Hematopoietic cell transplantation and cellular therapies in Switzerland. Evolution over 25 years. A report from the stem cell transplantation and cellular therapies working groups of the SBST 1997-2021.

The Swiss Blood Stem Cell Transplantation and Cellular Therapy Group (SBST) leads a mandatory national registry for all hematopoietic stem cell transplants (HCT) and cellular therapies. After 25 years, information was available for 11,226 patients receiving an HCT (4031 allogeneic and 7195 autologous), including 925 pediatric patients. We compared patient characteristics and outcome by quinquennia 1997-2001, 2002-2006, 2007-2011, 2012-2016, and 2017-2021. There were numerous changes over time. Allogeneic transplant recipients became older (median age 33.7 vs. 54.3) and had more frequently unrelated donors and reduced intensity conditioning in later quinquennia. Similarly, age increased for recipients of autologous HCT (median 48.3 vs. 59.9). We did not see a significant drop in transplant activity during the SARS-CoV-2 pandemic. Analysis of outcome showed overall survival (relative risk (RR) of death 0.664 (0.529-0.832) and progression free survival (RR 0.708 (0.577-0.870) being improved over time comparing the latest to the first quinquennium adjusting for risk factors. Non-relapse mortality decreased in recipients of allogeneic HCT (RR: 0.371 (0.270-0.509)) over time but relapse risks did not. Outcome of autologous HCT improved as well across quinquennia, this improvement was mainly due to decreased relapse risks (RR 0.681 (0.597-0.777)), possibly related to maintenance treatment or rescue treatment for relapse mainly in myeloma patients. Cellular therapies other than allogeneic or autologous HCT, particularly chimeric antigen receptor T-cells (CAR-T) treatment have started to increase after 2019, year of approval of the first commercial CAR-T product in Switzerland. Data on chimeric antigen receptor T-cell treatment are too early for comparative analyses. Detailed analyses of changes over time are presented. This study includes all HCTs, and cellular therapies, data useful for quality assurance programs, health care cost estimation and benchmarking. Between 50% and 60% of patients are long-term survivors after both types of HCT, indicating growing populations of surviving patients requiring long-term care.

Exploring grandparents' psychosocial responses to childhood cancer: A qualitative study.

OBJECTIVE: A childhood cancer diagnosis is a traumatic experience for patients and their families. However, little is known about the effect on grandparents. We aimed to investigate the negative psychosocial impact, coping strategies, and positive outcomes of grandparents of childhood cancer patients in Switzerland. METHODS: We collected data using a semi-structured interview guide and applied qualitative content analysis. RESULTS: We conducted 20 interviews with 23 grandparents (57% female; mean age = 66.9 years; SD = 6.4; range = 57.0-82.4) of 13 affected children (69% female; mean age = 7.5 years; SD = 6.1; range = 1.0-18.9) between January 2022 and April 2023. The mean time since diagnosis was 1.0 years (SD = 0.5; range = 0.4-1.9). Grandparents were in shock and experienced strong feelings of fear and helplessness. They were particularly afraid of a relapse or late effects. The worst part for most was seeing their grandchild suffer. Many stated that their fear was always present which could lead to tension and sleep problems. To cope with these negative experiences, the grandparents used internal and external strategies, such as accepting the illness or talking to their spouse and friends. Some grandparents also reported positive outcomes, such as getting emotionally closer to family members and appreciating things that had previously been taken for granted. CONCLUSIONS: Grandparents suffer greatly when their grandchild is diagnosed with cancer. Encouragingly, most grandparents also reported coping strategies and positive outcomes despite the challenges. Promoting coping strategies and providing appropriate resources could reduce the psychological burden of grandparents and strengthen the whole family system.

Simulation-Based Optimization of Sampling Schedules for Model-Informed Precision Dosing of Once-Daily and 4-Times-Daily Busulfan in Pediatric Patients.

BACKGROUND: Therapeutic drug monitoring (TDM) is crucial in optimizing the outcomes of hematopoietic stem cell transplantation by guiding busulfan (Bu) dosing. Limited sampling strategies show promise for efficiently adjusting drug doses. However, comprehensive assessments and optimization of sampling schedules for Bu TDM in pediatric patients are limited. We aimed to establish optimal sampling designs for model-informed precision dosing (MIPD) of once-daily (q24h) and 4-times-daily (q6h) Bu administration in pediatric patients. METHODS: Simulated data sets were used to evaluate the population pharmacokinetic model-based Bayesian estimation of the area under the concentration-time curve (AUC) for different limited sampling strategy designs. The evaluation was based on the mean prediction error for accuracy and root mean square error for precision. These findings were validated using patient-observed data. In addition, the MIPD protocol was implemented in the Tucuxi software, and its performance was assessed. RESULTS: Our Bayesian estimation approach allowed for flexible sampling times while maintaining mean prediction error within ±5% and root mean square error below 10%. Accurate and precise AUC0-24h and cumulative AUC estimations were obtained using 2-sample and single-sample schedules for q6h and q24h dosing, respectively. TDM on 2 separate days was necessary to accurately estimate cumulative exposure, especially in patients receiving q6h Bu. Validation with observed patient data confirmed the precision of the proposed limited sampling scenarios. Implementing the MIPD protocol in Tucuxi software yielded reliable AUC estimations. CONCLUSIONS: Our study successfully established precise limited sampling protocols for MIPD of Bu in pediatric patients. Our findings underscore the importance of TDM on at least 2 occasions to accurately achieve desired Bu exposures. The developed MIPD protocol and its implementation in Tucuxi software provide a valuable tool for routine TDM in pediatric hematopoietic stem cell transplantation.

Brain stem tumors in children less than 3 months: Clinical and radiologic findings of a rare disease.

PURPOSE: Brain stem tumors in children < 3 months at diagnosis are extremely rare. Our aim is to study a retrospective cohort to improve the understanding of the disease course and guide patient management. METHODS: This is a multicenter retrospective analysis across the European Society for Pediatric Oncology SIOP-E HGG/DIPG Working Group linked centers, including patients with a brainstem tumor diagnosed between 2009 and 2020 and aged < 3 months at diagnosis. Clinical data were collected, and imaging characteristics were analyzed blindly and independently by two neuroradiologists. RESULTS: Five cases were identified. No patient received any therapy. The epicenter of two tumors was in the medulla oblongata alone and in the medulla oblongata and the pons in three. For patients with tumor in equal parts in the medulla oblongata and the pons (n = 3), the extension at diagnosis involved the spinal cord; for the two patients with the tumor epicenter in the medulla oblongata alone (n = 2), the extension at diagnosis included the pons (n = 2) and the spinal cord (n = 1). Biopsy was performed in one patient identifying a pilocytic astrocytoma. Two patients died. In one patient, autopsy revealed a high-grade glioma (case 3). Three survivors showed either spontaneous tumor regression (n = 2) or stable disease (n = 1). Survivors were followed up for 10, 7, and 0.6 years, respectively. One case had the typical imaging characteristics of a dorsal exophytic low-grade glioma. CONCLUSIONS: No patient fulfilled the radiologic criteria defining a high-grade glioma. Central neuroradiological review and biopsy may provide useful information regarding the patient management.

Consensus classification of pediatric hepatocellular tumors: A report from the Children's Hepatic tumors International Collaboration (CHIC).

BACKGROUND: Liver tumors are rare in children with histologic heterogeneity that makes diagnosis challenging. Systematic histopathological review, performed as part of collaborative therapeutic protocols, identified relevant histologic subtypes that are important to distinguish. The Children's Hepatic tumors International Collaboration (CHIC) was established to study pediatric liver tumors on a global scale and led to establishment of a provisional consensus classification for use in international clinical trials. The current study is the validation of this initial classification and first large-scale application by international expert reviewers. PROCEDURE: The CHIC initiative includes data from 1605 children treated on eight multicenter hepatoblastoma (HB) trials. Review of 605 available tumors was performed by seven expert pathologists from three consortia (US, EU, Japan). Cases with discordant diagnoses were collectively reviewed to reach a final consensus diagnosis. RESULTS: Of 599 cases with sufficient material for review, 570 (95.2%) were classified as HB by all consortia, and 29 (4.8%) as non-HB, which included "hepatocellular neoplasm, NOS" and malignant rhabdoid tumors. 453 of 570 HBs were classified as epithelial by final consensus. Some patterns (i.e., small cell undifferentiated, macrotrabecular, cholangioblastic) were selectively identified by reviewers from different consortia. All consortia identified a similar number of mixed epithelial-mesenchymal HB. CONCLUSIONS: This study represents the first large-scale application and validation of the pediatric malignant hepatocellular tumors consensus classification. It is a valuable resource to train future generations of investigators on accurate diagnosis of these rare tumors and provides a framework for further international collaborative studies and refinement of the current classification of pediatric liver tumors.

[Precision medicine in the treatment of pediatric cancers]. / Médecine de précision dans le traitement des cancers pédiatriques.

Despite the progress in cure rates for pediatric cancers, several challenges remain, such as the management of diseases with poor prognosis. The efficacy of intensified chemotherapies is also accompanied by increased risks of severe acute and chronic toxicities. Thus, therapies specifically targeting tumor cells, or inhibiting oncogenic molecular aberrations, could provide more effective and less toxic treatments for pediatric cancers. Personalization of chemotherapies through pharmacogenetics and precision dosing could also improve the efficacy and toxicity of chemotherapies. In this review, we describe precision medicine strategies implemented or undergoing clinical evaluation in the treatment of pediatric cancers.

Malgré les progrès sur les taux de guérison des cancers pédiatriques, plusieurs défis restent à relever, comme la prise en charge des maladies à mauvais pronostic. L'efficacité des chimiothérapies intensives s'accompagne aussi de risques accrus de toxicités aiguës et chroniques graves. Ainsi, les thérapies ciblant spécifiquement les cellules tumorales, ou inhibant les aberrations moléculaires oncogéniques, pourraient offrir des traitements plus efficaces et moins toxiques pour les cancers pédiatriques. La personnalisation des chimiothérapies grâce à la pharmacogénétique et au dosage de précision pourrait également améliorer l'efficacité et la toxicité des chimiothérapies. Dans cet article de revue, nous décrivons les stratégies de médecine de précision implémentées ou en cours d'évaluation clinique dans le traitement des cancers pédiatriques.

Severity of hearing loss after platinum chemotherapy in childhood cancer survivors.

BACKGROUND: Hearing loss is a potential side effect from childhood cancer treatment. We described the severity of hearing loss assessed by audiometry in a representative national cohort of childhood cancer survivors (CCS) and identified clinical risk factors. PROCEDURE: We included all CCS from the Swiss Childhood Cancer Registry who were diagnosed ≤18 age and treated with platinum-based chemotherapy between 1990 and 2014. We extracted audiograms, treatment-related information, and demographic data from medical records. Two reviewers independently assessed the severity of hearing loss at latest follow-up using the Münster Ototoxicity Scale. We used ordered logistic regression to identify clinical risk factors for severity of hearing loss. RESULTS: We analyzed data from 270 CCS. Median time from cancer diagnosis to last audiogram was 5 years (interquartile range 2.5-8.1 years). We found 53 (20%) CCS with mild, 78 (29%) with moderate, and 75 (28%) with severe hearing loss. Higher severity grades were associated with (a) younger age at cancer diagnosis (odds ratio [OR] 5.4, 95% confidence interval [CI]: 2.5-12.0 for <5 years); (b) treatment in earlier years (OR 4.8, 95% CI: 2.1-11.0 for 1990-1995); (c) higher cumulative cisplatin doses (OR 13.5, 95% CI: 4.7-38.8 for >450 mg/m2 ); (d) concomitant cranial radiation therapy (CRT) (OR 4.4, 95% CI: 2.5-7.8); and (e) hematopoietic stem cell transplantation (HSCT) (OR 2.7, 95% CI: 1.0-7.2). CONCLUSION: Three of four CCS treated with platinum-based chemotherapy experienced some degree of hearing loss. We recommend closely monitoring patient's hearing function if treated at a young age with high cumulative cisplatin doses, and concomitant CRT as part of long-term care.

Sodium Thiosulfate for Protection from Cisplatin-Induced Hearing Loss.

BACKGROUND: Cisplatin chemotherapy and surgery are effective treatments for children with standard-risk hepatoblastoma but may cause considerable and irreversible hearing loss. This trial compared cisplatin with cisplatin plus delayed administration of sodium thiosulfate, aiming to reduce the incidence and severity of cisplatin-related ototoxic effects without jeopardizing overall and event-free survival. METHODS: We randomly assigned children older than 1 month and younger than 18 years of age who had standard-risk hepatoblastoma (≤3 involved liver sectors, no metastatic disease, and an alpha-fetoprotein level of >100 ng per milliliter) to receive cisplatin alone (at a dose of 80 mg per square meter of body-surface area, administered over a period of 6 hours) or cisplatin plus sodium thiosulfate (at a dose of 20 g per square meter, administered intravenously over a 15-minute period, 6 hours after the discontinuation of cisplatin) for four preoperative and two postoperative courses. The primary end point was the absolute hearing threshold, as measured by pure-tone audiometry, at a minimum age of 3.5 years. Hearing loss was assessed according to the Brock grade (on a scale from 0 to 4, with higher grades indicating greater hearing loss). The main secondary end points were overall survival and event-free survival at 3 years. RESULTS: A total of 109 children were randomly assigned to receive cisplatin plus sodium thiosulfate (57 children) or cisplatin alone (52) and could be evaluated. Sodium thiosulfate was associated with few high-grade toxic effects. The absolute hearing threshold was assessed in 101 children. Hearing loss of grade 1 or higher occurred in 18 of 55 children (33%) in the cisplatin-sodium thiosulfate group, as compared with 29 of 46 (63%) in the cisplatin-alone group, indicating a 48% lower incidence of hearing loss in the cisplatin-sodium thiosulfate group (relative risk, 0.52; 95% confidence interval [CI], 0.33 to 0.81; P=0.002). At a median of 52 months of follow-up, the 3-year rates of event-free survival were 82% (95% CI, 69 to 90) in the cisplatin-sodium thiosulfate group and 79% (95% CI, 65 to 88) in the cisplatin-alone group, and the 3-year rates of overall survival were 98% (95% CI, 88 to 100) and 92% (95% CI, 81 to 97), respectively. CONCLUSIONS: The addition of sodium thiosulfate, administered 6 hours after cisplatin chemotherapy, resulted in a lower incidence of cisplatin-induced hearing loss among children with standard-risk hepatoblastoma, without jeopardizing overall or event-free survival. (Funded by Cancer Research UK and others; SIOPEL 6 ClinicalTrials.gov number, NCT00652132 ; EudraCT number, 2007-002402-21 .).

Birth characteristics and childhood leukemia in Switzerland: a register-based case-control study.

PURPOSE: Initial genetic alterations in the development of childhood leukemia occur in utero or before conception; both genetic and environmental factors are suspected to play a role. We aimed to investigate the associations between childhood leukemia and perinatal characteristics including birth order, birth interval to older siblings, parental age, birth weight, and multiple birth. METHODS: We identified cases diagnosed between 1981 and 2015 and born in Switzerland between 1969 and 2015 from the Swiss Childhood Cancer Registry and randomly sampled five controls per case from national birth records matched on date of birth, sex, and municipality of residence at birth. We used conditional logistic regression to investigate associations between perinatal characteristics and leukemia at ages 0-15 and 0-4 years, and the subtypes acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). RESULTS: The study included 1,403 cases of leukemia. We observed increased risks associated with high birth weight (adjusted OR 1.37, 95% CI 1.12-1.69) and multiple birth (1.89, 1.24-2.86). These associations were similar for ALL and stronger for leukemia at ages 0-4 years. For AML, we observed an increased risk for higher birth order (3.08, 0.43-22.03 for fourth or later born children). We found no associations with other perinatal characteristics. CONCLUSION: This register-based case-control study adds to the existing evidence of a positive association between high birth weight and risk of childhood leukemia. Furthermore, it suggests children from multiple births are at an increased risk of leukemia.

Validation of questionnaire-reported chest wall abnormalities with a telephone interview in Swiss childhood cancer survivors.

BACKGROUND: Chest wall abnormalities are a poorly studied complication after treatment for childhood cancer. Chest wall abnormalities are not well-described in the literature, and little is known on the impact on daily life of survivors. METHODS: We investigated prevalence and risk factors of chest wall abnormalities in childhood cancer survivors in a nationwide, population-based cohort study (Swiss Childhood Cancer Survivor Study) with a questionnaire survey. We then interviewed a nested sample of survivors to validate types of chest wall abnormalities and understand their impact on the daily life of survivors. RESULTS: Forty-eight of 2382 (95%CI 2-3%) survivors reported a chest wall abnormality. Risk factors were older age at cancer diagnosis (16-20 years; OR 2.5, 95%CI 1.0-6.1), lymphoma (OR 3.8, 95%CI 1.2-11.4), and central nervous system tumors (OR 9.5, 95%CI 3.0-30.1) as underlying disease, and treatment with thoracic radiotherapy (OR 2.0, 95%CI 1.0-4.2), surgery to the chest (OR 4.5, 95%CI 1.8-11.5), or chemotherapy (OR 2.9, 95%CI 1.0-8.1). The nature of the chest wall abnormalities varied and included thoracic wall deformities (30%), deformations of the spine (5%) or both (55%), and scars (10%). Chest wall abnormalities affected daily life in two thirds (13/20) of those who reported these problems and necessitated medical attention for 15 (75%) survivors. CONCLUSION: It is important that, during follow-up care, physicians pay attention to chest wall abnormalities, which are rare late effects of cancer treatment, but can considerably affect the well-being of cancer survivors.

Busulfan-cyclophosphamide versus cyclophosphamide-busulfan as conditioning regimen before allogeneic hematopoietic cell transplantation: a prospective randomized trial.

Busulfan and cyclophosphamide (BuCy) is a frequently used myeloablative conditioning regimen for allogeneic hematopoietic cell transplantation (allo-HCT). Theoretical considerations and pharmacological data indicate that application of busulfan prior to subsequent cyclophosphamide (BuCy) may trigger liver toxicity. Reversing the order of application to cyclophosphamide-busulfan (CyBu) might be preferable, a hypothesis supported by animal data and retrospective studies. We performed a prospective randomized trial to determine impact of order of application of Bu and Cy before allo-HCT in 70 patients with hematological malignancy, 33 patients received BuCy and 37 CyBu for conditioning. In the short term, there were minimal differences in liver toxicity favoring CyBu over BuCy, significant only for alanine amino transferase at day 30 (p = 0.03). With longer follow-up at 4 years, non-relapse mortality (6% versus 27%, p = 0.05) was lower and survival (63% versus 43%, p = 0.06) was higher with CyBu compared to BuCy. Other outcomes, such as engraftment (p = 0.21), acute and chronic graft-versus-host disease (p = 0.40; 0.36), and relapse (p = 0.79), were similar in both groups. We prospectively show evidence that the order of application of Cy and Bu in myeloablative conditioning in allo-HCT patients has impact on outcome.

Predictors for participation in DNA self-sampling of childhood cancer survivors in Switzerland.

BACKGROUND: Research on germline genetic variants relies on enough eligible participants which is difficult to achieve for rare diseases such as childhood cancer. With self-collection kits, participants can contribute genetic samples conveniently from their home. Demographic and clinical factors were identified previously that influenced participation in mailed self-collection. People with pre-existing heritable diagnoses might participate differently in germline DNA collection which might render sampling biased in this group. In this nationwide cross-sectional study, we analysed predictive factors of participation in DNA self-collection including heritable diagnoses. METHODS: We identified childhood cancer survivors from the Swiss Childhood Cancer Registry for invitation to germline DNA self-sampling in September 2019. Participants received saliva sampling kits by postal mail at their home, were asked to fill them, sign an informed consent, and send them back by mail. Two reminders were sent to non-participants by mail. We compared demographic, clinical, and treatment information of participants with non-participants using univariable and multivariable logistic regression models. RESULTS: We invited 928 childhood cancer survivors in Switzerland with a median age of 26.5 years (interquartile range 19-37), of which 463 (50%) participated. After the initial send out of the sampling kit, 291 (63%) had participated, while reminder letters led to 172 additional participants (37%). Foreign nationality (odds ratio [OR] 0.5; 95%-confidence interval [CI] 0.4-0.7), survivors aged 30-39 years at study versus other age groups (OR 0.5; CI 0.4-0.8), and survivors with a known cancer predisposition syndrome (OR 0.5; CI 0.3-1.0) were less likely to participate in germline DNA collection. Survivors with a second primary neoplasm (OR 1.9; CI 1.0-3.8) or those living in a French or Italian speaking region (OR 1.3; CI 1.0-1.8) tended to participate more. CONCLUSIONS: We showed that half of childhood cancer survivors participated in germline DNA self-sampling relying completely on mailing of sample kits. Written reminders increased the response by about one third. More targeted recruitment strategies may be advocated for people of foreign nationality, aged 30-39 years, and those with cancer predisposition syndromes. Perceptions of genetic research and potential barriers to participation of survivors need to be better understood. TRIAL REGISTRATION: Biobank: https://directory.bbmri-eric.eu/#/collection/bbmri-eric:ID:CH_HopitauxUniversitairesGeneve:collection:CH_BaHOP Research project : Clinicaltrials.gov: NCT04702321 .

Predicting fever in neutropenia with safety-relevant events in children undergoing chemotherapy for cancer: The prospective multicenter SPOG 2015 FN Definition Study.

BACKGROUND: Fever in neutropenia (FN) remains a frequent complication in pediatric patients undergoing chemotherapy for cancer. Preventive strategies, like primary antibiotic prophylaxis, need to be evidence-based. PROCEDURE: Data on pediatric patients with any malignancy from the prospective multicenter SPOG 2015 FN Definition Study (NCT02324231) were analyzed. A score predicting the risk to develop FN with safety-relevant events (SRE; bacteremia, severe sepsis, intensive care unit admission, death) was developed using multivariate mixed Poisson regression. Its predictive performance was assessed by internal cross-validation and compared with the performance of published rules. RESULTS: In 238 patients, 318 FN episodes were recorded, including 53 (17%) with bacteremia and 68 (21%) with SRE. The risk-prediction score used three variables: chemotherapy intensity, defined according to the expected duration of severe neutropenia, time since diagnosis, and type of malignancy. Its cross-validated performance, assessed by the time needed to cover (TNC) one event, exceeded the performance of published rules. A clinically useful score threshold of ≥11 resulted in 2.3% time at risk and 4.1 months TNC. Using external information on efficacy and timing of intermittent antibiotic prophylaxis, 4.3 months of prophylaxis were needed to prevent one FN with bacteremia, and 5.2 months to prevent one FN with SRE, using a threshold of ≥11. CONCLUSIONS: This score, based on three routinely accessible characteristics, accurately identifies pediatric patients at risk to develop FN with SRE during chemotherapy. The score can help to design clinical decision rules on targeted primary antibiotic prophylaxis and corresponding efficacy studies.

Pediatric Acute B-Cell Lymphoblastic Leukemia Developing Following Recent SARS-CoV-2 Infection.

Coronavirus disease-2019 in children has been linked to various clinical presentation, from paucisymptomatic cutaneous eruptions, to multisystemic inflammatory syndrome. We report the case of an 8-year-old boy who presented with persistent fever and pancytopenia, associated to a skin rash. An extensive etiological workup showed a positive serology for severe acute respiratory syndrome coronavirus 2 and Epstein-Barr virus. A few weeks later, type B acute lymphocytic leukemia was diagnosed. This case underlines the polymorphic appearance of coronavirus disease-2019 and the need for critical appraisal.

Is Busulfan Clearance Different in Patients With Sickle Cell Disease? Let's Clear Up That Case With Some Controls.

In busulfan-based conditioning regimen for hematopoietic stem cell transplantation in children, accurate a priori determination of the first dose is important because of its narrow therapeutic window. Sickle cell disease (SCD) influences pharmacokinetics of the commonly used drugs by affecting organs responsible for drug metabolism and elimination. This pharmacokinetics study assesses the influence of SCD on the metabolic pathway of busulfan that is mainly metabolized in the liver. In this retrospective cross-sectional case-control study, 16 patients with SCD were matched to 50 patients without SCD on known busulfan clearance's covariates (glutathione-S-transferase alpha1 polymorphisms, age, weight). Clearance of the first dose of busulfan was not significantly different independently of genetic or anthropometric factors in patients with or without SCD.

Busulfan Pharmacokinetics in Adenosine Deaminase-Deficient Severe Combined Immunodeficiency Gene Therapy.

The pharmacokinetics of low-dose busulfan (BU) were investigated as a nonmyeloablative conditioning regimen for autologous gene therapy (GT) in pediatric subjects with adenosine deaminase-deficient severe combined immunodeficiency disease (ADA SCID). In 3 successive clinical trials, which included either γ-retroviral (γ-RV) or lentiviral (LV) vectors, subjects were conditioned with BU using different dosing nomograms. The first cohort received BU doses based on body surface area (BSA), the second cohort received doses based on actual body weight (ABW), and in the third cohort, therapeutic drug monitoring (TDM) was used to target a specific area under the concentration-time curve (AUC). Neither BSA-based nor ABW-based dosing achieved a consistent cumulative BU AUC; in contrast, TDM-based dosing led to more consistent AUC. BU clearance increased as subject age increased from birth to 18 months. However, weight and age alone were insufficient to accurately predict the dose that would consistently achieve a target AUC. Furthermore, various clinical, laboratory, and genetic factors (eg, genotypes for glutathione-S-transferase isozymes known to participate in BU metabolism) were analyzed, but no single finding predicted subjects with rapid versus slow clearance. Analysis of BU AUC and the postengraftment vector copy number (VCN) in granulocytes, a surrogate marker of the level of engrafted gene-modified hematopoietic stem and progenitor cells (HSPCs), demonstrated gene marking at levels sufficient for therapeutic benefit in the subjects who had achieved the target BU AUC. Although many factors determine the ultimate engraftment following GT, this work demonstrates that the BU AUC correlated with the eventual level of engrafted gene-modified HSPCs within a vector group (γ-RV versus LV), with significantly higher levels of granulocyte VCN in the recipients of LV-modified grafts compared to recipients of γ-RV-transduced grafts. Taken together, these findings provide insight into low-dose BU pharmacokinetics in the unique setting of autologous GT for ADA SCID, and these dosing principles may be applied to future GT trials using low-dose BU to open the bone marrow niche.

Genetic Susceptibility to Hepatic Sinusoidal Obstruction Syndrome in Pediatric Patients Undergoing Hematopoietic Stem Cell Transplantation.

Sinusoidal obstruction syndrome (SOS) is a well-recognized and potentially life-threatening complication of hematopoietic stem cell transplantation (HSCT). SOS arises from endothelial cell damage and hepatocellular injury mostly due to the transplantation conditioning regimens but also to other patient, disease, and treatment-related factors. Understanding risk factors associated with the development of SOS is critical for early initiation of treatment or prophylaxis. The knowledge about genetic contribution is limited; few studies investigated so far selected a set of genes. To get more comprehensive insight in the genetic component, we performed an exome-wide association study using genetic variants derived from whole-exome sequencing. The analyses were performed in a discovery cohort composed of 87 pediatric patients undergoing HSCT following a busulfan-containing conditioning regimen. Eight lead single-nucleotide polymorphisms (SNPs) were identified after correction for multiple testing and subsequently analyzed in a validation cohort (n = 182). Three SNPs were successfully replicated, including rs17146905 (P = .001), rs16931326 (P = .04), and rs2289971 (P = .03), located respectively in the UGT2B10, BHLHE22, and KIAA1715 genes. UGT2B10 and KIAA1715 were retained in a multivariable model while controlling for nongenetic covariates and previously identified risk variants in the GSTA1 promoter. The modulation of associations by conditioning regimens was noted; KIAA1715 was dependent on the intensity of the conditioning regimen, whereas the effect of UGT2B10 was equally applicable to all of them. Combined effect of associated loci was also observed (P = .00006) with a genotype-related SOS risk of 9.8. To our knowledge, this is the first study addressing the genetic component of SOS at an exome-wide level and identifying novel genetic variations conferring a higher risk of SOS, which might be useful for personalized prevention and treatment strategies.

Outcome of children relapsing after first allogeneic haematopoietic stem cell transplantation for acute myeloid leukaemia: a retrospective I-BFM analysis of 333 children.

Outcome of 333 children with acute myeloid leukaemia relapsing after a first allogeneic haematopoietic stem cell transplantation was analyzed. Four-year probability of overall survival (4y-pOS) was 14%. 4y-pOS for 122 children receiving a second haematopoietic stem cell transplantation was 31% and 3% for those that did not (P = <0·0001). Achievement of a subsequent remission impacted survival (P = <0·0001). For patients receiving a second transplant survival with or without achieving a subsequent remission was comparable. Graft source (bone marrow vs. peripheral blood stem cells, P = 0·046) and donor choice (matched family vs. matched unrelated donor, P = 0·029) positively impacted survival after relapse. Disease recurrence and non-relapse mortality at four years reached 45% and 22%.

Comparing Dried Blood Spots and Plasma Concentrations for Busulfan Therapeutic Drug Monitoring in Children.

BACKGROUND: Busulfan (Bu) is one of the conditioning regimen components for pediatric hematopoietic stem cell transplantation. Bu therapeutic drug monitoring (TDM) is essential for a successful treatment outcome and toxicity evasion. Dried blood spot (DBS) sampling is a rapid and simple method for Bu TDM, compared with conventional plasma sampling. This study evaluated the feasibility of using the DBS method for Bu TDM. The hematocrit (Hct) and conditioning day were also examined for their impact on the DBS method's performance. METHODS: Venous blood collected from 6 healthy volunteers was diluted, using their plasma into 4 samples of varying Hct values. Each sample was spiked with Bu calibrators (300, 600, and 1400 ng/mL), prepared using DBS and dried plasma spot (DPS) sampling and analyzed using a validated liquid-chromatography tandem-mass spectrometry method. Clinical blood samples (n = 153) from pediatric patients (n = 15) treated with Bu (mainly from doses 1, 2, 5, and 9) were used to prepare paired volumetric DBS and DPS samples. A Bland-Altman plot and Deming regression were used to define the agreement between the paired DBS and DPS measurements. Passing-Bablok regression analyses investigated the effects of Hct and conditioning day on the linearity between both methods. RESULTS: In vitro analyses showed good agreement between DBS and DPS measurements, with a mean difference of -5.4% and a 95% confidence interval on the limits of agreement of -15.3% to 4.6%. Clinical samples showed good correlation (Pearson correlation coefficient = 0.96; slope = 1.00) between the DBS and DPS methods. The DBS method met the clinical acceptance limits for clinical samples, with a bias <±20%. Bland-Altman plots showed good agreement, with only 5.8% of paired measurements exceeding the limits of agreement (±1.96 SD), although within its 95% confidence interval. Hct observations ranged from 21.7% to 34.7% and did not affect Bu concentrations measured from DBS in either the in vitro or in vivo studies. CONCLUSIONS: These results show that DBS is a useful method for Bu TDM, provided samples are analyzed on the collection day. DBS sampling offers advantages over traditional plasma sampling in infants and younger children because only small volumes of blood are required.

The importance of age as prognostic factor for the outcome of patients with hepatoblastoma: Analysis from the Children's Hepatic tumors International Collaboration (CHIC) database.

PURPOSE: Treatment outcomes for hepatoblastoma have improved markedly in the contemporary treatment era, principally due to therapy intensification, with overall survival increasing from 35% in the 1970s to 90% at present. Unfortunately, these advancements are accompanied by an increased incidence of toxicities. A detailed analysis of age as a prognostic factor may support individualized risk-based therapy stratification. METHODS: We evaluated 1605 patients with hepatoblastoma included in the CHIC database to assess the relationship between event-free survival (EFS) and age at diagnosis. Further analysis included the age distribution of additional risk factors and the interaction of age with other known prognostic factors. RESULTS: Risk for an event increases progressively with increasing age at diagnosis. This pattern could not be attributed to the differential distribution of other known risk factors across age. Newborns and infants are not at increased risk of treatment failure. The interaction between age and other adverse risk factors demonstrates an attenuation of prognostic relevance with increasing age in the following categories: metastatic disease, AFP < 100 ng/mL, and tumor rupture. CONCLUSION: Risk for an event increased with advancing age at diagnosis. Increased age attenuates the prognostic influence of metastatic disease, low AFP, and tumor rupture. Age could be used to modify recommended chemotherapy intensity.