Single-Dose Daily Fractionation Is Not Inferior to Twice-a-Day Fractionated Total-Body Irradiation Before Allogeneic Stem Cell Transplantation for Acute Leukemia: A Useful Practice Simplification Resulting From the SARASIN Study

Late effects following HSCT for childhood ALL: A national single-center study using three different modalities of delivery of total body irradiation

BACKGROUND

Total body irradiation (TBI) is a pivotal part of conditioning prior to hematopoietic stem cell transplantation (HSCT) for childhood acute lymphoblastic leukemia (ALL), yet evidence is sparse regarding the effect of TBI delivery techniques on acute and late toxicities.

DESIGN

In a national cohort of pediatric HSCT-recipients, we compared three TBI schedules; 12 Gray (Gy) delivered as (i) 4 Gy daily fractions from 2008 to 2011 (n = 12); (ii) 2 Gy fractions twice daily with two-dimensional (2D) planning technology from 2012 to 2015 (n = 16); and (iii) 2 Gy twice daily with three-dimensional (3D) planning intensity-modulated radiotherapy (IMRT) from 2016 to 2020 (n = 14).

RESULTS

The 5-year event-free survival was 75.0%, 81.3%, and 81.3% in Cohorts 1, 2, and 3, respectively. Acute toxicity assessed as maximum ferritin and C-reactive protein during the first 3 months post HSCT did not differ between cohorts, nor did the time to first hospital discharge (median 28, 32, and 31 days, p = .25). The incidences of acute graft-versus-host disease (GvHD) (66%, 56%, 71%) and chronic GvHD (25%, 31%, 14%) were comparable. Pulmonary function assessed by spirometry did not differ significantly. The 5-year cataract-free survival was 33.3%, 79%, and 100% in Cohorts 1, 2, and 3, respectively. We found a nonsignificant tendency toward more endocrinopathies in Cohort 1 compared to Cohorts 2 and 3.

CONCLUSION

The change of modality did not result in more relapses. More fractionation led to improvement with a lower incidence of cataract and a tendency toward fewer endocrinopathies. The effect of 3D-planning-IMRT technology requires further evaluation in larger studies.

Prognostic factors impacting post-transplant outcomes in adult T-cell acute lymphoblastic leukemia: a registry-based study by the EBMT acute leukemia working party

T-cell acute lymphoblastic leukemia (T-ALL) predominantly affects individuals in late childhood and young adulthood. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative modality particularly in the setting of poor risk genetics and/or persistent minimal residual disease. Limited studies have directly explored the impact of patient- and transplant-related factors on post-transplant outcomes in T-ALL. Using a large dataset from the European Society for Blood and Marrow Transplantation registry, we identified 1907 adult T-ALL patients (70% male) who underwent their first allo-HSCT in first complete remission (CR1) from matched sibling donors (MSD; 45%), unrelated donors (UD; 43%) or haploidentical donors (12%) between 2010 and 2021. The median age at transplant was 33.4 years (18.1-75). The median follow up was 2.9 years. Most patients underwent total body irradiation (TBI)-based myeloablative conditioning (69%). The 2-year overall survival (OS) was 69.4%, and leukemia -free survival (LFS) was 62.1%. In multivariate analysis, advanced age at transplant negatively affected LFS (for each 10-year increment, HR = 1.11, p = 0.004), GVHD-free, relapse-free survival (GRFS) (HR = 1.06, p = 0.04), OS (HR = 1.12, p = 0.002), and non-relapse mortality (NRM) (HR = 1.23, p < 0.001). More recent years of allo-HSCT were associated with improved GFRS (For each 3-year increment, HR = 0.89, p < 0.001), OS (HR = 0.9, p = 0.02), and decreased NRM (HR = 0.82, p = 0.008). TBI improved LFS. (HR = 0.79, p = 0.02), GRFS (HR = 0.83, p = 0.04), and relapse incidence (RI) (HR = 0.65, p < 0.001). Female-to-male transplant negatively affected GRFS (HR = 1.21, p = 0.02) and OS (HR = 1.23, p = 0.048). In vivo T-cell depletion significantly improved GFRS (HR = 0.74, p < 0.001). This large study identified prognostic factors, such as age at transplant conditioning regimen, in influencing post-transplant in adult T-ALL patients undergoing allo-HSCT. Importantly, a significant improvement over time was noted. These findings hold great promise for new adapted treatment strategies and can serve as a benchmark for future studies in that setting.

Non-contact scintillator imaging dosimetry for total body irradiation in radiotherapy

Objective.The goal of this work was to assess the potential use of non-contact scintillator imaging dosimetry for tracking delivery in total body irradiation (TBI).Approach. Studies were conducted to measure the time-gated light signals caused by radiation exposure to scintillators that were placed on tissue. The purpose was to assess efficacy in conditions common for TBI, such as the large source to surface distance (SSD) commonly used, the reduced dose rate, the inclusion of a plexiglass spoiler, angle of incidence and effects of peripheral patient support structures. Dose validation work was performed on phantoms that mimicked human tissue optical properties and body geometry. For this work, 1.5 cm diameter scintillating disks were developed and affixed to phantoms under various conditions. A time-gated camera synchronized to the linac pulses was used for imaging. Scintillation intensity was quantified in post processing and the values verified with simultaneous thermolumiescent dosimeter (TLD) measurements. Mean scintillation values in each region were compared to TLD measurements to produce dose response curves, and scatter effects from the spoiler and patient bed were quantified.Main results.The dose determined by scintillators placed in TBI conditions agreed with TLD dose determinations to within 2.7%, and did so repeatedly within 1.0% standard deviation variance. A linear fit between scintillator signal and TLD dose was achieved with anR2= 0.996 across several body sites. Scatter from the patient bed resulted in a maximum increase of 19% in dose.Significance.This work suggests that non-contact scintillator imaging dosimetry could be used to verify dose in real time to patients undergoing TBI at the prescribed long SSD and low dose rate. It also has shown that patient transport stretchers can significantly influence surface dose by increasing scatter.

Total marrow irradiation for second allogeneic hematopoietic stem cell transplantation in patients with advanced acute leukemia

BACKGROUND

Second allogeneic hematopoietic stem cell transplantation (HSCT) is a treatment option for patients with acute leukemia relapsing after a first HSCT. While a myeloablative (MA) conditioning regimen before the first HSCT is considered better than reduced intensity (RIC) in terms of disease control in acute leukemia patients, the optimal conditioning regimen for the second allogeneic HSCT remains controversial. The most important prognostic factors are the remission disease phase at the time of the second HSCT and more than 12 months from the first to the second HSCT. Total Marrow Irradiation (TMI) is an advanced high-precision radiation treatment that delivers therapeutic doses over extensively selected targets while substantially reducing radiation to vital organs compared to conventional Total Body Irradiation (TBI). Herein we report the results of a retrospective analysis on second allogeneic transplantation treated with TMI as a myeloablative conditioning regimen, intending to limit toxicity.

OBJECTIVE

We investigated the efficacy of a high dose per fraction TMI in combination with thiotepa, fludarabine and melphalan in 13 consecutive patients with acute leukemia relapsed after a first allogeneic HSCT treated between March 2018 and November 2021.

STUDY DESIGN

Donor type was haploidentical (HAPLO, n=10), unrelated (UD n=2), and HLA-identical sibling (SIB, n=1). The conditioning regimen consisted of TMI 8 Gy in 5 patients on day -8 -7 or TMI 12 Gy in 8 patients on day -9 -8 -7, plus Thiotepa 5 mg/Kg on day -6, Fludarabine 50 mg/mq on day -5 -4 -3, Melphalan 140 mg/mq on day -2. TMI was delivered in a hypofractionated daily single dose of 4 Gy for three consecutive fractions. The median age was 45 years (range, 19-70 years); 7 patients were in remission, and 6 had active disease at the time of the second allogeneic HSCT.

RESULTS

The median time to neutrophil counts of > 0.5×10e9/L was 16 days (range 13-22), and platelet counts of > 20×10e9/L were 20 days (range 14-34), respectively. All patients showed a complete donor chimerism on day 30 after the transplant. The cumulative incidence of grade I II acute GvHD (aGvHD) was 43%, and chronic GvHD (cGVHD) was 30%. The median follow-up was 1121 days (range 200-1540). Day +30 and +100 transplant-related mortality (TRM) was 0. Overall cumulative incidence of TRM, relapse rate, and disease free-survival (DFS) were respectively 27%,7%, and 67%.

CONCLUSIONS

This retrospective study showed the safety and efficacy of a hypofractionated TMI conditioning regimen in patients with acute leukemia receiving second HSCT with encouraging outcomes regarding engraftment, early toxicity, GvHD, and relapse.

Fludarabine/TBI 8 Gy versus fludarabine/treosulfan conditioning in patients with AML in first complete remission: a study from the Acute Leukemia Working Party of the EBMT

The optimal reduced intensity conditioning (RIC) regimen is a matter of debate. We retrospectively compared conditioning with fludarabine plus fractionated total body irradiation of 8 Gy (FluTBI) and fludarabine plus treosulfan 30, 36 or 42 g/m2 (FluTreo) in 754 patients with AML above the age of 40 years undergoing an allogeneic hematopoietic stem cell transplant (HSCT) in first complete remission (CR). After balancing patient characteristics by propensity score matching of 115 patients in each group, FluTBI was associated with a significantly lower probability of relapse compared to FluTreo (18.3% vs. 34.7%, p = 0.018) which was counteracted by a higher non-relapse mortality (NRM, 16.8% vs. 5.3%, p = 0.02). Thus, overall survival and graft-versus-host disease-free and relapse-free survival at 2 years were similar between groups (OS 66.9% vs. 67.8%, GRFS 50.3% vs. 45.6%). Univariate analysis by age group demonstrated a higher NRM exclusively in patients ≥55 years of age treated with FluTBI compared to FluTreo (27.6% vs. 5.8%, p = 0.02), while a similarly low NRM was observed in patients <55 years in both groups (6.0% vs. 4.7%, p = ns). We conclude that both conditioning regimens are effective and safe, but FluTBI may better be reserved for younger patients below the age of 55 years.

Total body irradiation plus fludarabine versus busulfan plus fludarabine as a myeloablative conditioning for adults with acute myeloid leukemia treated with allogeneic hematopoietic cell transplantation. A study on behalf of the Acute Leukemia Working Party of the EBMT

Cyclophosphamide is frequently substituted with fludarabine (Flu) in conditioning regimens before allogeneic hematopoietic cell transplantation (allo-HCT). We aimed to compare retrospectively, total body irradiation (12 Gy) plus Flu (FluTBI12) versus busulfan (Bu) plus Flu (FB4) as a myeloablative conditioning before allo-HCT in patients with acute myeloid leukemia (AML). Out of 3203 patients who met the inclusion criteria, 109 patients treated with FluTBI12 and 213 treated with FB4 were included in a final matched-pair analysis. In both groups, median patient age was 41 years, first or second complete remission (CR1/CR2) proportion was 78%/22%, allo-HCT from an unrelated donor was performed in 78% of patients. The probabilities of leukemia-free survival and overall survival at 2 years in FluTBI12 and FB4 groups were 65% vs. 60% (p = 0.64) and 70% vs. 72% (p = 0.87), respectively. The cumulative incidence of relapse was 19% vs. 29% (p = 0.11), while non-relapse mortality was 16% vs. 11%, respectively (p = 0.13). There were no statistical differences in both acute and chronic graft-versus-host disease (GVHD) incidence. The probability of GVHD-free, relapse-free survival (GRFS) was 49% for both groups. FluTBI12 and FB4 are comparable myeloablative regimens before allo-HCT in AML patients transplanted in CR1 and CR2.

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.

Conditioning regimens for allogeneic hematopoietic cell transplantation in acute myeloid leukemia: Real-world data from the Japanese registry studies

Conditioning regimens play a crucial role in preventing relapse of acute myeloid leukemia (AML) following allogeneic hematopoietic cell transplantation (HCT). In early times, myeloablative conditioning was used exclusively, but it was associated with significant toxicity. However, the advent of reduced-intensity conditioning has allowed allogeneic HCT to be performed more safely, leading to an expansion of our choices for conditioning regimens. As the transplantation methods have become highly diversified, it is reasonable to determine an optimal conditioning regimen in consideration of patient-, disease-, and transplantation-related factors. In this context, large-scale registry-based studies provide real-world data to allow for a detailed evaluation of the utility of individual conditioning regimens in specific clinical settings. The Japanese Society for Transplantation and Cellular Therapy has been conducting a nationwide survey for HCT since 1993 that currently covers >99% of all the transplantation centers nationwide, and >1,000 allogeneic HCTs performed for adults with AML are registered per year. We have been using the registry data to implement a number of studies focusing on adults with AML, and the large number of patients registered consecutively from nearly all transplantation centers nationwide represent real-world practice in Japan. This article reviews and discusses the results obtained from our registry-based studies pertaining to various conditioning regimens.

ESTRO ACROP and SIOPE recommendations for myeloablative Total Body Irradiation in children

BACKGROUND AND PURPOSE

Myeloablative Total Body Irradiation (TBI) is an important modality in conditioning for allogeneic hematopoietic stem cell transplantation (HSCT), especially in children with high-risk acute lymphoblastic leukemia (ALL). TBI practices are heterogeneous and institution-specific. Since TBI is associated with multiple late adverse effects, recommendations may help to standardize practices and improve the outcome versus toxicity ratio for children.

MATERIAL AND METHODS

The European Society for Paediatric Oncology (SIOPE) Radiotherapy TBI Working Group together with ESTRO experts conducted a literature search and evaluation regarding myeloablative TBI techniques and toxicities in children. Findings were discussed in bimonthly virtual meetings and consensus recommendations were established.

RESULTS

Myeloablative TBI in HSCT conditioning is mostly performed for high-risk ALL patients or patients with recurring hematologic malignancies. TBI is discouraged in children <3-4 years old because of increased toxicity risk. Publications regarding TBI are mostly retrospective studies with level III-IV evidence. Preferential TBI dose in children is 12-14.4 Gy in 1.6-2 Gy fractions b.i.d. Dose reduction should be considered for the lungs to <8 Gy, for the kidneys to ≤10 Gy, and for the lenses to <12 Gy, for dose rates ≥6 cGy/min. Highly conformal techniques i.e. TomoTherapy and VMAT TBI or Total Marrow (and/or Lymphoid) Irradiation as implemented in several centers, improve dose homogeneity and organ sparing, and should be evaluated in studies.

CONCLUSIONS

These ESTRO ACROP SIOPE recommendations provide expert consensus for conventional and highly conformal myeloablative TBI in children, as well as a supporting literature overview of TBI techniques and toxicities.

Residual effects of busulfan and irradiation on murine hematopoietic stem and progenitor cells

Exposure of young C57BL/6 (B6) mice to two courses of busulfan (BSF) injections or two rounds of sublethal total-body irradiation (TBI) induced significant damage to the function of hematopoietic stem and progenitor cells (HSPCs). Fifteen weeks after treatment, BSF- and TBI-treated mice had reduced white blood cells without significant change in red blood cells or platelets, indicating that BSF and TBI hematotoxicity was chronic, with leukocytes being the major targets. Hematopoietic damage induced by BSF or TBI persisted long term. Residual adverse effects were reflected by significantly decreased CD45R B cells and reduced recovery of total bone marrow cells, especially HSPCs carrying markers for KSL (Kit⁺Sca-1⁺Lin^-) cells, multipotent progenitor (MPP) cells (KSLCD34⁺CD135⁺), myeloid progenitor (MP) cells (Kit⁺Sca-1^-Lin^-), and common lymphoid progenitor (CLP) cells 62 wk posttreatment. Transplantation of bone marrow (BM) cells from BSF and TBI donors at 49 weeks after treatment into lethally irradiated hosts resulted in decreased engraftment of CD45R B cells in blood and reduced reconstitution of BM HSPCs including KSL cells, short-term hematopoietic stem cells (KSLCD34⁺CD135^-), MPP cells, and MP cell subsets. TBI donor had better reconstitution of CLP cells in recipients posttransplantation than did BSF donor, suggesting an impact of TBI and BSF on B cells at different development stages. In summary, BSF and TBI exposure produced long-lasting adverse effects on hematopoiesis with pronounced effects on mature B cells, immature ST-HSCs, and hematopoietic progenitor cells. Our results may have implications for therapy of human diseases.

Total Body Irradiation in Haematopoietic Stem Cell Transplantation for Paediatric Acute Lymphoblastic Leukaemia: Review of the Literature and Future Directions

Total body irradiation (TBI) has been a pivotal component of the conditioning regimen for allogeneic myeloablative haematopoietic stem cell transplantation (HSCT) in very-high-risk acute lymphoblastic leukaemia (ALL) for decades, especially in children and young adults. The myeloablative conditioning regimen has two aims: (1) to eradicate leukaemic cells, and (2) to prevent rejection of the graft through suppression of the recipient's immune system. Radiotherapy has the advantage of achieving an adequate dose effect in sanctuary sites and in areas with poor blood supply. However, radiotherapy is subject to radiobiological trade-offs between ALL cell destruction, immune and haematopoietic stem cell survival, and various adverse effects in normal tissue. To diminish toxicity, a shift from single-fraction to fractionated TBI has taken place. However, HSCT and TBI are still associated with multiple late sequelae, leaving room for improvement. This review discusses the past developments of TBI and considerations for dose, fractionation and dose-rate, as well as issues regarding TBI setup performance, limitations and possibilities for improvement. TBI is typically delivered using conventional irradiation techniques and centres have locally developed heterogeneous treatment methods and ways to achieve reduced doses in several organs. There are, however, limitations in options to shield organs at risk without compromising the anti-leukaemic and immunosuppressive effects of conventional TBI. Technological improvements in radiotherapy planning and delivery with highly conformal TBI or total marrow irradiation (TMI), and total marrow and lymphoid irradiation (TMLI) have opened the way to investigate the potential reduction of radiotherapy-related toxicities without jeopardising efficacy. The demonstration of the superiority of TBI compared with chemotherapy-only conditioning regimens for event-free and overall survival in the randomised For Omitting Radiation Under Majority age (FORUM) trial in children with high-risk ALL makes exploration of the optimal use of TBI delivery mandatory. Standardisation and comprehensive reporting of conventional TBI techniques as well as cooperation between radiotherapy centres may help to increase the ratio between treatment outcomes and toxicity, and future studies must determine potential added benefit of innovative conformal techniques to ultimately improve quality of life for paediatric ALL patients receiving TBI-conditioned HSCT.

Radiation-induced bystander effects impair transplanted human hematopoietic stem cells via oxidative DNA damage

Total body irradiation (TBI) is commonly used in host conditioning regimens for human hematopoietic stem cell (HSC) transplantation to treat various hematological disorders. Exposure to TBI not only induces acute myelosuppression and immunosuppression, but also injures the various components of the HSC niche in recipients. Our previous study demonstrated that radiation-induced bystander effects (RIBE) of irradiated recipients decreased the long-term repopulating ability of transplanted mouse HSCs. However, RIBE on transplanted human HSCs have not been studied. Here, we report that RIBE impaired the long-term hematopoietic reconstitution of human HSCs as well as the colony-forming ability of human hematopoietic progenitor cells (HPCs). Our further analyses revealed that the RIBE-affected human hematopoietic cells showed enhanced DNA damage responses, cell-cycle arrest, and p53-dependent apoptosis, mainly because of oxidative stress. Moreover, multiple antioxidants could mitigate these bystander effects, though at different efficacies in vitro and in vivo. Taken together, these findings suggest that RIBE impair human HSCs and HPCs by oxidative DNA damage. This study provides definitive evidence for RIBE on transplanted human HSCs and further justifies the necessity of conducting clinical trials to evaluate different antioxidants to improve the efficacy of HSC transplantation for the patients with hematological or nonhematological disorders.

Tandem autologous hematopoietic cell transplantation with sequential use of total marrow irradiation and high-dose melphalan in multiple myeloma

The goal of this phase II trial was to evaluate safety and efficacy of a tandem autologous hematopoietic cell transplantation (auto-HCT) using sequentially total marrow irradiation (TMI) at the dose of 12 Gy (4 Gy on days -3, -2, and -1) and melphalan 200 mg/m² for patients with multiple myeloma (MM). TMI was performed using helical tomotherapy. Additional "boosts" (total 24 Gy) were applied for patients with active lesions as revealed by PET-FDG. Fifty patients with median age 58 years (41-64 years) were included and received tandem auto-HCT. TMI resulted in absolute neutropenia in all patients. Grade 3 infections were reported in 30% patients. Other toxicities were rare. Proportion of patients who achieved at least very good partial response increased from 46% before the first auto-HCT to 82% after tandem transplantation. Complete remission rates changed from 10% to 42%, respectively. The probabilities of overall and progression-free survival at 5 years were 74% and 55%, respectively. No patient died without progression. We conclude that conditioning with TMI ± PET-guided "boosts" represents personalized treatment approach in MM and is characterized by very good toxicity profile. Tandem auto-HCT using TMI in sequence with high-dose melphalan appears safe with encouraging early efficacy.

Prognostic Impact of the Fractionation of Total Body Irradiation for Patients with Acute Myeloid Leukemia Undergoing Myeloablative Allogeneic Hematopoietic Cell Transplantation

Fractionated total body irradiation (TBI) at a total dose of 12 Gy is widely used for patients with acute myeloid leukemia (AML) undergoing allogeneic hematopoietic cell transplantation (HCT); however, there is limited information regarding the optimal number of fractions. To address this issue, Japanese nationwide transplantation registry data were analyzed. Because it was found that TBI was delivered almost exclusively in 4 (n = 1215, 30%) or 6 fractions (n = 2697, 67%), we focused on comparing 4- versus 6-fraction TBI. Compared to 6-fraction TBI, the 4-fraction version was associated with reduced risk of overall mortality (P = .002) and relapse (P = .018), while there was no difference in the risk of nonrelapse mortality (P = .422). The 4-fraction version did not aggravate acute graft-versus-host disease (GVHD), interstitial pneumonia, or sinusoidal obstruction syndrome of the liver. Chronic GVHD developed more frequently with the use of 4-fraction TBI, although the incidence of extensive chronic GVHD was similar. Subgroup analyses revealed that the 4-fraction version provided benefits for patients in non-complete remission (non-CR) but not for those in CR at transplantation. These findings suggest the advantage of 4-fraction over 6-fraction TBI for patients with AML undergoing allogeneic HCT in non-CR.

A rapid review of evidence and recommendations from the SIOPE radiation oncology working group to help mitigate for reduced paediatric radiotherapy capacity during the COVID-19 pandemic or other crises

OBJECTIVE

To derive evidence-based recommendations for the optimal utilisation of resources during unexpected shortage of radiotherapy capacity.

METHODS AND MATERIALS

We have undertaken a rapid review of published literature on the role of radiotherapy in the multimodality treatment of paediatric cancers governing the European practise of paediatric radiotherapy. The derived data has been discussed with expert paediatric radiation oncologists to derive a hierarchy of recommendations.

RESULTS

The general recommendations to mitigate the potential detriment of an unexpected shortage of radiotherapy facilities include: (1) maintain current standards of care as long as possible (2) refer to another specialist paediatric radiotherapy department with similar level of expertise (3) prioritise use of existing radiotherapy resources to treat patients with tumours where radiotherapy has the most effect on clinical outcome (4) use chemotherapy to defer the start of radiotherapy where timing of radiotherapy is not expected to be detrimental (5) active surveillance for low-grade tumours if appropriate and (6) consider iso-effective hypofractionated radiotherapy regimens only for selected patients with predicted poor prognosis. The effectiveness of radiotherapy and recommendations for prioritisation of its use for common and challenging paediatric tumours are discussed.

CONCLUSION

This review provides evidence-based treatment recommendations during unexpected shortage of paediatric radiotherapy facilities. It has wider applications for the optimal utilisation of facilities, to improve clinical outcome in low- and middle-income countries, where limited resources continue to be a challenge.

Pre-transplant MRD negativity predicts favorable outcomes of CAR-T therapy followed by haploidentical HSCT for relapsed/refractory acute lymphoblastic leukemia: a multi-center retrospective study

Background

Consolidative allogeneic hematopoietic stem cell transplantation is a controversial option for patients with relapsed/refractory acute lymphoblastic leukemia after chimeric antigen receptor T cell (CAR-T) therapy. We performed a multicenter retrospective study to assess whether patients can benefit from haploidentical hematopoietic stem cell transplantation after CAR-T therapy.

Methods

A total of 122 patients after CAR-T therapy were enrolled, including 67 patients without subsequent transplantation (non-transplant group) and 55 patients with subsequent haploidentical hematopoietic stem cell transplantation (transplant group). Long-term outcome was assessed, as was its association with baseline patient characteristics.

Results

Compared with the non-transplant group, transplantation recipients had a higher 2-year overall survival (OS; 77.0% versus 36.4%; P < 0.001) and leukemia-free survival (LFS; 65.6% versus 32.8%; P < 0.001). Multivariate analysis showed that minimal residual disease (MRD) positivity at transplantation is an independent factor associated with poor LFS (P = 0.005), OS (P = 0.035), and high cumulative incidence rate of relapse (P = 0.045). Pre-transplant MRD-negative recipients (MRD− group) had a lower cumulative incidence of relapse (17.3%) than those in the non-transplant group (67.2%; P < 0.001) and pre-transplant MRD-positive recipients (MRD+ group) (65.8%; P = 0.006). The cumulative incidence of relapse in MRD+ and non-transplant groups did not differ significantly (P = 0.139). The 2-year LFS in the non-transplant, MRD+, and MRD− groups was 32.8%, 27.6%, and 76.1%, respectively. The MRD− group had a higher LFS than the non-transplantation group (P < 0.001) and MRD+ group (P = 0.007), whereas the LFS in the MRD+ and non-transplant groups did not differ significantly (P = 0.305). The 2-year OS of the MRD− group was higher than that of the non-transplant group (83.3% versus 36.4%; P < 0.001) but did not differ from that of the MRD+ group (83.3% versus 62.7%; P = 0.069). The OS in the non-transplant and MRD+ groups did not differ significantly (P = 0.231).

Conclusion

Haploidentical hematopoietic stem cell transplantation with pre-transplant MRD negativity after CAR-T therapy could greatly improve LFS and OS in patients with relapsed/refractory acute lymphoblastic leukemia.

Trial registration

The study was registered in the Chinese clinical trial registry (ChiCTR1900023957).

Treatment of Adult Patients with Relapsed/Refractory B-Cell Philadelphia-Negative Acute Lymphoblastic Leukemia

The majority of adult patients affected by B-cell acute lymphoblastic leukemia (B-ALL) will relapse after an initial response, while approximately 20% will display primary resistant disease. Patients suffering from relapsed/refractory B-ALL have a very poor outcome. Allogeneic hematopoietic cell transplantation (HCT) still represents the only curative approach, but is not so frequently feasible, because of patient's fitness, donor availability, and the ability to achieve a remission prior to HCT. The estimated remission rates with conventional cytotoxic agents are around 30%, but they are short-lived. These disappointing results led to the introduction of new immunologic-based treatments-blinatumomab and inotuzumab. They produced a substantial improvement in terms of response rates, with the ability, in most cases, to induce a minimal residual disease (MRD)-negative status. Similarly, T cells engineered to express a CD19-specific chimeric antigen receptor (CAR-T) have yielded sensational results among patients with relapsed/refractory B-ALL, with unexpectedly high MRD-negative complete remissions rates. However, the first studies looking at long-term outcomes after CAR-T infusions told us that a significant fraction of such responses are not durable, and may benefit from a consolidation approach such as an allogeneic HCT.

Hematopoietic stem cell transplantation for adults with Philadelphia chromosome-negative acute lymphoblastic leukemia in first remission: a position statement of the European Working Group for Adult Acute Lymphoblastic Leukemia (EWALL) and the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation (EBMT)

Allogeneic hematopoietic stem cell transplantation (HSCT) in first complete remission is a standard of care for adult patients with Philadelphia chromosome (Ph)-negative acute lymphoblastic leukemia (ALL) and high risk of relapse. However, the stratification systems vary among study groups. Inadequate response at the level of minimal residual disease is the most commonly accepted factor indicating the need for alloHSCT. In this consensus paper on behalf of the European Working Group for Adult Acute Lymphoblastic Leukemia and the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation, we summarize available evidence and reflect current clinical practice in major European study groups regarding both indications for HSCT and particular aspects of the procedure including the choice of donor, source of stem cells and conditioning. Finally, we propose recommendations for daily clinical practice as well as for planning of prospective trials.