The paradigm of total body irradiation in acute lymphoblastic leukaemia: Therapeutic effectiveness versus the challenges of toxicity.

INTRODUCTION: Total body irradiation (TBI) is part of the myeloablative conditioning for hematopoietic stem cell transplantation (HSCT) in malignant hematologic disorders. This therapy has recently shown improved survival in acute lymphoblastic leukemia (ALL) compared to chemotherapy-based regimens. However, side effects are a significant limitation, especially in the pediatric population. PATIENTS AND METHODS: We retrospectively analyzed the survival of patients with ALL who underwent an HSCT at a tertiary hospital between 1996 and 2009 (N = 69 HSCT in 57 patients). We differentiated a cohort that received TBI (N = 44) from another that did not (N = 25). Subsequently, we interviewed the survivors from the TBI group with a minimum of 10 years of follow-up (N = 18), asking about the presence of side effects. RESULTS: The overall survival (OS) at 2 and 5 years was 79.1% and 65.2% respectively for the TBI group and 66.2% and 55.8% for the non-TBI group, although this difference was not significant (P=.31). The event-free survival (EFS) at 2 and 5 years was 77.3% and 63.6% respectively for the TBI group and 56% and 32% for the non-TBI group (P=.02). The probability of relapse (PR) at 2 years for those who received TBI was 10% compared to 28.6% for those who did not receive TBI (P=.005). Survivors who received TBI developed secondary neoplasms (39%), dyslipidemia (67%), cognitive impairments affecting memory (44%), recurrent respiratory infections (39%), thyroid abnormalities (45%), premature ovarian failure (89%), cataracts (22%), and psychological problems (44%). However, the quality of life, as self-assessed by the patients, was considered good for 83% of the participants.. CONCLUSIONS: Patients who received TBI had significantly higher EFS and lower PR. However, adverse effects are frequent and significant, although they do not subjectively affect quality of life.

Corrigendum: Impact of disease burden and late loss of B cell aplasia on the risk of relapse after CD19 chimeric antigen receptor T Cell (Tisagenlecleucel) infusion in pediatric and young adult patients with relapse/refractory acute lymphoblastic leukemia: role of B-cell monitoring.

[This corrects the article DOI: 10.3389/fimmu.2023.1280580.].

The challenge of standardizing CAR-T cell monitoring: A comparison of two flow-cytometry methods and correlation with qPCR technique.

Chimeric antigen receptor (CAR) T-cell therapy is a breakthrough in hematologic malignancies, such as acute B lymphoblastic leukemia (B-ALL). Monitoring this treatment is recommended, although standardized protocols have not been developed yet. This work compares two flow cytometry monitoring strategies and correlates this technique with qPCR method. CAR-T cells were detected by two different flow-cytometry protocols (A and B) in nine blood samples from one healthy donor and five B-ALL patients treated with Tisagenlecleucel (Kymriah®, USA). HIV-1 viral load allowed CAR detection by qPCR, using samples from seven healthy donors and nine B-ALL patients. CAR detection by protocol A and B did not yield statistically significant differences (1.9% vs. 11.8% CD3 + CAR+, p = 0.07). However, protocol B showed a better discrimination of the CD3 + CAR+ population. A strong correlation was observed between protocol B and qPCR (r = 0.7, p < 0.0001). CD3 + CAR+ cells were detected by flow cytometry only when HIV-1 viral load was above 104 copies/mL. In conclusion, protocol B was the most specific flow-cytometry procedure for the identification of CAR-T cells and showed a high correlation with qPCR. Further efforts are needed to achieve a standardized monitoring approach.

Impact of disease burden and late loss of B cell aplasia on the risk of relapse after CD19 chimeric antigen receptor T Cell (Tisagenlecleucel) infusion in pediatric and young adult patients with relapse/refractory acute lymphoblastic leukemia: role of B-cell monitoring.

Introduction: Loss of B-cell aplasia (BCA) is a well-known marker of functional loss of CD19 CAR-T. Most relapses and loss of BCA occur in the first months after CD19 CAR-T infusion. In addition, high tumor burden (HTB) has shown to have a strong impact on relapse, especially in CD19-negative. However, little is known about the impact of late loss of BCA or the relationship between BCA and pre-infusion tumor burden in patients infused with tisagenlecleucel for relapsed/refractory B-cell acute lymphoblastic leukemia. Therefore, the optimal management of patients with loss of BCA is yet to be defined. Methods: We conducted a Spanish, multicentre, retrospective study in patients infused with tisagenlecleucel after marketing authorization. A total of 73 consecutively treated patients were evaluated. Results: Prior to infusion, 39 patients had HTB (≥ 5% bone marrow blasts) whereas 34 had a low tumor burden (LTB) (<5% blasts). Complete remission was achieved in 90.4% of patients, of whom 59% relapsed. HTB was associated with inferior outcomes, with a 12-month EFS of 19.3% compared to 67.2% in patients with LTB (p<0.001) with a median follow-up of 13.5 months (95% CI 12.4 - 16.2). In the HTB subgroup relapses were mainly CD19-negative (72%) whereas in the LTB subgroup they were mainly CD19-positive (71%) (p=0.017). In the LTB group, all CD19-positive relapses were preceded by loss of BCA whereas only 57% (4/7) of HTB patients experienced CD19-positive relapse. We found a positive correlation between loss of BCA and CD19-positive relapse (R-squared: 74) which persisted beyond six months post-infusion. We also explored B-cell recovery over time using two different definitions of loss of BCA and found a few discrepancies. Interestingly, transient immature B-cell recovery followed by BCA was observed in two pediatric patients. In conclusion, HTB has an unfavorable impact on EFS and allo-SCT might be considered in all patients with HTB, regardless of BCA. In patients with LTB, loss of BCA preceded all CD19-positive relapses. CD19-positive relapse was also frequent in patients who lost BCA beyond six months post-infusion. Therefore, these patients are still at significant risk for relapse and close MRD monitoring and/or therapeutic interventions should be considered.

CD19+ lineage chimerism, an early biomarker after anti-CD19 CAR-T cell therapy in patients previously receiving a hematopoietic stem cell transplantation.

Treatment targeting CD19 by a chimeric antigen receptor expressed on T cells (anti-CD19 CAR-T) has led to a breakthrough in the management and treatment of relapsed and refractory B- cell acute lymphoblastic leukemia (B-ALL). After infusion, the efficacy of anti-CD19 CAR-T is monitored by bone marrow negative minimal residual disease and the absence of peripheral CD19+ B lymphocytes (B-cell aplasia). In patients who have received an allogenic Hematopoietic Stem Cell Transplantation (HSCT) prior to treatment with anti-CD19 CAR-T, monitoring lineage-specific chimerism could be helpful. We found that on 4 patients who received anti-CD19 CAR-T cells after HSCT and achieved early complete response, CD19+ lineage mixed chimerism but not CD3+ lineage mixed chimerism monitored by molecular techniques anticipated earlier than B-cell aplasia determined by flow cytometry, lack of effectiveness of anti-CD19 CAR-T and leukemia relapse. Donor lymphocyte infusions (DLIs) did not prevent relapse but recovered CD3+ full donor chimerism. We suggest that continuous lineage chimerism analysis should be done routinely in patients who receive anti-CD19 CAR-T cells after HSCT and achieve complete remission because it can support early treatment intervention. However, the role of DLI in this setting is unclear, so further prospective studies should be developed.

A mutation in the promoter region of BTK causes atypical XLA.

X-linked Agammaglobulinemia is a primary immunodeficiency caused by mutations in BTK, a tyrosine kinase essential for B lymphocytes differentiation. Patients usually have very low or absent B lymphocytes and are not able to develop humoral specific responses. Here we present a boy, diagnosed with XLA due to a mutation on the promoter region of the gene, whose phenotype is characterised by low percentage of B cells, hypogammaglobulinemia, oscillating neutropenia, antibodies responses to some antigens after vaccination and IgE-mediated allergy. Additional technology as flow cytometry was needed to demonstrate the pathological status of the variant. We focus on the idea that XLA should be suspected in males with B lymphopenia and hypogammaglobulinemia, even if they make humoral specific responses. We also highlight the importance of sequencing BTK's promoter region, as mutations on it can be disease-causing.

Study protocol for a phase II, multicentre, prospective, non-randomised clinical trial to assess the safety and efficacy of infusing allogeneic activated and expanded natural killer cells as consolidation therapy for paediatric acute myeloblastic leukaemia.

INTRODUCTION: Acute myeloblastic leukaemia (AML) constitutes the second most common haematological malignancy in the paediatric population. Current treatment regimens are based on the administration of polychemotherapy, combining high doses of cytarabine with anthracyclines and topoisomerase inhibitors. Allogeneic haematopoietic stem cell transplantation (HSCT) is an option for high-risk patients with AML (and for intermediate-risk patients if a sibling donor is available). With this strategy, AML survival has increased substantially; however, it has remained stagnant at approximately 60%, with relapse being the principal culprit. The predominant role of the immune system and natural killer (NK) cells in controlling paediatric AML has gained importance within the context of HSCT. In this protocol, we propose incorporating this cell therapy as an adjuvant treatment through the infusion of activated and expanded haploidentical NK (NKAE) cells in paediatric patients with AML who are in cytological remission after completing consolidation therapy, and with no indication for HSCT. METHODS AND ANALYSIS: Patients up to 30 years of age, diagnosed with AML, in their first cytological remission, who have completed both the induction and the consolidation phases of chemotherapy and do not meet the criteria for allogeneic HSCT are eligible. The patients will receive two doses of NKAE cells once a week, using a GMP K562-mbIL15-41BBL stimulus from a haploidentical donor and interleukin 2 subcutaneously. The patients will then be followed up for 36 months to assess the primary endpoint, which is the probability of relapse after NK cell infusion. ETHICS AND DISSEMINATION: This clinical trial was approved by the Clinical Research Ethics Committee of La Paz University Hospital and The Spanish Agency of Medicines and Medical Devices. Findings will be disseminated through peer-reviewed publications, conference presentations and community reporting. TRIAL REGISTRATION NUMBER: EudraCT code: 2015-001901-15, ClinicalTrials.gov Identifier: NCT02763475.