Reduced intensity conditioning regimen with fludarabine, busulfan, and low-dose TBI (Flu-BU2-TBI): clinical efficacy in high-risk patients

Outcomes of Busulfan, Fludarabine, and 400 cGy Total Body Irradiation Compared With Busulfan and Fludarabine Reduced-Intensity Conditioning Regimens for Allogeneic Stem Cell Transplantation in Adult Patients With Hematologic Diseases: A Single-Center Experience

BACKGROUND

Reduced intensity conditioning (RIC) regimens decrease the risk for nonrelapse mortality (NRM) in adult patients undergoing allogeneic hematopoietic stem cell transplantation for hematologic malignancies but increase the risk for relapse. The aim of this study was to compare the outcomes of fludarabine-total body irradiation (TBI) with fludarabine among patients with hematologic diseases.

PATIENTS AND METHODS

This retrospective study of 137 patients with different hematologic malignancies compared the outcomes of 63 patients who received a conventional RIC regimen with 2 days of IV busulfan (3.2 mg/kg/d × 2 days) and fludarabine with 74 patients who received the same regimen plus 400 cGy of fludarabine and busulfan (FB)-TBI divided in 2 doses over 1 day (200 cGy BID). Median follow-up was 4.62 years.

RESULTS

The donors were either HLA-matched siblings (36%) or HLA-matched unrelated donors (64%). The FB-TBI showed trends toward improvement in progression-free survival (PFS) and overall survival (OS) over FB (5-year PFS rates 50% vs 34%, P = .06, and 5-year OS rate 53% vs 39%, P = .13). Acute graft-vs-host disease (aGVHD), relapse, and NRM were similar between the 2 groups. The 5-year cumulative incidence of chronic GVHD (cGVHD) was lower in the FB-TBI group compared with the FB group (29% vs 52%, P = .003). Multivariable analysis revealed that grade III-IV aGVHD was the only independent risk factor for worse OS (P = .001) in both groups. A high disease risk index was possibly associated with inferior OS (P = .07) in both groups.

CONCLUSIONS

The FB-TBI is a safe and effective intensified RIC regimen for adult patients with hematologic malignancies. It predicted a lower risk for cGVHD and showed possibly improved PFS and OS compared with FB.

Comparison of Myeloablative (CyTBI, BuCy) versus Reduced-Intensity (FluBu2TBI400) Peripheral Blood Stem Cell Transplantation in Acute Myeloid Leukemia Patients with Pretransplant Low WT1 Expression

Relapse is a major concern with reduced-intensity conditioning. We analyzed 257 patients with acute myeloid leukemia (AML) who received allogeneic stem cell transplantation (SCT) and fulfilled the following criteria: intermediate- or poor-risk disease by National Comprehensive Cancer Network guidelines (2017, version 3), in first complete remission (CR1) at SCT, received either myeloablative conditioning (MAC; busulfan plus cyclophosphamide or cyclophosphamide plus total body irradiation) or reduced-intensity conditioning (RIC; FluBu2TBI400) peripheral blood SCT from 8/8 matched sibling or unrelated donor, and having bone marrow Wilms tumor gene 1 (WT1) expression results before transplant. We and other groups serially published a predictive value for pretransplant WT1 expression in patients with AML to identify patients at higher risk of relapse. Among the total 257 patients, 191 (74.3%) and 66 (25.7%) patients received MAC and RIC transplants, respectively. WT1 ≥250 copies/10⁴ABL was defined as WT1^high. WT1^high before SCT was found to be an independent prognostic factor for inferior overall survival (OS), disease-free survival (DFS), and higher cumulative incidence of relapse (CIR). There were 201 patients with WT1 low expression based upon pretransplant analysis. There was no significant difference in OS, DFS, CIR, and nonrelapse mortality between MAC and RIC patients. To conclude, post-transplant survival or relapse was not different by conditioning intensity in AML CR1 patients whose WT1 level was below 250 copies per 10⁴ABL at transplantation.

Haploidentical stem cell transplant with post-transplantation cyclophosphamide and mini-dose methotrexate in children

BACKGROUND

Haploidentical stem cell transplantation (haplo-SCT) is an option for patients without human leukocyte antigen-matched related or unrelated donor. Post-transplantation cyclophosphamide (PTCy) is an effective method of graft versus host disease (GVHD) prophylaxis and permits the use of T-cell replete grafts in settings were ex vivo manipulation is not feasible.

METHODS

A retrospective study among patients younger than 18 years, with a history of hematologic malignancies who underwent haplo-SCT between 2012 and 2016. All patients received a preparative regimen of fludarabine, busulfan, and 400 cGy total body irradiation or melphalan. Post-transplant GvHD prophylaxis consisted either of PTCy (50 mg/kg on Days + 3 and + 4) and cyclosporine (CSA) plus mycophenolate (MMF) (15 mg/kg/dose, thrice daily, per os), or mini-dose methotrexate (MTX; 5 mg/m² dose) on Days + 5, +7, +10, and + 15.

RESULTS

A total of 52 children were included, whose median age was 9 years (interquartile range, 4.9-14; range, 1.2-17 years), and 63% were males. The most common complications were cytomegalovirus reactivation (57%) and hemorrhagic cystitis (36%). The acute GVHD prophylaxis was PTCy, CSA, and mini-dose MTX in 42 (81%) patients, and 10 (19%) patients received PTCy, CSA, and MMF. The cumulative incidence of acute GvHD II-IV, acute GvHD III-IV, and chronic GvHD were 42%, 8.5%, and 19%, respectively. Grades I-IV acute GvHD occurred in 100% of the patients who received prophylaxis with CSA and MMF, and 62% who received CSA and mini-dose MTX (p = .055). The transplant-related mortality at 100 days was 18%. The 5-year overall and event-free survival were 59% and 57%, respectively.

CONCLUSIONS

Haplo-SCT with PT/Cy can be an available, safe, and feasible option for children with hematologic malignancies; meanwhile, the use of mini-dose of MTX was associated with lower rates of acute GVHD. However, our results require further support from prospective randomized studies to improve the efficacy of this prophylactic strategy.

Allogeneic Hematopoietic Stem Cell Transplantation after Conditioning Regimens with Fludarabine/melphalan or Fludarabine/busulfan for Patients with Hematological Malignancies: A Single-center Analysis

Objective Fludarabine plus melphalan (FM) and fludarabine plus busulfan (FB) are two major conditioning regimens for allogeneic hematopoietic stem cell transplantation (allo-HSCT). Methods We retrospectively analyzed patients who underwent allo-HSCT after a conditioning regimen consisting of FM or FB with/without total body irradiation for hematological malignancies between 2005 and 2014. Results There were 41 patients who met the criteria. The median follow-up time for the survivors was 3 years. Thirty-two patients received allo-HSCT after the FM regimen and nine patients received allo-HSCT after the FB regimen. Patients who received FB were older than those who received FM (p=0.041). There was no significant difference in the 3-year overall survival between patients who had received FB and those who had received FM (29.6% vs. 56.5%, p=0.267). The 3-year cumulative incidence of relapse was significantly higher in patients who had received FB than that in patients who had received FM (66.7% vs. 17.8%, p=0.004), and FB was an independent prognostic factor for relapse by a multivariate analysis (hazard ratio, 9.8; 95% confidential interval, 2.5-39.3; p=0.001). When we restricted the evaluation to patients with acute myeloid leukemia and myelodysplastic syndrome, the 3-year cumulative incidence of relapse was also significantly higher in patients who had received FB than that in patients who had received FM (75.0% vs. 16.1%, p=0.004). Conclusion The results suggest that FM may provide better disease control than FB.

A simplified method for busulfan monitoring using dried blood spot in combination with liquid chromatography/tandem mass spectrometry

RATIONALE

Busulfan (Bu) is an important component of the myeloablative conditioning regimen prior to hematopoietic stem cell transplantation (HSCT) especially in children. Intravenously administered Bu exhibits a therapeutic window phenomenon requiring therapeutic drug monitoring. Analytical methods developed for Bu routine monitoring were aimed at using low volumes of biological fluids and development of simple procedures to facilitate the dosage adjustment. In this report, we describe a simple, rapid method for Bu measurement using dried blood spots (DBS) from only 5 μL of whole blood.

METHODS

Bu extracted from DBS with methanol was measured by high-performance liquid chromatography with electrospray ionization and tandem mass spectrometry in multiple reaction monitoring mode using D8-Bu as an internal standard. The method was in-house validated evaluating trueness, repeatability, within-laboratory reproducibility, specificity and the lower limit of quantification (LLOQ).

RESULTS

The method was linear in the calibration range of 100-2000 ng mL(-1) (r(2)>0.99) encompassing the therapeutic concentrations of Bu. A good trueness (<14%), precision (<10%), and recovery (100%) were observed during validation of the method with quality controls of 300, 600 and 1400 ng mL(-1). The LLOQ was determined as 50 ng mL(-1) and no matrix or carryover effects were observed. The validated method was applied to measure Bu levels in four children receiving infusion of Bu prior to HSCT. A good correlation was observed between the Bu levels measured by DBS and dried plasma spot (DPS) (r(2) =0.96) and between DPS and the GC/MS method (r(2) =0.92). Bu was found to be stable in DBS up to 6 h at room temperature and for 24 h at 4 °C.

CONCLUSIONS

The new DBS method facilitates earlier dosage adjustment during Bu therapy by its specific and simple procedure using 5 μL of whole blood.

Survival benefits from reduced-intensity conditioning in allogeneic stem cell transplantation for young lower-risk MDS patients without significant comorbidities

OBJECTIVE

The aim of this study was to determine the optimum conditioning intensity for allogeneic stem cell transplantation (SCT) in young (age ≤50), lower-risk (INT-1 by IPSS) Myelodysplastic syndrome (MDS) patients without significant comorbidities (hematopoietic cell transplantation-comorbidity index score ≤3).

METHODS

Transplant outcomes from 46 consecutive patients were retrospectively analyzed according to the conditioning intensity: reduced-intensity conditioning (RIC; n = 14), intensified RIC by adding low-dose total body irradiation (iRIC; n = 15), and myeloablative conditioning (MAC; n = 17).

RESULTS

After a median follow-up of 73.7 months, RIC had a better 4-yr overall survival (OS) (92.9%) compared with the iRIC (64.2%) or MAC (70.6%). Multivariate analysis showed that RIC was associated with improved OS compared with the MAC [relative risk (RR) of 0.08, P = 0.022] because of a lower transplant-related mortality (TRM) (RR, 0.08, P = 0.035). iRIC failed to show survival benefits over the MAC (RR of 0.77, P = 0.689) because of similarly high TRM (RR of 0.41, P = 0.480). Cumulative incidence of acute and chronic graft-versus-host disease (GVHD) after RIC was higher, but GVHD-specific survival was significantly better (RIC 100% vs. iRIC 45.7% vs. MAC, P = 0.018). Relapse rate was not different among the three groups, but in the RIC group, azacitidine was available and useful for inducing remission in two patients.

CONCLUSION

This study shows that RIC improved OS by directly lowering TRM and indirectly giving an additional chance for relapsed MDS in the era of hypomethylating treatment. RIC-SCT should be considered for relative healthy lower-risk MDS patients.

Reduced-intensity conditioning regimen combined with low-dose total body irradiation in the treatment of myelodysplastic syndrome

Although reduced-intensity conditioning (RIC) has been increasingly used in patients with myelodysplastic syndrome (MDS) to reduce transplant-related mortality, a high relapse rate in RIC remains an unresolved problem. Considering the additive antileukemic effect of low-dose total body irradiation (TBI), we evaluated the feasibility of combining RIC regimens with low-dose TBI in de novo MDS. The RIC regimen combined with low-dose TBI in this study consisted of fludarabine (150 mg/m(2)), intravenous busulfan (6.4 mg/kg), and TBI (400 cGy). Antithymocyte globulin was used to overcome HLA mismatching. A total of 31 subjects were recruited with a median age of 39 years (range 19-63). The patients received transplants from siblings (n = 20) or unrelated donors (n = 11). All patients rapidly achieved full-donor chimerism. At a median follow-up for survivors of 35 months (range 6.0-54.9), the 3-year overall survival, event-free survival, transplantation-related mortality, and relapse rates were 67.6, 63.2, 20.5 and 11.4%, respectively. The 3-year cumulative incidence of acute (grades II-IV) and chronic extensive graft-versus-host disease in patients who survived at least 100 days was 39.2 and 44.6%, respectively. These results suggest that an RIC combined with low-dose TBI may be a feasible therapeutic approach for treating de novo MDS.

Stem cell transplantation using non-myeloablative conditioning regimen with fludarabine for hematological malignancies

Stem cell transplantation (SCT) is a useful treatment for hematological malignancies, but it is limited to younger patients because of its high treatment-related mortality. Fludarabine (Flu), a novel anticancer agent with potent immunosuppressive activity, used as a conditioning regimen (reduced intensity transplantation; RIST), can decrease treatment-related mortality, as recently reported. However, the best drug combination and the best timing for RIST remain unknown. We herein report the SCT outcomes of 36 patients undergoing Flu treatment at our institution since December 2002 and retrospectively analyze the results. RIST conditioning with Flu was well-tolerated. No severe toxicity related conditioning regimens was observed in our patients, even though there were 10 patients with a history of autologous (n = 5) or allogeneic stem cell transplantation (n = 5). Hematological engraftment was found in 33 patients. The median times for reconstitution of WBCs, RBCs, and platelets were 16 days, 27.5 days and 34 days, respectively. Stable complete donor chimerism after SCT was present in all patients with WBC engraftment, and no patients experienced late rejection. Thirty-two patients were evaluated for acute graft versus host disease (aGVHD). Nine patients had no aGVHD. The incidence of grade I/II and III/IV aGVHD was 78% and 22%, respectively. Skin lesions were the major sites of involvement. Gut involvement was present in 9 patients. All 4 patients with grade IV GVHD had stage four hepatic GVHD. Twenty-two patients were analyzed for chronic GVHD (cGVHD). Twelve patients had no cGVHD, 6 had limited type and 4 had extended type. The overall survival (OS), relapse rate (RR), and non-relapse mortality (NRM) in all patients over 7 years were found to be 41.7%, 20.1%, and 34.6%, respectively. Induction failures were present in 5 cases of AML and 1 case of NHL. Disease progression was the primary cause of death, which occurred in 12 of 21 patients. Six patients died of grade IV GVHD (n = 2) or complicated fungal infection contracted during the GVHD treatment (n = 4). One patient died of secondary MSD, which originated from donor hematopoietic cells. Two patients died of cerebral bleeding and cardiac rapture, respectively. We found that the patients' state on SCT was the most important factor in long-term survival. The OS of standard risk and high risk patients with hematological malignancies were 75% and 30.3%. We concluded that stem cell transplantation using a non-myeloablative conditioning regimen with Flu was a useful therapeutic approach for patients with hematological malignancies.