Comparison of outcomes after donor lymphocyte infusion with or without prior chemotherapy for minimal residual disease in acute leukemia/myelodysplastic syndrome after allogeneic hematopoietic stem cell transplantation

Treatment of minimal residual disease in myeloid malignancies after allo-HSCT with venetoclax-based regimens in patients ineligible for or failed in the immunotherapy

BACKGROUND

Relapse was the major cause of treatment failure in patients with myeloid malignancies after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Patients who still suffer from the disease while cannot be detected by morphological analysis can be identified by the minimal residual disease (MRD) monitoring. The most used first-line regimens for MRD are immunotherapies. However, for patients who were ineligible for or failed in first-line immunotherapies, options were limited.

METHODS

A total of 20 patients with myeloid malignancies with recurrent MRD after allo-HSCT were included in this study. The safety and efficacy of venetoclax-based regimens were analyzed.

RESULTS

There were 13 patients (65%) treated with venetoclax combined with hypomethylating agents concomitantly and seven patients (35%) treated with venetoclax monotherapy. After venetoclax-based regimens, MRD was eliminated in 11 patients (55%) with 6 subsequently developing recurrent MRD and 5 remaining in molecular remission. MRD declined in two patients (10%), and no responses in seven patients (35%). Among the two patients with declined MRD, one patient finally eliminated MRD after two cycles of the venetoclax-based regimen, and the other patient's MRD further declined after the second regimen. The objective response rate (ORR) was 65%. The median duration of response was 103 (12-313) days. The incidences of grades 3-4 neutropenia, anemia, and thrombocytopenia independently of pretreatment status were 30%, 20% and 20%, respectively.

CONCLUSION

Venetoclax-based regimens are efficient and safe for MRD in patients with myeloid malignancies ineligible for or failed in the first-line immunotherapies after allo-HSCT.

Donor Lymphocyte Infusion for Relapsed Acute Leukemia or Myelodysplastic Syndrome after Hematopoietic Stem Cell Transplantation: A Single-Institute Retrospective Analysis

Objective The prognosis of the patients who relapsed after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is poor, and therapeutic options are limited. In the present study, we investigated the efficacy and factors associated with the survival in patients with acute leukemia or myelodysplastic syndrome (MDS) who relapsed following allo-HSCT and were treated with donor lymphocyte infusion (DLI) in real-world practice. Patients Twenty-nine patients with acute myeloid leukemia21, acute lymphoid leukemia4 or MDS4 were enrolled. Eleven patients were diagnosed with hematological relapse, and 18 were diagnosed with molecular or cytogenetic relapse. Results The median injection number and median total number of infused CD3+ T cells were 2 and 5.0×107/kg, respectively. The cumulative incidence of acute graft-versus-host disease (aGVHD) of grade ≥II at 4 months after the initiation of DLI was 31.0%. Extensive chronic graft-versus-host disease (cGVHD) occurred in 3 (10.3%) patients. The overall response rate was 51.7%, including 3 cases of hematological complete remission (CR) and 12 cases of molecular/cytogenetic CR. Cumulative relapse rates at 24 and 60 months following DLI in patients who achieved CR were 21.4% and 30.0%, respectively. The overall survival rates at 1, 2 and 3 years after DLI were 41.4%, 37.9% and 30.3%, respectively. Molecular/cytogenetic relapse, a longer interval from HSCT to relapse, and concomitant chemotherapy with 5-azacytidine (Aza) were significantly associated with a relatively long survival following DLI. Conclusion These results indicated that DLI was beneficial for patients with acute leukemia or MDS who relapsed after allo-HSCT and suggested that DLI in combination with Aza for molecular or cytogenetic relapse might result in favorable outcomes.

Prophylactic versus Preemptive modified donor lymphocyte infusion for high-risk acute leukemia after allogeneic hematopoietic stem cell transplantation: a multicenter retrospective study

Donor lymphocyte infusion (DLI) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) has been widely used in preventing post-transplant relapse. We conducted this study to compare the superiority of prophylactic modified DLI (pro-DLI) and preemptive modified DLI (pre-DLI) in patients with high-risk relapse features acute leukemia. Pro-DLI was performed in 95 patients, whereas the pre-DLI cohort included 176 patients. In the pre-DLI cohort, 42 patients relapsed without chance for pre-DLI while 95 patients remained CR without detectable minimal residual disease (MRD). Thirty-nine patients in the pre-DLI cohort became minimal MRD positive/mixed chimerism and received pre-DLI. Pro-DLI cohort had higher 3-year progression-free-survival (PFS) (63.4%vs.53.0%, P = 0.026) and overall survival (OS) (65.2% vs. 57.0%, P = 0.14) compared to the pre-DLI cohort. The 3-year cumulative incidence of relapse (CIR) was 25.3% in the pro-DLI cohort which was significantly lower than 36.7% in the pre-DLI cohort (P = 0.02). The cumulative incidence of grade III-IV aGVHD, cGVHD and non-relapse mortality were comparable between cohorts. Multivariable analysis demonstrated strong protective effect of pro-DLI on OS (hazard ratio (HR) = 0.63, P = 0.04), PFS (HR = 0.54, P = 0.005) and CIR (HR = 0.50, P = 0.005). In high-risk patients with acute leukemia, early scheduled pro-DLI rather than pre-DLI after detectable MRD would reduce post-transplant relapse and improve long-term survival.

Outcomes of haploidentical haematopoietic stem cell transplantation for adolescent and young adults with acute myeloid leukaemia

We aimed to identify the efficacy of haploidentical related donor (HID) haematopoietic stem cell transplantation (HSCT) in adolescent and young adults (AYAs) with acute myeloid leukaemia (AML) in a large cohort. Consecutive AML AYAs (15-39 years old, n = 599) receiving HID HSCT in complete remission (CR) were included. The 3-year cumulative incidence of measurable residual disease occurrence, relapse and non-relapse mortality after HID HSCT was 28.6% (95% CI: 25.0-32.2), 11.6% (95% CI: 9.0-14.2) and 6.7% (95% CI: 4.7-8.7) respectively. The 3-year probability of event-free survival, leukaemia-free survival (LFS) and overall survival (OS) after HID HSCT was 60.7% (95% CI: 56.9-64.8), 81.7% (95% CI: 78.7-84.9) and 85.6% (95% CI: 82.8-88.4) respectively. In multivariable analysis, AML risk category at diagnosis and comorbidity burdens before HID HSCT were independently associated with LFS and OS. Compared to the older adults (≥ 40 years, n = 355) with AML receiving HID HSCT in CR during the same time period, AYAs have a lower incidence of non-relapse mortality and higher probabilities of LFS and OS. Thus, we firstly confirmed the safety and efficacy of HID HSCT in AYAs with AML-CR.

The delicate balance of graft versus leukemia and graft versus host disease after allogeneic hematopoietic stem cell transplantation

INTRODUCTION

The curative basis of allogeneic hematopoietic stem cell transplantation (HSCT) relies in part upon the graft versus leukemia (GvL) effect, whereby donor immune cells recognize and eliminate recipient malignant cells. However, alloreactivity of donor cells against recipient tissues may also be deleterious. Chronic graft versus host disease (cGvHD) is an immunologic phenomenon wherein alloreactive donor T cells aberrantly react against host tissues, leading to damaging inflammatory symptoms.

AREAS COVERED

Here, we discuss biological insights into GvL and cGvHD and strategies to balance the prevention of GvHD with maintenance of GvL in modern HSCT.

EXPERT OPINION/COMMENTARY

Relapse remains the leading cause of mortality after HSCT with rates as high as 40% for some diseases. GvHD is a major cause of morbidity after HSCT, occurring in up to half of patients and responsible for 15-20% of deaths after HSCT. Intriguingly, the development of chronic GvHD may be linked to lower relapse rates after HSCT, suggesting that GvL and GvHD may be complementary sides of the immunologic foundation of HSCT. The ability to fine tune the balance of GvL and GvHD will lead to improvements in survival, relapse rates, and quality of life for patients undergoing HSCT.

Preemptive interferon-α therapy could prevent relapse of acute myeloid leukemia following allogeneic hematopoietic stem cell transplantation: A real-world analysis

Introduction

Measurable residual disease (MRD)-directed interferon-a treatment (i.e. preemptive IFN-α treatment) can eliminate the MRD in patients with acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Therefore, this study aimed to further assess its efficacy in a multicenter retrospective study in a real-world setting.

Methods

A total of 247 patientswho received preemptive IFN-α treatment were recruited from 4 hospitals in China. The protocols for MRD monitoring mainly based on quantitative polymerase chain reaction [qPCR] and multiparameter flow cytometry [MFC].

Results

The median duration of IFN-α treatment was 56 days (range, 1-1211 days). The cumulative incidences of all grades acute graft-versus-host disease (aGVHD), all grades chronic graft-versus-host disease (cGVHD), and severe cGVHD at 3 years after IFN-α therapy were 2.0% (95% confidence interval [CI], 0.3-3.8%), 53.2% (95% CI, 46.8-59.7%), and 6.2% (95% CI, 3.1-9.2%), respectively. The cumulative incidence of achieving MRD negative state at 2 years after IFN-α treatment was 78.2% (95% CI, 72.6-83.7%). The 3-year cumulative incidences of relapse and non-relapse mortality following IFN-α therapy were 20.9% (95% CI, 15.5-26.3%) and 4.9% (95%CI, 2.0-7.7%), respectively. The probabilities of leukemia-free survival and overall survival at 3 years following IFN-α therapy were 76.9% (95% CI, 71.5-82.7%) and 84.2% (95% CI, 78.7-90.1%), respectively. Multivariable analysis showed that MRD positive state by qPCR and MFC before IFN-α treatment, high-risk disease risk index before allo-HSCT, and receiving identical sibling donor HSCT were associated with a higher risk of relapse and a poorer leukemia-free survival. Severe cGVHD was associated with an increased risk of non-relapse mortality.

Discussion

Thus, real-world data suggest that preemptive IFN-α is effective for treating patients with AML with MRD after allo-HSCT.

Ruxolitinib on acute graft-versus-host disease prophylaxis after modified donor lymphocyte infusion

OBJECTIVE

To evaluate the effectiveness of ruxolitinib on acute graft-versus-host disease (aGVHD) prophylaxis and its impact on graft-versus-leukemia (GVL) effect in patients after modified donor lymphocyte infusion (mDLI).

METHODS

We retrospectively included patients with relapsed leukemia after allogeneic hematopoietic stem cell transplantation (allo-HSCT) who received ruxolitinib prophylaxis between October 2018 and April 2020. The incidence of aGVHD, disease-free survival (DFS), overall survival (OS), and treatment safety were evaluated.

RESULTS

Seventeen patients were followed up for a median time of 8 months (range: 1-26 months). The incidence of aGVHD on Day 30 after mDLI was 41.2% and ranged from Grade 1 to 4; ten of 17 patients (58.8%) achieved a complete response (CR), and two (11.8%) had a partial response (PR). Cytomegalovirus (CMV) reactivation rate was 23.5%, and the median time from mDLI to CMV reactivation was 48.5 days. The mean DFS and OS after mDLI were 1.0 (95% CI 0.0-3.5) and 9.0 (95% CI 1.2-16.8) months, respectively. The causes of death for 10 patients were leukemia relapse (n = 5), aGVHD and septic shock (n = 3), intracranial lesion (n = 1), and COVID-19 (n = 1).

CONCLUSIONS

We reported encouraging results of ruxolitinib monotherapy in the prevention of aGVHD and maintenance of GVL for post-transplantation relapsed patients, even though being at high risk with poor initial prognosis.

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.

Optimization of Donor Lymphocyte Infusion for AML Relapse After Allo-HCT in the Era of New Drugs and Cell Engineering

Donor lymphocyte infusion (DLI) is a key strategy for the treatment of AML relapse after allogeneic hematopoietic cell transplantation (allo-HCT) and has been used for either prophylactic, pre-emptive, or therapeutic purposes. However, the prognosis of these patients remains dismal even after DLI infusion (2-year overall survival, ~25%), and the efficacy is achieved at the cost of toxicities such as graft-versus-host (GVH) disease. Attempts to optimize DLI efficacy and safety, such as dose/timing modification and the use of cytoreduction, before DLI have been performed previously. Recently, a great number of novel targeted and immunomodulatory agents have emerged. Some of them, such as hypomethylating agents, FLT3 and Bcl-2 inhibitors, have been used in combination with DLI, aiming to enhance the graft-versus-leukemia effect. Moreover, manipulation of the DLI graft through cell selection (e.g., donor NK cells) or cell engineering (donor CAR-T cells) has shown potentially superior anti-tumor effects but less GVH effect than conventional DLI in clinical trials. This review summarizes the recent advances on the use of DLI for the prophylaxis/treatment of AML relapse and discusses future strategies which may further improve the treatment efficacy.

Preemptive Interferon-α Therapy Could Protect Against Relapse and Improve Survival of Acute Myeloid Leukemia Patients After Allogeneic Hematopoietic Stem Cell Transplantation: Long-Term Results of Two Registry Studies

For allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients, preemptive interferon-α (IFN-α) therapy is considered as a useful method to eliminate the minimal residual disease (MRD). Our purpose is to assess the long-term efficacy of preemptive IFN-α therapy in acute myeloid leukemia (AML) patients following allo-HSCT based on two registry studies (#NCT02185261 and #NCT02027064). We would present the final data and unpublished results of long-term clinical outcomes with extended follow-up. We adopted polymerase chain reaction (PCR) and multiparameter flow cytometry (MFC) to monitor MRD, and a positive result of bone marrow specimen examined by either of them would be identified as the MRD-positive status. Subcutaneous injections of recombinant human IFN-α-2b were performed for 6 cycles, and prolonged IFN-α therapy could be permitted at the request of patients. The median cycles were 3.5 (range, 0.5-30.5) cycles. A total of 9 patients suffered from grade ≥3 toxicities (i.e., infectious: n = 6; hematologic: n = 3). The 6-year cumulative incidences of relapse and non-relapse mortality following IFN-α therapy were 13.0% (95% confidence interval [CI], 5.4-20.6%) and 3.9% (95%CI, 0.0-17.6%), respectively. The probability of disease-free survival at 6 years following IFN-α therapy was 83.1% (95%CI, 75.2-91.9%). The probability of overall survival at 6 years following IFN-α therapy was 88.3% (95%CI, 81.4-95.8%). The cumulative incidences of total chronic graft-versus-host disease (cGVHD) and severe cGVHD at 6 years following IFN-α therapy were 66.2% (95%CI, 55.5-77.0%) and 10.4% (95%CI, 3.6-17.2%), respectively. Multivariable analysis showed that an alternative donor was associated with a lower risk of relapse and the better disease-free survival. Thus, preemptive IFN-α therapy could clear MRD persistently, prevent relapse truly, and improve long-term survival in AML patients following allo-HSCT.

Preemptive Immunotherapy for Minimal Residual Disease in Patients With t(8;21) Acute Myeloid Leukemia After Allogeneic Hematopoietic Stem Cell Transplantation

In patients with t(8;21) acute myeloid leukemia (AML), recurrent minimal residual disease (MRD) measured by RUNX1-RUNX1T1 transcript levels can predict relapse after allogeneic hematopoietic stem cell transplantation (allo-HSCT). This study aimed to compare the efficacy of preemptive interferon (IFN)-α therapy and donor lymphocyte infusion (DLI) in patients with t(8;21) AML following allo-HSCT. We also evaluated the appropriate method for patients with different levels of RUNX1-RUNX1T1 transcripts. In this retrospective study, consecutive patients who had high-risk t(8;21) AML and received allo-HSCT were enrolled. The inclusion criteria were as follows: (1) age ≤65 years; (2) regained MRD positive following allo-HSCT. MRD positive was defined as the loss of a ≥4.5-log reduction and/or <4.5-log reduction in the RUNX1-RUNX1T1 transcripts, and high-level, intermediate-level, and low-level MRDs were, respectively, defined as <2.5-log, 2.5-3.5-log, and 3.5-4.5-log reductions in the transcripts compared with the pretreatment baseline level. Patients with positive RUNX1-RUNX1T1 could receive preemptive IFN-α therapy or DLI, which was primarily based on donor availability and the intentions of physicians and patients. The patients received recombinant human IFN-α-2b therapy by subcutaneous injection twice a week every 4 weeks. IFN-α therapy was scheduled for six cycles or until the RUNX1-RUNX1T1 transcripts were negative for at least two consecutive tests. The rates of MRD turning negative for patients with low-level, intermediate-level, and high-level RUNX1-RUNX1T1 receiving IFN-α were 87.5%, 58.1%, and 22.2%, respectively; meanwhile, for patients with intermediate-level and high-level RUNX1-RUNX1T1 receiving DLI, the rates were 50.0% and 14.3%, respectively. For patients with low-level and intermediate-level RUNX1-RUNX1T1, the probability of overall survival at 2 years was higher in the IFN-α group than in the DLI group (87.6% vs. 55.6%; p = 0.003). For patients with high levels of RUNX1-RUNX1T1, the probability of overall survival was comparable between the IFN-α and DLI groups (53.3% vs. 83.3%; p = 0.780). Therefore, patients with low-level and intermediate-level RUNX1-RUNX1T1 could benefit more from preemptive IFN-α therapy compared with DLI. Clinical outcomes were comparable between preemptive IFN-α therapy and DLI in patients with high-level RUNX1-RUNX1T1; however, they should be further improved.

Donor lymphocyte infusions after first allogeneic hematopoietic stem-cell transplantation in adults with acute myeloid leukemia: a single-center landmark analysis

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is potentially curative for acute myeloid leukemia (AML). The inherent graft-versus-leukemia activity (GvL) may be optimized by donor lymphocyte infusions (DLI). Here we present our single-center experience of DLI use patterns and effectiveness, based on 342 consecutive adult patients receiving a first allo-HSCT for AML between 2009 and 2017. The median age at transplantation was 57 years (range 19-79), and the pre-transplant status was active disease in 58% and complete remission (CR) in 42% of cases. In a combined landmark analysis, patients in CR on day +30 and alive on day +100 were included. In this cohort (n=292), 93 patients received cryopreserved aliquots of peripheral blood-derived grafts for DLI (32%) and median survival was 55.7 months (2-year/5-year probability: 62%/49%). Median survival for patients receiving a first dose of DLI "preemptively," in the absence of relapse and guided by risk marker monitoring (preDLI; n=42), or only after hematological relapse (relDLI; n=51) was 40.9 months (2-year/5-year: 64%/43%) vs 10.4 months (2-year/5-year: 26%/10%), respectively. Survival was inferior when preDLI was initiated at a time of genetic risk marker detection vs mixed chimerism or clinical risk only. Time to first-dose preDLI vs time to first-dose relDLI was similar, suggesting that early warning and intrinsically lower dynamics of AML recurrence may contribute to effectiveness of preDLI-modified GvL activity. Future refinements of the preemptive DLI concept will benefit from collaborative efforts to diagnose measurable residual disease more reliably across the heterogeneous genomic spectrum of AML.

Wilms' tumor gene 1 is an independent prognostic factor for pediatric acute myeloid leukemia following allogeneic hematopoietic stem cell transplantation

BACKGROUND

Sequential monitoring of Wilms' tumor gene 1 (WT1) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) could predict relapse in adult acute myeloid leukemia (AML). However, the prognostic role of WT1 in pediatric AML after allo-HSCT is unclear. Thus, we determined to see whether sequential monitoring of WT1 after allo-HSCT could predict relapse in AML children.

METHODS

Pediatric AML patients receiving allo-HSCT from January 21, 2012 to December 20, 2018 at the Peking University Institute of Hematology were included in this study. WT1 expression level was determined by TaqMan-based reverse transcription-polymerase chain reaction. WT1 sequential monitoring was performed 1, 2, 3, 4.5, 6, 9, and 12 months post-transplantation and at 6-month intervals thereafter. The primary end point was relapse. The secondary end points included disease-free survival (DFS), overall survival (OS), and non-relapse mortality (NRM). Kaplan-Meier analysis was used for DFS and OS estimates, while competing risk analysis was used for estimating relapse and NRM.

RESULTS

Of the 151 consecutive patients included, the median age was 10 years (range, 1-17). The optimal cutoff value of WT1 within 1 year after allo-HSCT to predict relapse was 0.8% (80 WT1 copies/104 ABL copies), with a sensitivity of 60% and specificity of 79%. Compared with WT1 expression < 0.8%, WT1 expression ≥0.8% indicated significantly higher 5-year cumulative incidence of relapse (CIR, 35.1% vs. 11.3%; P = 0.001), lower 5-year disease-free survival (DFS, 60.4% vs. 80.8%; P = 0.009), and lower 5-year overall survival (OS, 64.9% vs. 81.6%; P = 0.038) rates. Multivariate analyses showed that WT1 was an independent risk factor for relapse (HR 2.89; 95% confidence interval (CI), 1.25-6.71; P = 0.014). Both the CIR (5-year CIR: 8.3% vs. 11.3%; P = 0.513) and DFS (5-year DFS: 91.7% vs. 80.8%; P = 0.208) were comparable between patients achieving minimal residual disease (MRD) negativity after preemptive interferon-α (IFN-α) treatment and those without MRD after allo-HSCT, which were better than those of MRD-positive patients without preemptive therapies.

CONCLUSIONS

Sequential monitoring of WT1 could predict relapse in pediatric AML after allo-HSCT. WT1-directed immunotherapy may have the potential to prevent relapse and improve survival.

Minimal residual disease monitoring and preemptive immunotherapies for frequent 11q23 rearranged acute leukemia after allogeneic hematopoietic stem cell transplantation

The prognosis of 11q23/KMT2A-rearranged (KMT2A-r) acute leukemia (AL) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is poor. Minimal residual disease (MRD) is an important prognostic factor for relapse. Thus, we aimed to identify the evolution of KMT2A before and after allo-HSCT and the efficacy of preemptive immunotherapies for KMT2A-r AL patients receiving allo-HSCT. KMT2A expression was determined through TaqMan-based RQ-PCR technology. Preemptive immunotherapies included interferon-α and donor lymphocyte infusion. We collected 1751 bone marrow samples from 177 consecutive KMT2A-r AL patients. Pre-HSCT KMT2A positivity was correlated with post-HSCT KMT2A positivity (correlation coefficient=0.371, P<0.001). The rates of achieving KMT2A negativity after allo-HSCT were 96.6%, 92.9%, and 68.8% in the pre-HSCT low-level group (>0, <0.1%), intermediate-level group (≥ 0.1%, <1%), and high-level group (≥1%), respectively. The rates of regaining KMT2A positivity after allo-HSCT were 7.7%, 35.7%, 38.5%, and 45.5% for the pre-HSCT KMT2A-negative, low-level, intermediate-level, and high-level groups, respectively (P<0.001). The 4-year cumulative incidence of relapse after allo-HSCT was as high as 53.7% in the pre-HSCT KMT2A expression ≥ 0.1% group, which was compared to the KMT2A-negative group (15.1%) and KMT2A <0.1% group (31.2%). The clinical outcomes of patients with post-HSCT KMT2A positivity were poorer than those of patients with persistent KMT2A negativity. Although post-HSCT preemptive immunotherapies might help to achieve KMT2A negativity, the long-term efficacy was unsatisfactory. Thus, pre-HSCT KMT2A positivity was significantly associated with post-HSCT KMT2A positivity. The clinical outcomes of patients with post-HSCT KMT2A positivity were poor, which might not be overcome by commonly used immunotherapies.

Comparison of Two Strategies for Prophylactic Donor Lymphocyte Infusion in Patients With Refractory/Relapsed Acute Leukemia

Prophylactic donor lymphocyte infusion (pDLI) could reduce relapse in patients with refractory/relapsed acute leukemia (RRAL) undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT), but optimal timing of pDLI remains uncertain. We compared the outcomes of two strategies for pDLI based on time from transplant and minimal residual disease (MRD) status in patients with RRAL. For patients without grade II–IV acute graft-versus-host disease (aGVHD) on day +60, pDLI was given on day +60 regardless of MRD in cohort 1, and was given on day +90 unless MRD was positive on day +60 in cohort 2. A total of 161 patients with RRAL were enrolled, including 83 in cohort 1 and 78 in cohort 2. The extensive chronic GVHD (cGVHD) incidence in cohort 2 was lower than that in cohort 1 (10.3% vs. 27.9%, P = 0.006) and GVHD-free/relapse-free survival (GRFS) in cohort 2 was superior to that in cohort 1 (55.1% vs. 41.0%, P = 0.042). The 2-year relapse rate, overall and leukemia-free survival were comparable between the two cohorts (29.0% vs. 28.2%, P = 0.986; 63.9% vs. 64.1%, P = 0.863; 57.8% vs. 61.5%, P = 0.666). Delaying pDLI to day +90 based on MRD for patients with RRAL undergoing allo-HSCT could lower extensive cGVHD incidence and improve GRFS without increasing incidence of leukemia relapse compared with pDLI on day +60.

Donor Lymphocyte Infusions After Allogeneic Stem Cell Transplantation in Acute Leukemia: A Survey From the Gruppo Italiano Trapianto Midollo Osseo (GITMO)

We conducted a retrospective multicenter study including pediatric and adult patients with acute leukemia (AL) who received donor lymphocyte infusions (DLIs) after allogeneic hematopoietic stem cell transplantation (HCT) between January 1, 2010 and December 31, 2015, in order to determine the efficacy and toxicity of the immune treatment. Two hundred fifty-two patients, median age 45.1 years (1.6–73.4), were enrolled from 34 Italian transplant centers. The underlying disease was acute myeloid leukemia in 180 cases (71%). Donors were HLA identical or 1 locus mismatched sibling (40%), unrelated (40%), or haploidentical (20%). The first DLI was administered at a median time of 258 days (55–3,784) after HCT. The main indication for DLI was leukemia relapse (73%), followed by mixed chimerism (17%), and pre-emptive/prophylactic use (10%). Ninety-six patients (38%) received one single infusion, whereas 65 (26%), 42 (17%), and 49 patients (19%) received 2, 3, or ≥4 infusions, respectively, with a median of 31 days between two subsequent DLIs. Forty percent of evaluable patients received no treatment before the first DLI, whereas radiotherapy, conventional chemotherapy or targeted treatments were administered in 3, 39, and 18%, respectively. In informative patients, a few severe adverse events were reported: grade III–IV graft versus host disease (GVHD) (3%), grade III–IV hematological toxicity (11%), and DLI-related mortality (9%). Forty-six patients (18%) received a second HCT after a median of 232 days (32–1,390) from the first DLI. With a median follow-up of 461 days (2–3,255) after the first DLI, 1-, 3-, and 5- year overall survival (OS) of the whole group from start of DLI treatment was 55, 39, and 33%, respectively. In multivariate analysis, older recipient age, and transplants from haploidentical donors significantly reduced OS, whereas DLI for mixed chimerism or as pre-emptive/prophylactic treatment compared to DLI for AL relapse and a schedule including more than one DLI significantly prolonged OS. This GITMO survey confirms that DLI administration in absence of overt hematological relapse and multiple infusions are associated with a favorable outcome in AL patients. DLI from haploidentical donors had a poor outcome and may represent an area of further investigation.

Preemptive low-dose interleukin-2 or DLI for late-onset minimal residual disease in acute leukemia or myelodysplastic syndrome after allogeneic hematopoietic stem cell transplantation

Minimal residual disease (MRD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) heralds high risk of relapse. Whether preemptive recombinant interleukin-2 (pre-IL2) is effective for patients with late-onset MRD (LMRD) remains unknown. We retrospectively compared the efficacy and safety of pre-IL2 (n = 30) and pre-DLI (n = 25) for LMRD in patients receiving allo-HSCT for acute leukemia or myelodysplastic syndrome. The 1-year overall survival (OS) and disease-free survival (DFS) rates were 86.7% and 78.4% (P = 0.267), 83.3% and 75.6% (P = 0.329), the cumulative incidence of grades III-IV acute graft-versus-host disease (aGVHD) at 100 days post-preemptive intervention was 3.3% and 12.0% (P = 0.226) in the pre-IL2 group and pre-DLI group, respectively. The 1-year cumulative incidence of moderate/severe chronic GVHD (cGVHD), relapse (CIR), and non-relapse mortality (NRM) were 7.7% and 27.9% (P = 0.018), 13.6% and 20.0% (P = 0.561) and 3.3% and 5.5% (P = 0.321) in the two groups, respectively. No remarkable differences in CIR, OS, and DFS between the two intervention groups were found in multivariate analysis. The GVHD-free and relapse-free survival (GRFS) were better in the pre-IL2 group than in the pre-DLI group (HR = 0.31, 95% confidence interval (CI), 0.12-0.76; P = 0.011). In conclusion, preemptive low-dose IL2 and preemptive DLI yield comparable outcomes for patients with LMRD receiving allo-HSCT, in terms of aGVHD, NRM, relapse, OS, and DFS. However, preemptive low-dose IL2 has a lower incidence of moderate/severe cGVHD and a higher CRFS. Preemptive low-dose IL2 may be an alternative method for patients who develop LMRD after allo-HSCT, particularly for patients who cannot receive preemptive DLI.

Mechanisms of Leukemia Immune Evasion and Their Role in Relapse After Haploidentical Hematopoietic Cell Transplantation

Over the last decade, the development of multiple strategies to allow the safe transfer from the donor to the patient of high numbers of partially HLA-incompatible T cells has dramatically reduced the toxicities of haploidentical hematopoietic cell transplantation (haplo-HCT), but this was not accompanied by a similar positive impact on the incidence of post-transplantation relapse. In the present review, we will elaborate on how the unique interplay between HLA-mismatched immune system and malignancy that characterizes haplo-HCT may impact relapse biology, shaping the selection of disease variants that are resistant to the “graft-vs.-leukemia” effect. In particular, we will present current knowledge on genomic loss of HLA, a relapse modality first described in haplo-HCT and accounting for a significant proportion of relapses in this setting, and discuss other more recently identified mechanisms of post-transplantation immune evasion and relapse, including the transcriptional downregulation of HLA class II molecules and the enforcement of inhibitory checkpoints between T cells and leukemia. Ultimately, we will review the available treatment options for patients who relapse after haplo-HCT and discuss on how a deeper insight into relapse immunobiology might inform the rational and personalized selection of therapies to improve the largely unsatisfactory clinical outcome of relapsing patients.

Impact of prophylactic/preemptive donor lymphocyte infusion and intensified conditioning for relapsed/refractory leukemia: a real-world study

Prophylactic/preemptive donor lymphocyte infusion (p/pDLI) and intensified conditioning have shown promising results in experimental studies of refractory/relapsed acute leukemia (RRAL), but real-world data remain scarce. We conducted a multicenter, population-based analysis of 932 consecutive patients. The three-year leukemia-free survival (LFS) rates were 56% for patients receiving both p/pDLI and intensified myeloablative conditioning (MAC) (intenseMAC) and 30% for those who received neither therapy per landmark analysis. Multivariable analyses were run separately for acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL), and p/pDLI treatment was linked to significantly higher LFS than non-DLI for both AML and ALL patients without increasing the nonrelapse mortality. IntenseMAC was associated with significantly lower relapse and higher LFS than nonintensified MAC despite higher nonrelapse mortality rates in ALL, while there was no impact of intenseMAC observed in AML. p/pDLI achieved superior outcomes in both matched-sibling donor (MSD) and haploidentical donor transplantation, while intenseMAC only influenced MSD outcomes. Data suggest that RRAL patients receiving "total therapy" by way of p/pDLI and intensified conditioning treatment have an improved chance for LFS, with p/pDLI being safer with a more extensive impact relative to intenseMAC. Patients with RRAL can tolerate both interventions and achieve a reasonable outcome.

Clinical applications of donor lymphocyte infusion from an HLA-haploidentical donor: consensus recommendations from the Acute Leukemia Working Party of the EBMT

Donor lymphocyte infusion has been used in the management of relapsed hematologic malignancies after allogeneic hematopoietic cell transplantation. It can eradicate minimal residual disease or be used to rescue a hematologic relapse, being able to induce durable remissions in a subset of patients. With the increased use of haploidentical hematopoietic cell transplantation, there is renewed interest in the use of donor lymphocytes to either treat or prevent disease relapse post transplant. Published retrospective and small prospective studies have shown encouraging results with therapeutic donor lymphocyte infusion in different haploidentical transplantation platforms. In this consensus paper, finalized on behalf of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation, we summarize the available evidence on the use of donor lymphocyte infusion from haploidentical donor, and provide recommendations on its therapeutic, pre-emptive and prophylactic use in clinical practice.

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.

Prognostic impact of circulating tumor DNA status post–allogeneic hematopoietic stem cell transplantation in AML and MDS

This study was performed to assess the utility of tumor-derived fragmentary DNA, or circulating tumor DNA (ctDNA), for identifying high-risk patients for relapse of acute myeloid leukemia and myelodysplastic syndrome (AML/MDS) after undergoing myeloablative allogeneic hematopoietic stem cell transplantation (alloSCT). We retrospectively collected tumor and available matched serum samples at diagnosis and 1 and 3 months post-alloSCT from 53 patients with AML/MDS. After identifying driver mutations in 51 patients using next-generation sequencing, we designed at least 1 personalized digital polymerase chain reaction assay per case. Diagnostic ctDNA and matched tumor DNA exhibited excellent correlations with variant allele frequencies. Sixteen patients relapsed after a median of 7 months post-alloSCT. Both mutation persistence (MP) in bone marrow (BM) at 1 and 3 months post-alloSCT and corresponding ctDNA persistence (CP) in the matched serum (MP1 and MP3; CP1 and CP3, respectively) were comparably associated with higher 3-year cumulative incidence of relapse (CIR) rates (MP1 vs non-MP1, 72.9% vs 13.8% [P = .0012]; CP1 vs non-CP1, 65.6% vs 9.0% [P = .0002]; MP3 vs non-MP3, 80% vs 11.6% [P = .0002]; CP3 vs non-CP3, 71.4% vs 8.4% [P &lt; .0001]). We subsequently evaluated whether subset analysis of patients with 3 genes associated with clonal hematopoiesis, DNMT3A, TET2, and ASXL1 (DTA), could also be helpful in relapse prediction. As a result, CP based on DTA gene mutations also had the prognostic effect on CIR. These results, for the first time, support the utility of ctDNA as a noninvasive prognostic biomarker in patients with AML/MDS undergoing alloSCT.

Minimal residual disease-directed immunotherapy for high-risk myelodysplastic syndrome after allogeneic hematopoietic stem cell transplantation

The efficacy of minimal residual disease (MRD)-directed immunotherapy, including interferon-α (IFN- α) treatment and chemotherapy plus granulocyte colony-stimulating factor-primed donor leukocyte infusion (chemo-DLI), was investigated in patients with high-risk myelodysplastic syndrome (MDS) who were MRD-positive after allogeneic hematopoietic stem cell transplantation (allo-HSCT). High-risk MDS patients who received non-T-cell-depleted allo-HSCT at the Peking University Institute of Hematology and were MRD-positive after allo-HSCT were studied (n = 47). The MRD-positive status was considered if leukemia-associated aberrant immune phenotypes or Wilms' tumor gene 1 expression is present in a single bone marrow sample. The cumulative incidence of the relapse and non-relapse mortality 2 years after immunotherapy were 14.5% and 21.4% (P = 0.377) and 9.1% and 0.0% (P = 0.985) for patients in the IFN-α and chemo-DLI groups, respectively. The probability of disease-free and overall survival 2 years after immunotherapy were 76.4% and 78.6% (P = 0.891) and 84.3% and 84.6% (P = 0.972) for patients in the IFN-α and chemo-DLI groups, respectively. Persistent MRD after immunotherapy was associated with poor survival. Thus, the MRD-directed immunotherapy was effective for patients with high-risk MDS who were MRD-positive after allo-HSCT, and the efficacy was comparable between chemo-DLI and IFN-α treatment.

Successful treatment of acute myeloid leukemia co-expressing NUP98/NSD1 and FLT3/ITD with preemptive donor lymphocyte infusions

Patients with acute myeloid leukemia (AML) co-expressing NUP98/NSD1 and FLT3/ITD have a dismal prognosis despite undergoing hematopoietic stem cell transplantation (HSCT). There are a few studies on successful treatment of relapsed AML co-expressing NUP98/NSD1 and FLT3/ITD. We report a refractory case of molecular relapse of AML co-expressing NUP98/NSD1 and FLT3/ITD post-matched sibling HSCT. Donor lymphocyte infusion (DLI) at an early stage of post-transplantation resulted in complete molecular remission for 29 months with durable chronic graft-versus-host disease. Our case suggests the clinical efficacy of preemptive DLI following minimal residual disease analysis for the treatment of refractory AML.

Prophylaxis and treatment of relapse after haploidentical stem cell transplantation: What is known vs unknown?

In recent years, the human leukocyte antigen-haploidentical stem cell transplantation (haplo-SCT) approach is an attractive option for patients who require transplantation, but relapse is still the main reason that affects the curative effect of transplantation. Some studies have shown that haplo-SCT is superior to sibling or unrelated matching donor transplantation in preventing leukemia relapse after transplantation. In this review, we discussed the known and unknown aspects of relapse post haplo-SCT. Encouragingly, haplo-SCT experienced lower or similar incidence of relapse. But there is currently a lack of multicenter prospective studies evaluating the outcomes of different haplo-SCT strategies. The combination of common prophylactic strategies and pre-emptive interventions might help prevent relapse after transplantation. Novel methods such as target drugs therapy and chimeric antigen receptor T cell therapy may be useful in treatment of relapse.

The consensus on the monitoring, treatment, and prevention of leukemia relapse after allogeneic hematopoietic stem cell transplantation in China

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an important curative therapy for patients with leukemia. However, relapse remains the leading cause of death after transplantation. In recent years, substantial progress has been made by Chinese physicians in the field of establishment of novel transplant modality, patient selection, minimal residual disease (MRD) monitoring, and immunological therapies, such as modified donor lymphocyte infusion (DLI) and chimeric antigen receptor T (CART) cells, as well as MRD-directed intervention for relapse. Most of these unique systems are distinct from those in the Western world. In this consensus, we reviewed the efficacy of post-HSCT relapse management practice from available Chinese studies on behalf of the HSCT workgroup of the Chinese Society of Hematology, Chinese Medical Association, and compared these studies withthe consensus or guidelines outside China. We summarized the consensus on routine practices of post-HSCT relapse management in China and focused on the recommendations of MRD monitoring, risk stratification directed strategies, and modified DLI system. This consensus will likely contribute to the standardization of post-HSCT relapse management in China and become an inspiration for further international cooperation to refine global practices.

Interferon-α Is Effective for Treatment of Minimal Residual Disease in Patients with t(8;21) Acute Myeloid Leukemia After Allogeneic Hematopoietic Stem Cell Transplantation: Results of a Prospective Registry Study

BACKGROUND

RUNX1-RUNX1T1 transcript levels were established as a powerful marker for predicting relapse in patients with t(8;21) acute myeloid leukemia (AML). We aimed to identify the efficacy of minimal residual disease (MRD)-directed interferon-alpha (IFN-α) treatment in patients with t(8;21) AML who were positive for MRD after allogeneic hematopoietic stem cell transplantation (allo-HSCT; n=42).

SUBJECTS, MATERIALS, AND METHODS

MRD-positive status was defined as a <4.5-log reduction from diagnosis in RUNX1-RUNX1T1 transcripts and/or the loss of a ≥4.5-log reduction after 3 months after HSCT. Patients with positive MRD received six cycles of IFN-α treatment (twice or thrice weekly of every 4 weeks cycle).

RESULTS

The 1-year cumulative incidence of severe acute and chronic graft-versus-host disease after MRD-directed IFN-α treatment was 7.1% and 4.8%, respectively. After the treatment, 15 (35.7%), 5 (11.9%), 3 (7.1%), and 9 (21.5%) patients achieved MRD negativity at 1, 2, 3, and >3 months, respectively. Three patients relapsed after the IFN-α treatment, in which the 1-year cumulative incidence of relapse was 7.2%. One patient died of severe infection at 460 days after treatment. The 1-year probabilities of event-free survival, disease-free survival, and overall survival after treatment were 76.0%, 92.4%, and 92.5%, respectively. The clinical outcomes in patients who received MRD-directed IFN-α treatment were significantly better than those of the MRD-positive patients without any interventions in the historical cohort.

CONCLUSION

MRD-directed IFN-α treatment is effective for patients with t(8;21) AML who were MRD-positive after allo-HSCT. The study was registered at http://clinicaltrials.gov as NCT02027064.

IMPLICATIONS FOR PRACTICE

In patients with t(8;21) acute myeloid leukemia (AML), the presence of post-allogeneic hematopoietic stem cell transplantation (allo-HSCT) minimal residual disease (MRD), measured by RUNX1-RUNX1T1 transcript levels, has been established as a powerful marker for predicting relapse. Interferon-alpha (IFN-α) could exert a relatively strong graft-versus-leukemia effect, and MRD-directed IFN-α treatment is effective for patients with t(8;21) AML who were MRD-positive after allo-HSCT.

The prognostic role of E2A-PBX1 expression detected by real-time quantitative reverse transcriptase polymerase chain reaction (RQ-PCR) in B cell acute lymphoblastic leukemia after allogeneic hematopoietic stem cell transplantation

The E2A-PBX1 rearrangement is common in B cell acute lymphoblastic leukemia (B-ALL). However, whether this fusion gene can be used as a reliable marker for minimal residual disease (MRD) following allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains unknown. In this study, clinical data were collected from 28 consecutive B-ALL patients who received allo-HSCT. Their MRD was evaluated by E2A-PBX1 and leukemia-associated immunophenotype (LAIP). The median follow-up was 374 days (55-2342 days). Of the enrolled patients, seven (25%) patients died of leukemia relapse. A total of nine (32.1%) patients experienced relapse at a median of 164 days (75-559 days) after transplantation. The median expression level in the first positive sample was 0.14% (0.0071-902.4%). The duration from E2A-PBX1-positive results to hematological relapse was 74 days (30-469 days). E2A-PBX1 expression generally became positive prior to flow cytometry. Patients with positive E2A-PBX1 gene expression pre-transplantation were more likely to have positive E2A-PBX1 expression after transplantation. Taken all together, E2A-PBX1 expression determined by real-time quantitative reverse transcriptase polymerase chain reaction (RQ-PCR) could be used to evaluate MRD status after allo-HSCT. Patients with positive E2A-PBX1 expression after transplant will have a poor prognosis.

Mesenchymal Stem Cells in Myeloid Malignancies: A Focus on Immune Escaping and Therapeutic Implications

The importance of the bone marrow microenvironment forming the so-called niche in physiologic hemopoiesis is largely known, and recent evidences support the presence of stromal alterations from the molecular to the cytoarchitectural level in hematologic malignancies. Various alterations in cell adhesion, metabolism, cytokine signaling, autophagy, and methylation patterns of tumor-derived mesenchymal stem cells have been demonstrated, contributing to the genesis of a leukemic permissive niche. This niche allows both the ineffective haematopoiesis typical of myelodysplastic syndromes and the differentiation arrest, proliferation advantage, and clone selection which is the hallmark of acute myeloid leukemia. Furthermore, the immune system, both adaptive and innate, encompassing mesenchymal-derived cells, has been shown to take part to the leukemic niche. Here, we critically review the state of art about mesenchymal stem cell role in myelodysplastic syndromes and acute myeloid leukemia, focusing on immune escaping mechanisms as a target for available and future anticancer therapies.