Comparison of reduced-intensity conditioning regimens in patients with acute lymphoblastic leukemia >45 years undergoing allogeneic stem cell transplantation—a retrospective study by the Acute Leukemia Working Party of EBMT

A multicenter study of posttransplantation low-dose inotuzumab ozogamicin to prevent relapse of acute lymphoblastic leukemia

ABSTRACT

The curative potential of allogeneic hematopoietic transplantation (allo-HCT) in patients with acute lymphoblastic leukemia (ALL) is hampered by relapse. Inotuzumab ozogamicin (INO) is an anti-CD22 monoclonal antibody bound to calicheamicin, which has significant activity against ALL. We hypothesized that low-dose INO would be safe and feasible after allo-HCT. Therefore, we conducted a phase 1 study to determine the dose and safety in this setting. Patients were eligible if they were aged 16 to 75 years, had undergone allo-HCT for CD22+ ALL, were in complete remission (CR) after allo-HCT, had high risk of recurrence, were between day 40 and 100 after allo-HCT with adequate graft function, and did not have a history of sinusoidal obstruction syndrome (SOS). The objectives of this trial were to define INO maximum tolerated dose (MTD), to determine post-allo-HCT INO safety, and to measure 1-year progression-free survival (PFS). The trial design followed a "3+3" model. The treatment consisted of INO given on day 1 of 28-day cycles. Dose levels were 0.3 mg/m2, 0.4 mg/m2, 0.5 mg/m2, and 0.6 mg/m2. Median age was 44 years (range, 17-66 years; n = 18). Disease status at transplantation was first CR (n = 14) or second CR or beyond (n = 4). Preparative regimen was of reduced intensity in 72% of patients who received transplantation. Most common toxicity was thrombocytopenia. There were no instances of SOS; the MTD was 0.6 mg/m2. One-year nonrelapse mortality was 5.6%. With a median follow-up of 18.1 months (range, 8.6-59 months) 1-year post-allo-HCT PFS and overall survival is 89% and 94%, respectively. Low-dose INO has a favorable safety profile and was associated with high rates of 1-year PFS. This trial was registered at www.clinicaltrials.gov as #NCT03104491.

Thiotepa-Based Regimens Are Valid Alternatives to Total Body Irradiation-Based Reduced-Intensity Conditioning Regimens in Patients with Acute Lymphoblastic Leukemia: A Retrospective Study on Behalf of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Total body irradiation (TBI) at myeloablative doses is superior to chemotherapy-based regimens in young patients with acute lymphoblastic leukemia (ALL) undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, in elderly and unfit patients, in whom reduced-intensity conditioning (RIC) regimens are preferred, whether a TBI-based or a chemotherapy-based approach is better is unexplored. Thiotepa can be used as part of ALL conditioning regimens. The current study aimed to compare transplantation outcomes after RIC with TBI-based or thiotepa-based regimens in patients with ALL. The study cohort comprised patients aged ≥40 years undergoing allo-HSCT for ALL in first complete remission between 2000 and 2020 who received an RIC regimen containing either TBI (4 to 6 Gy) or thiotepa. We identified a total of 265 patients, including 117 who received a TBI-based RIC regimen and 148 who received a thiotepa-based RIC regimen. Univariate analysis revealed no significant differences in the following transplantation outcomes for TBI versus thiotepa: relapse, 23% versus 28% (P = .24); nonrelapse mortality, 20% versus 26% (P = .61); leukemia-free survival, 57% versus 46% (P = .12); overall survival, 67% versus 56% (P = .18); graft-versus-host disease (GVHD]/relapse-free survival, 45% versus 38% (P = .21); grade II-IV acute GVHD, 30% in both groups (P = .84); grade III-IV acute GVHD, 9% versus 10% (P = .89). The sole exception was the incidence of chronic GVHD, which was higher in the recipients of TBI-based regimens (43% versus 29%; P = .03). However, multivariate analysis revealed no differences in transplantation outcomes between the 2 groups. In patients aged ≥40 years receiving RIC, use of a thiotepa-based regimen may represent a valid alternative to TBI-based regimens, as no differences were observed in the main transplantation outcomes.

Allogeneic Stem Cell Transplantation in Patients >40 Years of Age With Acute Lymphoblastic Leukemia: Reduced Intensity Versus Myeloablative Conditioning

BACKGROUND

The outcome in older patients with acute lymphoblastic leukemia (ALL) remains unsatisfactory due to high relapse and nonrelapse mortality (NRM) rates. Allogeneic stem cell transplantation (alloHSCT) as postremission therapy has an important role in reducing relapse rate, albeit its application is limited in older adult patients due to alloHSCT-related morbidity and mortality. Reduced-intensity conditioning (RIC) alloHSCT has been developed as a less toxic conditioning regimen, but comparative studies with myeloablative conditioning (MAC) are limited in patients with ALL.

METHODS

In this retrospective study, RIC-alloHSCT (n = 111) was compared with MAC-alloHSCT (n = 77) in patients aged 41 to 65 y with ALL in first complete remission. MAC was predominantly applied by combining high-dose total body irradiation and cyclophosphamide, whereas RIC mainly consisted of fludarabine and 2 Gy total body irradiation.

RESULTS

Unadjusted overall survival was 54% (95% confidence interval [CI], 42%-65%) at 5 y in MAC recipients compared with 39% (95% CI, 29%-49%) in RIC recipients. Overall survival and relapse-free survival were not significantly associated with type of conditioning after adjusted for the covariates age, leukemia risk status at diagnosis, donor type, and donor and recipient gender combination. NRM was significantly lower after RIC (subdistribution hazard ratio: 0.41, 95% CI, 0.22-0.78; P  = 0.006), whereas relapse was significantly higher (subdistribution hazard ratio: 3.04, 95% CI, 1.71-5.40; P < 0.001).

CONCLUSIONS

Collectively, RIC-alloHSCT has resulted in less NRM, but it was also found to be associated with a significantly higher relapse rate. These results suggest that MAC-alloHSCT may provide a more effective type of consolidation therapy for the reduction of relapse and that RIC-alloHSCT may be restricted to patients at higher risk for NRM.

The current landscape: Allogeneic hematopoietic stem cell transplant for acute lymphoblastic leukemia

One of the consistent features in development of hematopoietic stem cell transplant (HCT) for Acute Lymphoblastic Leukemia (ALL) is the rapidity with which discoveries in the laboratory are translated into innovations in clinical care. Just a few years after murine studies demonstrated that rescue from radiation induced marrow failure is mediated by cellular not humoral factors, E. Donnall Thomas reported on the transfer of bone marrow cells into irradiated leukemia patients. This was followed quickly by the first descriptions of Graft versus Leukemia (GvL) effect and Graft versus Host Disease (GvHD). Despite the pivotal nature of these findings, early human transplants were uniformly unsuccessful and identified the challenges that continue to thwart transplanters today - leukemic relapse, regimen related toxicity, and GvHD. While originally only an option for young, fit patients with a matched family donor, expansion of the donor pool to include unrelated donors, umbilical cord blood units, and more recently the growing use of haploidentical donors have all made transplant a more accessible therapy for patients with ALL. Novel agents for conditioning, prevention and treatment of GvHD have improved outcomes and investigators continue to develop novel treatment strategies that balance regimen related toxicity with disease control. Our evolving understanding of how to prevent and treat GvHD and how to prevent relapse are incorporated into novel clinical trials that are expected to further improve outcomes. Here we review current considerations and future directions for both adult and pediatric patients undergoing HCT for ALL, including indication for transplant, donor selection, cytoreductive regimens, and outcomes.

Total body irradiation versus busulfan based intermediate intensity conditioning for stem cell transplantation in ALL patients >45 years-a registry-based study by the Acute Leukemia Working Party of the EBMT

Allogeneic hematopoietic cell transplantation is a potentially curative treatment in high-risk acute lymphoblastic leukemia (ALL). Conditioning regimens based on ≥12 Gray total body irradiation (TBI) represent the current standard in patients ≤45 years, whereas elderly patients frequently receive intermediate intensity conditioning (IIC) to reduce toxicity. To evaluate the role of TBI as a backbone of IIC in ALL, a retrospective, registry-based study included patients >45 years transplanted from matched donors in first complete remission, who had received either fludarabine/TBI 8 Gy (FluTBI8, n = 262), or the most popular, irradiation-free alternative fludarabine/busulfan, comprising busulfan 6.4 mg/kg (FluBu6.4, n = 188) or 9.6 mg/kg (FluBu9.6, n = 51). At two years, overall survival (OS) was 68.5%, 57%, and 62.2%, leukemia-free survival (LFS) was 58%, 42.7%, and 45%, relapse incidence (RI) was 27.2%, 40%, and 30.9%, and non-relapse-mortality (NRM) was 23.1%, 20.7%, and 26.8% for patients receiving FluTBI8Gy, FluBu6.4, and FluBu9.6, respectively. In multivariate analysis, the risk of NRM, acute and chronic graft-versus-host disease was not influenced by conditioning. However, RI was higher after FluBu6.4 (hazard ratio [HR] [95% CI]: 1.85 [1.16-2.95]), and LFS was lower after both FluBu6.4 (HR: 1.56 [1.09-2.23]) and FluBu9.6 (HR: 1.63 [1.02-2.58]) as compared to FluTBI8. Although only resulting in a non-significant advantage in OS, this observation indicates a stronger anti-leukemic efficacy of TBI-based intermediate intensity conditioning.

Allogeneic stem cell transplant outcomes between TBI-containing reduced intensity and myeloablative conditioning regimens for ALL in complete remission

Total-body irradiation (TBI)-based conditioning regimen is preferred in acute lymphoblastic leukemia (ALL). We retrospectively evaluated allogeneic stem cell transplant (alloSCT) outcomes of 86 adult ALL patients in complete remission (CR) who received TBI-containing reduced intensity (RIC) (Flu/Mel/TBI = 31) and myeloablative conditioning (MAC) (VP16/TBI = 47; CY/TBI = 8) between January 2005 and December 2019. All patients received peripheral blood allografts. Patients in the RIC group were older than the MAC group (61 years old versus 36 years, p < .001). Donor was 8/8 HLA-matched in 83% and unrelated in 65% of patients. Three-year survival was 56.04% for RIC and 69.9% for MAC (HR 0.64; p = .19). Propensity score-based multivariable Cox analyses (PSCA) did not demonstrate any difference in grade III-IV acute graft versus host disease (GVHD) (SHR 1.23, p = .91), chronic GVHD (SHR 0.92, p = .88), survival (HR 0.94, p = .92), and relapse-free survival (HR 0.66, p = .47) between both groups, while relapse rate was lower (SHR 0.21, p = .02) for MAC compared to RIC. Our study did not demonstrate any difference in survival for TBI-containing RIC and MAC alloSCT for adult ALL in CR.

[Acute lymphoblastic leukemia in developing countries: Management from the transplant indication (allo/auto) until post-transplant follow-up. Guidelines from the SFGM-TC]

Management of acute lymphoblastic leukemia (ALL) patients in countries with limited resources depends on the means of prognostic stratification, available treatment and logistics. During the 12th annual harmonization workshops of the francophone Society of bone marrow transplantation and cellular therapy (SFGM-TC), a designated working group reviewed the literature in order to elaborate unified guidelines for allogeneic hematopoietic cell transplantation (Allo-HCT) in this disease. Conventional poor prognostic factors can be used to determine the indication of allo-HCT in first remission. Patients lacking a HLA-matched related donor can be allografted with a haploidentical donor allo-HCT if available. Chemotherapy based conditioning regimen can be used if TBI is not available, because the probability to find a radiotherapy department with the capacity for total body irradiation is low. For patients with Philadelphia chromosome positive (Phi+) ALL, post-transplantation tyrosine kinase inhibitors as a systematic maintenance strategy is recommended. Autologous HCT is optional for Phi+ ALL patients with negative minimal residual disease, who not eligible for allo-HCT. Patients with refractory/relapsed disease have a poor prognosis which highlights the importance of acquiring in the future new therapies such as: blinatumumab, inotuzumab, and CAR-T cells.

Fludarabine or cyclophosphamide in combination with total body irradiation as myeloablative conditioning prior to allogeneic hematopoietic cell transplantation for acute lymphoblastic leukemia: an analysis by the Acute Leukemia Working Party of the EBMT

In this registry-based study we retrospectively compared outcomes of allogeneic hematopoietic cell transplantation (allo-HCT) for adult patients with acute lymphoblastic leukemia (ALL) following conditioning with total body irradiation (TBI) combined with either cyclophosphamide (Cy) or fludarabine (Flu). TBI 12 Gy + Cy was used in 2105 cases while TBI 12 Gy + Flu was administered to 150 patients in first or second complete remission. In a multivariate model adjusted for other prognostic factors, TBI/Cy conditioning was associated with a reduced risk of relapse (HR = 0.69, p = 0.049) and increased risk of grade 2-4 acute graft-versus-host disease (GVHD, HR = 1.57, p = 0.03) without significant effect on other transplantation outcomes. In a matched-pair analysis the use of TBI/Cy as compared to TBI/Flu was associated with a significantly reduced rate of relapse (18% vs. 30% at 2 years, p = 0.015) without significant effect on non-relapse mortality, GVHD and survival. We conclude that the use of myeloablative TBI/Cy as conditioning prior to allo-HCT for adult patients with ALL in complete remission is associated with lower risk of relapse rate compared to TBI/Flu and therefore should probably be considered a preferable regimen.

Autologous versus allogeneic hematopoietic cell transplantation for older patients with acute lymphoblastic leukemia. An analysis from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Allogeneic hematopoietic cell transplantation (allo-HCT) with reduced intensity conditioning (RIC) is an option for elderly patients with acute lymphoblastic leukemia (ALL). We retrospectively compared results of RIC-allo-HCT from either a matched sibling donor (MSD, n = 209) or matched unrelated donor (MUD, n = 209) with autologous (auto, n = 142) HCT for patients aged 55 years or more treated in first complete remission (CR1) between 2000 and 2018. The probabilities of leukemia-free survival (LFS) at 5 years were 34% for RIC-allo-HCT versus 39% for auto-HCT (p = 0.11) while overall survival (OS) rates were 42% versus 45% (p = 0.23), respectively. The incidence of relapse (RI) and non-relapse mortality (NRM) was 41% versus 51% (p = 0.22) and 25% versus 10% (p = 0.001), respectively. In a multivariate model, using auto-HCT as reference, the risk of NRM was increased for MSD-HCT (Hazard ratio [HR] = 2.1, p = 0.02) and MUD-HCT (HR = 3.08, p < 0.001), which for MUD-HCT translated into a decreased chance of LFS (HR = 1.55, p = 0.01) and OS (HR = 1.62, p = 0.008). No significant associations were found with respect to the risk of relapse. We conclude that for patients with ALL in CR1, aged above 55 years, auto-HCT may be considered a transplant option alternative to RIC-allo-HCT, although its value requires verification in prospective trials.

Thiotepa, busulfan and fludarabine conditioning-regimen is a promising approach for older adult patients with acute lymphoblastic leukemia treated with allogeneic stem cell transplantation

For acute lymphoblastic leukemia (ALL) patients, total body irradiation (TBI)- based conditioning regimens are the first choice specially in young population. However, several studies have shown an equivalence in clinical outcomes with thiotepa-based conditioning regimen. We performed a retrospective study to evaluate the outcome of adult ALL patients who received allogeneic hematopoietic stem cell transplantation (allo-HCT) with a thiotepa-busulfan-fludarabine (TBF) myeloablative conditioning regimen with reduced toxicity. Fifty-five patients received a TBF regimen. The median age of the patients was 51 years (range, 17 to 72.4). Most patients had a diagnosis of B-ALL (93%) with 7% having T-ALL. Two - and 5-year overall survival was 73.2% and 64%, respectively. At 2 years, leukemia-free survival and GVHD-free, relapse-free survival were 59.5% and 57.6%, and at 5 years, 53.4% and 51.8%, respectively. The 5-year non-relapse mortality was 15%. The day 180 cumulative incidence (CI) of grade II-IV acute GVHD and grade III-IV acute GVHD were 38.2% and 5.5%, respectively. At 2 years, the CI of chronic GVHD and extensive chronic GVHD was 16.9% and 1.9%, respectively. Our study results do suggest that using TBF as the conditioning regimen in adult ALL patients is a promising option with acceptable toxicity.

Curative allogeneic hematopoietic stem cell transplantation following reduced toxicity conditioning in adults with primary immunodeficiency

Primary immunodeficiencies (PID) are heterogeneous inborn errors of the immune system. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is curative and safe at the pediatric age but remains underperformed in adults. We report our experience on 32 consecutive adult patients with various PID including 17 (53%) with a combined immune deficiency, six (19%) with a disease of immune dysregulation and nine (28%) with a chronic granulomatous disease (CGD) who underwent an allo-HSCT between 2011 and 2020. The median age at transplant was 27 years (17-41). All assessable patients engrafted. The majority of patients received a fludarabine-Busulfan (FB) based regimen (FB2-3 in 16, FB4 in 12). Overall survival (OS) was 80.4% (100% for CGD and 74% for other PID patients) at 9 months and beyond (median follow-up 51.6 months). Six patients died, all in the first-year post-transplant. Cumulative incidences of grade II-IV acute GVHD/chronic GVHD were 18%/22%. Stem cell source, GVHD prophylaxis and conditioning intensity had no impact on OS. All surviving patients had over 90% donor chimerism, immune reconstitution, no sign of active PID related complications and were clinically improved. Allo-HSCT is effective in young adults PID patients with an acceptable toxicity and should be discussed in case of life-threatening PID.

In-vivo T-cell depleted reduced-intensity conditioned allogeneic haematopoietic stem-cell transplantation for patients with acute lymphoblastic leukaemia in first remission: results from the prospective, single-arm evaluation of the UKALL14 trial

BACKGROUND

The outcome of chemotherapy in patients older than 40 years with acute lymphoblastic leukaemia is poor and myeloablative allogeneic haematopoietic stem-cell transplantation (HSCT) has a high transplant-related mortality (TRM) in this age cohort. The aim of this study was to assess the activity and safety of reduced-intensity conditioned allogeneic HSCT in this patient population.

METHODS

This was a single-arm, prospective study within the UKALL14 trial done in 46 centres in the UK, which recruited patients to the transplantation substudy. Participants in UKALL14 had B-cell or T-cell acute lymphoblastic leukaemia, were aged 25-65 years (BCR-ABL1-negative) or 18-65 years (BCR-ABL1-positive), and for this subcohort had a fit, matched sibling donor or an 8 out of 8 allelic matched unrelated donor (HLA-A, HLA-B, HLA-C, and HLA-DR). On June 20, 2014, the protocol was amended to allow 7 out of 8 matched unrelated donors if the patient had high risk cytogenetics or was minimal residual disease (MRD)-positive after the second induction course. Patients were given fludarabine, melphalan, and alemtuzumab (FMA; intravenous fludarabine 30 mg/m² on days -6 to -2, melphalan 140 mg/m² on day -2, and alemtuzumab 30 mg on day -1 [sibling donor] and days -2 and -1 [unrelated donor]) before allogeneic HSCT (aged ≥41 years patient pathway). Donor lymphocyte infusions were given from 6 months for mixed chimerism or MRD. The primary endpoint was event-free survival and secondary and transplantation-specific endpoints included overall survival, relapse incidence, TRM, and acute and chronic graft-versus-host disease (GVHD). This study is registered with ClinicalTrials.gov, NCT01085617.

FINDINGS

From Feb 22, 2011, to July 26, 2018, 249 patients (236 aged ≥41 years and 13 younger than 41 years) considered unfit for a myeloablative allograft received an FMA reduced-intensity conditioned HSCT. 138 (55%) patients were male and 111 (45%) were female. 88 (35%) participants received transplantations from a sibling donor and 160 (64%) received transplantations from unrelated donors. 211 (85%) participants had B-precursor acute lymphoblastic leukaemia. High-risk cytogenetics were present in 43 (22%) and another 63 (25%) participants were BCR-ABL1-positive. At median follow-up of 49 months (IQR 36-70), 4-year event-free survival was 46·8% (95% CI 40·1-53·2) and 4-year overall survival was 54·8% (48·0-61·2). 4-year cumulative incidence of relapse was 33·6% (27·9-40·2) and 4-year TRM was 19·6% (15·1-25·3). 27 (56%) of 48 patients with TRM had infection as the named cause of death. Seven (15%) of 48 patients had fungal infections, 13 (27%) patients had bacterial infections (six gram-negative), and 11 (23%) had viral infections (three cytomegalovirus and two Epstein-Barr virus). Acute GVHD grade 2-4 occurred in 29 (12%) of 247 patients and grade 3-4 occurred in 12 (5%) patients. Chronic GVHD incidence was 84 (37%) of 228 patients (50 [22%] had extensive chronic GVHD). 49 (30%) of 162 patients had detectable end-of-induction MRD, which portended worse outcomes with event-free survival (HR 2·40 [95% CI 1·46-3·93]) and time-to-relapse (HR 2·41 [1·29-4·48]).

INTERPRETATION

FMA reduced-intensity conditioned allogeneic HSCT in older patients with acute lymphoblastic leukaemia in first complete remission provided good disease control with moderate GVHD, resulting in better-than-expected event-free survival and overall survival in this high-risk population. Strategies to reduce infection-related TRM will further improve outcomes.

FUNDING

Cancer Research UK.

Predictive Factors for Outcome of First Allogeneic Transplant for Elderly Patients With Acute Lymphoblastic Leukemia

INTRODUCTION/BACKGROUND

The treatment of acute lymphoblastic leukemia (ALL) in patients older than 70 is extremely challenging with dismal outcome. Allogeneic stem cell transplantation (alloHCT) has seen many advancements in the last decades showing benefits in younger ALL patients, but this treatment modality is decreasingly used with increasing age due to high treatment-related mortality.

PATIENTS AND METHODS

We identified 84 ALL patients 70 to 84 years old allografted In 2002 to 2019 from a matched related (23%), unrelated (58%), haploidentical (17%), or cord blood (2%) donor at EBMT participating centers with a median follow-up of 23 months.

RESULTS

The 2-year relapse incidence (RI) and non-relapse mortality were 37% and 28%, respectively, and 2-year leukemia-free survival (LFS), overall survival (OS) and GVHD-free, relapse-free survival (GRFS) were 35%, 39% and 23%, respectively. The strongest predictor of outcome was disease status at transplant whereby patients in first complete remission (CR1) had >50% 2-year OS, reflected in multivariate analysis (MVA) with significant improvement in RI, LFS, and GRFS (HR 0.23, 0.49, and 0.54, respectively). Furthermore, karnofsky score ≥90 reflective of good functional status positively influenced non-relapse mortality in both univariate and MVA (HR 0.37), and interestingly, donor CMV positivity appeared to negatively affect RI, LFS and OS in univariate analysis and RI in MVA (HR 2.87).

CONCLUSION

Our data suggest that alloHCT is an option for elderly ALL patients, particularly those carefully selected and transplanted in CR1 especially if failed or without access to novel non-chemotherapy-based approaches.