First Transcriptome Analysis of Hepatoblastoma in Brazil: Unraveling the Pivotal Role of Noncoding RNAs and Metabolic Pathways.

Hepatoblastoma stands as the most prevalent liver cancer in the pediatric population. Characterized by a low mutational burden, chromosomal and epigenetic alterations are key drivers of its tumorigenesis. Transcriptome analysis is a powerful tool for unraveling the molecular intricacies of hepatoblastoma, shedding light on the effects of genetic and epigenetic changes on gene expression. In this study conducted in Brazilian patients, an in-depth whole transcriptome analysis was performed on 14 primary hepatoblastomas, compared to control liver tissues. The analysis unveiled 1,492 differentially expressed genes (1,031 upregulated and 461 downregulated), including 920 protein-coding genes (62%). Upregulated biological processes were linked to cell differentiation, signaling, morphogenesis, and development, involving known hepatoblastoma-associated genes (DLK1, MEG3, HDAC2, TET1, HMGA2, DKK1, DKK4), alongside with novel findings (GYNG4, CDH3, and TNFRSF19). Downregulated processes predominantly centered around oxidation and metabolism, affecting amines, nicotinamides, and lipids, featuring novel discoveries like the repression of SYT7, TTC36, THRSP, CCND1, GCK and CAMK2B. Two genes, which displayed a concordant pattern of DNA methylation alteration in their promoter regions and dysregulation in the transcriptome, were further validated by RT-qPCR: the upregulated TNFRSF19, a key gene in the embryonic development, and the repressed THRSP, connected to lipid metabolism. Furthermore, based on protein-protein interaction analysis, we identified genes holding central positions in the network, such as HDAC2, CCND1, GCK, and CAMK2B, among others, that emerged as prime candidates warranting functional validation in future studies. Notably, a significant dysregulation of non-coding RNAs (ncRNAs), predominantly upregulated transcripts, was observed, with 42% of the top 50 highly expressed genes being ncRNAs. An integrative miRNA-mRNA analysis revealed crucial biological processes associated with metabolism, oxidation reactions of lipids and carbohydrates, and methylation-dependent chromatin silencing. In particular, four upregulated miRNAs (miR-186, miR-214, miR-377, and miR-494) played a pivotal role in the network, potentially targeting multiple protein-coding transcripts, including CCND1 and CAMK2B. In summary, our transcriptome analysis highlighted disrupted embryonic development as well as metabolic pathways, particularly those involving lipids, emphasizing the emerging role of ncRNAs as epigenetic regulators in hepatoblastomas. These findings provide insights into the complexity of the hepatoblastoma transcriptome and identify potential targets for future therapeutic interventions.

Prevalence and clinical implications of germline pathogenic variants in cancer predisposing genes in young patients across sarcoma subtypes.

BACKGROUND: Sarcomas are a rare and diverse group of cancers occurring mainly in young individuals for which an underlying germline genetic cause remains unclear in most cases. METHODS: Germline DNA from 177 children, adolescents and young adults with soft tissue or bone sarcomas was tested using multigene panels with 113 or 126 cancer predisposing genes (CPGs) to describe the prevalence of germline pathogenic/likely pathogenic variants (GPVs). Subsequent testing of a subset of tumours for loss of heterozygosity (LOH) evaluation was performed to investigate the clinical and molecular significance of these variants. RESULTS: GPVs were detected in 21.5% (38/177) of the patients (15.8% in children and 21.6% in adolescents and young adults), with dominant CPGs being altered in 15.2% overall. These variants were found in genes previously associated with the risk of developing sarcomas (TP53, RB1, NF1, EXT1/2) but also in genes where that risk is still emerging/limited (ERCC2, TSC2 and BRCA2) or unknown (PALB2, RAD50, FANCM and others). The detection rates of GPVs varied from 0% to 33% across sarcoma subtypes and GPV carriers were more likely to present more than one primary tumour than non-carriers (21.1%×6.5%; p=0.012). Loss of the wild-type allele was detected in 48% of tumours from GPV carriers, mostly in genes definitively associated with sarcoma risk. CONCLUSION: Our findings reveal that a high proportion of young patients with sarcomas presented a GPV in a CPG, underscoring the urgency of establishing appropriate genetic screening strategies for these individuals and their families.

Preserved executive functioning and low stress symptoms in children treated for acute lymphoblastic leukemia.

Pediatric cancer treatment can negatively impact cognitive and psychosocial development, although it has been suggested that these adverse effects may be minimized when children have higher resilience and better executive functioning. We aimed to evaluate the impact of pediatric Acute Lymphoblastic Leukemia (ALL) treatment on executive function, resilience and stress in survivors and to investigate correlations between executive functioning and resilience and between executive functioning and stress. The neuropsychological assessment was performed in 32 ALL survivors aged 7-17 years and 28 age-, sex- and socioeconomic status matched controls. Executive functioning was assessed by inhibitory control, mental flexibility and working memory tasks. Children's self-report scales were used to assess stress symptoms and resilience. Results revealed no executive function impairment nor stress symptom differences between ALL survivors and control group. In the ALL group, executive function and resilience were positively correlated, whereas executive function and stress were negatively correlated. We concluded that ALL treatment was not associated with impairment in executive functioning nor to increased stress symptoms in our sample. ALL survivors with better performance in mental flexibility and inhibition tasks reported fewer stress symptoms and more resilience, indicating a possible relationship between these variables.

Copy Number Alterations in Hepatoblastoma: Literature Review and a Brazilian Cohort Analysis Highlight New Biological Pathways.

Hepatoblastoma (HB) is a rare embryonal tumor, although it is the most common pediatric liver cancer. The aim of this study was to provide an accurate cytogenomic profile of this type of cancer, for which information in cancer databases is lacking. We performed an extensive literature review of cytogenetic studies on HBs disclosing that the most frequent copy number alterations (CNAs) are gains of 1q, 2/2q, 8/8q, and 20; and losses at 1p and 4q. Furthermore, the CNA profile of a Brazilian cohort of 26 HBs was obtained by array-CGH; the most recurrent CNAs were the same as shown in the literature review. Importantly, HBs from female patients, high-risk stratification tumors, tumors who developed in older patients (> 3 years at diagnosis) or from patients with metastasis and/or deceased carried a higher diversity of chromosomal alterations, specifically chromosomal losses at 1p, 4, 11q and 18q. In addition, we distinguished three major CNA profiles: no detectable CNA, few CNAs and tumors with complex genomes. Tumors with simpler genomes exhibited a significant association with the epithelial fetal subtype of HBs; in contrast, the complex genome group included three cases with epithelial embryonal histology, as well as the only HB with HCC features. A significant association of complex HB genomes was observed with older patients who developed high-risk tumors, metastasis, and deceased. Moreover, two patients with HBs exhibiting complex genomes were born with congenital anomalies. Together, these findings suggest that a high load of CNAs, mainly chromosomal losses, particularly losses at 1p and 18, increases the tendency to HB aggressiveness. Additionally, we identified six hot-spot chromosome regions most frequently affected in the entire group: 1q31.3q42.3, 2q23.3q37.3, and 20p13p11.1 gains, besides a 5,3 Mb amplification at 2q24.2q24.3, and losses at 1p36.33p35.1, 4p14 and 4q21.22q25. An in-silico analysis using the genes mapped to these six regions revealed several enriched biological pathways such as ERK Signaling, MicroRNAs in Cancer, and the PI3K-Akt Signaling, in addition to the WNT Signaling pathway; further investigation is required to evaluate if disturbances of these pathways can contribute to HB tumorigenesis. The analyzed gene set was found to be associated with neoplasms, abnormalities of metabolism/homeostasis and liver morphology, as well as abnormal embryonic development and cytokine secretion. In conclusion, we have provided a comprehensive characterization of the spectrum of chromosomal alterations reported in HBs and identified specific genomic regions recurrently altered in a Brazilian HB group, pointing to new biological pathways, and relevant clinical associations.

Hepatoblastomas exhibit marked NNMT downregulation driven by promoter DNA hypermethylation.

Hepatoblastomas exhibit the lowest mutational burden among pediatric tumors. We previously showed that epigenetic disruption is crucial for hepatoblastoma carcinogenesis. Our data revealed hypermethylation of nicotinamide N-methyltransferase, a highly expressed gene in adipocytes and hepatocytes. The expression pattern and the role of nicotinamide N-methyltransferase in pediatric liver tumors have not yet been explored, and this study aimed to evaluate the effect of nicotinamide N-methyltransferase hypermethylation in hepatoblastomas. We evaluated 45 hepatoblastomas and 26 non-tumoral liver samples. We examined in hepatoblastomas if the observed nicotinamide N-methyltransferase promoter hypermethylation could lead to dysregulation of expression by measuring mRNA and protein levels by real-time quantitative polymerase chain reaction, immunohistochemistry, and Western blot assays. The potential impact of nicotinamide N-methyltransferase changes was evaluated on the metabolic profile by high-resolution magic angle spinning nuclear magnetic resonance spectroscopy. Significant nicotinamide N-methyltransferase downregulation was revealed in hepatoblastomas, with two orders of magnitude lower nicotinamide N-methyltransferase expression in tumor samples and hepatoblastoma cell lines than in hepatocellular carcinoma cell lines. A specific TSS1500 CpG site (cg02094283) of nicotinamide N-methyltransferase was hypermethylated in tumors, with an inverse correlation between its methylation level and nicotinamide N-methyltransferase expression. A marked global reduction of the nicotinamide N-methyltransferase protein was validated in tumors, with strong correlation between gene and protein expression. Of note, higher nicotinamide N-methyltransferase expression was statistically associated with late hepatoblastoma diagnosis, a known clinical variable of worse prognosis. In addition, untargeted metabolomics analysis detected aberrant lipid metabolism in hepatoblastomas. Data presented here showed the first evidence that nicotinamide N-methyltransferase reduction occurs in hepatoblastomas, providing further support that the nicotinamide N-methyltransferase downregulation is a wide phenomenon in liver cancer. Furthermore, this study unraveled the role of DNA methylation in the regulation of nicotinamide N-methyltransferase expression in hepatoblastomas, in addition to evaluate the potential effect of nicotinamide N-methyltransferase reduction in the metabolism of these tumors. These preliminary findings also suggested that nicotinamide N-methyltransferase level may be a potential prognostic biomarker for hepatoblastoma.

Evaluation of whole-body MRI with diffusion-weighted sequences in the staging of pediatric cancer patients.

BACKGROUND: The purpose of this study was to determine whether whole-body MRI (WBMRI) with diffusion-weighted sequences, which is free of ionizing radiation, can perform as well as traditional methods when used alone for staging or follow-up of pediatric cancer patients. METHODS: After obtaining approval from our institutional research ethics committee and appropriate informed consent, we performed 34 examinations in 32 pediatric patients. The examinations were anonymized and analyzed by two radiologists with at least 10 years' experience. RESULTS: The sensitivity and specificity findings, respectively, were as follows: 100% and 100% for primary tumor; 100% and 86% for bone metastasis; 33% and 100% for lung metastasis; 85% and 100% for lymph node metastasis; and 100% and 62% for global investigation of primary or secondary neoplasias. We observed excellent interobserver agreement for WBMRI and excellent agreement with standard staging examination results. CONCLUSIONS: Our results suggest that pediatric patients can be safely imaged with WBMRI, although not as the only tool but in association with low-dose chest CT (for subcentimeter pulmonary nodules). However, additional exams with ionizing radiation may be necessary for patients who tested positive to correctly quantify and locate the lesions.

TET Upregulation Leads to 5-Hydroxymethylation Enrichment in Hepatoblastoma.

Hepatoblastoma is an embryonal liver tumor carrying few genetic alterations. We previously disclosed in hepatoblastomas a genome-wide methylation dysfunction, characterized by hypermethylation at specific CpG islands, in addition to a low-level hypomethylation pattern in non-repetitive intergenic sequences, in comparison to non-tumoral liver tissues, shedding light into a crucial role for epigenetic dysregulation in this type of cancer. To explore the underlying mechanisms possibly related to aberrant epigenetic modifications, we evaluated the expression profile of a set of genes engaged in the epigenetic machinery related to DNA methylation (DNMT1, DNMT3A, DNMT3B, DNMT3L, UHRF1, TET1, TET2, and TET3), as well as the 5-hydroxymethylcytosine (5hmC) global level. We observed in hepatoblastomas a general disrupted expression of these genes from the epigenetic machinery, mainly UHRF1, TET1, and TET2 upregulation, in association with an enrichment of 5hmC content. Our findings support a model of active demethylation by TETs in hepatoblastoma, probably during early stages of liver development, which in combination with UHRF1 overexpression would lead to DNA hypomethylation and an increase in overall 5hmC content. Furthermore, our data suggest that decreased 5hmC content might be associated with poor survival rate, highlighting a pivotal role of epigenetics in hepatoblastoma development and progression.

DNA methylation landscape of hepatoblastomas reveals arrest at early stages of liver differentiation and cancer-related alterations.

Hepatoblastomas are uncommon embryonal liver tumors accounting for approximately 80% of childhood hepatic cancer. We hypothesized that epigenetic changes, including DNA methylation, could be relevant to hepatoblastoma onset. The methylomes of eight matched hepatoblastomas and non-tumoral liver tissues were characterized, and data were validated in an independent group (11 hepatoblastomas). In comparison to differentiated livers, hepatoblastomas exhibited a widespread and non-stochastic pattern of global low-level hypomethylation. The analysis revealed 1,359 differentially methylated CpG sites (DMSs) between hepatoblastomas and control livers, which are associated with 765 genes. Hypomethylation was detected in hepatoblastomas for ~58% of the DMSs with enrichment at intergenic sites, and most of the hypermethylated CpGs were located in CpG islands. Functional analyses revealed enrichment in signaling pathways involved in metabolism, negative regulation of cell differentiation, liver development, cancer, and Wnt signaling pathway. Strikingly, an important overlap was observed between the 1,359 DMSs and the CpG sites reported to exhibit methylation changes through liver development (p<0.0001), with similar patterns of methylation in both hepatoblastomas and fetal livers compared to adult livers. Overall, our results suggest an arrest at early stages of liver cell differentiation, in line with the hypothesis that hepatoblastoma ontogeny involves the disruption of liver development. This genome-wide methylation dysfunction, taken together with a relatively small number of driver genetic mutations reported for both adult and pediatric liver cancers, shed light on the relevance of epigenetic mechanisms for hepatic tumorigenesis.

The genetic and epigenetic landscapes of hepatoblastomas

Primary liver cancers are rare in children, and the most common type is hepatoblastoma (HB), an embryonal tumor with histological features that resemble different stages of liver cell differentiation. However, mainly because of its rarity, molecular data on HB tumorigenesis remain scarce. This article reviews the current knowledge regarding genetic and epigenetic alterations reported in HB cases, with emphasis on the recent findings of next-generation sequencing studies (AU)

Upregulated genes at 2q24 gains as candidate oncogenes in hepatoblastomas.

AIM: Cytogenetic data of hepatoblastomas, a rare embryonal tumor of the liver, mostly consist of descriptions of whole-chromosome aneuploidies and large chromosome alterations. High-resolution cytogenetics may provide clues to hepatoblastoma tumorigenesis and indicate markers with clinical significance. PATIENTS & METHODS: We used array-CGH (180K) to screen for genomic imbalances in nine hepatoblastomas. Additionally, we investigated the expression pattern of selected genes exhibiting copy number changes. RESULTS: Analysis showed mainly whole-chromosome or chromosome-arm aneuploidies, but some focal aberrations were also mapped. Expression analysis of 48 genes mapped at one 10 Mb amplification at 2q24 revealed upregulation of DAPL1, ERMN, GALNT5, SCN1A and SCN3A in the set of tumors compared with differentiated livers. CONCLUSION: These genes appear as candidates for hepatoblastoma tumorigenesis.

Large germline copy number variations as predisposing factor in childhood neoplasms.

AIMS: Constitutive genetic factors are believed to predispose to cancer in children. This study investigated the role of rare germline copy number variations (CNVs) in pediatric cancer predisposition. PATIENTS & METHODS: A total of 54 patients who developed cancer in infancy were screened by array-CGH for germline CNVs. RESULTS: In total, 12 rare CNVs were detected, including a Xq27.2 triplication, and two >1.8 Mb deletions: one of them at 13q31, containing only RNA genes, and another at 3q26.33-q27.1, in a patient with congenital malformations. Detected rare CNVs are significantly larger than those identified in controls, and encompass genes never implicated in cancer predisposition. CONCLUSION: Our results suggest that constitutive CNVs contribute to the etiology of pediatric neoplasms, revealing new candidate genes for tumorigenesis.

Pleuropulmonary blastoma type II: a case report

Pleuropulmonary blastoma (PPB) is a rare embrionary mesenchymal neoplasm but is recognized as the most common pulmonary malignancy of childhood. It may present metastasis to the brain and also be indicative of other neoplasms in affected individuals or in their relatives. Being such a rare disease, it is considered a difficult diagnosis to be made. A 3-year-old female presented with fever and respiratory distress. At first, she had been treated for pneumonia with antibiotics for 14 days in another hospital with no response. Computed tomography (CT) scan showed a right lung/mediastinal mass. The patient was referred to our institution and a new CT-scan evidenced a complex mass of irregular borders, cystic areas and solid projections, along with a right pneumotorax. The mass was biopsied and hematoxylin-and-eosin (HE) stained histological sections showed a neoplasm composed of small and round cells with hyperchromatic nuclei and scant cytoplasm. The immunohistochemical profile demonstrated positivity for desmin, myogenin and Myo-D1, suggesting the diagnosis of rhabdomyosarcoma. After two weeks of hospitalization, the patient was clinically stable and initiated the first chemotherapy cycle. Surgical resection of the mass was performed and the HE slides demonstrated a neoplasm composed of anaplastic and condrossarcomatous cells with extensive necrosis. The correlation of clinical data, radiological and morphological features were conclusive of a PPB type II. The recognition and diagnosis of this entity is of great importance due to its clinical and prognostic particularities.

Imunoexpressão de WT1, ß-cateinina, E-caderina e APC em tumor de Wilms esporádico / Expression of WT1, p53, Beta-catenina, E-cadherina and APC in sporadic Wilms tumor

O tumor de Wilms é uma neoplasia embrionária, constituída classicamente por três componentes histológicos: blastema, epitélio e mesênquima (estroma), os quais podem ser encontrados em diferentes proporções em cada tumor. ... Este estudo tem como principal objetivo determinar a freqüência da expressão das proteínas WT1, p53, Beta-catenina, E-caderina e APC nos diferentes componentes histológicos do tumor de Wilms, assim como correlacionar estes achados com o prognóstico. Para estudar a expressão dos marcadores, foi utilizado a imunoistoquímica, através da construção de Tissue Macroarray (TMA), o qual permite a análise de muitas amostras teciduais em uma única lâmina, otimizando custo e tempo. Nos nossos resultados, WT1 e p53 foram mais freqüentemente expressos no componente blastema (WT1: 97% e p53: 63% dos casos) e epitélio (WT1: 87% e p53: 58% dos casos), quando comparados com o estroma (WT1: 13% e p53: 22% dos casos) e com o tecido renal não tumoral (ausência de expressão em todos os casos estudados). ... A imunoexpressão nuclear ocorreu principalmente nos componentes blastematoso e estromal. Houve imunoexpressão de E-caderina na membrana em 47% dos casos, em citoplasma em 44% e em núcleo em 12%. O acúmulo em núcleo foi encontrado principalmente nos componentes blastema e mesênquima, 21 e 25% respectivamente. A imunoexpressão do APC ocorreu em núcleo em 95% dos tumores avaliados, em citoplasma em 9% e nenhum apresentou expressão em membrana. Nos componentes blastematoso e epitelial houve imunopositividade nuclear em 100% dos casos avaliados. No componente mesenquimal a positividade nuclear ocorreu em 89% dos casos. Os pacientes com estádios precoces tiveram mais freqüentemente positividade do WT1. Não houve associação dos outros fatores clínicos, epidemiológicos e evolução dos pacientes com expressão dos marcadores estudados.

Wilms tumor is a triphasic malignant neoplasm compromised of variable proportions of epithelial, blastemal and mesenchymal (stromal) elements. Different components have different clinical behavior. Patients with tumors predominant epithelial and/or stromal has more frequently low stage while predominant blastema has advanced disease. This study was undertaken to evaluate the expression of WT1, beta-catenins, E-cadherin and APC in Wilms tumor and correlate this expression with clinical characteristics, histologic cell type and prognosis. We studied the immunohistochemical expression of WT1, p53, beta-catenins, E-cadherin in different component of Wilms tumor using a tissue array. WT1 and p53 were more often expressed on blastema component (WT1: 97% and p53: 63% of cases) and on epithelial (WT1: 87% and p53: 58% of cases), when compare with the stromal component (WT1: 13% and p53: 22% of cases) and the normal renal tissue where it was not expressed. Immunopositivity of WT1 and p53 were significantly correlated. Immunopositivity of ß-catenina was seen in 85 % at the membrane (85%), 94% cytoplasm and 24% nuclear. Nuclear immunoexpression was detected specially on blastema and stromal component. Immunohistochemical expression of E-cadherina was detected in 47% at the membrane, 44% cytoplasm and 12% nuclear. Nuclear expression was seen more often at the blastema and stromal component (21%, 25% respectively). Immunopositivity of APC occurs at 95% on nucleus, cytoplasm (9%) and none at membrane. Among the blastema and the epithelial component 100% was positive on nucleus. On the stromal component 89% was positive at the nucleus. Immunoexpression of WT1 was correlated with local stage. The expression status of WT1, E-cadherin, ßcatenina, APC in this cohort was not of prognostic value.

Estudo dos fatores de prognóstico em crianças e adolescentes portadores de tumor de Ewing ósseo do Centro de Tratamento e Pesquisa Hospital do Câncer / Study of prognostic factors in children and adolescents with bone Ewing's tumor at the Cancer Hospital Treatment and Research Center

O tumor de Ewing é a segunda mais freqüente neoplasia primária de osso entre crianças e adolescentes. Com a associação de múltiplos agentes quimioterápicos, o prognóstico desses pacientes tem melhorado significativamente nos últimos anos. A identificação dos fatores de risco para recidiva, permite direcionar o tratamento mais intensivo para o grupo de pacientes com fatores de pior prognóstico. Como descrito na literatura, não existem dúvidas que a presença de metástase detectável macroscopicamente ao diagnóstico, é um importante fator de pior prognóstico. Outros fatores de prognóstico que têm sido descritos na literatura são idade, sítio do tumor primário, volume tumoral, nível sérico de desidrogenase láctica (DHL), resposta histológica à quimioterapia, diferenciação neural. Este estudo teve como principal objetivo, identificar os fatores que influenciaram o prognóstico dos 105 pacientes com tumor de Ewing, tratados em uma única instituição, em um período de 12 anos Uunho de 1984 a dezembro de 1996). A média de idade foi 11 anos; 49% eram do sexo feminino e 51% do sexo masculino. Oitenta por cento dos pacientes eram brancos. Dos 105 pacientes 4 7 tinham tumor primário em sítio axial e 58 em extremidades. Trinta e quatro pacientes foram considerados como metastáticos ao diagnóstico. Em 7 4 pacientes o nível sé rico de DHL foi avaliado, destes pacientes 17 tinham níveis elevados (>370U/L). O tratamento foi realizado com administração de quimioterapia em todos os pacientes, cirurgia do tumor primário em 7 4 e radioterapia local em 40 pacientes. Resposta histológica a terapia neoadjuvante foi determinada através do método de Huvos, sendo 52 casos avaliados. A sobrevida global em 5 anos foi 50°/o e a sobrevida livre de eventos foi 47°/o. A análise univariada mostrou como fatores prognóstico: nível de DHL aumentado (HR=4.40 Cl 95% 2.25-8.62; p<0.0001 ), ausência de reposta clínica à quimioterapia (HR=8.40 CI 95°/o 0.04-0.15; p<0.0001 ), necrose tu moral (grade 1+11) (HR=1.65 CI 95°/o 0.09-0.58; p=0.008), presença de metástases (HR=1.20 Cl 95°/o 1.15-3.45;p=0.014). Na análise múltipla os únicos fatores de prognóstico independentes foram DHL sérico (HR=2.20,CI 95% 1.43-6.26 p=0.003) e ausência de resposta clínica à quimioterapia (HR= 11.30 CI 95% 4.87 -26.22; p<0.0001 ). Nível de DHL sérico foi o fator de prognóstico pré-tratamento mais importante neste estudo. Por ser um método sensível, simples e de baixo custo deveria ser considerado como fator capaz de estratificar os pacientes em grupos de riscos para recidiva e direcionar o tratamento.

Ewing's tumor is the second most frequent bane neoplasm in children and adolescents. Local therapy alone was used before the 1970 and it was associated with an approximately 1 0°/o 5-years event-free survival rate. With the addition of multidrug chemotherapy regimens in the last years, the prognosis has significantly improved. The identification of risk factors for relapse provides important information for the selection of the most intensive treatment for a group of patient with worst factors. Accordjng to the literature, there are no doubts that in Ewing, s tumor the metastatic disease at presentation is particularly an adverse prognosis. Other factors have been reported to influence survival in Ewing tumor, age, tumor site, tumor volume, rum laotate dehydrogenase (LDH), histological response to chemotherapy, neural differentiation. The aim of this study was to review the 12-t years experience of a single institution applying a combined modality of treatment of Ewing's tumor, and to identify prognostic factors. Mean age was 11 years; 49% female and 51% male; 80°/o were white. Primary sites were axial 47 cases and extremity 58. At diagnosis 71 had localized disease and 34 were metastic LDH leveis at diagnosis were evaluated in 72 and high LDH values ( >370 U/L) were observed in 17. Treatment included initial chemotherapy in all cases surgery of the primary site in 7 4 and radiation in 40. Histological effect of preoperative treatment according to the Huvos systêm was evaluated in 52 cases. Five years overall survival was 50% and event free survival was 47%. Univariate analysis showed as prognostic factors: raised LDH (HR=4.40 CI b~ 2.25-8.62; p<0.0001 ), no clinicai response to chemotherapy (HR=8.40 CI 95% 0.04-0.15; p<0.0001), tumor necrosis HUVOS (grade 1+11) (HR=1.65 Cl 95% 0.09-0.58; p=0.008), metastases (HR=1.20 Cl 95% 1.15-3.45;p=0.014) Cox multiple regression analysis showed that raised serum LDH leveis (HR=2.20,CI 95% 1.43-6.26 p=0.003) and no clinicai response to chemotherapy (HR= 11.30 CI 95% 4.87 -26.22; p<0.0001) were independent prognostic factors. The se rum levei of LDH was the most important pretreatment prognostic factor in this series. LDH levei, at the time of diagnosis, should be considered as a factor to treat patients in different groups. lt is a sensitive, simple and cost effective method