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

Pretransplantation risk factors for positive MRD after allogeneic stem cell transplantation in AML patients: a prospective study

We aimed to prospectively explore the risk factors for measurable residual disease (MRD) positivity after allogeneic stem cell transplantation (allo-SCT) in AML patients (n = 478). The cumulative incidences (CIs) of post-SCT MRD positivity at 100 days, 360 days and 3 years were 4.6%, 12.1% and 18.3%, respectively. Positive pre-SCT MRD and pre-SCT active disease were risk factors for post-SCT MRD positivity at both 360 days and 3 years (P < 0.001). European LeukemiaNet (ELN) 2017 risk stratification was a risk factor for positive post-SCT MRD at 360 days (P = 0.044). A scoring system for predicting post-SCT MRD positivity at 360 days was established by using pre-SCT MRD, pre-SCT active disease and ELN 2017 risk stratification. The CI of positive post-SCT MRD at 3 years was 13.2%, 23.7%, and 43.9% for patients with scores of 0, 1, and 2, respectively (P < 0.001). Multivariate analysis demonstrated that the scoring system was associated with a higher CI of post-SCT MRD positivity, leukemia relapse and inferior survival. Our data indicate that positive pre-SCT MRD status, pre-SCT active disease, and ELN 2017 risk stratification are risk factors for positive post-SCT MRD status in AML patients.

Busulfan Plus Fludarabine Compared With Busulfan Plus Cyclophosphamide for AML Undergoing HLA-Haploidentical Hematopoietic Cell Transplantation: A Multicenter Randomized Phase III Trial

PURPOSE

The busulfan plus fludarabine (BuFlu) conditioning regimen has lower transplant-related mortality (TRM) than busulfan plus cyclophosphamide (BuCy) in HLA-matched transplantation. We aimed to compare outcomes of the BuFlu regimen with those of the BuCy regimen in HLA-haploidentical hematopoietic cell transplantation (haplo-HCT).

METHODS

We performed an open-label, randomized phase III trial at 12 hospitals in China. Eligible patients with AML (18-65 years) were randomly assigned 1:1 to receive BuFlu (busulfan 0.8 mg/kg four times per day on days -6 to -3; fludarabine 30 mg/m2 once daily on days -7 to -3) or BuCy (same dose of busulfan; cyclophosphamide 60 mg/kg once daily on days -3 and -2). The primary end point was 1-year TRM in the intention-to-treat population and safety in the per-protocol population. This trial is registered with ClinicalTrials.gov (identifier: NCT02487069) and is complete.

RESULTS

From November 20, 2015, to September 30, 2019, 386 patients were randomly assigned to receive the BuFlu (n = 194) or BuCy (n = 192) regimen. The median follow-up was 55.0 (IQR, 46.5-69.0) months after random assignment. The 1-year TRM was 7.2% (95% CI, 4.1 to 11.4) and 14.1% (95% CI, 9.6 to 19.4; hazard ratio [HR], 0.51; 95% CI, 0.27 to 0.97; P = .041), the 5-year relapse was 17.9% (95% CI, 9.6 to 28.3) and 14.2% (95% CI, 9.1 to 20.5; HR, 1.12; 95% CI, 0.65 to 1.95; P = .670), and the 5-year overall survival was 72.5% (95% CI, 62.2 to 80.4) and 68.2% (95% CI, 58.9 to 75.9; HR, 0.84; 95% CI, 0.56 to 1.26; P = .465) in two groups, respectively. Grade 3 regimen-related toxicity (RRT) was reported for 0 of 191 patients following the BuFlu regimen and 9 (4.7%) of 190 patients following the BuCy regimen (P = .002). At least one type of grade 3-5 adverse event was reported for 130 (68.1%) of the 191 patients and 147 (77.4%) of the 190 patients in two groups, respectively (P = .041).

CONCLUSION

The BuFlu regimen has a lower TRM and RRT and similar relapse for patients with AML undergoing haplo-HCT compared with the BuCy regimen.

Prognostic factors and clinical outcomes in patients with relapsed acute leukemia after allogeneic hematopoietic stem cell transplantation

Relapse is a significant barrier to allogeneic hematopoietic stem cell transplantation (allo-HSCT) success. To explore the prognosis of patients who underwent relapse after allo-HSCT, we retrospectively examined 740 consecutive acute leukemia patients in our single center transplanted between January 2013 and December 2018, of which 178 relapsed. The median survival was 204 days (95%CI, 160.7-247.3) from relapse, and the 3-year post-relapse overall survival (prOS) rate was 17.8% (95%CI, 12.5-25.3%). Overall complete remission (CR) or CR with incomplete hematologic recovery (CRi) was achieved in 32.1% for the acute myeloid leukemia and 45.3% for acute lymphoblastic leukemia patients after salvage therapy, respectively. Grade III-IV acute graft-versus-host disease (GVHD) after transplantation and >20% bone marrow blasts at relapse were associated with worse prOS, while patients with chronic GVHD after transplantation, relapse later than 1 year after transplantation, and solitary extramedullary disease had better prOS. Therefore, we developed a concise risk scoring system for prOS based on the number of risk factors affecting prOS. This scoring system was validated with another cohort of post-transplant relapsed acute leukemia patients who received allo-HSCT between 2019 and 2020. Identifying relapse risk factors and providing personalized care for patients with poor prognoses is crucial for improving survival.

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.

Haploidentical versus HLA-matched sibling transplantation for refractory acute leukemia undergoing sequential intensified conditioning followed by DLI: an analysis from two prospective data

BACKGROUND

Compared with HLA-matched sibling donor (MSD) transplant, the outcomes of haploidentical donor (HID) transplant for refractory acute leukemia need to be further explored. In this study, we compared the outcomes of HID with MSD for refractory acute leukemia.

PATIENTS AND METHODS

This study population came from two prospective multicenter trials (NCT01883180, NCT02673008). Two hundred and seventy-eight patients with refractory acute leukemia were enrolled in this study, including 119 in HID group and 132 in MSD group. Sequential intensified conditioning was employed in all patients, and donor lymphocyte infusion (DLI) was administered in patients in the absence of active GVHD and according to minimal residual disease (MRD) from day + 60 post-transplantation for preventing relapse.

RESULTS

The complete remission of leukemia by day + 30 post-transplant were 94% and 93%, respectively, in HID and MSD groups (p = .802). The 1-year incidence of grades II-IV acute GVHD was 62% and 54% (p = .025), and 3-year incidence of chronic GVHD was 55% and 55% (p = .789), respectively, in two groups. HID transplant had lower incidence of first episode of MRD positivity and relapse than MSD transplant (28% vs 45%, p = .006; 26% vs 38%, p = .034). There was higher infection-related mortality in HID than MSD (8% vs 2%, p = .049) within the first 100 days' post-transplant. The 5-year overall survival was 46% and 42% (p = .832), respectively; the 5-year disease-free survival was 43% and 39% (p = .665), in HID and MSD groups, respectively.

CONCLUSIONS

HID transplant has lower relapse, but higher infection-related mortality and similar survival rates in refractory acute leukemia by the strategy of sequential intensified conditioning followed by DLI compared with MSD transplant.