PURPOSE:Molecular biomarkers are increasingly used for risk stratification, particularly in up-front surgery settings (Children's Oncology Group trials), whereas in preoperative chemotherapy setting, the ongoing International Society of Pediatric Oncology (SIOP)-Renal Tumor Study Group-2016 UMBRELLA study aims to validate selected biomarkers for future risk-adapted treatment strategies. This systematic review summarizes all literature on the prognostic value of these biomarkers. MATERIALS AND METHODS:A systematic literature review (PubMed and Embase; up to January 2025) included studies with ≥50 de novo Wilms tumors (WTs). Eligible biomarkers included copy number variations; 1q gain, 1p and/or 16q loss of heterozygosity (LOH)/loss, 12 gain, 14q loss, 22 loss, 11p15 LOH/loss of imprinting (LOI), and structural somatic variants (TP53 [and/or 17p loss], MYCN, FBXW7, WT1, WTX, SIX1/SIX2, DROSHA, DGCR8, AMER1, CTNNB1, GPC3, MLLT1, DICER1, DIS3L2). Outcome included relapse-free survival, event-free survival (EFS), and overall survival (OS). Risk of bias was assessed with quality in prognosis studies tool. RESULTS:Low-bias multivariable/stratified analyses identified 1q gain as worse EFS and 1p and/or 16q LOH/loss as worse EFS/OS prognostic factors, in up-front nephrectomy settings. Preoperative chemotherapy settings revealed similar trends with lacking significance. TP53 and MYCN were adverse prognostic in univariate analyses. No prognostic data were available for the remaining variants. CONCLUSION:1q gain and 1p and/or 16q LOH/loss emerge as independent prognostic biomarkers in up-front nephrectomy settings. Evidence remains limited in preoperative chemotherapy settings, particularly when using SIOP-oriented treatment algorithms. Prognostic value of TP53, MYCN, and 11p15 LOH/LOI warrants further validation in both settings. This highlights the need for adequately powered prospective studies, specifically in the preoperative chemotherapy setting, to establish reliable molecular biomarkers.

Background: Second or subsequent relapses of Wilms tumour (WT) are rarely reported. We assessed the characteristics, treatments, and outcome of such patients through a retrospective international cohort study of patients treated according to recent SIOP-RTSG protocols. Methods: Patients with a second or subsequent relapse enrolled in SIOP WT 2001 and the UK-IMPORT study, and registered in the SIOP-RTSG database between 2001 and 2021 were included. Risk groups were defined per the SIOP-RTSG-2016 UMBRELLA protocol (AA-BB (second relapse after initial standard risk (AA) relapse), BB-CC (initial high risk (BB) relapse), and CC-CC (initial very high risk (CC) relapse). Five-year event-free survival (EFS) and overall survival (OS) rates were estimated using Kaplan-Meier and competing risk methods; survival between relapse risk groups was compared with log-rank testing. Findings: Among 572 patients with first relapse, 114 (20%) patients experienced a subsequent relapse. The estimated 5-year EFS and OS after second relapse were 17.7% (95% Confidence Interval (CI): 11.1-28.0%) and 22.4% (95% CI: 15.3-32.9%). In group AA-BB (n = 39) 5-year EFS and OS were 39.0% (95% CI: 25.0-60.7%) and 41.0% (95% CI: 26.8-62.8%). In group BB-CC (n = 32), 5-year EFS was 14.8% (95% CI: 6.05-36.3%) and 5year OS was 21.9% (95% CI: 10.9-44.0%). All CC-CC patients (n = 35) either died within 3 years of the second relapse or lacked adequate follow-up. Group AA-BB had predominantly been treated with ICE/CyCE regimens, and group BB-CC patients mainly with VIT/TOTEM regimens. Conclusion: A second relapse WT remains curable in a proportion of AA-BB patients. In contrast, survival rates for BB-CC patients are minimal and dismal for CC-CC patients, who should be allocated to a relevant early-phase trial if feasible.

Paediatric kidney tumours are generally associated with a favourable survival rate. Most children are diagnosed with Wilms tumour, which has a 90

Approximately 20 In this Review, the authors provide a comprehensive historical overview of the advancements in the understanding of biology and genetics of paediatric renal non-Wilms tumours, and discuss how this information can be used to develop new targeted therapies for these rare cancers.

BACKGROUND:Patients with a Wilms tumor (WT) who relapse following initial therapy with more than only vincristine and actinomycin-D are considered high-risk (group BB) or very high-risk (group CC) relapse by the International Society of Pediatric Oncology - Renal Tumor Study Group (SIOP-RTSG). We aimed to retrospectively analyze the characteristics and outcome of BB and CC patients. METHODS:We included all patients with first relapsed WT that would currently be considered BB (n = 148) and CC (n = 72) relapse and registered in the SIOP 2001/UK-IMPORT study. We collected information on relapse treatment and calculated 5-year event-free (EFS) and overall survival (OS) rates per relapse risk group and treatment. Multivariable Cox regression analysis was performed to identify patient and tumor characteristics that were significantly associated with survival. FINDINGS:The 5-year estimated EFS and OS rates of BB patients were 62·7% (95% CI: 54·9-71·6%) and 67·6% (95% CI: 59·8-76·4%), respectively. Five-year survival rates for the subset of BB patients treated with VAD and RT (n = 42/94) were 58·7% (95% CI: 45·0-76·6%) for EFS and 66·5% (95% CI: 53·1-83·2%) for OS. Five-year estimated EFS and rates for CC patients were 17·4% (95% CI: 10·4-29·0%) and 18·6% (95% CI: 11·3-30·5%), respectively. In multivariable Cox regression analysis, patients seemed to benefit from high dose chemotherapy and autologous stem cell rescue (HDCT) and surgery at first relapse. INTERPRETATION:Second-line treatment was able to rescue two-thirds of BB relapse patients. In contrast, survival rates in CC patients at first relapse remain poor with conventional drugs, even with camptothecin-containing regimens. A subset of BB and CC patients may benefit from HDCT and surgery at relapse. However, to validate these findings, they must be reevaluated in future trials to eliminate bias from the analyses that is inherent to retrospective studies.

IntroductionAngiogenesis is critical for tumor growth and metastasis. Bevacizumab is an antiangiogenic drug used to treat various adult and childhood solid tumors. Its potential efficacy in Wilms tumor (WT) with poor prognosis is not established.Areas coveredThe response to bevacizumab-containing regimens in relapsed or refractory WT was reviewed in available literature. Searches were conducted using PubMed, Scopus, and ClinicalTrials.gov databases. Eight papers were identified, published between 2007 and 2020, including six treatment regimens, predominantly vincristine, irinotecan, and bevacizumab (VIB) +/- temozolomide (VITB). Among 16 evaluable patients, there were two complete responses, seven partial responses, five patients achieved stable disease (SD), and two patients had progressive disease. Objective responses (OR) were observed in 56% of all cases. OR or SD was observed in 89% (8/9) patients who received VIB/VITB. Bevacizumab was generally well tolerated. Related toxicities included hypertension, proteinuria, and delayed wound healing.Expert OpinionThis review suggests potential effectiveness and good tolerability of bevacizumab in the setting of relapsed/refractory WT when used in combination with other drugs. Such combination therapies may serve as a bridging treatment option to other interventions and more personalized treatment options in the future; however, focused trials are needed to obtain additional evidence.

Few studies investigated the genetics of relapsed Wilms tumor (WT), suggesting the SIX1 gene, the microRNA processing genes, and the MYCN network as possibly involved in a relevant percentage of relapses. We investigated 28 relapsing WT patients (10 new cases and 18 cases in which the involvement of SIX and miRNAPG had been excluded) with a panel of ∼5000 genes. We identified variants affecting genes involved in DNA damage prevention and repair in 12/28 relapsing patients (42.9%), and affecting genes involved in chromatin modification and regulation in 6/28 relapsing patients (21.4%), widening the spectrum of anomalies detected in relapsed tumors. The disclosure of molecular pathways possibly underlying tumor progression might allow to use molecularly targeted therapies at relapse. Surprisingly, germline anomalies, mostly affecting DNA damage prevention and repair genes, were identified in 13/28 patients (46.4%), raising the issue of performing a genetic testing to all children presenting with a WT.

The modern study of Wilms tumour was prompted nearly 50 years ago, when Alfred Knudson proposed the ‘two-hit’ model of tumour development. Since then, the efforts of researchers worldwide have substantially expanded our knowledge of Wilms tumour biology, including major advances in genetics — from cloning the first Wilms tumour gene to high-throughput studies that have revealed the genetic landscape of this tumour. These discoveries improve understanding of the embryonal origin of Wilms tumour, familial occurrences and associated syndromic conditions. Many efforts have been made to find and clinically apply prognostic biomarkers to Wilms tumour, for which outcomes are generally favourable, but treatment of some affected individuals remains challenging. Challenges are also posed by the intratumoural heterogeneity of biomarkers. Furthermore, preclinical models of Wilms tumour, from cell lines to organoid cultures, have evolved. Despite these many achievements, much still remains to be discovered: further molecular understanding of relapse in Wilms tumour and of the multiple origins of bilateral Wilms tumour are two examples of areas under active investigation. International collaboration, especially when large tumour series are required to obtain robust data, will help to answer some of the remaining unresolved questions.

Patients with Wilms tumor (WT) in general have excellent survival, but the prognosis of patients belonging to the subgroup of WT with diffuse anaplasia (DA) is poor due to frequent resistance to chemotherapy. We hypothesized that DA WT cells might undergo changes, such as acquiring a persistent tolerance to DNA damage and copy number aberrations (CNAs), which could eventually lead to their resistance to chemotherapy treatment. Tissue sections from chemotherapy-treated DA WTs (n = 12) were compared with chemotherapy-treated nonanaplastic WTs (n = 15) in a tissue microarray system, enabling analysis of 769 tumor regions. All regions were scored for anaplastic features and immunohistochemistry was used to quantify p53 expression, proliferation index (Ki67), and DNA double-strand breaks (γH2AX). CNAs were assessed by array-based genotyping and TP53 mutations using targeted sequencing. Proliferation index and the frequency of DNA double-strand breaks (γH2AX dot expression) increased with higher anaplasia scores. Almost all (95.6%) areas with full-scale anaplasia had TP53 mutations or loss of heterozygosity, along with an increased amount of CNAs. Interestingly, areas with wild-type TP53 with loss of heterozygosity and only one feature of anaplasia (anaplasia score 1) also had significantly higher proliferation indices, more DNA double-strand breaks, and more CNAs than regions without any anaplastic features (score 0); such areas may be preanaplastic cell populations under selective pressure for TP53 mutations. In conclusion, we suggest that chemoresistance of DA WTs may be partly explained by a high proliferative capability of anaplastic cells, which also have a high burden of double-stranded DNA breaks and CNAs, and that there is a gradual emergence of anaplasia in WT.

Clear cell sarcoma of the kidney (CCSK) is a rare pediatric renal tumor with a worse prognosis than Wilms' tumor. Although recently, BCOR internal tandem duplication (ITD) has been found as a driver mutation in more than 80% of cases, a deep molecular characterization of this tumor is still lacking, as well as its correlation with the clinical course. The aim of this study was to investigate the differential molecular signature between metastatic and localized BCOR-ITD-positive CCSK at diagnosis. Whole-exome sequencing (WES) and whole-transcriptome sequencing (WTS) were performed on six localized and three metastatic BCOR-ITD-positive CCSKs, confirming that this tumor carries a low mutational burden. No significant recurrences of somatic or germline mutations other than BCOR-ITD were identified among the evaluated samples. Supervised analysis of gene expression data showed enrichment of hundreds of genes, with a significant overrepresentation of the MAPK signaling pathway in metastatic cases (p < 0.0001). Within the molecular signature of metastatic CCSK, five genes were highly and significantly over-expressed: FGF3, VEGFA, SPP1, ADM, and JUND. The role of FGF3 in the acquisition of a more aggressive phenotype was investigated in a cell model system obtained by introducing the ITD into the last exon of BCOR by Crispr/Cas9 gene editing of the HEK-293 cell line. Treatment with FGF3 of BCOR-ITD HEK-293 cell line induced a significant increase in cell migration versus both untreated and scramble cell clone. The identification of over-expressed genes in metastatic CCSKs, with a particular focus on FGF3, could offer new prognostic and therapeutic targets in more aggressive cases.

Intra-tumor heterogeneity (ITH) fosters tumor evolution, resistance to therapy, and relapse. Recently, many evidence have been accumulated on the occurrence of genetic ITH in pediatric cancers. With this study we aimed to address the downstream effects that genetic and epigenetic ITH, and tumor-microenvironment interactions may produce within a tumor mass. To this aim, we investigated by high-throughput gene expression multiple samples of 5 hepatoblastomas, 5 neuroblastomas, 5 rhabdomyosarcomas, and 5 Wilms tumors. Principal component analysis, single sample hallmark gene sets analysis, and weighted gene co-expression network analysis were performed on gene expression data. We observed that the different tumors clustered by histotype, and then by case, and in addition, a variable degree of ITH was visible in all the investigated cases. The ITH highlighted in this study can represent a challenge in tumor treatment since we demonstrated that different druggable hallmarks and targets may be heterogeneously present within the same tumor mass, and this can potentially lead to therapeutic failure. Despite this heterogeneity, we could highlight some commonalities among the different histotypes investigated, supporting the feasibility to move in the clinic from a histotype-driven to a target-driven, sometimes agnostic, approach at least in some cases.

In this issue of Cell Reports Medicine, Gadd and colleagues presented on behalf of the Children's Oncology Group their comprehensive analysis of genetic changes associated with relapse in children with favorable histology Wilms tumor.

Purpose: Society of International Pediatric Oncology - Renal Tumor Study Group (SIOP-RTSG) treatment recommendations for relapsed Wilms tumour (WT) are stratified by the intensity of first-line treatment. To explore the evidence for the treatment of patients relapsing after vincristine and actinomycin-D (VA) treatment for primary WT, we retrospectively evaluated rescue treatment and survival of this patient group. Patients and methods: We included 109 patients with relapse after VA therapy (no radiotherapy) for stage I-II primary low-or intermediate-risk WT from the SIOP 93-01 and SIOP 2001 studies. Univariate Cox regression analysis was performed to study the effect of relapse treatment intensity on event-free survival (EFS) and overall survival (OS). Relapse treatment intensity was classified into vincristine, actinomycin-D, and either doxorubicin or epirubicin (VAD), and more intensive therapies (ifosfamide/carboplatin/etoposide [ICE]/> 4 drugs/ high-dose chemotherapy with haematopoietic stem cell transplantation [HD HSCT]). Results: Relapse treatment regimens included either VAD, or cyclophosphamide/carboplatin/ etoposide/doxorubicin (CyCED), or ICE backbones. Radiotherapy was administered in 62 patients and HD HSCT in 15 patients. Overall, 5-year EFS and OS after relapse were 72.3% (95% confidence interval [CI]: 64.0-81.6%) and 79.3% (95% CI: 71.5-88.0%), respectively. Patients treated with VAD did not fare worse when compared with patients treated with more intensive therapies (hazard ratio EFS: 0.611 [95% CI: 0.228-1.638] [p-value = 0.327] and hazard ratio OS: 0.438 [95% CI: 0.126-1.700] [p-value = 0.193]). Conclusion: Patients with relapsed WT after initial VA-only treatment showed no inferior EFS and OS when treated with VAD regimens compared with more intensive rescue regimens. A subset of patients relapsing after VA may benefit from less intensive rescue treatment than ICE/CyCED-based regimens and deserve to be pinpointed by identifying additional (molecular) prognostic factors in future studies. (C) 2021 The Authors. Published by Elsevier Ltd.

Approximately 5% of patients with Wilms tumor present with synchronous bilateral disease. The development of synchronous bilateral Wilms tumor (BWT) is highly suggestive of a genetic or epigenetic predisposition. Patients with known germline predisposition to Wilms tumor (WT1 variants, Beckwith Wiedemann spectrum, TRIM28 variants) have a higher incidence of BWT. This Children's Oncology Group (COG)-International Society for Pediatric Oncology (SIOP-) HARMONICA initiative review for pediatric renal tumors details germline genetic and epigenetic predisposition to BWT development, with an emphasis on alterations in 11p15.5 (ICR1 gain of methylation, paternal uniparental disomy, and postzygotic somatic mosaicism), WT1, TRIM28, and REST. Molecular mechanisms that result in BWT are often also present in multifocal Wilms tumor (multiple separate tumors in one or both kidneys). We identify priority areas for international collaborative research to better understand how predisposing genetic or epigenetic factors associate with response to neoadjuvant chemotherapy, oncologic outcomes, and long-term renal function outcomes.

To the Editor: Osteopathia striata with cranial sclerosis (OSCS,MIM#300373) is a rare X-linked dominant skeletal dysplasia characterised by linear striations in the metaphyseal region of the long bones and pelvis in combination with cranial sclerosis owing to increased osteoblast activity.1,2 The rarity and heterogeneity of its phenotype makes a diagnosis of OSCS challenging, leading to the risk that it can actually be missed for many years. Jenkins et al. found that OSCS is caused by germline deletions/mutations of the AMER1 gene (MIM#300647, NM_152424.4) located on Xq11.2.3 Somatic mutations in AMER1 are found in 7–29% ofWilms tumours (WT).4–7 To date, and to the best of our knowledge, just five cases of paediatric tumours, fourWTandonehepatoblastoma, havebeen reported in patientswithOSCS8–10 despite two large studies investigating cohorts of patients (including adults) with OSCS did not find an increased risk of cancer.3,11 Herein, we report a clinical and molecular description of an additional girl affected byOSCSwho developed aWT. The girl was born at 35 weeks of gestation to healthy nonconsanguineous parents. At her birth, macrocephaly, a prominent forehead, retrognathia, anteverted nares, hypertelorism and pectus excavatum were all observed. The neonatal audiometry was normal. The brain magnetic resonance imaging was unremarkable except for the evidence of macrocephaly. During follow-up, a mild intellectual disability (ID) became evident in the girl, particularly in speech ability. Later, at the age of 4, the patient began to experience a painless rapid increase in abdominal volume. A computed tomography (CT) scan showedacapsulatedpolycyclic hypo-vascularised retroperitoneal mass with necrotic areas, compatible with a renal tumour. A chest CT was also performed and resulted negative for metastases, but intriguingly, the chest X-ray inadvertently revealed longitudinal sclerotic striations in the humeral metaphysis (Figure 1). Similarly, the radiographs of her long bones demonstrated prominent linear sclerotic striations in the metaphyses and epiphyses and fan-like striations of the iliac crest (Figure 1). The girl underwent a core needle biopsy of the lesion, which confirmed our suspicion ofWT. After this diagnosis, the girl started neoadjuvant chemotherapy according to the contemporary national protocol. At nephrectomy, pathology inspection revealed a mixed epithelial and blastemal WT, with no associated nephrogenic rests, stage

Wilms tumour (WT) accounts for about 6% of all childhood cancers and overall survival of WT is about 90% in international protocols. However, for WT subgroups with much poorer prognoses, i.e. typically high-risk (unfavorable) histology and/or relapse, there is an unmet need to better understand the biology of WT and to translate biological findings into clinics through early phase clinical trials that evaluate innovative therapies. The main challenges are the small numbers of children suitable for early phase trials, the genetic heterogeneity of WT and the low number of somatic mutations that are currently considered 'druggable'. Accordingly, a joint meeting between clinical and biology experts from the international cooperative groups of the Renal Tumour Study Group of the International Society of Paediatric Oncology, the Renal Tumour Committee of the Children's Oncology Group and the European Innovative Therapies for Children with Cancer consortium and parents representatives was organised during the first SIOPE meeting in Prague, 2019. We reviewed WT molecular features, ongoing/planned early phase trials and explored available knowledge on organoid technology. The key messages were: (1) relapsed WT should undergo whenever possible thorough molecular characterization and be enrolled in protocols or trials with systematic data collecting and reporting; (2) WT displays few known 'actionable' targets and currently no novel agent has appeared promising; (3) we need to improve the enrolment rate of WT candidates in early phase trials especially for the relatively small subgroup of relapses with an adverse prognostic signature; (4) despite some agnostic early phase trials existing, development of WT-focused trials are warranted; (5) growing organoids with parallel testing of drug panels seems feasible and may direct individual treatment and encourage clinical researchers to incorporate the most promising agents into early phase trials.