacitidine treatment for hematological relapse is associated with poor outcome; nevertheless, a proportion of patients may benefit from it, including patients receiving subsequent salvage allo-HSCT.

Pharmacologic Therapies to Prevent Relapse of Acute Myeloid Leukemia After Allogeneic Hematopoietic Stem Cell Transplantation

Relapse is the main cause of mortality in patients with acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Adverse cytogenetic or molecular risk factors, as well as refractory disease or persistent measurable residual disease (MRD) at the time of transplantation are associated with an increased risk of recurrence. Salvage therapy for AML relapse after allo-HSCT is often limited to chemotherapy, donor lymphocyte infusions and/or second transplants and is rarely successful. Effective post-transplant preventive intervention in high risk AML may be crucial. The most frequent and promising approach is the use of post-transplant maintenance with hypomethylating agents or with FLT3 tyrosine kinase inhibitors when the target is present. Moreover, IDH1/IDH2 inhibitors and BCL-2 inhibitors in combination with other strategies are promising approaches in the maintenance setting. Here we summarize the current knowledge about the preemptive and prophylactic use of pharmacologic agents after allo-HSCT to prevent relapse of AML.

Prediction of Response and Survival Following Treatment with Azacitidine for Relapse of Acute Myeloid Leukemia and Myelodysplastic Syndromes after Allogeneic Hematopoietic Stem Cell Transplantation

To provide long-term outcome data and predictors for response and survival, we retrospectively analyzed all 151 patients with relapse of myeloid neoplasms after allogeneic hematopoietic stem cell transplantation (allo-HSCT) who were uniformly treated with first-line azacitidine (Aza) salvage therapy at our center. Patients were treated for molecular (39%) or hematologic relapse (61%), with a median of 5 cycles of Aza and at least one donor lymphocyte infusion in 70% of patients. Overall response was 46%, with 41% achieving complete (CR) and 5% achieving partial remission. CR was achieved after a median of 4 cycles and lasted for a median of 11 months (range 0.9 to 120 months). With a median follow-up of 22 months (range: 1 to 122 months), the 2-year survival rate was 38% ± 9%, including 17 patients with ongoing remission for >5 years. Based on results from multivariate analyses, molecular relapse and time to relapse were integrated into a score, clearly dividing patients into 3 subgroups with CR rates of 71%, 39%, and 29%; and 2-year survival rates of 64%, 38%, and 27%, respectively. In the subgroup of MDS and secondary AML, receiving upfront transplantation was associated with superior response and survival, and therefore pretransplant strategy was integrated together with relapse type into a MDS–sAML-specific score. Overall, Aza enables meaningful responses and long-term survival, which is a predictable with a simple-to-use scoring system.

Hypomethylating agent-based post-transplant strategies to maximize the outcome of high-risk acute myeloid leukemia after allogeneic stem cell transplantation

INTRODUCTION

Clinical outcomes of patients diagnosed with high-risk acute myeloid leukemia (AML) are poor, and relapse or refractoriness is main cause of treatment failure, even in those who underwent standard allogeneic stem cell transplantation (allo-SCT). Therefore, innovative or additional approaches are necessary to overcome refractoriness to the graft-versus-leukemia (GVL) effect immediately after allo-SCT.

AREAS COVERED

Hypomethylating agents (HMA) present a feasible option that can be adopted during the post-transplant phase. Moreover, combination strategies based on HMA may induce a synergistic effect by promoting anti-leukemic effects that overcome residual leukemic burden, and it is a well-tolerated therapeutic option for high-risk disease. Relevant literatures published in the last 30 years were searched from PubMed to review the topic of AML, allo-SCT, and HMAs.

EXPERT OPINION

Post-transplant therapy is strongly needed to improve the outcomes of allogeneic transplantation for certain AML patients classified with high-risk disease. In that sense, prophylactic and preemptive HMAs are a promising additive therapy for allogeneic recipients.

Immunological and Clinical Impact of Manipulated and Unmanipulated DLI after Allogeneic Stem Cell Transplantation of AML Patients

Allogeneic stem cell transplantation (allo-SCT) is the preferred curative treatment for several hematological malignancies. The efficacy of allo-SCT depends on the graft-versus-leukemia (GvL) effect. However, the prognosis of patients with relapsed acute myeloid leukemia (AML) following allo-SCT is poor. Donor lymphocyte infusion (DLI) is utilized after allo-SCT in this setting to prevent relapse, to prolong progression free survival, to establish full donor chimerism and to restore the GvL effect in patients with hematological malignancies. Thus, there are different options for the administration of DLI in AML patients. DLI is currently used prophylactically and in the setting of an overt relapse. In addition, in the minimal residual disease (MRD) setting, DLI may be a possibility to improve overall survival. However, DLI might increase the risk of severe life-threatening complications such as graft-versus-host disease (GvHD) as well as severe infections. The transfusion of lymphocytes has been tested not only for the treatment of hematological malignancies but also chronic infections. In this context, manipulated DLI in a prophylactic or therapeutic approach are an option, e.g., virus-specific DLI using different selection methods or antigen-specific DLI such as peptide-specific CD8+ cytotoxic T lymphocytes (CTLs). In addition, T cells are also genetically engineered, using both chimeric antigen receptor (CAR) genetically modified T cells and T cell receptor (TCR) genetically modified T cells. T cell therapies in general have the potential to enhance antitumor immunity, augment vaccine efficacy, and limit graft-versus-host disease after allo-SCT. The focus of this review is to discuss the different strategies to use donor lymphocytes after allo-SCT. Our objective is to give an insight into the functional effects of DLI on immunogenic antigen recognition for a better understanding of the mechanisms of DLI. To ultimately increase the GvL potency without raising the risk of GvHD at the same time.

Checkpoint inhibitors in AML: are we there yet?

Immunotherapy is distinct from traditional chemotherapy in that it acts on immune cells rather than cancer cells themselves. Monoclonal antibodies targeting immune checkpoints on T cells - CTLA-4 and PD-1 - and PD-L1 on the cells of immune microenvironment are now approved for clinical use in several solid tumors and hematological malignancies. This article provides a general overview of the use of checkpoint inhibitors in hematologic malignancies with a special focus in acute myeloid leukemia.

Very early lineage-specific chimerism after reduced intensity stem cell transplantation is highly predictive of clinical outcome for patients with myeloid disease

BACKGROUND

The importance of chimerism status in the very early period after hematopoietic stem cell transplantation is unclear. We determined PBMC and T-cell donor chimerism 50 days after transplantation and related this to disease relapse and overall survival.

METHODS

144 sequential patients underwent transplantation of which 90 had AML/MDS and 54 had lymphoma. 'Full donor chimerism' was defined as ≥99% donor cells and three patient groups were defined: 40% with full donor chimerism (FC) in both PBMC and T-cells; 25% with mixed chimerism (MC) within both compartments and 35% with 'split' chimerism (SC) characterised by full donor chimerism within PBMC and mixed chimerism within T-cells.

RESULTS

In patients with myeloid disease a pattern of mixed chimerism (MC) was associated with a one year relapse rate of 45% and a five year overall survival of 40% compared to values of 8% and 75%, and 17% and 60%, for those with SC or FC respectively. The pattern of chimerism had no impact on clinical outcome for lymphoma.

CONCLUSION

The pattern of lineage-specific chimerism at 50 days after transplantation is highly predictive of clinical outcome for patients with myeloid malignancy and may help to guide subsequent clinical management.

Prospective phase II study of prophylactic low-dose azacitidine and donor lymphocyte infusions following allogeneic hematopoietic stem cell transplantation for high-risk acute myeloid leukemia and myelodysplastic syndrome

Thirty patients, with high-risk acute myeloid leukemia (AML, n = 20) or myelodysplastic syndrome (MDS, n = 10), were enrolled in a phase II trial entailing prophylactic post-transplant azacitidine (AZA) plus escalated doses of donor lymphocyte infusion (DLI). The median number of AZA cycles was 5 (1-12) with 10 patients (33%) completing the 12 projected cycles. DLI were performed in 17 patients: 5 received one DLI, 2 received 2 DLI and 8 received 3 infusions. AZA was well tolerated, but discontinued in 20 patients primarily due to graft-versus-host disease (GvHD) and relapse. The cumulative incidence (CI) of grade 1-3 acute GvHD was 31.5% and the chronic GvHD CI was 53% at 2 years. At a median follow-up of 49 months (27-63), 18 patients are alive. The overall and disease-free survivals are 65.5% (CI 95% = 48.2-82.8) at 2 years. Cause of death was mainly relapse for 9 patients. The median time to relapse was 7 months (2.5-58) and the cumulative incidence of relapse at 2 years was 27.6% (CI 95% = 12.8-44.6). These results confirm that AZA is well tolerated as a prophylactic treatment to reduce the risk of post-transplantation relapse and compared favorably to those of patients who receive no post-transplant maintenance.

Low-Dose Azacitidine with DNMT1 Level Monitoring to Treat Post-Transplantation Acute Myelogenous Leukemia or Myelodysplastic Syndrome Relapse

Patients with early relapse of acute myelogenous leukemia (AML) or myelodysplastic syndrome (MDS) after hematopoietic cell transplantation (HCT) have a poor prognosis, and no standard treatment. Twenty-nine patients with early disease recurrence post-transplantation were treated with azacitidine (AZA; median dose, 40 mg/m²/day for 5 to 7 days). At a median follow-up of 6.3 months (range, 1.3 to 41.1 months), 7 patients (27%) had a response to AZA, defined as complete remission, hematologic improvement, or improved donor chimerism. Response occurred after a median of 3 cycles, and the median duration of response was 70 days (range, 26 to 464 days). Median survival was 6.8 months (95% confidence interval, 3.8 to 11.1 months). Survival was similar in the patients receiving an AZA dose ≤40 mg/m² and those receiving an AZA dose >40 mg/m². Six patients receiving donor lymphocyte infusion with AZA had a response or stable disease without worsening graft-versus-host-disease. We retrospectively used a flow cytometry assay to explore DNA-methyltransferase-1 in blood mononuclear cells as a potential pharmacodynamic marker to assess intracellular drug targeting in 8 patients. No correlation with AZA dose or response was observed. Low-dose AZA appears to have comparable efficacy to higher-dose AZA post-HCT. A significant proportion of this poor-risk population responded to low-dose AZA, suggesting a dose-independent, noncytotoxic mechanism for antileukemic activity.

Mechanisms of immune escape after allogeneic hematopoietic cell transplantation

Relapse of the original disease is a major cause of death after allogeneic hematopoietic cell transplantation for acute leukemias. There is growing evidence that relapses may be explained not only by resistance to chemotherapy but also by the escape of tumor cells from the control of the allogeneic immune response. Mechanisms of immune evasion can involve abrogation of leukemia cell recognition due to loss of HLA genes, immunosuppression by immune-checkpoint ligand expression, production of anti-inflammatory factors, release of metabolically active enzymes, loss of proinflammatory cytokine production, and acquisition of novel driver mutations that promote leukemia outgrowth. These mechanisms, and therapeutic targeting of immune escape, will be discussed. We divide the evidence in support of immune-escape mechanisms into animal studies, human laboratory studies, and human clinical experience. A better understanding of the molecular pathways connected to immune escape and relapse may help to improve our therapeutic armamentarium against acute myeloid leukemia relapse.

Low-dose azacitidine maintenance therapy after allogeneic stem cell transplantation for high-risk pediatric acute myeloid leukemia

The dismal prognosis of pediatric acute myeloid leukemia (AML) relapsing after hematopoietic stem cell transplantation (HSCT) requires exploration of novel strategies to prevent relapse. Azacitidine (AZA) maintenance therapy could potentially reduce the recurrence rate post HSCT. Here, we presents the cases of three children with high-risk AML post HSCT who were treated with low-dose AZA maintenance therapy, demonstrating the feasibility of this therapy. Currently, all three are in complete remission for 13-41 months despite their high-risk characteristics. Our encouraging data warrant larger prospective studies to assess the efficacy and safety of low-dose AZA maintenance therapy post HSCT for pediatric patients with high-risk AML.

HYPOMETHYLATING AGENTS IN TREATMENT OF MYELODYSPLASTIC SYNDROME

Thelkey to the successful treatment of myelodysplastic syndrome is the careful characterization and diagnosis of the disease, which includes clinical, cytogenetic, biological and molecular investigation of individual patients. Today therapeutic approaches to the treatment of such patients are differentiated and depend, first of all, on the subtype of the disease, age, general condition of the patients and the possibility of allogeneic hematopoietic cell transplantation. For young patients, the best option is transplantation, whereas in older patients, the standard of therapy is the use of hypomethylating agents (azacitidine, decitabine). These drugs promote hematologic improvement, elimination of transfusion dependence and prolongation of the duration of both general and leukemia free survival in elderly patients with concomitant pathology. Despite the fact that therapy with hypomethylating drugs is widely used and has good results, many respondents are losing their response within 1–2 years. Reasons for the development of resistance to this type of treatment are still unclear, and the insensitivity to drugs is associated with very poor prognosis in patients with all subtypes of myelodysplastic syndrome. Such data and the presence of numerous genetic and epigenetic mechanisms for the development of this pathology have prompted the use of combinations of drugs with different application points and are relevant in terms of research. In the literature review, the results of clinical studies on the use of hypomethylating agents in patients with MDS of low and high risk, as in monotherapy and combined schemes are presented. The nearest prospect of treatment of myelodysplastic syndrome is the creation of new treatment regimens based on a combination of drugs of different pathogenetic direction for the elimination of the dysplastic clone in order to achieve not only long-term remissions, but also lengthening the duration of overall survival, especially for patients with high risk myelodysplastic syndrome.

DNA-hypomethylating agents as epigenetic therapy before and after allogeneic hematopoietic stem cell transplantation in myelodysplastic syndromes and juvenile myelomonocytic leukemia

Myelodysplastic syndrome (MDS) is a clonal bone marrow disorder, typically of older adults, which is characterized by ineffective hematopoiesis, peripheral blood cytopenias and risk of progression to acute myeloid leukemia. Juvenile myelomonocytic leukemia (JMML) is an aggressive myeloproliferative neoplasm occurring in young children. The common denominator of these malignant myeloid disorders is the limited benefit of conventional chemotherapy and a particular responsiveness to epigenetic therapy with the DNA-hypomethylating agents 5-azacytidine (azacitidine) or decitabine. However, hypomethylating therapy does not eradicate the malignant clone in MDS or JMML and allogeneic hematopoietic stem cell transplantation (HSCT) remains the only curative treatment option. An emerging concept with intriguing potential is the combination of hypomethylating therapy and HSCT. Possible advantages include disease control with good tolerability during donor search and HSCT preparation, improved antitumoral alloimmunity, and reduced risk of relapse even with non-myeloablative regimens. Herein we review the current role of pre- and post-transplant therapy with hypomethylating agents in MDS and JMML.

Decitabine for relapsed acute lymphoblastic leukemia after allogeneic hematopoietic stem cell transplantation

Relapse after allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains a main question on treatment failure. Current strategies for management that usually include salvage chemotherapy, donor lymphocytic infusion and second transplantation. Our study assessed the efficacy of decitabine (DAC) for treating patients with acute lymphoblastic leukemia (ALL) who relapsed after allogeneic hematopoietic stem cell transplantation (allo-HSCT). We retrospectively analyzed the outcomes of 12 patients with relapsed ALL after allo-HSCT who received DAC therapy. Nine patients received DAC combined with chemotherapy and donor stem cell infusion, and 3 patients received single- agent DAC. Ten of the 12 patients achieved complete remission (CR), 1 achieved a partial remission (PR), and 1 had no response (NR) after treatment at the latest follow-up (LFU), the median survival was 11.2 months (range, 3.8-34, 7 months). The 1- and 2-year overall survival (OS) rates were 50% (6/12) and 25% (3/12), respectively. Five patients were still alive; 4 had maintained CR and 1 was alive with disease. Patients with Philadelphia chromosome-positive ALL had higher survival rate than patients with Philadelphia chromosome-negative ALL (57.1% vs. 20%). No aggravated flares of graft-versus-host disease (GVHD) were observed during DAC treatment. Therefore, DAC may be a promising therapeutic agent for ALL recurrence after allo-HSCT.

Early mixed T-cell chimerism is predictive of pediatric AML or MDS relapse after hematopoietic stem cell transplant

Patients with acute myeloid leukemia (AML) who relapse after hematopoietic stem cell transplantation (HCT) have dismal outcomes. Our ability to predict those at risk for relapse is limited. We examined chimerism trends post-HCT in 63 children who underwent HCT for AML or myelodysplastic syndrome (MDS). Mixed T-cell chimerism at engraftment and absence of chronic graft versus host disease (cGVHD) were associated with relapse (P = 0.04 and P = 0.02, respectively). Mixed T-cell chimerism at engraftment was predictive in patients without cGVHD (P = 0.03). Patients with engraftment mixed T-cell chimerism may warrant closer disease monitoring and consideration for early intervention.

Donor-Cell Origin High-Risk Myelodysplastic Syndrome Synchronous with an Intracranial Meningioma-Like Tumor, 8 Years after Allogeneic Hematopoietic Stem Cell Transplantation for Chronic Lymphocytic Leukemia

Secondary neoplasias are well known consequences of radiotherapy or chemotherapy for a primary cancer. In this report, we describe two rare secondary neoplasias occurring in the same patient: a meningioma-like intracranial tumor and high-risk myelodysplastic syndrome (MDS) of donor-cells origin, both diagnosed simultaneously, 8 years after an allogeneic hematopoietic stem cell transplantation (allo-HSCT) for chronic lymphocytic leukemia (CLL). Due to an engraftment failure during the first allo-HSCT of a matched related donor for CLL treatment, the salvage treatment was a second allo-HSCT. At the moment of meningioma-like tumor diagnosis, the patient was pancytopenic due to high-risk MDS, so it was decided to postpone a surgical intervention until hematological improvement. For the high-risk MDS of donor-cells origin the chosen treatment was induction with intensive chemotherapy. Due to refractory disease, the patient was treated with 5-azacitidine and donor-lymphocytes infusion with no response and, finally, a third allo-HSCT of a matched unrelated donor was performed. The patient died 6 months after the third allo-HSCT, in cytogenetic remission but without hematological recovery, due to an intracranial hemorrhage with origin in the meningioma-like tumor.

Azacitidine as a bridge to allogeneic hematopoietic cell transplantation in a pediatric patient with Fanconi anemia and acute myeloid leukemia

HCT is the definitive therapy for patients with FA and AML. Conventional cytotoxic agents cause potential DNA damage, and currently, there is no established regimen for these patients prior to HCT. A 13-year-old male with FA and refractory AML was given azacitidine, achieved morphologic remission and underwent HCT. At 95 days after HCT, he relapsed. Azacitidine along with DLI was used as first salvage therapy. Azacitidine was overall well tolerated with minimal side effects. In patients with AML and FA, azacitidine can be considered an alternative to conventional chemotherapy.

Factors Determining Responses to Azacitidine in Patients with Myelodysplastic Syndromes and Acute Myeloid Leukemia with Early Post-Transplantation Relapse: A Prospective Trial

Retrospective analyses suggest a benefit of therapy with hypomethylating agents in patients with myelodysplastic syndromes (MDS) or acute myeloid leukemia (AML) who relapse after allogeneic hematopoietic cell transplantation (HCT). We conducted a prospective trial in 39 patients with MDS or AML who relapsed within 100 days of HCT. Relapse was documented by morphology, flow cytometry, or cytogenetics. Treatment consisted of 5-azacitidine, 75 mg/m2/day for 7 days, administered every 28 days. Patients were followed by sequential marrow examinations, and responses were assessed at 6 months. There were 3 complete remissions and 9 partial remissions (30%); an additional 3 patients had stable disease by International Working Group criteria. In multivariate analysis, only the type of induction chemotherapy given before HCT was significantly associated with post-HCT response to 5-azacitidine and overall survival (P = .004). These data support the use of hypomethylating therapy for post-HCT relapse in patients with MDS and AML and suggest that pre-HCT therapy may affect the likelihood of response to this salvage approach.

Hypomethylating agents after allogeneic blood stem cell transplantation

Allogeneic blood stem cell transplantation (allo-SCT) is a potentially curative treatment for patients with myeloid malignancies such as acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS), but relapse remains the major cause of treatment failure. So far, therapeutic options for patients with AML or MDS who relapse after allo-SCT generally consisted of palliative care, low-dose or intensive chemotherapy as well as cellular therapies such as donor lymphocyte infusions (DLI) and second transplantation in selected cases. Nevertheless, the prognosis of patients with myeloid malignancies relapsing after allo-SCT remains dismal therefore asking for novel treatment strategies. Considering their well-balanced profile of good efficacy and moderate toxicity in the non-transplant setting, the hypomethylating agents (HMA) azacitidine (Aza) and decitabine (DAC) have also been tested either alone or in combination with DLI in the post-transplant period. This review summarizes the current knowledge about the use of these two HMA as pre-emptive, salvage or consolidation therapy mostly retrieved from retrospective studies but also from a few prospective trials. Within this review, we also comment on some practical issues such as optimal dose and schedule, the choice of HMA candidates and the role of additional cellular interventions. Finally, we also give an overview on the assumed mode of actions, ongoing research, clinical studies and potential combination partners aiming to improve this treatment approach.

Donor lymphocyte infusion after allogeneic stem cell transplantation

Allogeneic stem cell transplantation (allo-SCT) is considered the cornerstone in the treatment of several malignant and not malignant hematological diseases. However, relapse of hematological disease after allo-SCT is considered the most challenging point in the field. The risk can be reduced through optimal patients, donor and disease selection before allo-SCT, but harnessing donor immune system is an appealing way to treat or avoid disease relapse. Donor lymphocyte infusion (DLI) is a simple and effective therapy after allo-SCT. In this paper, the efficacy of DLI will be analyzed in different hematological diseases, focusing also on their therapeutic or pre-emptive use.

Clinical activity of azacitidine in patients who relapse after allogeneic stem cell transplantation for acute myeloid leukemia

Disease relapse is the most common cause of treatment failure after allogeneic stem cell transplantation for acute myeloid leukemia and myelodysplastic syndromes, yet treatment options for such patients remain extremely limited. Azacitidine is an important new therapy in high-risk myelodysplastic syndromes and acute myeloid leukemia but its role in patients who relapse post allograft has not been defined. We studied the tolerability and activity of azacitidine in 181 patients who relapsed after an allograft for acute myeloid leukemia (n=116) or myelodysplastic syndromes (n=65). Sixty-nine patients received additional donor lymphocyte infusions. Forty-six of 157 (25%) assessable patients responded to azacitidine therapy: 24 (15%) achieved a complete remission and 22 a partial remission. Response rates were higher in patients transplanted in complete remission (P=0.04) and those transplanted for myelodysplastic syndromes (P=0.023). In patients who achieved a complete remission, the 2-year overall survival was 48% versus 12% for the whole population. Overall survival was determined by time to relapse post transplant more than six months (P=0.001) and percentage of blasts in the bone marrow at time of relapse (P=0.01). The concurrent administration of donor lymphocyte infusion did not improve either response rates or overall survival in patients treated with azacitidine. An azacitidine relapse prognostic score was developed which predicted 2-year overall survival ranging from 3%-37% (P=0.00001). We conclude that azacitidine represents an important new therapy in selected patients with acute myeloid leukemia/myelodysplastic syndromes who relapse after allogeneic stem cell transplantation. Prospective studies to confirm optimal treatment options in this challenging patient population are required.

Long-term follow-up of patients with acute myeloid leukemia surviving and free of disease recurrence for at least 2 years after autologous stem cell transplantation: A report from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

BACKGROUND

Leukemia recurrence is a major cause of treatment failure after autologous stem cell transplantation for acute myeloid leukemia (AML). It usually occurs within the first 2 years after transplantation. The goal of the current retrospective study was to assess the follow-up of and characterize risk factors for outcome among patients who survived free of disease recurrence after this period.

METHODS

The analysis included 3567 adults (median age, 45 years) with AML who underwent autografting during the first (86% of patients) or second (14% of patients) complete remission between 1990 and 2008. The stem cell source was the bone marrow in 32% of patients or the peripheral blood in 68% of patients. The median follow-up was 6.9 years.

RESULTS

At 5 years and 10 years after transplantation, the probability of leukemia-free survival was 86% and 76%, respectively; the recurrence incidence was 11% and 16%, respectively; and the nonrecurrence mortality rate was 3% and 8%, respectively. The observed survival was decreased compared with the expected survival of the general European population. In a multivariate analysis, decreased probability of leukemia-free survival was demonstrated for patients who underwent peripheral blood autologous stem cell transplantation; had French-American-British subtypes M0, M6, or M7; and were of an older age. The same factors were found to be associated with an increased risk of disease recurrence. Nonrecurrence mortality was found to be affected by older age.

CONCLUSIONS

The results of the current analysis indicate that late recurrences remain a major concern after autologous stem cell transplantation among patients with AML, indicating the need for close monitoring of minimal residual disease and additional leukemic control measures after transplantation. Cancer 2016;122:1880-7. © 2016 American Cancer Society.

Autologous stem cell transplantation for adult acute leukemia in 2015: time to rethink? Present status and future prospects

The use of autologous stem cell transplantation (ASCT) as consolidation therapy for adult patients with acute leukemia has declined over time. However, multiple randomized studies in the past have reported lower relapse rates after autologous transplantation compared with chemotherapy and lower non-relapse mortality rates compared with allogeneic transplantation. In addition, quality of life of long-term survivors is better after autologous transplantation than after allogeneic transplantation. Further, recent developments may improve outcomes of autograft recipients. These include the use of IV busulfan and the busulfan+melphalan combination, better detection of minimal residual disease (MRD) with molecular biology techniques, the introduction of targeted therapies and post-transplant maintenance therapy. Therefore, ASCT may nowadays be reconsidered for consolidation in the following patients if and when they reach a MRD-negative status: good- and at least intermediate-1 risk acute myelocytic leukemia in first CR, acute promyelocytic leukemia in second CR, Ph-positive acute lymphocytic leukemia. Conversely, patients with MRD-positive status or high-risk leukemia should not be considered for consolidation with ASCT.

Treatment strategies in patients with AML or high-risk myelodysplastic syndrome relapsed after Allo-SCT

Non-relapse mortality after Allo-SCT has significantly decreased over the last years. Nevertheless, relapse remains a major cause for post SCT mortality in patients with AML and high-risk myelodysplastic syndrome (MDS). In this retrospective single-center analysis, we have analyzed the treatment outcomes of 108 patients with AML or MDS, who relapsed after Allo-SCT. Seventy of these patients (65%) were treated with salvage therapies containing chemotherapy alone, allogeneic cell-based treatment or the combination of both. Thirty-eight patients (35%) received palliative treatment. Median OS after diagnosis of relapse was 130 days. Compared with patients who received chemotherapy alone, response to salvage therapy was significantly improved in patients treated with a combination of chemo- and allogeneic cell-based therapy (CR rate 57% vs 13%, P=0.002). Among risk factors concerning pretreatment characteristics, disease status before first Allo-SCT, and details of transplantation, only the time interval from Allo-SCT to relapse was an independent predictor of response to salvage therapy and OS. These data confirmed that time to relapse after transplantation is an important prognostic factor. Up to now, only patients eligible for treatment regimens containing allogeneic cell-based interventions achieved relevant response rates.