Treatment of relapsed acute myeloid leukemia after allogeneic bone marrow transplantation with chemotherapy followed by G-CSF-primed donor leukocyte infusion: a high incidence of isolated extramedullary relapse

Multiple small-dose infusions of G-CSF-mobilized haploidentical lymphocytes after autologous haematopoietic stem cell transplantation for acute myeloid leukaemia

This retrospective study analysed 106 acute myeloid leukaemia (AML) patients undergoing autologous haematopoietic stem cell transplantation (ASCT) to assess the impact of multiple small-dose infusions of granulocyte-colony-stimulating factor (G-CSF)-mobilized haploidentical lymphocytes as post-ASCT maintenance therapy. Among them, 50 patients received lymphocyte maintenance therapy, 21 received alternative maintenance therapy, and 35 received no maintenance therapy. Patients receiving lymphocyte maintenance therapy demonstrated significantly higher overall survival (OS) and disease-free survival (DFS) compared to those without maintenance therapy, with 4-year OS and DFS rates notably elevated. While there were no significant differences in recurrence rates among the three groups, lymphocyte maintenance therapy showcased particular benefits for intermediate-risk AML patients, yielding significantly higher OS and DFS rates and lower relapse rates compared to alternative maintenance therapy and no maintenance therapy. The study suggests that multiple small-dose infusions of G-CSF-mobilized haploidentical lymphocytes may offer promising outcomes for AML patients after ASCT, particularly for those classified as intermediate-risk. These findings underscore the potential efficacy of lymphocyte maintenance therapy in reducing disease relapse and improving long-term prognosis in this patient population.

MRD as Biomarker for Response to Donor Lymphocyte Infusion after Allogeneic Hematopoietic Cell Transplantation in Patients with AML

Donor lymphocyte infusions (DLIs) can directly target leukemic cells through a graft-versus-leukemia effect and play a key role in the prevention and management of relapse after allogeneic hematopoietic cell transplantation (alloHCT). Predictors of response to DLIs are not well established. We evaluated measurable residual disease (MRD) before, 30 and 90 days after DLI treatment as biomarkers of response. MRD was assessed by next-generation sequencing in 76 DLI-treated acute myeloid leukemia patients. MRD status before DLI treatment was independently prognostic for event-free survival (EFS, p < 0.001) and overall survival (OS, p < 0.001). Within 90 days of DLI treatment, 73% of MRD+ patients converted to MRD- and 32% of patients without remission achieved remission. MRD status 90 days after DLI treatment was independently prognostic for the cumulative incidence of relapse (CIR, p = 0.011) and relapse-free survival (RFS, p = 0.001), but not for OS. To evaluate the role of DLI treatment in MRD- patients, 23 MRD- patients who received DLIs were compared with a control cohort of 68 MRD- patients not receiving DLIs. RFS (p = 0.23) and OS (p = 0.48) were similar between the two cohorts. In conclusion, MRD is prognostic before (EFS, OS) and after (CIR, RFS) DLI treatment and may help in the selection of patients who benefit most from DLIs.

Immunotherapy in leukaemia

Leukaemia is the common name for a group of malignant diseases of the haematopoietic system with complex classifications and characteristics. Remarkable progress has been made in basic research and preclinical studies for acute leukaemia compared to that of the many other types/subtypes of leukaemia, especially the exploration of the biological basis and application of immunotherapy in acute myeloid leukaemia (AML) and B-cell acute lymphoblastic leukaemia (B-ALL). In this review, we summarize the basic approaches to immunotherapy for leukaemia and focus on the research progress made in immunotherapy development for AML and ALL. Importantly, despite the advances made to date, big challenges still exist in the effectiveness of leukaemia immunotherapy, especially in AML. Therefore, we use AML as an example and summarize the mechanisms of tumour cell immune evasion, describe recently reported data and known therapeutic targets, and discuss the obstacles in finding suitable treatment targets and the results obtained in recent clinical trials for several types of single and combination immunotherapies, such as bispecific antibodies, cell therapies (CAR-T-cell treatment), and checkpoint blockade. Finally, we summarize novel immunotherapy strategies for treating lymphocytic leukaemia and clinical trial results.

Comparison of the effect of DLI according to cell sources in relapsed AML after allogeneic stem cell transplantation

For relapsed acute myeloid leukemia (AML) patients who received allogeneic hematopoietic stem cell transplantation, donor lymphocyte infusion (DLI) is an effective therapy. However, the cell source of DLI remains a topic of debate. In this study, we aimed to compare the efficacy and safety of G-CSF mobilized cells (G-DLI) with conventionally collected DLI (C-DLI). A total of 81 patients (50 C-DLI vs. 31 G-DLI) were assessed for clinical outcomes. There were no statistically significant differences in the baseline characteristics between the two groups including AML risk, donor types, interval from relapse to DLI, and infused CD3⁺ cell count. Although not statistically significant, complete remission (CR) and chimerism conversion rates were higher in G-DLI than in C-DLI: 51.6% vs. 28.0%, P = 0.057 and 42.3% vs. 28.2%, P = 0.363, respectively. There was no difference in acute graft-versus-host disease (GVHD) incidence and severity of acute GVHD between the two groups. The median overall survival (OS) of the G-DLI and C-DLI groups was 139 days and 106 days, respectively (P = 0.58). In conclusion, G-DLI appears to be a safe and an equally efficacious substitute for C-DLI, which is more readily available.

A phase II study of chidamide, cytarabine, aclarubicin, granulocyte colony-stimulating factor, and donor lymphocyte infusion for relapsed acute myeloid leukemia and myelodysplastic syndrome after allogeneic hematopoietic stem cell transplantation

Chemotherapy followed by donor lymphocyte infusion (DLI) is a promising treatment for relapsed acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, the best strategy for administering this therapy is still unclear. This study sought to explore the efficacy and safety of chidamide and CAG (cytarabine, aclarubicin, and granulocyte colony-stimulating factor) (CCAG) regimen followed by DLI in relapsed AML/MDS after allo-HSCT. This was a single-arm, phase II trial in patients with relapsed AML/MDS after allo-HSCT. CCAG regimen followed by DLI was given according to the inclusion and exclusion criteria. Twenty adult patients were enrolled. The median follow-up time was 12 months. The complete remission (CR) rate was 45% and the partial remission (PR) rate was 5%. The 1-year overall survival (OS) was 56.7% (95% confidence interval (95% CI), 31.6-75.6%), and the median OS was 19 months. The 1-year relapse-free survival (RFS) was 83.3% (95% CI, 27.3-97.5%). Patients relapsing more than 6 months after HSCT and achieving CR/PR after CCAG plus DLI regimen attained significantly higher survival rates. The cumulative incidence of grade III-IV acute graft-versus-host disease (aGVHD) was 9.4%. There was no treatment-related mortality (TRM). These data suggest that CCAG plus DLI regimen is safe and induces durable remission and superior survival in patients with relapsed AML/MDS after allo-HSCT. Trial registration number: ChiCTR.org identifier: ChiCTR1800017740 and date of registration: August 12, 2018.

Can GCSF-stimulated donor lymphocyte infusions improve outcomes for relapsed disease following allogeneic hematopoietic cell transplantation? A systematic review and meta-analysis

Donor lymphocyte infusions (DLI) can produce graft-versus tumor effects to treat relapse after allogeneic hematopoietic cell transplantation, however, durable responses remain uncommon. A systematic review and meta-analysis are needed to clarify whether DLI collected after stimulation with granulocyte colony-stimulating factor (GCSF; G-DLI) can improve clinical outcomes. Sixteen studies (4 controlled) involving 585 patients were identified in a systematic search up to 17 September 2020. A meta-analysis demonstrated no significant difference in the risk of all-cause mortality (RR: 0.94, 95% CI 0.52-1.68, p = 0.82; n = 3 studies) or relapse-related mortality (RR: 0.72, 0.44-1.18, p = 0.19; n = 3 studies) between G-DLI and conventional DLI (C-DLI) groups. G-DLI products had similar mean CD3+ cells compared to C-DLI products, but median CD34+ cells/kg were increased. No improvement in disease progression, complete response rates, or risk of developing GVHD was observed with G-DLI, however, greater non-relapse mortality was observed compared to C-DLI. Alternative approaches to enhancing graft-versus-tumor effects are needed.

Role of radiotherapy in treatment of extramedullary relapse following total marrow and lymphoid irradiation in high-risk and/or relapsed/refractory acute leukemia

BACKGROUND

Total Marrow and Lymphoid Irradiation (TMLI) is a promising component of the preparative regimen for hematopoietic cell transplantation in patients with high-risk acute myeloid leukemia (AML) and acute lymphoid leukemia (ALL). Extramedullary (EM) relapse after TMLI is comparable to TBI and non-TBI conditioning regimens. This study evaluates outcomes of patients treated with radiotherapy (RT) with EM relapse previously treated with TMLI.

METHODS

A retrospective analysis of five prospective TMLI trials was performed. TMLI targeted bones and major lymphoid tissues using image-guided tomotherapy, with total dose ranging from 12 to 20 Gy. EM recurrences were treated at the discretion of the hematologist and radiation oncologist using RT ± chemotherapy. Descriptive statistics and survival analysis were then performed on this cohort.

RESULTS

In total, 254 patients with refractory or relapsed AML or ALL were treated with TMLI at our institution. Twenty-one patients were identified as receiving at least one subsequent course of radiation. A total of 67 relapse sites (median=2 sites/patient, range=1-16) were treated. Eleven relapsed patients were initially treated with curative intent. Following the initial course of subsequent RT, 1-year, 3-year and 5-year estimates of OS were 47.6%, 32.7% and 16.3%, respectively. OS was significantly better in patients treated with curative intent, with median OS of 50.7 months vs 1.6 months (p<0.001). 1-year, 3-year and 5-year estimates of PFS were 23.8%, 14.3% and 14.3%, respectively. PFS was significantly better in patients treated with curative intent, with median PFS of 6.6 months vs 1.3 months (p<0.001). Following RT, 86.6% of the sites had durable local control.

CONCLUSIONS

RT is an effective modality to treat EM relapse in patients with acute leukemia who relapse after HCT achieving high levels of local control. In patients with limited relapse amenable to curative intent, radiation confers favorable long-term survival. Radiation as salvage treatment for EM relapse after HCT warrants further evaluation.

Improved outcome in AML relapse after allogeneic transplant with high-intensity chemotherapy followed by 2nd allogeneic stem cell transplant or donor lymphocyte infusion

Acute myeloid leukemia (AML) relapse after allogeneic stem cell transplant (alloSCT) remains a major therapeutic challenge. While patients with longer remission after initial alloSCT are recommended to receive cell therapy (CT) such as 2^ndalloSCT or donor lymphocyte infusion (DLI), survival for patients who relapse within 6 months of alloSCT has been dismal. We evaluated the outcomes of AML relapse after alloSCT to assess the impact of different treatments on long-term survival. One hundred and seventy-two patients with AML underwent alloSCT at the Penn State Cancer Institute from January 2014 to August 2019. Sixty-nine patients relapsed (median age, 60 years; range, 10-75). Of these, 4 patients underwent 2^ndalloSCT, and 26 received DLI. One-year overall survival (OS) in all cases was 20.3% (95% CI: 11.8-30.4%). Patients with ECOG performance status (PS) 0-2 at relapse showed a better 1-year OS than those with PS 3-4. Median OS for patients who received chemotherapy only or chemotherapy with CT was 74 or 173.5 days, respectively (p < 0.001). Relapsed patients receiving conventional re-induction chemotherapy were categorized as the high-intensity chemotherapy (H) group, while those receiving treatments such as hypomethylating agents or targeted agents were categorized as the low-intensity chemotherapy (L) group. The H group showed a better 1-year OS compared with the L group. Patients who received H + CT showed a better 1-year OS of 52.9% than the other 3 groups (p < 0.001). Even for patients with post-alloSCT remission duration of less than 6 months, the statistical significance was preserved. Factors including age, donor source at 1^stalloSCT, time to relapse, blast counts, PS at relapse, and treatment type after post-alloSCT relapse were used for a multivariate analysis, and matched or mismatched related donor and H + CT after alloSCT were identified as independent factors associated with OS. These findings support the use of H + CT as the treatment option of choice for AML patients who relapse after alloSCT when feasible.

Second unmanipulated allogeneic transplantation could be used as a salvage option for patients with relapsed acute leukemia post-chemotherapy plus modified donor lymphocyte infusion

Relapse is the main problem after allogeneic hematopoietic stem cell transplantation (allo-HSCT). The outcome of a second allo-HSCT (HSCT2) for relapse post-HSCT has shown promising results in some previous studies. However, little is known about the efficacy of HSCT2 in patients with relapsed/refractory acute leukemia (AL) post-chemotherapy plus modified donor lymphocyte infusion (post-Chemo + m-DLI) after the first allo-HSCT (HSCT1). Therefore, we retrospectively analyzed the efficacy of HSCT2 in 28 patients with relapsed/refractory AL post-Chemo + m-DLI in our center. With a median follow-up of 918 (457-1732) days, 26 patients (92.9%) achieved complete remission, and 2 patients exhibited persistent disease. The probabilities of overall survival (OS) and disease-free survival (DFS) 1 year after HSCT2 were 25.0% and 21.4%, respectively. The cumulative incidences of nonrelapse mortality on day 100 and at 1 year post-HSCT2 were 7.1% ± 4.9% and 25.0% ± 8.4%. The cumulative incidences of relapse were 50.0% ± 9.8% and 53.5% ± 9.9% at 1 and 2 years post-HSCT2, respectively. Risk stratification prior to HSCT1 and percentage of blasts before HSCT2 were independent risk factors for OS post-HSCT2, and relapse within 6 months post-HSCT1 was an independent risk factor for DFS and relapse post-HSCT2. Our findings suggest that HSCT2 could be a salvage option for patients with relapsed AL post-Chemo + m-DLI.

Different Kinetics and Risk Factors for Isolated Extramedullary Relapse after Allogeneic Hematopoietic Stem Cell Transplantation in Children with Acute Leukemia

Relapse after allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the most frequent cause of post-transplantation mortality. Isolated extramedullary (EM) relapse (iEMR) after HSCT is relatively rare and not well characterized, particularly in pediatric patients. We retrospectively analyzed 1527 consecutive pediatric patients with acute leukemia after allo-HSCT to study the incidence, risk factors, and outcome of iEMR compared with systemic relapse. The 5-year cumulative incidence of systemic relapse (either bone marrow [BM] only or BM combined with EMR) was 24.8%, and that of iEMR was 5.5%. The onset of relapse after allo-HSCT was significantly longer in EM sites than in BM sites (7.19 and 5.58 months, respectively; P = .013). Complete response (CR) 2+/active disease at transplantation (hazard ratio [HR], 3.1; P < .001) and prior EM disease (HR, 2.3; P = .007) were independent risk factors for iEMR. Chronic graft-versus-host disease reduced the risk of systemic relapse (HR, 0.5; P = .043) but did not protect against iEMR. The prognosis of patients who developed iEMR remained poor but was slightly better than that of patients who developed systemic relapse (3-year overall survival, 16.5% versus 15.3%; P = .089). Patients experiencing their first systemic relapse continued to have further systemic relapse, but only a minority progressed to iEMR, whereas those experiencing their iEMR at first relapse developed further systemic relapse and iEMR at approximately similar frequencies. A second iEMR was more common after a first iEMR than after a first systemic relapse (58.8% versus 13.0%; P = .001) and was associated with poor outcome. iEMR has a poor prognosis, particularly after a second relapse, and effective strategies are needed to improve outcomes.

Hypomethylating Agents and Immunotherapy: Therapeutic Synergism in Acute Myeloid Leukemia and Myelodysplastic Syndromes

Decitabine and guadecitabine are hypomethylating agents (HMAs) that exert inhibitory effects against cancer cells. This includes stimulation of anti-tumor immunity in acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) patients. Treatment of AML and MDS patients with the HMAs confers upregulation of cancer/testis antigens (CTAs) expression including the highly immunogenic CTA NY-ESO-1. This leads to activation of CD4⁺ and CD8⁺ T cells for elimination of cancer cells, and it establishes the feasibility to combine cancer vaccine with HMAs to enhance vaccine immunogenicity. Moreover, decitabine and guadecitabine induce the expression of immune checkpoint molecules in AML cells. In this review, the accumulating knowledge on the immunopotentiating properties of decitabine and guadecitabine in AML and MDS patients are presented and discussed. In summary, combination of decitabine or guadecitabine with NY-ESO-1 vaccine enhances vaccine immunogenicity in AML patients. T cells from AML patients stimulated with dendritic cell (DC)/AML fusion vaccine and guadecitabine display increased capacity to lyse AML cells. Moreover, decitabine enhances NK cell-mediated cytotoxicity or CD123-specific chimeric antigen receptor-engineered T cells antileukemic activities against AML. Furthermore, combination of either HMAs with immune checkpoint blockade (ICB) therapy may circumvent their resistance. Finally, clinical trials of either HMAs combined with cancer vaccines, NK cell infusion or ICB therapy in relapsed/refractory AML and high-risk MDS patients are currently underway, highlighting the promising efficacy of HMAs and immunotherapy synergy against these malignancies.

Post-transplant leukemia relapse in organs: biology. and behavior in 585 reports

Resistance of extramedullary leukemia growth post-transplant prevents cure. Review of its behavior detailed in 585 published cases should lead to better treatment. Leukemic tumors were found up to 13 years after transplant, most in sites inaccessible to physical exam. In 83%, marrow was not in morphologic relapse; next relapse was most often extramedullary. Induction protocols alone produced few durable responses in acute leukemias and fatal marrow aplasia in 17 %. Overall, 120 patients survived over 2 years, 43 relapse-free up to 18 years, the majority after combined tumor-directed and systemic therapy. Overall median survival was 9 months. This review highlights how results can improve: by defining extent of leukemia involvement with scans before transplant, and emergently when leukemic tumor is found after, ablating tumor directly to abort metastasis, and determining dosing of systemic chemotherapy that protects, without ablating, donor marrow. Monitoring total body remission with body scans should increase transplant cures.

Lysyl oxidase expression is associated with inferior outcome and Extramedullary disease of acute myeloid leukemia

BACKGROUND

Lysyl oxidase (LOX) has been described as necessary for premetastatic niche formation in epithelium-derived malignancies and its expression level therefore correlates with risk of metastatic disease and overall survival. However, its role in acute myeloid leukemia (AML) has not been sufficiently analyzed.

METHODS

We investigated LOX plasma expression in 683 AML patients (age 17-60 years) treated within the prospective AML2003 trial (NCT00180102). The optimal cut-off LOX value was determined using a minimal-p-value method dichotomizing patients into a LOX-high group (> 109 ng/mL, n = 272, 40%) and a LOX-low group (≤ 109 ng/mL, n = 411, 60%).

RESULTS

Higher LOX expression was associated with lower peripheral white blood cells, lower serum LDH, and a lower frequency of FLT3-ITD and NPM1 mutations at diagnosis. Higher LOX expression was found significantly more frequently in patients with secondary AML and therapy-related AML, in patients with French-American-British M5 subtypes, and in patients with adverse-risk cytogenetics. Comparing patients in the LOX-high group and the LOX-low group revealed a 3-year overall survival (OS) of 47 and 53% (p = 0.022) and 3-year event-free survival (EFS) of 27 and 35% (p = 0.005), respectively. In the LOX-high group significantly more patients had extramedullary AML compared to the LOX-low group (p = 0.037). Combining extramedullary AML and LOX as interacting factors in a multivariate analysis resulted in an independent impact on survival for the LOX-high-extramedullary interaction for OS (HR = 2.25, p = 0.025) and EFS (HR = 2.48, p = 0.008). Furthermore, in patients with extramedullary disease (n = 59) the LOX level predicted survival. Patients within the LOX-low group had an OS of 43% and EFS of 36% as compared to the LOX-high group with an OS of 13% and EFS of 6% (p = 0.002 and p = 0.008, respectively).

CONCLUSION

We hypothesize LOX expression to be a new potential biomarker to predict outcome in AML, specifically in AML subgroups such as the prognostic heterogeneous group of AML patients with extramedullary disease.

TRIAL REGISTRATION

This retrospective study was performed with patient samples registered within the prospective AML2003 trial (NCT00180102). Patients were enrolled between December 2003 and November 2009.

Extramedullary relapse of leukemia after allogeneic hematopoietic stem cell transplantation: A retrospective study

Extramedullary relapse (EMR) rarely occurs after allogeneic hematopoietic stem cell transplantation (HSCT) in leukemia. This study was to investigate the clinical characteristics of EMR.We retrospectively investigated 316 consecutive patients undergoing HSCT for acute leukemia or chronic myeloid leukemia (CML) at 2 institutions between January 2012 and February 2017. Furthermore, we analyzed and compared the risk factors and outcomes between EMR and bone marrow relapse (BMR).The 5-year cumulative incidence of EMR was 14.1%. The EMR incidence in acute myeloid leukemia, lymphoblastic leukemia, and CML was 17.5%, 18.9%, and 5.3%, respectively. CML had a lower EMR incidence rate. Compared to the BMR group, the EMR group had a longer median relapse-free time (10.5 months vs 5 months, P = .02), and the EMR group had a higher incidence rate of chronic graft-versus-host disease (50.0% vs 20.9%, P = .009). EMR had better estimated 3-year survival rates post-HSCT, and post-relapse, than did BMR (39.5% vs 9.5%, P < .001, and 21.9% vs 10.8%, P = .001). Multivariate analysis identified that adverse cytogenetics (hazard ratio [HR] = 9.034, P < .001) and extramedullary leukemia before HSCT (HR = 2.685, P = .027) were the independent risk factors for EMR after HSCT. In the EMR group, patients who achieved complete remission (CR) had a significantly better, estimated 3-year survival than did patients who did not achieve CR (38.4% vs 14.3%, P = .014).EMR is a significant contributor to mortality after HSCT, which appears to be resistant to most of the current therapies. Establishing effective strategies for EMR is important in improving outcomes after HSCT.

Effects of preemptive interferon-α monotherapy in acute leukemia patients with relapse tendency after allogeneic hematopoietic stem cell transplantation: a case-control study

Interferon-α (IFN-α) inhibits tumor growth and mimics graft-versus-leukemia after allogeneic hematopoietic stem cell transplantation (allo-HSCT). In the current case-control study, we compared treatment responses in acute leukemia patients with relapse tendency post-allo-HSCT receiving preemptive IFN-α after withdrawal of immunosuppressants (n = 31) vs. receiving no IFN-α (n = 67). In the IFN-α group, 25 patients responded to the treatment without progressing to hematological relapse. In the non-IFN-α group, only 22 patients responded to the treatment. The response rate differed significantly (80.6 vs. 32.8%, P < 0.001). The 2-year cumulative incidence of relapse was 31.6 and 61.2% in the IFN-α and the non-IFN groups, respectively (P = 0.006). The 2-year leukemia-free survival and overall survival rate was 57.4 vs. 28.4% (P < 0.001) and 67.6 vs. 32.9% (P = 0.001), respectively. Among the 31 patients in the IFN-α group, 18 patients (58.1%) developed graft-versus-host disease (GVHD): 6 acute and 12 limited chronic GVHD. Patients who developed GVHD had higher treatment response rate than patients without GVHD (88.9 vs. 53.8%, P = 0.022). In conclusion, preemptive IFN-α therapy is a safe and effective treatment to prevent disease progression in high-risk patients with relapse tendency post-allo-HSCT.

Strategies to enhance the graft versus tumour effect after allogeneic haematopoietic stem cell transplantation

Relapse of haematological malignancies after allogeneic haematopoietic stem cell transplant is a major cause of mortality. The immunological mechanisms that may lead to disease relapse may include immunological immaturity prior to reconstitution of the allogeneic immune system, tumour antigen downregulation or promotion of T-cell exhaustion by interactions with the tumour microenvironment. Current therapeutic strategies for post-transplant relapse are limited in their efficacy and alternative approaches are required. In this review, we discuss the mechanisms of T and NK-cell immune evasion that facilitate relapse of haematological malignancies after allogeneic stem cell transplantation, and explore emerging strategies to augment the allogeneic immune system in order to construct a more potent graft versus tumour response.

Myeloid Sarcoma after Allogenic Stem Cell Transplantation for Acute Myeloid Leukemia: Successful Consolidation Treatment Approaches in Two Patients

Myeloid sarcoma is an extramedullary (EM) manifestation (i.e., manifestation outside the bone marrow) of acute myeloid leukemia (AML); it is assumed to be relatively uncommon and can be the only manifestation of leukemia relapse after allogenic stem cell transplantation (allo-SCT). An EM sarcoma can manifest in any part of the body, although preferentially manifesting in immunological sanctuary sites as a single or multiple tumors. The development of myeloid sarcoma after allo-SCT is associated with certain cytogenetic abnormalities, developing of graft versus host disease (GVHD), and treatment with donor lymphocytes infusion (DLI). It is believed that posttransplant myeloid sarcomas develop because the EM sites evade immune surveillance. We present two patients with EM myeloid sarcoma in the breast and epipharynx, respectively, as the only manifestation of leukemia relapse. Both patients were treated with a combination of local and systemic therapy, with successfully longtime disease-free survival. Based on these two case reports, we give an updated review of the literature and discuss the pathogenesis, diagnosis, and treatment of EM sarcoma as the only manifestation of AML relapse after allo-SCT. There are no standard guidelines for the treatment of myeloid sarcomas in allotransplant recipients. In our opinion, the treatment of these patients needs to be individualized and should include local treatment (i.e., radiotherapy) combined with systemic therapy (i.e., chemotherapy, immunotherapy, DLI, or retransplantation). The treatment has to consider both the need for sufficient antileukemic efficiency versus the risk of severe complications due to cumulative toxicity.

Three relapses after a haploidentical transplantation in a pediatric patient: Cure with no further transplantation

Isolated extramedullary relapse (EMR) after hematopoietic stem cell transplantation (HSCT) is a highly fatal condition that creates uncertainty regarding treatment options. Although certain approaches such as repeat HSCT and donor lymphocyte infusion are recommended, we report a patient with acute lymphoblastic leukemia who had three isolated EMRs after HSCT at different locations and at different times that were responsive to local and systemic therapies, without the need for a second transplantation.

Optimizing peripheral blood stem cells transplantation outcome through amend relapse and graft failure: a review of current literature

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) has been considered as a valuable approach in treatment of numerous malignant and none malignant hematologic disorders. However, relapse and poor graft function (PGF) after allo-SCT remain to be controversial issues which may affect the transplantation outcome. Relevant articles were searched in MEDLINE database (2000–2016) using keywords and phrases: donor lymphocyte infusions, allogeneic stem cells transplantation, relapsed hematologic malignancies, booster schedules, cell dose, laboratory monitoring protocols and technical aspects of apheresis. Relapse of disease and PGF could be reduced via noting some main points such as choosing the suitable time and patient for donor lymphocyte infusion (DLI) and also determination of patients who ought to candidate for second allogeneic HSCT or for the use of stem cell boost. DLI and stem cell booster are promising treatment strategies noted in this review. Finally, this paper discusses indications and technical aspects of DLI and stem cell booster in hematological malignancies and emphasizes their therapeutic or pre-emptive potentials.

The role of second transplants for leukemia

Management of relapsed leukemia following allogeneic transplantation is challenging. Intensive chemotherapy, donor lymphocyte infusions (DLI), or second transplantation have some value, but most reported series describe only a limited number of patients surviving beyond 2 or 3 years following relapse. Additionally, understandable selection-bias of reports describing the outcomes of intensive management approaches for relapsed leukemia confound generalizability to a broader population. However numerous reports suggest that second allogeneic transplantation for relapsed leukemia following an initial transplant may produce extended disease control and survival for patients with favorable performance status, remission at the time of second transplant, and most importantly a long interval between initial transplant and relapse. Reduced intensity conditioning for second allografts may be preferable and little data exists to suggest that a new donor will improve disease control by inducing a stronger graft-versus-leukemia effect. Improved measures to prevent the first relapse, however, may protect more patients and produce a greater fraction enjoying extended leukemia-free survival.

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.

New strategies of DLI in the management of relapse of hematological malignancies after allogeneic hematopoietic SCT

DLI is an effective strategy for patients with recurrent hematological malignancies after allogeneic hematopoietic SCT (allo-HSCT). DLI has been widely applied to boost the graft vs tumor (GVT) or GVL effects. However, given the potentially severe complications associated with conventional DLI and transient GVL effect, new strategies for DLI are emerging. In this review, we have discussed the recent important studies on DLI as a prophylactic or therapeutic modality for relapsed hematological disorders after allo-HSCT. The strategies to separate GVL from GVHD have also been discussed. Leukemia-targeting therapy and lymphodepletion combined with DLI, and prophylactic DLI after allo-HSCT are often employed for patients with high risk of relapse, which has been reviewed as well. In addition, we have also discussed the issues on DLI to be further addressed, such as the doses, timing and frequency of DLI in different clinical settings, leukemic antigen-specific DLI as well as how to augment GVL effect while attenuating GVHD.

Donor lymphocyte infusion after allogeneic hematopoietic stem cell transplantation

Donor lymphocyte infusion, a rescue therapy after hematopoietic stem cell transplantation, has been increasingly adopted, as modalities of stem cell transplantation have widened. First described as donor lymphocyte transfusion or cell therapy, it consists of infusion of donor lymphocytes, collected in steady state or after growth factor enhancement. As in literature the most used name is donor lymphocyte infusion, we'll adopt it here. Its most striking efficacy is observed in patients with chronic myelogenous leukemia, who relapsed after allogeneic stem cells transplantation. However, graft-versus-host disease, its main complication, may still hamper its feasibility.

PD-1(hi)TIM-3(+) T cells associate with and predict leukemia relapse in AML patients post allogeneic stem cell transplantation

Prognosis of leukemia relapse post allogeneic stem cell transplantation (alloSCT) is poor and effective new treatments are urgently needed. T cells are pivotal in eradicating leukemia through a graft versus leukemia (GVL) effect and leukemia relapse is considered a failure of GVL. T-cell exhaustion is a state of T-cell dysfunction mediated by inhibitory molecules including programmed cell death protein 1 (PD-1) and T-cell immunoglobulin domain and mucin domain 3 (TIM-3). To evaluate whether T-cell exhaustion and inhibitory pathways are involved in leukemia relapse post alloSCT, we performed phenotypic and functional studies on T cells from peripheral blood of acute myeloid leukemia patients receiving alloSCT. Here we report that PD-1^hiTIM-3⁺ cells are strongly associated with leukemia relapse post transplantation. Consistent with exhaustion, PD-1^hiTIM-3⁺ T cells are functionally deficient manifested by reduced production of interleukin 2 (IL-2), tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ). In addition, these cells demonstrate a phenotype consistent with exhausted antigen-experienced T cells by losing T_N and T_EMRA subsets. Importantly, increase of PD-1^hiTIM-3⁺ cells occurs before clinical diagnosis of leukemia relapse, suggesting their predictive value. Results of our study provide an early diagnostic approach and a therapeutic target for leukemia relapse post transplantation.

The expanding horizon of immunotherapy in the treatment of malignant disorders: allogeneic hematopoietic stem cell transplantation and beyond

Allogeneic hematopoietic stem cell transplantation (allo-SCT) is a very effective therapeutic modality with curative potential in patients with hematological malignancies. The therapeutic efficacy is mainly based on the alloreactive reaction of donor lymphocytes against malignant cells of the recipient named as 'graft-versus-leukemia' or 'graft-versus-tumor' (GVL, GVT) effect. However, besides the beneficial GVL effect, alloreactive reaction attacks normal cells and provokes the deleterious 'graft-versus-host disease' (GVHD) which represents the major limitation of allo-SCT. Current trials have focused on a dual goal: augmentation of GVL and complete abolishment of GVHD. From a theoretical point of view complete dissociation of GVL from GVHD can occur by selecting antigenic targets present on malignant and absent from normal cells. Hematopoietic tissue-restricted minor histocompatibility antigens and leukemia or tumor-associated antigens are ideal candidates for tumor-targeted immunotherapy. Other options for inducing anti-tumor immunity in the absence of GVHD are natural killer (NK) cell immunotherapy, amplification of immune responses by using monoclonal antibodies, and bispecific T and NK-cell engagers. Genetically modified immune effectors such as T-cells armed with chimeric antigen receptors (CAR) or transduced with T-cell receptors with anti-tumor specificity are another exciting field of immunotherapy against malignancies.

Complications of allogeneic hematopoietic stem cell transplantation

Infection, graft-versus-host disease (GVHD), and to a lesser extent sinusoidal obstructive syndrome (SOS) represent the major causes of morbidity and mortality in patients undergoing allogeneic hematopoietic stem cell transplantation (AHSCT). During the last decade, progress in prevention and treatment of these complications led to improvement in the outcome of these patients. Despite the fact that nonmyeloablative regimens have been increasingly used in elderly patients and in patients with co-morbidities, the nonrelapse related mortality remains a challenge and long-term follow-up is required. The objective of this manuscript is to provide an updated concise review of the complications of AHSCT and of the available treatment interventions.

Clinical outcomes of AML patients relapsing after matched-related donor and umbilical cord blood transplantation

AML relapse remains the leading cause of transplant failure among Allo-SCT recipients. A single institution study was conducted on 348 patients with AML who received an Allo-SCT from an umbilical cord blood (UCB, 222) or HLA-matched-related (RD, 126) donor between 2000-2011. Relapse after Allo-SCT occurred in 72 UCB and 32 RD transplant recipients. Three patients achieved CR after withdrawal of immune suppression with no further therapy. Fifty-two patients received intensive post-relapse therapy, defined as systemic chemotherapy (22 UCB, 7 RD), second Allo-SCT (nine UCB, two RD), or DLI±systemic chemotherapy (0 UCB, 12 RD); of these, 25% achieved CR (21% UCB vs 35% RD, P=0.16). Survival at 1 year after relapse was 22% for all patients (19% UCB vs 28% RD, P=0.36). In multivariable analysis, post-relapse mortality was lower in patients receiving intensive therapy for relapse (hazard ratio (HR)=0.4; 95% confidence interval (CI) 0.2-0.6, P<0.01) and higher in patients with peripheral blood blasts above the median (HR=3.8; 95% CI 2.2-6.6, P<0.01), active infection (HR=1.9; 95% CI 1.0-3.5, P=0.05) and non-infectious medical complications (HR=2.0; 95% CI 1.2-3.5, P=0.01). In conclusion, patients with AML relapsing after Allo-SCT who were in good-enough clinical condition to receive intensive therapy had superior short-term survival.

Prognostic index for relapsed acute leukemia after allogeneic stem cell transplant

We retrospectively studied patients who relapsed after allogeneic stem cell transplantation (SCT) to identify factors influencing outcomes. Of the 296 patients (196 with AML and 100 with ALL), 102 (34%) experienced relapse at a median of 222 days (range: 30-2,748) after SCT. Multivariable analysis showed that high disease risk (hazard risk [HR]: 1.95; 95% confidence interval [CI]: 1.17-3.24; p = 0.010), unrelated donor (HR: 1.76; 95% CI: 1.10-2.80; p = 0.018), and interval of < 180 days from SCT to relapse (HR: 2.10; 95% CI: 1.26-3.51; p = 0.004) were independent factors of 2-year post-relapse survival (PRS). These factors were used as a prognostic index for PRS. The 2-year PRS in patients of score 0, score 1, score 2, and score 3 was 38%, 19%, 3%, and 0%, respectively (p < 0.001). Our new prognostic index may be helpful for selecting the treatment for relapsed patients after SCT.

Extramedullary relapse of acute leukemia after allogeneic hematopoietic stem cell transplantation: different characteristics between acute myelogenous leukemia and acute lymphoblastic leukemia

Extramedullary relapse (EMR) of acute leukemia (AL) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a contributor to post-transplantation mortality and remains poorly understood, especially the different characteristics of EMR in patients with acute myelogenous leukemia (AML) and those with acute lymphoblastic leukemia (ALL). To investigate the incidence, risk factors, and clinical outcomes of EMR for AML and ALL, we performed a retrospective analysis of 362 patients with AL who underwent allo-HSCT at the First affiliated Hospital of Soochow University between January 2001 and March 2012. Compared with patients with AML, those with ALL had a higher incidence of EMR (12.9% versus 4.6%; P = .009). The most common site of EMR was the central nervous system, especially in the ALL group. Multivariate analyses identified the leading risk factors for EMR in the patients with AML as advanced disease status at HSCT, hyperleukocytosis at diagnosis, history of extramedullary leukemia before HSCT, and a total body irradiation-based conditioning regimen, and the top risk factors for EMR in the patients with ALL as hyperleukocytosis at diagnosis, adverse cytogenetics, and transfusion of peripheral blood stem cells. The prognosis for EMR of AL is poor, and treatment options are very limited; however, the estimated 3-year overall survival (OS) was significantly lower in patients with AML compared with those with ALL (0 versus 18.5%; P = .000). The characteristics of post-allo-HSCT EMR differed between the patients with AML and those with ALL, possibly suggesting different pathogenetic mechanisms for EMR of AML and EMR of ALL after allo-HSCT; further investigation is needed.

Immunotherapy following relapse of acute leukaemia after T-cell-replete allogeneic peripheral blood progenitor cell transplantation: importance of new onset chronic graft-versus-host disease

INTRODUCTION

To further define the relative impact of immunotherapy and subsequent development of graft-versus-host disease (GVHD) on survival in patients with relapsed acute leukaemia postallogeneic hematopoietic stem cell transplant (SCT), we performed a single-centre retrospective analysis of 32 actively treated patients between 2003 and 2011.

METHODS

A total of 13 patients were identified who were treated actively with cessation of immunosuppression ± Fludarabine, Cytarabine, G-CSF (FLAG) induction, but no donor leucocyte infusion (DLI) (non-DLI group) and 19 patients received the same step-wise therapy plus G-CSF mobilized DLI (G-DLI group).

RESULTS

Groups were not statistically different with regards to baseline characteristics; however, the G-DLI group contained more sibling donors as opposed to unrelated donors than the non-DLI group. With a median follow-up of 47 months, the median overall survival (OS) of the non-DLI and G-DLI groups was not statistically different (8 months vs. 9 months, respectively, P = 0.5). Survival at 3 years was <10% in both groups. Univariate analysis identified response to FLAG, and new onset chronic GVHD as the only factors associated with improved OS.

CONCLUSION

Second donor stem cell infusions are unwarranted in the treatment of relapse after allogeneic SCT and therapeutic strategies should focus on cytoreduction followed by immune modulation with the aim of invoking chronic GVHD.

Chemotherapy followed by modified donor lymphocyte infusion as a treatment for relapsed acute leukemia after haploidentical hematopoietic stem cell transplantation without in vitro T-cell depletion: superior outcomes compared with chemotherapy alone and an analysis of prognostic factors

We retrospectively compared the antileukemic effects of chemotherapy alone and chemotherapy followed by modified donor lymphocyte infusion (DLI) in 82 patients with relapsed acute leukemia after haploidentical hematopoietic stem cell transplantation (HSCT) without in vitro T-cell depletion. We also investigated prognostic factors in patients receiving chemotherapy followed by modified DLI. Thirty-two patients received chemotherapy alone, and the remaining 50 patients received chemotherapy followed by modified DLI. In patients receiving chemotherapy followed by modified DLI, complete remission rate was significantly higher (64.0% vs. 12.5%, P = 0.000), the incidence of relapse was significantly lower (50.0% vs. 100.0%, P = 0.000), and disease-free survival was significantly improved (36.0% vs. 0.0%, P = 0.000) compared with patients receiving chemotherapy alone. Multivariate analysis demonstrated that patients with chronic graft-versus-host disease (GVHD) after intervention (P = 0.000) and patients receiving chemotherapy followed by modified DLI (P = 0.037) were associated with a lower relapse rate. Furthermore, in patients receiving chemotherapy followed by modified DLI, multivariate analysis demonstrated that chronic GVHD after modified DLI (P = 0.039) and duration of minimal residual disease (MRD) (-) ≥4 months after modified DLI (P = 0.001) were associated with a lower relapse rate. Our study is the first to suggest that chemotherapy followed by modified DLI is associated with stronger antileukemic effects and better survival in relapsed acute leukemia after haploidentical HSCT without in vitro T-cell depletion. Furthermore, our study suggests that lack of chronic GVHD and duration of MRD (-) <4 months after modified DLI are associated with higher relapse rates in patients receiving chemotherapy followed by modified DLI.

Second allograft for hematologic relapse of acute leukemia after first allogeneic stem-cell transplantation from related and unrelated donors: the role of donor change

PURPOSE

To evaluate the role of a second allogeneic hematopoietic stem-cell transplantation (HSCT2) given for relapsed acute leukemia (AL) after related or unrelated first hematopoietic stem-cell transplantation (HSCT1) and to analyze the role of donor change for HSCT2 in both settings.

PATIENTS AND METHODS

We performed a retrospective registry study on 179 HSCT2s given for relapse after HSCT1 from matched related donors (n = 75) or unrelated donors (n = 104), using identical or alternative donors for HSCT2. Separate analyses were performed according to donor at HSCT1.

RESULTS

Independent of donor, 74% of patients achieved complete remission after HSCT2, and half of these patients experienced relapse again. Overall survival (OS) at 2 years was 25% ± 4% (39% ± 7% after related HSCT2; 19% ± 4% after unrelated HSCT2). Long-term survivors were observed even after two unrelated HSCT2s. Multivariate analysis for OS from HSCT2 confirmed established risk factors (remission duration after HSCT1: hazard ratio [HR], 2.37; 95% CI, 1.61 to 3.46; P < .001; stage at HSCT2: HR, 0.53; 95% CI, 0.34 to 0.83; P = .006). Outcome of HSCT2 was better after related HSCT1 than after unrelated HSCT1 (2-year OS: 37% ± 6% v 16% ± 4%, respectively; HR, 0.68; 95% CI, 0.47 to 0.98; P = .042, multivariate Cox regression). After both related and unrelated HSCT1, selecting a new donor for HSCT2 did not result in a relevant improvement in OS compared with HSCT2 from the original donor; however, donor change was not detrimental either.

CONCLUSION

After relapse from allogeneic HSCT1, HSCT2 can induce 2-year OS in approximately 25% of patients. Unrelated HSCT2 is feasible after related and unrelated HSCT1. Donor change for HSCT2 is a valid option. However, a clear advantage in terms of OS could not be demonstrated.

Primary treatment of leukemia relapses after allogeneic hematopoietic stem cell transplantation with reduced-intensity conditioning second transplantation from the original donor

Acute leukemia relapsing after allogeneic hematopoietic stem cell transplantation (HSCT) has dismal outcome. Consecutive consenting patients (acute myeloid leukemia: N = 71; acute lymphoblastic leukemia: N = 37), at a median age of 37 (16-57) years, who had relapsed 7.9 (1.3-132) months post-HSCT, were treated with three cytarabine-based intensive regimens as reduced-intensity conditioning (RIC), followed by infusion of mobilized HSC from the original donors. There were four treatment-related mortalities (TRMs). Of 104 evaluable cases, 72 patients (67%) achieved complete remission (CR)/CR with incomplete hematologic recovery (CRi). The median overall survival (OS) of the entire cohort was 11.6 months. The OS of patients achieving CR/CRi after the first RIC/HSCT was 18.8 months, as compared with 3.9 months for those not (P < 0.01). For 32 patients with nonremission, 11 received a repeat RIC-HSCT, leading to CR/CRi in three cases. Therefore, 75/108 (69%) of patients achieved CR/CRi after one or two courses of RIC-HSCT. Among CR/CRi patients, 48 cases relapsed again after 6.1 (1.0-64.4) months. Thirty cases received a repeat RIC-HSCT, leading to CR/CRi in 22 patients. Multivariate analyses showed a significant impact of remission duration after initial HSCT (P = 0.026) and the presence of acute graft-versus-host disease after RIC-HSCT (P = 0.011) on CR/CRi. RIC-HSCT as primary treatment for acute leukemic relapses post-HSCT induced a high CR rate with low TRM. Optimal postremission treatment remains to be defined.

Cellular therapy following allogeneic stem-cell transplantation

Allogeneic hematopoietic stem-cell transplantation (HSCT) is the most effective approach for many patients with hematologic malignancies. Unfortunately, relapse remains the most common cause of death after allogeneic HSCT, and the prognosis of relapsed disease is poor for most patients. Induction of a graft-versus-leukemia (GVL), or graft-versus-tumor, effect through the use of donor leukocyte infusion (DLI), or donor lymphocyte infusion, has been remarkably successful for relapsed chronic myelogenous leukemia. Unfortunately, response to DLI in other hematologic malignancies is much less common and depends on many factors including histology, pace and extent of relapse, and time from HSCT to relapse. Furthermore, graft-versus-host disease (GVHD) is common after DLI and often limits successful immunotherapy. Ultimately, manipulations to minimize GVHD while preserving or enhancing GVL are necessary to improve outcomes for relapse after allogeneic HSCT.

Donor lymphocyte infusion for relapsed hematological malignancies after allogeneic hematopoietic cell transplantation: prognostic relevance of the initial CD3+ T cell dose

The impact of donor lymphocyte infusion (DLI) initial cell dose on its outcome is known in patients with chronic myeloid leukemia but limited in patients with other hematological malignancies. In this retrospective study, we evaluated the effect of initial DLI CD3(+) cell dose on graft-versus-host disease (GVHD) and overall survival after DLI given for relapse of any hematological malignancies after allogeneic hematopoietic cell transplantation (HCT) with high- or reduced-intensity conditioning. The cohort included 225 patients. Initial DLI CD3(+) cell dose per kilogram of recipient body weight was ≤ 1 × 10(7) (n = 84; group A), >1.0 to <10 × 10(7) (n = 58; group B), and ≥ 10 × 10(7) (n = 66; group C). The initial cell dose was unknown for the remaining 17 patients. Cumulative incidence rates of GVHD at 12 months after DLI were 21%, 45%, and 55% for groups A, B, and C, respectively. Multivariate analysis showed that initial DLI CD3(+) cell ≥ 10 × 10(7) dose per kilogram is associated with an increased risk of GVHD after DLI (P = .03). Moreover, an initial DLI CD3(+) cell dose of 10 × 10(7) or higher did not decrease the risk of relapse and did not improve overall survival. Thus, these results support the use of less than 10 × 10(7) CD3(+) cell per kilogram as the initial cell dose of DLI for treatment of persistent or recurrent hematological malignancy after HCT.

Clinical characteristics and outcome of isolated extramedullary relapse in acute leukemia after allogeneic stem cell transplantation: a single-center analysis

Isolated extramedullary relapse (EMR) of acute leukemia (AL) is a rare occurrence. However, it appears to be more common after allogeneic stem cell transplantation (allo-SCT). To characterize what has been observed in isolated EMR, we investigated 287 consecutive AL patients (144 acute myeloid leukemia; 138 acute lymphocytic leukemia; 5 acute mixed-lineage leukemia) who underwent allo-SCT. Twelve cases experienced relapse at extramedullary sites without concomitant involvement of the bone marrow (BM). The onset to relapse after allo-SCT was longer in extramedullary sites than in the BM (median, 10 months versus 5.5 months). EMR sites varied widely and included the central nervous system, skin, bone, pelvis and breasts. Univariate analysis demonstrated that cytogenetic abnormalities were correlated significantly with the onset of isolated EMR (P=0.001). The prognosis for patients who develop EMR remained poor but was relatively better than that after BM relapse (overall survival, 10 versus 18 months). Compared with local or single therapy, patients treated with systemic treatment in combination with local treatment could yield a favorable prognosis. In conclusion, we observed a significant number of isolated cases of EMR in AL patients after allo-SCT, cytogenetic abnormalities were correlated significantly with the onset of isolated EMR. We found that intensive approaches combining local and systemic therapy could produce favorable responses which may cure a proportion of these patients.

Donor lymphocyte infusions for relapse after allogeneic transplantation: when, if and for whom?

Donor lymphocyte infusion (DLI) using unstimulated leukapheresis is one of the most effective treatment strategies for patients with hematological malignancies; its graft-versus-leukemia effects make it especially effective in chronic myeloid leukemia patients who relapsed after allogeneic stem cell transplantation (allo-HSCT). However, DLI application is limited by the development of graft-versus-host disease and aplasia, and thus cannot be routinely applied for prophylaxis. Therefore, important questions remain to be answered, such as when, and whom to DLI? Recent advances enable DLI using allografts of granulocyte colony-stimulating factor-mobilized peripheral blood progenitor cells; allodepleted donor T cells; and infusions of donor-derived, ex vivo-expanded, CD8(+) cytotoxic T lymphocyte, which can decrease relapse and improve transplant outcomes. Preemptive immunotherapy of relapse was also introduced based on the determination of mixed chimerism and minimal residual disease. In this review, we summarize the latest developments in recent strategies that will affect future DLI efficacy - focusing on the disadvantages and advantages of each protocol for the treatment, preemptive therapy, and prophylaxis of relapse.

A novel nonradioactive CFDA assay to monitor the cellular immune response in myeloid leukemia

BACKGROUND

Donor lymphocyte transfusion (DLT) may induce the graft-versus-leukemia (GVL) effect for patients with AML relapsed after transplant. However, AML is a highly diverse disease and the limited overall efficacy of DLT in clinical practice emphasizes the importance of identifying a specific subgroup of patients who might benefit from this treatment approach.

OBJECTIVE

To monitor the cellular immune response after DLT, we developed an active specific immunization strategy using in vitro generated AML-trained T cells to induce a highly specific antileukemic T-cell response and thus established a novel nonradioactive assay system to assess the antileukemia immunity by flow cytometry, correlated with [3H]-thymidine uptake.

METHODS

The myeloid blasts derived from five patients with AML relapsed post-allogeneic hematopoietic stem cell transplantation (allo-HSCT) were first labeled with CFDA (5,6-carboxyfluorescein diacetate succinimidyl ester). To analyze the growth inhibitory potential of the donor T cells trained by AML progenitor cells, the myeloid blasts were induced to proliferate by means of a cytokine cocktail (50ng/mL of SCF; 25ng/mL of IL-3; 100ng/mL of GM-CSF; 100ng/mL of G-CSF; 2U/mL of EPO; 0.47g/L of transferrin; and 5×10(-5)mmol/L of 2-ME). The T cell mediated growth inhibitory potential was detected after 5 days by flow cytometry and correlated with [3H]-thymidine uptake. The simultaneous use of TO-PRO-dye and calibrate beads allowed not only the cell viability to be known but also allowed quantification of the effector function.

RESULTS

Here, we applied a CFDA dye to track the proliferation and expansion of AML blasts in response to the cytokine cocktail in vitro. AML-trained T cells, expressed high levels of the activation markers CD25 and CD69, and were generated to recognize the leukemic progenitor cells and inhibit cytokine-induced leukemic cell proliferation, which is an active specific immunization strategy circumventing the identification of leukemia-associated antigens. The capability of proliferation inhibition of AML-trained T cells evaluated with our nonradioactive, CFDA-based assay provided comparable results with the classic [3H]-thymidine assay with an even lower ratio of effector to target cells.

CONCLUSION

Taken together, the novel, nonradioactive, CFDA-based assay was a robust tool to monitor the antileukemic immune response after DLT in myeloid leukemias.

Extramedullary relapse of acute myeloid leukemia after allogeneic hematopoietic stem cell transplantation: an easily overlooked but significant pattern of relapse

Acute myeloid leukemia may manifest as myeloid sarcoma in a variety of extramedullary (EM) tissues at diagnosis or at relapse. Although EM relapse after allogeneic hematopoietic stem cell transplantation (alloSCT) has been considered to be rare, recent studies have suggested that it occurs in 5% to 12% of patients who receive alloSCT, accounting for 7% to 46% of total relapses. The incidence of EM relapse after immunomodulation (eg, donor lymphocyte infusion) or a second SCT is even higher. Moreover, patients with EM relapse are more likely to have had preceding acute graft-versus-host disease or chronic graft-versus-host disease relative to those with bone marrow relapse. Collectively, these observations suggest that the preferential occurrence of the graft-versus-leukemia effect underlies the pathogenesis of EM relapse. Establishing an early diagnosis of EM relapse has been challenging because of the immense diversity in the relapse sites; however, recent studies have suggested the usefulness of (18)F-fluorodeoxyglucose positron emission tomography scans in the detection of EM relapse. As a treatment for EM relapse, a combination of local and systemic therapy should be considered, because local therapy alone often results in subsequent systemic relapse. The prognosis for patients who develop EM relapse after SCT remains poor but is slightly better than that after bone marrow relapse. In addition to an early diagnosis with new modalities, clinical studies using new agents that may offer systemic activity while preserving the graft-versus-leukemia effect are warranted as part of an effort to improve the clinical outcome.