ABSTRACT:We evaluated long-term outcomes of 288 children with refractory-Langerhans cell histiocytosis (R-LCH) from 26 countries, who were prescribed off-label MAPK inhibitors (MAPKis) according to clinical indications. MAPKi indications included 148 R-risk-organ-positive (R-RO+), 67 R-risk-organ-negative (R-RO-), 13 lung destruction (lung), 9 sclerosing cholangitis (SC), 49 neurodegeneration (ND), and 2 diabetes insipidus (DI) cases. Median ages at diagnosis and MAPKi onset were 1.3 and 2.3 years, respectively, with median follow-up of 3.7 years (1166 person-years). Agents mostly prescribed as monotherapies were 184 prescriptions of vemurafenib, 115 of dabrafenib, 3 of encorafenib, 42 of cobimetinib, 45 of trametinib, and/or 1 prescription of binimetinib; followed 51 times by various chemotherapies or hematopoietic stem-cell transplantation, or 28 times by combined anti-BRAF-anti-MEK. Short-term responses (<8 weeks) ranged from 98% (R-RO+ and R-RO-), to 30% (lung) to none (ND, DI, and SC); although long-term lung and ND responses could be observed. Skin rash was the most frequent adverse event (∼55%), and 7 others included 1 case of cardiomyopathy and 6 of retinitis. Five developed MAPKi-unrelated tumors and 9 patients died. Five-year survival was 98%. After 113 patients with R-LCH discontinued MAPKi, 69 experienced disease reactivation. None of the various empirical maintenance therapies were able to prevent secondary reactivation. Among the 143 assessable patients without ND-LCH at MAPKi onset, 60 developed ND (45%, 5-year risk). MAPKis appeared to be safe and effective in children with R-RO+/RO-LCH, whereas other indications' responses were less frequent or occurred later. Further studies are needed to find effective maintenance-therapy approaches, particularly to prevent frequently observed secondary ND.

Persistent selective T-lymphocytopenia is found both in SCID and congenital athymia. Without molecular diagnosis, it is challenging to determine whether HCT or thymus transplantation ought to be performed. Ex vivo T-lymphopoiesis assays have been proposed to assist clinical decision-making for genetically undefined patients. We investigated 20 T-lymphocytopenic patients, including 13 patients awaiting first-line treatment and 7 patients with failed immune reconstitution after previous HCT or thymus transplantation. Whilst developmental blocks in ex vivo T-lymphopoiesis indicated hematopoietic cell-intrinsic defects, successful T-lymphocyte differentiation required careful interpretation, in conjunction with clinical status, immunophenotyping, and genetic investigations. Of the 20 patients, 13 proceeded to treatment, with successful immune reconstitution observed in 4 of the 6 patients post-HCT and 4 of the 7 patients after thymus transplantation, the latter including two patients who had previously undergone HCT. Whilst further validation and standardization are required, we conclude that assessing ex vivo T-lymphopoiesis during the diagnostic pathway for genetically undefined T-lymphocytopenia improves patient outcomes by facilitating corrective treatment choice.

Newborn screening for severe combined immunodeficiency promotes early diagnosis and timely treatment, improving clinical outcomes. Selective T-lymphocytopaenia is found both in haematopoietic cell-intrinsic and thymic stromal cell-intrinsic defects, including congenital athymia which is associated with a T-B + NK + immunophenotype. Without a molecular diagnosis, it is challenging to determine whether haematopoietic cell transplantation (HCT) or thymus transplantation ought to be performed. Ex vivo T-lymphocyte differentiation assays have been proposed to assist clinical decision-making for genetically undefined T-lymphocytopaenic patients by assessing the intrinsic potential of their haematopoietic progenitors to differentiate into mature T-lymphocytes. We investigated 18 T-lymphocytopaenic patients, including 12 patients awaiting first-line treatment and 6 patients with failed immune reconstitution after previous HCT or thymus transplantation. Whilst early developmental blocks in ex vivo T-lymphopoiesis indicated haematopoietic cell-intrinsic defects, successful differentiation of mature T-lymphocytes required careful interpretation, in conjugation with clinical status and presentation, immunophenotyping, and available genetic investigations. 5 patients were referred for HCT and 12 for thymus transplantation. 12/18 patients proceeded to treatment with successful immune reconstitution in 4/5 patients after HCT and 4/7 after thymus transplantation, the latter including two patients previously treated with HCT. Two treated patients died, either after HCT or after thymus transplantation, due to pre-existing complications, and two patients have yet to show immune reconstitution seven months and one year after thymus transplantation respectively. Overall, we conclude that including ex vivo T-lymphocyte differentiation assays in the diagnostic pathway for genetically undefined T-lymphocytopaenia improves patient outcomes by facilitating corrective treatment choice between HCT and thymus transplantation.

Acute Graft-versus-Host Disease (aGvHD) is a frequent complication after a Hematopoietic Stem Cell Transplantation (HSCT). Its gastrointestinal subtype is associated with a high mortality, especially in steroid-refractory cases. Managing Steroid-Refractory aGvHD (SR-aGvHD) remains challenging due to the lack of validated second-line immunosuppressive strategies. Mesenchymal Stromal Cells (MSCs) are a therapeutic option for SR-aGvHD, but its efficacy and clinical response in children varies. Two recent studies using pooled bone marrow mononuclear cells from multiple donors, MSC-FFM, have shown satisfactory overall response rates but the literature is still lacking in children.

Sinusoidal obstruction syndrome (SOS), also known as hepatic veno-occlusive disease (VOD), is a well-known complication of allogeneic hematopoietic stem cell transplantation (HSCT) associated with a mortality rate of up to 85%.  Defibrotide has shown efficacy in treatment of SOS/VOD. Moreover, evidence exists supporting the efficacy of defibrotide as SOS/VOD prophylaxis. We have previously reported our single center experience on 52 HSCT recipients receiving defibrotide as SOS/VOD prophylaxis, which has shown that the patients did not develop any SOS/VOD under this prophylaxis. The aim of the present study was to see if we can confirm the previous results, mainly on the decrease incidence of SOS/VOD, as well as improve event-free survival (EFS) on a larger study population. We extended our previous study in a single-center retrospective analysis to include 237 consecutive patients (248 transplantations) who underwent transplantation between 1999 and 2009 for hematological diseases and receiving intravenous defibrotide as prophylaxis. This cohort was compared to 241 patients (248 transplantations) treated before 1999 or after 2009 when defibrotide prophylaxis was not routinely used in our center. Median follow-up for the study group was 10 (range 2-16) years and for the control group 2.7 (range 1-18) years. None of the 237 patients in the defibrotide group developed SOS/VOD. The cumulative incidence (CI) of SOS/VOD was 0% in the defibrotide group as compared to 4.8% (95% confidence interval [CI], 2.6-8%; P= .00046) in the control group. There was also a better 1-year EFS with 38% (95% CI, 32%-44%) in the defibrotide group versus 28% (95% CI, 22%-34%) (P= .00969) and decreased cumulative incidence of acute graft-versus-host disease (GvHD) in the defibrotide group 31% (95% CI, 25%-37%) versus 42% (95% CI, 36%-48%) (P= .026). The 1-year overall survival, relapse incidence, and non-relapse mortality were not statistically different. Multivariable analysis, performed taking into account clinical factors known to influence the risk of SOS/VOD, confirmed the favorable impact of defibrotide on SOS/VOD (HR 1.38e-08 [95% CI, 3.28e-09-5.80e-08]; P< .00001). Conversely, multivariable analysis failed to confirm the impact of defibrotide on 1-year EFS or acute GvHD. This large retrospective study on SOS/VOD-prophylaxis with defibrotide suggests that this approach may be of benefit. These results need to be confirmed in a prospective randomized trial.

Testicular tissue cryopreservation is the only option of fertility preservation in prepubertal boys. While it is considered experimental, since procedures to obtain mature spermatozoa from prepubertal testicular tissue are still under development, testicular tissue cryopreservation programs have emerged worldwide. Our aim was to study the feasibility and safety of a program of testicular tissue cryopreservation in prepubertal and adolescent boys facing gonadotoxic treatment in three University hospitals in Switzerland. Testicular tissue cryopreservation was accepted by 90% of families, with a total of 35 patients included. The average patient age was 8.5 years (range 7 months to 18.5 years). Malignancies were the most common diagnosis (31 patients, 88.6%) with 16 (45.7%) solid tumors and 15 (42.9%) hematological malignancies. Four (11.4%) patients had a benign condition. The main indication for testicular tissue cryopreservation was conditioning for hematologic stem cell transplantation (25 patients, 71.4%). Testicular tissue was cryopreserved according to the freezing protocol of Louvain Catholic University (Belgium), which includes either only immature testicular tissue freezing, or mature and immature testicular tissue freezing depending on the age of the patient and the presence or absence of haploid cells. The median number of spermatogonia per tubule cross-section was 2 (range 0–6) and spermatozoa were found in only one patient. Tumoral cells were found in one testicular biopsy of a leukemic patient. There were two minor adverse events and none of them required medical treatment or surgical revision. Five patients died during follow-up. Our data demonstrate the feasibility and safety of a program of testicular tissue cryopreservation coordinated by a multidisciplinary team of fertility preservation. Despite the experimental aspect of the procedure, the acceptation rate was high, which highlights the willingness of families and patients to participate in testicular tissue cryopreservation.

SummaryHaematopoietic stem cell transplantation (HSCT) remains the only curative option in Fanconi anaemia (FA). We analysed the outcome of children transplanted for FA between 1999 and 2018 in the UK. A total of 94 transplants were performed in 82 patients. Among the donors, 51·2% were matched related donors (MRD) while the remainder were alternative donors. Most patients received a fludarabine–cyclophosphamide (Flu–Cy)‐based conditioning regimen (86·6%) and in vivo T‐cell depletion with alemtuzumab (69·5%). Five‐year overall survival (OS) was 85·4% [70·4–93.2] with MRD, 95·7% [72·9–99.4] with matched unrelated donors (MUD), 44·4% [6·6–78.5] with mismatched unrelated donors (MMUD) and 44·4% [13·6–71.9] with mismatched related donors (MMRD) (P < 0·001). Other factors significantly impacting OS were pre‐transplant bone marrow status, source of stem cells, cytomegalovirus (CMV) serostatus, preparation with Flu–Cy, use of total body irradiation (TBI) and alemtuzumab as serotherapy. In multivariate analysis, absence of myelodysplastic syndrome (MDS) or leukaemia, bone marrow as source of stem cells, cytomegalovirus (CMV) other than +/− (Recipient/Donor) and Flu–Cy were protective factors for five‐year OS. Five‐year chronic graft‐versus‐host‐disease (cGVHD)‐free event‐free survival was 75·4% with the same risk factors except for CMV serostatus. Five‐year non‐relapse mortality was 13·8% [7·3–22.3]. Only five patients (6·1%) developed grade II–IV acute GVHD and two patients chronic GVHD. These data confirm the excellent outcome of matched related or unrelated HSCT in children with FA.

Rituximab (RTX) is an anti-CD20 monoclonal antibody that targets B cells—from the immature pre-B-cell stage in the bone marrow to mature circulating B cells—while preserving stem cells and plasma cells. It is used to treat autoimmune diseases, hematological malignancies, or complications after hematopoietic stem cell transplantation (HSCT). Its safety profile is acceptable; however, a subset of patients can develop persistent hypogammaglobulinemia and associated severe complications, especially in pediatric populations. We report the unrelated cases of two young men aged 17 and 22, presenting with persistent hypogammaglobulinemia more than 7 and 10 years after treatment with RTX, respectively, and administered after HSCT for hemolytic anemia and Epstein–Barr virus reactivation, respectively. Both patients’ immunological workups showed low levels of total immunoglobulin, vaccine antibodies, and class switched-memory B cells but an increase in naive B cells, which can also be observed in primary immunodeficiencies such as those making up common variable immunodeficiency. Whole exome sequencing for one of the patients failed to detect a pathogenic variant causing a Mendelian immunological disorder. Annual assessments involving interruption of immunoglobulin replacement therapy each summer failed to demonstrate the recovery of endogenous immunoglobulin production or normal numbers of class switched-memory B cells 7 and 10 years after the patients’ respective treatments with RTX. Although the factors that may lead to prolonged hypogammaglobulinemia after rituximab treatment (if necessary) remain unclear, a comprehensive immunological workup before treatment and long-term follow-up are mandatory to assess long-term complications, especially in children.

Ovarian failure is a major long-term adverse event following gonadotoxic treatment of malignant diseases. Ovarian tissue cryopreservation can be offered in some conditions to preserve fertility. We report the case of a 13-year-old female with a diagnosis of acute myeloid leukemia, who presented with hypergonadotropic hypogonadism after unilateral ovariectomy for fertility preservation and before highly gonadotoxic treatment. Even though damage seemed only partial, this case suggests that the remaining contralateral ovarian function may be compromised after ovarian tissue cryopreservation, leading per se to a hypergonadotropic hypogonadism. Although indication of ovarian cryopreservation is not called into question in situations of highly gonadotoxic therapy, this procedure should only be performed after evaluation by a specialized multidisciplinary team and provided a solid indication.

Many primary immunodeficiencies (PIDs) are recognised as being associated with malignancies, particularly lymphoid malignancies, which represent the highest proportion of cancers occurring in conjunction with this underlying condition. When patients present with genetic errors of immunity, clinicians must often reflect on whether to manage antitumoral treatment conventionally or to take a more personalised approach, considering possible existing comorbidities and the underlying status of immunodeficiency. Recent advances in antitumoral immunotherapies, such as monoclonal antibodies, antigen-specific adoptive cell therapies or compounds with targeted effects, potentially offer significant opportunities for optimising treatment for those patients, especially with lymphoid malignancies. In cases involving PIDs, variable oncogenic mechanisms exist, and opportunities for antitumoral immunotherapies can be considered accordingly. In cases involving a DNA repair defect or genetic instability, monoclonal antibodies can be proposed instead of chemotherapy to avoid severe toxicity. Malignancies secondary to uncontrolled virus-driven proliferation or the loss of antitumoral immunosurveillance may benefit from antivirus cell therapies or allogeneic stem cell transplantation in order to restore the immune antitumoral caretaker function. A subset of PIDs is caused by gene defects affecting targetable signalling pathways directly involved in the oncogenic process, such as the constitutive activation of phosphoinositol 3-kinase/protein kinase B (PI3K/AKT) in activated phosphoinositide 3-kinase delta syndrome (APDS), which can be settled with PI3K/AKT inhibitors. Therefore, immunotherapy provides clinicians with interesting antitumoral therapeutic weapons to treat malignancies when there is an underlying PID.