Proactive systematic hemophilia carrier screening: a step toward gender equity in hemophilia care.

ABSTRACT: Despite numerous efforts to raise awareness, many hemophilia carriers and female persons with hemophilia (PWHs) remain undiagnosed. Between May 2021 and April 2023, we identified potential and obligate carriers of hemophilia A (HA) and hemophilia B (HB) by updating pedigrees of all PWHs followed at the Cliniques universitaires Saint-Luc, Brussels. Retrospective data on previously screened females were collected, including bleeding history, coagulation factor levels, and testing for the proband's pathogenic variant. In addition, a proactive approach involved sending 125 invitation letters to unscreened or incompletely screened individuals, through related PWHs. In pedigrees of 287 male PWHs (226 HA and 61 HB) and 7 female index patients from 236 families (184 HA and 52 HB), a total of 900 female individuals were identified. Of those, 454 were obligate and/or genetically proven carriers, and 118 were noncarriers. Genetic testing was conducted in 133 obligate, 237 potential, and 4 sporadic carriers, with 190 obligate and 328 potential carriers remaining untested. Among carriers with known factor levels (261/454), 42 HA (23.0%) and 23 HB carriers (29.5%) had a factor level <40 IU/dL. Carriers with a factor deficiency were screened on average 6 years earlier than other females (P = .034). This study, to our knowledge, represents the first systematic effort to identify potential carriers among families of all PWHs within a single center, emphasizing the challenges in comprehensive screening for female individuals genetically linked to one or more PWHs. Such initiatives are vital for achieving equitable access to hemophilia care for all potentially affected individuals, irrespective of gender. This trial was registered at www.ClinicalTrials.gov as #NCT05217992.

Acute myeloid leukemia stem cell signature gene EMP1 is not an eligible therapeutic target.

BACKGROUND: Relapse in pediatric acute myeloid leukemia (pedAML) patients is known to be associated with residual leukemic stem cells (LSC). We have previously shown that epithelial membrane protein 1 (EMP1) is significantly overexpressed in LSC compared to hematological stem cell fractions. EMP1 was also documented as part of the 17-gene stemness score and a 6-membrane protein gene score, both correlating high EMP1 expression with worse overall survival. However, its potential as a therapeutic target in pedAML is still unexplored. METHODS: Association analyses of EMP1 expression with clinical and molecular AML characteristics were performed. Expression of EMP1 was evaluated in pedAML and cord blood samples. Expression in normal blood cells and tissues was evaluated by flow cytometry and immunohistochemistry, respectively. RESULTS: In silico analyses showed variable mRNA expression of EMP1 in multiple pedAML datasets, and a significant correlation between high EMP1 transcript levels and the presence of inv(16). Flow cytometry showed overexpression of EMP1 in pedAML samples, as well as expression in normal blood subsets. Importantly, immunohistochemistry revealed EMP1 expression in multiple normal tissues. CONCLUSION: Although EMP1 presents as an interesting membrane-associated target in pedAML, its abundant expression in normal blood cells and tissues will impede it from further exploration as a therapeutic target. IMPACT: EMP1 is highly expressed in multiple cancer types, but expression in acute myeloid leukemia (AML) and normal tissues is unexplored. As EMP1 is investigated in other cancer types, expression in normal tissues and blood cells is relevant in predicting the success of EMP1-targeted therapies. In this study, we showed expression of EMP1 in multiple tissues, predicting high on-target off-tumor toxicity, which will warn other researchers of possible toxicities when generating EMP1-targeted therapy. Finally, we showed that high EMP1 expression is associated with better overall survival of pediatric AML patients, reducing the need for EMP1-targeted therapy.

Clinical and biological landscape of constitutional mismatch-repair deficiency syndrome: an International Replication Repair Deficiency Consortium cohort study.

BACKGROUND: Constitutional mismatch repair deficiency (CMMRD) syndrome is a rare and aggressive cancer predisposition syndrome. Because a scarcity of data on this condition contributes to management challenges and poor outcomes, we aimed to describe the clinical spectrum, cancer biology, and impact of genetics on patient survival in CMMRD. METHODS: In this cohort study, we collected cross-sectional and longitudinal data on all patients with CMMRD, with no age limits, registered with the International Replication Repair Deficiency Consortium (IRRDC) across more than 50 countries. Clinical data were extracted from the IRRDC database, medical records, and physician-completed case record forms. The primary objective was to describe the clinical features, cancer spectrum, and biology of the condition. Secondary objectives included estimations of cancer incidence and of the impact of the specific mismatch-repair gene and genotype on cancer onset and survival, including after cancer surveillance and immunotherapy interventions. FINDINGS: We analysed data from 201 patients (103 males, 98 females) enrolled between June 5, 2007 and Sept 9, 2022. Median age at diagnosis of CMMRD or a related cancer was 8·9 years (IQR 5·9-12·6), and median follow-up from diagnosis was 7·2 years (3·6-14·8). Endogamy among minorities and closed communities contributed to high homozygosity within countries with low consanguinity. Frequent dermatological manifestations (117 [93%] of 126 patients with complete data) led to a clinical overlap with neurofibromatosis type 1 (35 [28%] of 126). 339 cancers were reported in 194 (97%) of 201 patients. The cumulative cancer incidence by age 18 years was 90% (95% CI 80-99). Median time between cancer diagnoses for patients with more than one cancer was 1·9 years (IQR 0·8-3·9). Neoplasms developed in 15 organs and included early-onset adult cancers. CNS tumours were the most frequent (173 [51%] cancers), followed by gastrointestinal (75 [22%]), haematological (61 [18%]), and other cancer types (30 [9%]). Patients with CNS tumours had the poorest overall survival rates (39% [95% CI 30-52] at 10 years from diagnosis; log-rank p<0·0001 across four cancer types), followed by those with haematological cancers (67% [55-82]), gastrointestinal cancers (89% [81-97]), and other solid tumours (96% [88-100]). All cancers showed high mutation and microsatellite indel burdens, and pathognomonic mutational signatures. MLH1 or MSH2 variants caused earlier cancer onset than PMS2 or MSH6 variants, and inferior survival (overall survival at age 15 years 63% [95% CI 55-73] for PMS2, 49% [35-68] for MSH6, 19% [6-66] for MLH1, and 0% for MSH2; p<0·0001). Frameshift or truncating variants within the same gene caused earlier cancers and inferior outcomes compared with missense variants (p<0·0001). The greater deleterious effects of MLH1 and MSH2 variants as compared with PMS2 and MSH6 variants persisted despite overall improvements in survival after surveillance or immune checkpoint inhibitor interventions. INTERPRETATION: The very high cancer burden and unique genomic landscape of CMMRD highlight the benefit of comprehensive assays in timely diagnosis and precision approaches toward surveillance and immunotherapy. These data will guide the clinical management of children and patients who survive into adulthood with CMMRD. FUNDING: The Canadian Institutes for Health Research, Stand Up to Cancer, Children's Oncology Group National Cancer Institute Community Oncology Research Program, Canadian Cancer Society, Brain Canada, The V Foundation for Cancer Research, BioCanRx, Harry and Agnieszka Hall, Meagan's Walk, BRAINchild Canada, The LivWise Foundation, St Baldrick Foundation, Hold'em for Life, and Garron Family Cancer Center.

Incidence, survival, and mortality of cancer in children and young adolescents in Belgium and the Netherlands in 2004-2015: A comparative population-based study.

International comparisons of cancer surveillance measures may provide insight into inequalities in registration practices, etiological factors, and treatment strategies. This study aimed to compare incidence, survival, and mortality of cancer in children and young adolescents between Belgium and the Netherlands. All children (0-14 years) and young adolescents (15-17 years) diagnosed with cancer between 2004 and 2015 were selected from the population-based cancer registries of Belgium (N = 4739) and the Netherlands (N = 7322). Differences in incidence and mortality were expressed as standardized rate ratios (SRR; BE/NL). Five-year observed survival was calculated using the Kaplan-Meier method. During 2004-2015, the overall cancer incidence among children and young adolescents was similar in both countries. Incidence of neuroblastoma was significantly higher in Belgian children (2010-2015: SRR = 1.3, 95% CI 1.0-1.6). Five-year survival of all malignant cancers was comparable in 2010-2015, exceeding 80% in both age groups. Remarkable differences in survival existed in children for malignant central nervous system (CNS) tumors in 2004-2009 (BE = 62%, NL = 45%), for acute myeloid leukemia (BE = 68%, NL = 78%) and rhabdomyosarcomas (BE = 60%, NL = 79%) in 2010-2015, and for neuroblastoma in both periods (2004-2009: BE = 76%, NL = 64%; 2010-2015: BE = 82%, NL = 64%). Overall cancer mortality in children decreased by approximately 3 percent-points annually in both countries, but was slightly lower in Belgium in 2004-2009 (SRR = 0.9, 95% CI 0.7-1.0). Despite differences for specific cancer types, overall cancer incidence, survival, and mortality were comparable between Dutch and Belgian children and young adolescents in 2010-2015. Variability in screening, diagnosis, and registration practices probably explains the observed differences in incidence and survival of neuroblastoma and malignant CNS tumors.

Combined Immunotherapy Improves Outcome for Replication-Repair-Deficient (RRD) High-Grade Glioma Failing Anti-PD-1 Monotherapy: A Report from the International RRD Consortium.

Immune checkpoint inhibition (ICI) is effective for replication-repair-deficient, high-grade gliomas (RRD-HGG). The clinical/biological impact of immune-directed approaches after failing ICI monotherapy is unknown. We performed an international study on 75 patients treated with anti-PD-1; 20 are progression free (median follow-up, 3.7 years). After second progression/recurrence (n = 55), continuing ICI-based salvage prolonged survival to 11.6 months (n = 38; P < 0.001), particularly for those with extreme mutation burden (P = 0.03). Delayed, sustained responses were observed, associated with changes in mutational spectra and the immune microenvironment. Response to reirradiation was explained by an absence of deleterious postradiation indel signatures (ID8). CTLA4 expression increased over time, and subsequent CTLA4 inhibition resulted in response/stable disease in 75%. RAS-MAPK-pathway inhibition led to the reinvigoration of peripheral immune and radiologic responses. Local (flare) and systemic immune adverse events were frequent (biallelic mismatch-repair deficiency > Lynch syndrome). We provide a mechanistic rationale for the sustained benefit in RRD-HGG from immune-directed/synergistic salvage therapies. Future approaches need to be tailored to patient and tumor biology. SIGNIFICANCE: Hypermutant RRD-HGG are susceptible to checkpoint inhibitors beyond initial progression, leading to improved survival when reirradiation and synergistic immune/targeted agents are added. This is driven by their unique biological and immune properties, which evolve over time. Future research should focus on combinatorial regimens that increase patient survival while limiting immune toxicity. This article is featured in Selected Articles from This Issue, p. 201.

Extradural malignant rhabdoid tumor of the spine in children: A case-based review.

BACKGROUND: Extradural malignant rhabdoid tumors of the spine are highly malignant and invasive tumors (WHO grade IV) with poor prognosis, most frequently occurring in young children before 2 years of age. Pain and motor deficit are the most common presenting signs. CASE DESCRIPTION: We report a case of a 2-year-old girl presenting with axial ataxia and paraparesis related to an extradural malignant rhabdoid tumor causing posterior thoracic spinal cord compression (D3-D6). She underwent two near-total removal of the tumor, adjuvant chemotherapy according to the Eu-Rhab protocol and proton beam therapy. She then developed multiple cranial nerve paresis (meningeal carcinomatosis) after 4 cycles of chemotherapy and died at 4.32 months of follow-up. DISCUSSION AND CONCLUSION: The role of the PET scan was essential to guide us to remove a residue, while two concomitant spinal MRIs were considered negative. We reviewed the 16 cases reported in the literature. Multiple surgeries and radiotherapy seem to be correlated with longer survival. No child younger than 2 years old had a documented survival higher than 4.32 months.

Preliminary results of the European multicentric phase III trial regarding sirolimus in slow-flow vascular malformations.

BACKGROUNDSlow-flow vascular malformations frequently harbor activating mutations in the PI3K/AKT/mTOR cascade. Phase II trials pinpointed sirolimus effectiveness as a drug therapy. Efficacy and safety of sirolimus thus need to be evaluated in large prospective phase III trials.METHODSThe Vascular Anomaly-Sirolimus-Europe (VASE) trial, initiated in 2016, is a large multicentric prospective phase III trial (EudraCT 2015-001703-32), which evaluates efficacy and safety of sirolimus for 2 years in pediatric and adult patients with symptomatic slow-flow vascular malformations. In this interim analysis, we studied all patients enrolled up to October 2021 who received sirolimus for 12 or more months or who prematurely stopped the treatment.RESULTSThirty-one pediatric and 101 adult patients were included in this analysis; 107 completed 12 or more months of sirolimus, including 61 who were treated for the whole 2-year period. Sirolimus resulted in a clinical improvement in 85% of patients. The efficacy appeared within the first month for the majority of them. Grade 3-4 adverse events were observed in 24 (18%) patients; all resolved after treatment interruption/arrest. Sirolimus increased feasibility of surgery or sclerotherapy in 20 (15%) patients initially deemed unsuitable for intervention. Among the 61 patients who completed the 2-year treatment, 33 (54%) reported a recurrence of symptoms after a median follow-up of 13 months after sirolimus arrest. While there was no difference in efficacy, clinical improvement was faster but subsided more rapidly in PIK3CA-mutated (n = 24) compared with TIE2-mutated (n = 19) patients.CONCLUSIONSirolimus has a high efficacy and good tolerance in treatment of slow-flow vascular malformations in children and adults.TRIAL REGISTRATIONClinicalTrials.gov NCT02638389 and EudraCT 2015-001703-32.FUNDINGThe Fonds de la Recherche Scientifique (FNRS grants T.0247.19, P.C005.22, T.0146.16, and P.C013.20), the Fund Generet managed by the King Baudouin Foundation (grant 2018-J1810250-211305), the Walloon Region through the FRFS-WELBIO strategic research programme (WELBIO-CR-2019C-06), the MSCA-ITN network V.A. Cure no. 814316, the Leducq Foundation Networks of Excellence Program grant "ReVAMP" (LFCR grant 21CVD03), the European Union's Horizon 2020 research and innovation programme under grant agreement no. 874708 (Theralymph), the Swiss National Science Foundation under the Sinergia project no. CRSII5_193694, and a Pierre M. fellowship.

Building a haemophilia-specific navigator in Epic® Electronic Health Records: Single-centre preliminary experience.

INTRODUCTION: With the increasing complexity of haemophilia care and the advent of numerous therapeutic innovations, there is an unmet need for documentation and data collection tools tailored to people with haemophilia (PwH). To date, no fully integrated haemophilia-specific electronic health record (EHR) has been described in the literature. AIM: To evaluate the feasibility of integrating a haemophilia-specific navigator into the Epic EHR. METHODS: Based on clinical experience and registry datasets, we identified key variables describing both PwH and carriers of haemophilia. These were then incorporated into a REDCap database, which served as a starting point for the development of a comprehensive haemophilia flowsheet. We built a dedicated haemophilia navigator within Epic that includes a flowsheet featuring up to 212 variables, as well as customised note templates and patient lists integrating data from the haemophilia flowsheet. RESULTS: It was feasible to develop a haemophilia navigator within Epic over the course of 12 months. The navigator's flowsheet enables systematic and comprehensive clinical assessment of PwH and carriers, while customised patient lists provide a quick summary of each patient's profile to the haemophilia treatment centre staff and highlight issues that require an intervention. In our clinical practice, patients actively participated in the new documentation process and responded positively to the navigator. CONCLUSION: Adapting EHRs to the needs of PwH and carriers promotes holistic care for this population and provides an opportunity for patient empowerment. Such haemophilia-specific EHRs are expected to promote standardisation of care and facilitate the collection of registry data on a national and international level.

LOGGIC Core BioClinical Data Bank: Added clinical value of RNA-Seq in an international molecular diagnostic registry for pediatric low-grade glioma patients.

BACKGROUND: The international, multicenter registry LOGGIC Core BioClinical Data Bank aims to enhance the understanding of tumor biology in pediatric low-grade glioma (pLGG) and provide clinical and molecular data to support treatment decisions and interventional trial participation. Hence, the question arises whether implementation of RNA sequencing (RNA-Seq) using fresh frozen (FrFr) tumor tissue in addition to gene panel and DNA methylation analysis improves diagnostic accuracy and provides additional clinical benefit. METHODS: Analysis of patients aged 0 to 21 years, enrolled in Germany between April 2019 and February 2021, and for whom FrFr tissue was available. Central reference histopathology, immunohistochemistry, 850k DNA methylation analysis, gene panel sequencing, and RNA-Seq were performed. RESULTS: FrFr tissue was available in 178/379 enrolled cases. RNA-Seq was performed on 125 of these samples. We confirmed KIAA1549::BRAF-fusion (n = 71), BRAF V600E-mutation (n = 12), and alterations in FGFR1 (n = 14) as the most frequent alterations, among other common molecular drivers (n = 12). N = 16 cases (13%) presented rare gene fusions (eg, TPM3::NTRK1, EWSR1::VGLL1, SH3PXD2A::HTRA1, PDGFB::LRP1, GOPC::ROS1). In n = 27 cases (22%), RNA-Seq detected a driver alteration not otherwise identified (22/27 actionable). The rate of driver alteration detection was hereby increased from 75% to 97%. Furthermore, FGFR1 internal tandem duplications (n = 6) were only detected by RNA-Seq using current bioinformatics pipelines, leading to a change in analysis protocols. CONCLUSIONS: The addition of RNA-Seq to current diagnostic methods improves diagnostic accuracy, making precision oncology treatments (MEKi/RAFi/ERKi/NTRKi/FGFRi/ROSi) more accessible. We propose to include RNA-Seq as part of routine diagnostics for all pLGG patients, especially when no common pLGG alteration was identified.

Recombinant factor VIII Fc fusion protein for first-time immune tolerance induction: final results of the verITI-8 study.

Inhibitor development remains a major challenge in factor VIII (FVIII) replacement therapy. verITI-8 is the first prospective study of a recombinant FVIII Fc fusion protein (rFVIIIFc; efmoroctocog alfa) for first-time immune tolerance induction (ITI) in males with severe hemophilia A and high-titer inhibitors (historical peak ≥5 Bethesda units [BU]/mL). In this single-arm, open-label, multicenter study, screening was followed by ITI (rFVIIIFc 200 IU/kg per day until tolerization or maximum of 48 weeks). Those who achieved ITI success entered a tapering period, returning to standard prophylaxis, and then entered follow-up. Primary end point was time to tolerization with rFVIIIFc defined by inhibitor titer <0.6 BU/mL, incremental recovery (IR) ≥66% of expected IR (IR ≥1.32 IU/dL per IU/kg), and half-life (t½) ≥7 hours within 48 weeks. Sixteen patients received ≥1 rFVIIIFc dose. Twelve (75%), 11 (69%), and 10 patients (63%), respectively, achieved negative inhibitor titers, an IR ≥66%, and a t½ ≥7 hours (ie, tolerance) within 48 weeks. Median times in weeks to achieve these markers of success were 7.4 (interquartile range [IQR], 2.2-17.8), 6.8 (IQR, 5.4-22.4), and 11.7 (IQR, 9.8-26.2), respectively. All patients experienced ≥1 treatment-emergent adverse event (TEAE), and 1 reported ≥1 related TEAE (injection site pain). Nine patients experienced ≥1 treatment-emergent serious AE. No thrombotic events, discontinuations because of AEs, or deaths were reported during the study. As the first extended half-life rFVIII with prospective data in ITI, rFVIIIFc offered short time to tolerization with durable responses in almost two-thirds of patients and was well tolerated. This trial was registered at www.clinicaltrials.gov as #NCT03093480.

Genomic Microsatellite Signatures Identify Germline Mismatch Repair Deficiency and Risk of Cancer Onset.

PURPOSE: Diagnosis of Mismatch Repair Deficiency (MMRD) is crucial for tumor management and early detection in patients with the cancer predisposition syndrome constitutional mismatch repair deficiency (CMMRD). Current diagnostic tools are cumbersome and inconsistent both in childhood cancers and in determining germline MMRD. PATIENTS AND METHODS: We developed and analyzed a functional Low-pass Genomic Instability Characterization (LOGIC) assay to detect MMRD. The diagnostic performance of LOGIC was compared with that of current established assays including tumor mutational burden, immunohistochemistry, and the microsatellite instability panel. LOGIC was then applied to various normal tissues of patients with CMMRD with comprehensive clinical data including age of cancer presentation. RESULTS: Overall, LOGIC was 100% sensitive and specific in detecting MMRD in childhood cancers (N = 376). It was more sensitive than the microsatellite instability panel (14%, P = 4.3 × 10-12), immunohistochemistry (86%, P = 4.6 × 10-3), or tumor mutational burden (80%, P = 9.1 × 10-4). LOGIC was able to distinguish CMMRD from other cancer predisposition syndromes using blood and saliva DNA (P < .0001, n = 277). In normal cells, MMRDness scores differed between tissues (GI > blood > brain), increased over time in the same individual, and revealed genotype-phenotype associations within the mismatch repair genes. Importantly, increased MMRDness score was associated with younger age of first cancer presentation in individuals with CMMRD (P = 2.2 × 10-5). CONCLUSION: LOGIC was a robust tool for the diagnosis of MMRD in multiple cancer types and in normal tissues. LOGIC may inform therapeutic cancer decisions, provide rapid diagnosis of germline MMRD, and support tailored surveillance for individuals with CMMRD.

A case report of sirolimus use in early fetal management of lymphatic malformation.

Sirolimus, by targeting the mammalian target of rapamycin (mTOR) pathway, has demonstrated efficacy on lymphatic malformations (LMs) in adults and neonates. The current hypothesis is that the earlier the lesion is treated, the better it responds. This has prompted the idea that sirolimus administration might be efficacious to treat fetal LMs as well. Here we report a successful management of a cervicofacial fetal LM with sirolimus taken orally by the mother from the 22nd week of pregnancy until 2 weeks before planned delivery. Repeated cordocentesis recorded a 30% transplacental crossing of sirolimus. Continuation of sirolimus after birth allowed resection of the residual mass. We have followed the physical and neurological evolution of the child for 6 years since the fetal administration of sirolimus. We conclude that early administration of sirolimus during pregnancy with maternal serum monitoring may be proposed to high-risk fetal LMs in selected cases.

Deciphering the Non-Coding RNA Landscape of Pediatric Acute Myeloid Leukemia.

Pediatric acute myeloid leukemia (pedAML) is a heterogeneous blood cancer that affects children. Although survival rates have significantly improved over the past few decades, 20-30% of children will succumb due to treatment-related toxicity or relapse. The molecular characterization of the leukemic stem cell, shown to be responsible for relapse, is needed to improve treatment options and survival. Recently, it has become clear that non-coding RNAs, including long non-coding RNAs (lncRNAs) and microRNAs (miRNAs), play a role in the development of human diseases, including pediatric cancer. Nevertheless, non-coding RNA expression data in pedAML are scarce. Here, we explored lncRNA (n = 30,168) and miRNA (n = 627) expression in pedAML subpopulations (leukemic stem cells (LSCs) and leukemic blasts (L-blasts)) and their normal counterparts (hematopoietic stem cells and control myeloblasts). The potential regulatory activity of differentially expressed lncRNAs in LSCs (unique or shared with the L-blast comparison) on miRNAs was assessed. Moreover, pre-ranked gene set enrichment analyses of (anti-) correlated protein-coding genes were performed to predict the functional relevance of the differentially upregulated lncRNAs in LSCs (unique or shared with the L-blast comparison). In conclusion, this study provides a catalog of non-coding RNAs with a potential role in the pathogenesis of pedAML, paving the way for further translational research studies.

Avelumab in paediatric patients with refractory or relapsed solid tumours: dose-escalation results from an open-label, single-arm, phase 1/2 trial.

BACKGROUND: We report dose-escalation results from an open-label, phase 1/2 trial evaluating avelumab (anti-PD-L1) in paediatric patients with refractory/relapsed solid tumours. METHODS: In phase 1, patients aged < 18 years with solid (including central nervous system [CNS]) tumours for which standard therapy did not exist or had failed were enrolled in sequential cohorts of 3-6 patients. Patients received avelumab 10 or 20 mg/kg intravenously every 2 weeks. Primary endpoints were dose-limiting toxicities (DLTs) and grade ≥ 3 treatment-emergent adverse events (AEs). RESULTS: At data cut-off (27 July 2021), 21 patients aged 3-17 years had received avelumab 10 mg/kg (n = 6) or 20 mg/kg (n = 15). One patient had three events that were classified as a DLT (fatigue with hemiparesis and muscular weakness associated with pseudoprogression; 20 mg/kg cohort). Grade ≥ 3 AEs occurred in five (83%) and 11 (73%) patients in the 10 and 20 mg/kg cohorts, respectively, and were treatment-related in one patient (7%; grade 3 [DLT]) in the 20 mg/kg cohort. Avelumab exposure in paediatric patients receiving 20 mg/kg dosing, but not 10 mg/kg, was comparable or higher compared with approved adult dosing (10 mg/kg or 800 mg flat dose). No objective responses were observed. Four patients with CNS tumours (20 mg/kg cohort) achieved stable disease, which was ongoing in two patients with astrocytoma at cut-off (for 24.7 and 30.3 months). CONCLUSION: In paediatric patients with refractory/relapsed solid tumours, avelumab monotherapy showed a safety profile consistent with previous adult studies, but clinical benefits were limited.

Genomic predictors of response to PD-1 inhibition in children with germline DNA replication repair deficiency.

Cancers arising from germline DNA mismatch repair deficiency or polymerase proofreading deficiency (MMRD and PPD) in children harbour the highest mutational and microsatellite insertion-deletion (MS-indel) burden in humans. MMRD and PPD cancers are commonly lethal due to the inherent resistance to chemo-irradiation. Although immune checkpoint inhibitors (ICIs) have failed to benefit children in previous studies, we hypothesized that hypermutation caused by MMRD and PPD will improve outcomes following ICI treatment in these patients. Using an international consortium registry study, we report on the ICI treatment of 45 progressive or recurrent tumors from 38 patients. Durable objective responses were observed in most patients, culminating in a 3 year survival of 41.4%. High mutation burden predicted response for ultra-hypermutant cancers (>100 mutations per Mb) enriched for combined MMRD + PPD, while MS-indels predicted response in MMRD tumors with lower mutation burden (10-100 mutations per Mb). Furthermore, both mechanisms were associated with increased immune infiltration even in 'immunologically cold' tumors such as gliomas, contributing to the favorable response. Pseudo-progression (flare) was common and was associated with immune activation in the tumor microenvironment and systemically. Furthermore, patients with flare who continued ICI treatment achieved durable responses. This study demonstrates improved survival for patients with tumors not previously known to respond to ICI treatment, including central nervous system and synchronous cancers, and identifies the dual roles of mutation burden and MS-indels in predicting sustained response to immunotherapy.

Characterization and risk factors of hyperglycaemia during treatment of childhood hematologic malignancies.

BACKGROUND: Secondary forms of diabetes are often understudied and underdiagnosed in children and adolescents with cancer. The objectives of our cohort study were to study the incidence and risk factors for hyperglycaemia in leukaemia and lymphoma patients. METHODS: We retrospectively collected 15 years of data from paediatric patients treated for acute lymphoblastic leukaemia (ALL), Hodgkin's lymphoma (HL), and non-Hodgkin's lymphoma (NHL) immediately at cancer diagnosis. We studied risk factors for hyperglycaemia in univariate and multivariate analyses. RESULTS: Our study cohort included 267 patients corresponding to 179 patients with ALL, 48 with NHL and 40 with HL. Eighteen per cent of ALL patients (32/179) and 17% of NHL patients (8/48) developed hyperglycaemia, with more than 61% developing hyperglycaemia within the first month of treatment. No hyperglycaemia was observed in HL patients. Multivariate analysis showed the following hyperglycaemia risk factors for ALL patients: overweight or obesity (OR 3.793) and pubertal onset (OR 4.269) at cancer diagnosis, steroid-resistant disease (OR 3.445) and hematopoietic stem cell transplant (HSCT) (OR 4.754). CONCLUSION: In our cohort, 18% of patients with ALL or NHL developed early-onset hyperglycaemia after chemotherapy/radiotherapy. Patients with ALL with increased hyperglycaemia risk can be readily identified by measuring BMI and puberty stage at cancer diagnosis. Also, glucose monitoring should be reinforced when patients show steroid-resistant disease and/or require HSCT.

Clinical and Biomechanical Progression after Ankle Joint Distraction in a Young Adolescent Patient with Haemophilia.

Ankle joint distraction (AJD) has been described to be a valuable joint-sparing alternative to arthrodesis or arthroplasty; however, clinical endpoints associated to this surgical intervention are lacking. The current case report describes clinical and biomechanical outcome measures of ankle joint distraction in a 14-year-old patient with severe haemophilia A. Because of persistent and incapacitating pain and the poor response to conservative and invasive treatment options, ankle joint distraction was performed in this 14-year-old patient using an external fixator encompassing two Ilizarov full rings in the tibia and a foot ring fixed to the foot by four K-wires. State-of-the-art medical imaging and non-invasive skin marker-based 3D multi-segment foot modelling were performed in a pre- and post-operative stage. From a structural viewpoint, this AJD was a success since it improved and stabilised the osteo-cartilaginous lesions of the ankle. Biomechanical outcome measures associated with the 18-month follow-up were found to be suboptimal, showing an early plantarflexion pattern at the ankle joint during midstance and a tendency towards increased power absorption at the midfoot with peak power absorption being almost two times higher when compared to boys of the same age. From a functional viewpoint, we observed a clear reduction in the patients' physical activities until one year after AJD. Despite these functional and structural improvements, recurrent painful phenomena, including the development of a complex regional pain syndrome (CRPS) and a stress fracture of the third metatarsal bone, were observed which are probably related with the development of recurrent subchondral oedema.

Retrospective study of diffuse intrinsic pontine glioma in the Belgian population: a 25 year experience.

INTRODUCTION: Diffuse intrinsic pontine glioma is a rare disease with a high mortality. Our primary aim was to determine the incidence of this disease in Belgium. Secondly, we wanted to compare the treatment approach of Belgian pediatric oncology centres, to investigate possibilities for improvement. METHODS: We retrospectively collected and analysed data on DIPG-patients diagnosed between 1994 and 2018 and recorded in the Belgian Cancer Registry. We included patients ≤ 18 years who were followed in one of the eight Belgian pediatric oncology centres. RESULTS: We included 100 patients. Files were complete in 87 patients. We observed an increase in diagnoses with an incidence of 3.1 per 1,000,000 persons (aged 0-≤ 18) per year over the last 5 years compared to an overall incidence of 1.8. Biopsy was performed at diagnosis in 51.7% of patients. In one fifth this was study-related. Mutation analysis was known in eight patients, of which six showed the H3 K27M-mutation. 58.8% of patients received chemotherapy, without a significant survival benefit. 12.6% of patients were included in a clinical trial. Biopsy rate and the use of chemotherapy differed widely between centres. Mean OS and PFS were 10.49 and 4.87 months respectively. We observed an improved survival over time. CONCLUSIONS: Over the past 25 years, we observed an increase of new DIPG-diagnoses. Outcome in our cohort is comparable with literature findings. We demonstrate an important heterogeneity in treatment approach between different centres and limited inclusion in clinical trials. Therefore, collaboration between centres and inclusion of patients in clinical trials is much needed.

Detection of alternative lengthening of telomeres mechanism on tumor sections.

The vast majority of adult cancer cells achieve cellular immortality by activating a telomere maintenance mechanism (TMM). While this is mostly achieved by the de-silencing of hTERT telomerase gene expression, an alternative homologous recombination-based and telomerase-independent mechanism, known as ALT (Alternative Lengthening of Telomeres), is frequently activated in a subset of tumors, including paediatric cancers. Being absent from normal cells, the ALT mechanism offers interesting perspectives for new targeted cancer therapies. To date, however, the development of better translationally applicable tools for ALT detection in tumor sections is still needed. Here, using a newly derived ALT-positive cancer cell mouse xenograft model, we extensively examined how the previously known ALT markers could be used as reliable tools for ALT diagnosis in tumor sections. We found that, together with the detection of ultra-bright telomeric signals (UBS), an ALT hallmark, native telomeric FISH, that detects single-stranded C-rich telomeric DNA, provides a very sensitive and robust tool for ALT diagnosis in tissues. We applied these assays to paediatric tumor samples and readily identified three ALT-positive tumors for which the TMM was confirmed by the gold-standard C-circle amplification assay. Although the latter offers a robust assay for ALT detection in the context of research laboratories, it is more difficult to set up in histopathological laboratories and could therefore be conveniently replaced by the combination of UBS detection and native telomeric FISH.

Clinical Spectrum of Ras-Associated Autoimmune Leukoproliferative Disorder (RALD).

Ras-associated autoimmune leukoproliferative disorder (RALD) is a clinical entity initially identified in patients evaluated for an autoimmune lymphoproliferative syndrome (ALPS)-like phenotype. It remains a matter of debate whether RALD is a chronic and benign lymphoproliferative disorder or a pre-malignant condition. We report the case of a 7-year-old girl diagnosed with RALD due to somatic KRAS mutation who progressed to a juvenile myelomonocytic leukemia phenotype and finally evolved into acute myeloid leukemia. The case report prompted a literature review by a search for all RALD cases published in PubMed and Embase. We identified 27 patients with RALD. The male-to-female ratio was 1:1 and median age at disease onset was 2 years (range 3 months-36 years). Sixteen patients (59%) harbored somatic mutations in KRAS and 11 patients (41%) somatic mutations in NRAS. The most common features were splenomegaly (26/27 patients), autoimmune cytopenia (15/16 patients), monocytosis (18/24 patients), pericarditis (6 patients), and skin involvement (4 patients). Two patients went on to develop a hematopoietic malignancy. In summary, the current case documents an additional warning about the long-term risk of malignancy in RALD.