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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

A study of the aetiology and epidemiology of cancers in teenagers and young adults

Arora, Ramandeep January 2011 (has links)
Introduction: Little is known about the aetiology of cancer in teenagers and young adults (TYA) aged 15-24 years, although in England, cancer is the most common cause of disease-related mortality in this age group. The most common cancers at this age are lymphomas, central nervous system (CNS) tumours and germ cell tumours (GCT). The commonest carcinomas seen at older ages including lung, breast, large bowel and prostate account for only 3-4% of TYA cancers. In this thesis I describe the incidence patterns of selected cancers in TYA and the variation seen with geography, time and in population subgroups. The focus is on CNS tumours, GCT and bone tumours as they either peak in incidence in TYA and/or contribute disproportionately to cancer related mortality in TYA. This will allow formulation of hypotheses regarding aetiology of cancer in this age group which can then be tested by further research. Methods: For the majority of the analysis, anonymised national cancer registration data from England on individual patients of all ages with newly diagnosed cancer between 1979 and 2003 were used. To contrast the incidence patterns in England with that of India, data from five Indian urban population based cancer registries were used for part of the analysis. Age, sex, site and histology specific incidence rates were calculated and expressed per million person years. All rates, where appropriate, were adjusted to the world standard population using direct methods. To explore the link of growth with development of osteosarcoma and Ewing sarcoma, a random-effects meta-analysis was undertaken on studies which investigated an association of these tumours with height at diagnosis. Results: The incidence of cancer in TYA overall in England exceeded that of India. This was also true for most individual sites including epithelial cancers of lung, colon/rectum, breast, ovary and cervix, and non-epithelial cancers including melanoma, Hodgkin lymphoma and testicular cancer. Notable exceptions to this pattern were cancers of the mouth, gall bladder and stomach (females only) where incidence was higher in India. In England, CNS tumours in TYA were a composite of pilocytic astrocytomas and embryonal tumours (representing tail end of childhood CNS tumours), pituitary tumours, nerve sheath tumours, high grade astrocytomas and meningiomas (representing early-onset of CNS tumours that peak in incidence in the 6th and 7th decade of life), and of CNS GCTs, pleomorphic xanthoastrocytomas and neurocytomas which show a peak incidence in TYA. Irrespective of site or histology, GCT in England showed a peak in incidence between ages of 10 to 39 years which was more marked in males. This however varied by site and the peak incidence was seen at 10 to 14 years in the CNS, 15 to 19 years in ovary, 25 to 29 in mediastinum & thorax and abdomen & pelvis, and 30 to 34 years in testicular tumours. Osteosarcoma and Ewing sarcoma were the predominant bone tumours in TYA in England and showed a distinct peak of incidence at 10 to 14 years age in females and a larger peak at 15 to 19 years age in males. The peak incidence of osteosarcoma of long bones of the lower limb was six times more than that at any other site while the peak incidence of Ewing sarcomas located in the bones of the central axis exceeded those in long bones of the lower limb. The average height of patients with osteosarcoma at diagnosis was found to be significantly above the average height of the reference population, at the 95% level. The association of greater height at diagnosis with Ewing sarcoma was also significant at the 95% level but much weaker. Conclusion: In this thesis I have explored the epidemiology of cancer in TYA using some of the established methodologies which have previously been used in advancing our knowledge of childhood and older adult cancers. These studies provide some clues to aetiology. Variation in environmental exposures and lifestyle factors between England and India can explain the majority of the differences in incidence patterns observed. Genetic predisposition to cancer along with carcinogen exposure could lead to early onset of some cancers generally seen in older adults. Regardless of site, the similarity in age-incidence patterns of GCT, suggests a common initiation of these tumours in embryonic/foetal life with variable rates of tumour progression as a result of local factors or events during postnatal and pubertal period. The incidence patterns of osteosarcoma along with the strong and consistent association with a greater height at diagnosis indicate that bone growth is important in the development of this tumour while different biological pathways which may be unrelated to growth could also be relevant for Ewing sarcoma.
32

DEVELOPMENT OF MITHRAMYCIN ANALOGUES WITH IMPROVED EFFICACY AND REDUCED TOXICITY FOR TREATMENT OF ETS-DEPENDENT TUMORS IN EWING SARCOMA AND PROSTATE CANCER

Eckenrode, Joseph Michael 01 January 2019 (has links)
Introduction: Genetic rearrangements in Ewing sarcoma, prostate, and leukemia cells result in activation of oncogenic ETS transcription factor fusions. Mithramycin (MTM) has been identified as an inhibitor of EWS-FLI1 transcription factor, a gene fusion product responsible for oncogenesis in Ewing sarcoma. Despite preclinical success, a phase I/II clinical trial testing MTM therapy in refractory Ewing sarcoma was terminated. Liver and blood toxicities resulted in dose de-escalation and sub-therapeutic exposures. However, the promise of selectively targeting oncogenic ETS transcription factors like EWS-FLI1 prompted us to undertake the discovery of more selective, less toxic analogues of MTM. MTM is a potent inhibitor of ubiquitous SP1 transcription factor, likely inducing non-specific toxicity. In collaboration with two medicinal chemistry groups, two semi-synthetic efforts were implemented to develop novel analogues of MTM. The first effort utilized the biosynthetic product mithramycin SA (MTMSA) to modify C3-side chain. The second effort utilized an oxime linker directly formed on MTM’s C3-side chain (MTM-oxime; MTMox). Here I present the pharmacological assessment of over 75 novel MTM analogues towards selectively targeting oncogenic ETS transcription factors, like EWS-FLI1, over ubiquitous transcription factors, like SP1. Methods: Novel MTM analogues were evaluated for selective cytotoxicity against ETS fusion-dependent cell lines. Selectively cytotoxic analogues were evaluated for inhibitory effects on several gene promoters in TC-32 reporter cell lines, a Ewing sarcoma cell line dependent on EWS-FLI1, transfected with luciferase reporter vector. Cloned reporter vectors incorporated NR0B1 (EWS-FLI1 binding), β-actin (SP1 binding) and CMV (non-specific) gene promoters. Furthermore, gene (mRNA) and protein expression changes of EWS-FLI1 and SP1, as well as regulated target genes, namely NR0B1, VEGFA and BCL-2 were evaluated with MTM analogue treatments. The MTM analogues with most selective activity in vitro were administered to mice by intravenous bolus dose for pharmacokinetic analysis. The MTM analogues with highest systemic exposure from each semi-synthetic effort, namely MTMSA-Trp-A10 and MTMox-24, were further evaluated. Metabolic stabilities in whole blood, plasma, and tumor cell matrices, and across multiple species were compared with MTM. Moreover, intrinsic hepatic clearances were estimated using mouse liver microsomes. Tumor and liver distributions were estimated in tumor bearing mice. Additionally, the effect of organic anionic transporter polypeptides (OATP) on distribution of MTM was investigated. Maximum tolerated doses were evaluated for lead MTM analogues, having both selective activities in vitro and high systemic exposure, compared to MTM. Complete blood cell counts and plasma alanine aminotransferase activity were measured to evaluate dose-dependent blood and liver toxicities, respectively. ETS fusion-dependent and non-dependent cell lines were implanted subcutaneously into immunocompromised mice for efficacy studies. Average tumor volumes and survival were tracked for mice receiving treatment, compared to MTM and vehicle treatment. Results: Evaluation of MTM analogues from both semi-synthetic efforts revealed that conjugation of MTM C3-side chain with tryptophan (Trp) and/or phenylalanine (Phe) improved selective cytotoxicity against ETS fusion-dependent cell lines. This was highlighted by MTMSA-Trp-A2 (also refer to as MTMSA-Phe-Trp) and MTMSA-Trp-A10 (also refer to as MTMSA-Trp-Trp), with selective indices of 19.1 and 15.6, respectively, compared to MTM (1.5). Similarly, MTMox-23 (also refer to as MTMox-Phe-Trp) and MTMox-20 (also refer to as MTMox-Trp) had selectivity indices of 4.6 and 4.5, respectively. These selectively cytotoxic MTM analogues inhibited EWS-FLI1-mediated transcription 10-fold more effectively than both non-specific CMV-mediated and SP1-mediated (via β-actin promoter) transcription in TC-32 reporter cell lines. Moreover, gene (mRNA) and protein expression of EWS-FLI1 and regulated gene, NR0B1, were inhibited with MTM analogue treatment (GI50, 6-hour) in TC-32 cells. Similarly, SP1 and target genes, VEGFA and BCL-2, gene (mRNA) and protein expressions were also inhibited with MTM analogue treatment (GI50, 6-hour) in TC-32 cells. Conjugation of Trp and/or Phe to C3-side chain of MTM increased systemic exposure in vivo. Most impressively, the addition of two Trp residues, namely MTMSA-Trp-A10 and MTMox-24 (also refer to as MTMox-Trp-Trp), resulted in systemic exposure increases of 218- and 42-fold, respectively, after intravenous (IV) bolus dose. Metabolically, tryptophan/phenylalanine conjugated MTM analogues are liable to esterase activity on carboxy-methyl functional group. Very rapid de-methylation in biological matrix was observed with MTMox-24, compared to MTMSA-Trp-A10, suggesting a regiospecific effect. However, esterase activity was limited to rodent matrices and demethylation occurred at significantly diminished rates in non-human primate and human plasma. MTM analogues were not susceptible to p450-mediated metabolism, with negligible loss in mouse liver microsome assay compared to verapamil control. MTM (1mg/kg) and MTMox-24 (6mg/kg) were detected in subcutaneously implanted (flank) LL2 tumors and liver homogenates after IV bolus dose. Interestingly, MTMSA-Trp-A10 (2mg/kg) was not. Despite a 3-fold increase in systemic exposure with rifampin oral pretreatment, an OATP inhibitor, exposure of MTM was unaffected in Oatp knockout mouse model. Exposure of MTM in liver tissue was 8.4-fold higher compared to tumor tissue with low tissue clearance. This agrees with the lack of metabolism observed in liver microsomes and may provide a mechanism for clinically observed liver toxicity. MTMSATrp-A10 had a single maximum tolerated dose (MTD) of 0.75mg/kg, compared to 1mg/kg for MTM, administered by IV bolus. In contrast, MTM-oxime analogues (MTMox-20, -23, -24 and -25) had single maximum tolerated doses of 20 – 25mg/kg. These increased tolerances are the result of additive differences in whole blood stability, cytotoxicity and systemic exposure. At a dose of 0.75mg/kg, administered every 3 days, MTMSA-Trp-A10 did not result in an efficacious result in tumor xenograft studies. These studies remain under further investigation, but the result may indicate high plasma protein binding of MTMSA-Trp-A10 and lack of free fraction available within tumor. The most selective MTM-oxime analogue in vitro, MTMox-23, significantly inhibited TC-32 (EWS-FLI1+) tumor xenograft growth (p=0.0025, day 16, one-way ANOVA multiple comparisons test) compared to MTM (p=0.1174, day 16) and extending survival for 17 days out of 48 days on study (p=0.0003, Log Rank (Mantel-Cox) single comparison test) with treatment at MTD every 3 days, compared to vehicle. Additionally, the MTM-oxime analogue with highest systemic exposure, MTMox-24, also significantly inhibited TC-32 (EWS-FLI1+) tumor xenograft growth (p=0.0003, day 21, one-way ANOVA multiple comparisons test) compared to MTM (p=0.032, day 21) and extending survival for 12 days out of 37 days on study (p=0.0004, Log Rank (Mantel-Cox) single comparison test) with treatment, compared to vehicle. Conclusion: These studies in whole highlight the importance of exposure (pharmacokinetics; PK), toxicity and efficacy (pharmacodynamics; PD) relationships. The cytotoxicity and high systemic exposure of MTMSA-Trp-A10 directly contributes to its lower tolerated dose. However, despite a similar tolerated dose to MTM, systemic exposure remains 163-fold higher at the MTD. High systemic exposure may be attributed to high plasma protein binding, but also reduces the exposure of free MTMSA-Trp-A10 within the tumor tissue, which drives the efficacious response. In contrast, the less cytotoxic and rapidly de-methylated MTM-oxime analogues allow for 25-fold higher tolerances in mice. This unique metabolism and clearance may prevent exposures required to induced systemic blood and liver toxicities induced by MTM. Moreover, at these highly tolerated doses, the initial systemic exposure at MTD is highest among analogues tested, which resulted in an efficacious response with MTMox-23 and MTMox-24 treatment in tumor xenograft models. It remains to be determined if these PK/PD relationships can be reproduced in additional animal models, including human, without inducing toxicity. Nonetheless, these initial studies in mice demonstrate that a more selective, more tolerated analogue of MTM has potential for clinical success in treating ETS fusion-dependent tumors.
33

Synthetic Lethality and Metabolism in Ewing Sarcoma : Knowledge Through Silence / Létalité synthétique et Métabolisme dans le Sarcome d'Ewing : connaissance grâce au Silence

Jonker, Anneliene 08 September 2014 (has links)
Le sarcome de Ewing est la seconde tumeur pédiatrique de l’os la plus fréquente. Elle est caractérisée par une translocation chromosomique résultant à la fusion de EWSR1 avec un membre de la famille ETS. Chez 85% des patients, cette fusion conduit à l’expression de la protéine chimérique EWS-FLI1 qui est l’oncogène majeur de ce sarcome. Ce dernier agit principalement par son action transcriptionelle sur des cibles qui lui sont propres. Au niveau thérapeutique, le sarcome d’Ewing est traité par chimiothérapie, chirurgie locale et par radiothérapie. La survie à long terme des patients est de l’ordre de 70%, mais beaucoup plus basse pour les patients métastatiques et quasi nulle lors d’une récidive. Parmi maintes caractéristiques, certains cancers présentent une dérégulation énergétique. L’influence d’EWS-FLI1 sur cet aspect n’a fait l’objet d’aucune étude dans le contexte du sarcome d’Ewing. Nous avons donc étudié par profilage métabolomique des cellules de sarcome d’Ewing en présence ou en absence d’EWS-FLI1. En comparant ces deux conditions, des modulations du profil énergétique relatif au cycle de Krebs, des précurseurs de le glycosylation ainsi que des métabolites de la voie de la méthionine et du tryptophane ont été observés. En parallèle, grâce à un crible de banque de shRNAs réalisé dans des conditions expérimentales similaires à l’étude métabolomique (lignée d’Ewing avec ou sans EWS-FLI1), nous avons pu identifier des gènes présentant des caractéristiques « synthétique létales », c'est-à-dire tuant uniquement les cellules du sarcome d’Ewing en présence de son oncogène. / Ewing sarcoma, the second most commonly occurring pediatric bone tumor, is most often characterized by a chromosomal translocation between EWSR1 and FLI1. The gene fusion EWS-FLI1 accounts for 85% of all Ewing sarcoma and is considered the major oncogene and master regulator of Ewing sarcoma. EWS-FLI1 is a transcriptional modulator of targets, both directly and indirectly. Ewing sarcoma is aggressively treated with chemotherapy, localized surgery and radiation and has an overall survival of about 70%, however, survival for metastasis or relapsed cases remains low. One of the cancer hallmarks, metabolic deregulation, is most likely partly dependent on EWS-FLI1 in Ewing sarcoma cells. In order to get a better understanding of Ewing sarcoma biology and oncogenesis, it might be of high interest to investigate the influence of EWS-FLI1 in Ewing sarcoma cells. We therefore performed a global metabolic profiling of Ewing sarcoma cells with or without inhibition of EWS-FLI1. Several changes in the energy metabolism were observed throughout this study; the observed changes were consistent with an energy profile that moved from a cancer cell energy metabolism towards the energy metabolism of a more normal cell upon EWS-FLI1 inhibition, primarily based on the TCA cycle. Levels of TCA intermediates, glycosylation precursors, methionine pathway metabolites and amino acids, especially changes in the tryptophan metabolic pathway, were altered upon EWS-FLI1 inhibition. Parallel to this study, we performed a high-throughput synthetic lethality screen, in order to not only identify essential genes for cell survival and proliferation, but also to identify new synthetic lethal targets that could specifically target Ewing sarcoma cells carrying the EWS-FLI1 fusion gene.
34

Análise da frequência de submissão de um projeto de pesquisa aos comitês de ética e da aplicação do termo de consentimento de um estudo clínico cooperativo de oncologia pediátrica

Gamboa, Maryelle Moreira Lima January 2012 (has links)
OBJETIVO: Analisar a frequência da submissão do protocolo de pesquisa aos Comitês de Ética em Pesquisa e da aplicação do Termo de Consentimento Livre e Esclarecido do projeto intitulado “Protocolo Brasileiro para o Tratamento de Pacientes com Tumores da Família de Sarcoma de Ewing”. MÉTODOS: Trata-se de estudo transversal retrospectivo. Através das fichas clínicas dos pacientes foi realizada uma análise do trâmite regulatório, bem como, do processo de obtenção do Termo de Consentimento Livre e Esclarecido de 180 pacientes de 16 instituições. RESULTADOS: Dez dos dezesseis centros submeteram o Protocolo ao Comitê de Ética em Pesquisa local. Em relação ao Termo de Consentimento Livre e Esclarecido, 161 dos 180 pacientes e/ou seus representantes legais consentiram e assinaram o Termo aplicado pelo pesquisador. Destes, 123 assinaram o Termo de Consentimento específico do protocolo e 38 assinaram o Termo de Consentimento institucional. Em relação à data da assinatura do consentimento, 141 dos 161 pacientes assinaram o Termo de Consentimento após receberem as informações referentes ao estudo clínico e antes de iniciar o tratamento. CONCLUSÃO: A maioria das instituições participantes apresenta uma estrutura adaptada ao assistencialismo e não estavam familiarizadas com aspectos éticos, legais e regulatórios que envolvem um projeto desta natureza. / OBJECTIVE: To analyze the frequency of submission of the research protocol to the Institutional Research Board and application of Informed Consent Form related to a clinical trial entitled “Treatment of Patients with Ewing Sarcoma Family of Tumors: A study of the Brazilian Cooperative Group”. METHODS: Retrospective cross-sectional study. Through patient records were performed an analysis of the regulatory proceeding and the signing of the Informed Consent Form by 180 patients from 16 institutions. RESULTS: Ten of the sixteen centers submitted the Protocol to the local Institutional Review Board. Regarding the Informed Consent Form, 161 of 180 patients and/or their legal representatives consented and signed the Form applied by the researcher. Of these, 123 signed the consent form specific to the protocol and 38 signed an institutional form. Regarding the date the consent form was signed, 141 of 161 patients signed it after receiving information about the trial and before starting treatment. CONCLUSION: Most of the participating institutions had a structure adapted to welfare and were not familiar with the ethical, legal and regulatory systems involved in a project like this.
35

Análise da frequência de submissão de um projeto de pesquisa aos comitês de ética e da aplicação do termo de consentimento de um estudo clínico cooperativo de oncologia pediátrica

Gamboa, Maryelle Moreira Lima January 2012 (has links)
OBJETIVO: Analisar a frequência da submissão do protocolo de pesquisa aos Comitês de Ética em Pesquisa e da aplicação do Termo de Consentimento Livre e Esclarecido do projeto intitulado “Protocolo Brasileiro para o Tratamento de Pacientes com Tumores da Família de Sarcoma de Ewing”. MÉTODOS: Trata-se de estudo transversal retrospectivo. Através das fichas clínicas dos pacientes foi realizada uma análise do trâmite regulatório, bem como, do processo de obtenção do Termo de Consentimento Livre e Esclarecido de 180 pacientes de 16 instituições. RESULTADOS: Dez dos dezesseis centros submeteram o Protocolo ao Comitê de Ética em Pesquisa local. Em relação ao Termo de Consentimento Livre e Esclarecido, 161 dos 180 pacientes e/ou seus representantes legais consentiram e assinaram o Termo aplicado pelo pesquisador. Destes, 123 assinaram o Termo de Consentimento específico do protocolo e 38 assinaram o Termo de Consentimento institucional. Em relação à data da assinatura do consentimento, 141 dos 161 pacientes assinaram o Termo de Consentimento após receberem as informações referentes ao estudo clínico e antes de iniciar o tratamento. CONCLUSÃO: A maioria das instituições participantes apresenta uma estrutura adaptada ao assistencialismo e não estavam familiarizadas com aspectos éticos, legais e regulatórios que envolvem um projeto desta natureza. / OBJECTIVE: To analyze the frequency of submission of the research protocol to the Institutional Research Board and application of Informed Consent Form related to a clinical trial entitled “Treatment of Patients with Ewing Sarcoma Family of Tumors: A study of the Brazilian Cooperative Group”. METHODS: Retrospective cross-sectional study. Through patient records were performed an analysis of the regulatory proceeding and the signing of the Informed Consent Form by 180 patients from 16 institutions. RESULTS: Ten of the sixteen centers submitted the Protocol to the local Institutional Review Board. Regarding the Informed Consent Form, 161 of 180 patients and/or their legal representatives consented and signed the Form applied by the researcher. Of these, 123 signed the consent form specific to the protocol and 38 signed an institutional form. Regarding the date the consent form was signed, 141 of 161 patients signed it after receiving information about the trial and before starting treatment. CONCLUSION: Most of the participating institutions had a structure adapted to welfare and were not familiar with the ethical, legal and regulatory systems involved in a project like this.
36

Análise da frequência de submissão de um projeto de pesquisa aos comitês de ética e da aplicação do termo de consentimento de um estudo clínico cooperativo de oncologia pediátrica

Gamboa, Maryelle Moreira Lima January 2012 (has links)
OBJETIVO: Analisar a frequência da submissão do protocolo de pesquisa aos Comitês de Ética em Pesquisa e da aplicação do Termo de Consentimento Livre e Esclarecido do projeto intitulado “Protocolo Brasileiro para o Tratamento de Pacientes com Tumores da Família de Sarcoma de Ewing”. MÉTODOS: Trata-se de estudo transversal retrospectivo. Através das fichas clínicas dos pacientes foi realizada uma análise do trâmite regulatório, bem como, do processo de obtenção do Termo de Consentimento Livre e Esclarecido de 180 pacientes de 16 instituições. RESULTADOS: Dez dos dezesseis centros submeteram o Protocolo ao Comitê de Ética em Pesquisa local. Em relação ao Termo de Consentimento Livre e Esclarecido, 161 dos 180 pacientes e/ou seus representantes legais consentiram e assinaram o Termo aplicado pelo pesquisador. Destes, 123 assinaram o Termo de Consentimento específico do protocolo e 38 assinaram o Termo de Consentimento institucional. Em relação à data da assinatura do consentimento, 141 dos 161 pacientes assinaram o Termo de Consentimento após receberem as informações referentes ao estudo clínico e antes de iniciar o tratamento. CONCLUSÃO: A maioria das instituições participantes apresenta uma estrutura adaptada ao assistencialismo e não estavam familiarizadas com aspectos éticos, legais e regulatórios que envolvem um projeto desta natureza. / OBJECTIVE: To analyze the frequency of submission of the research protocol to the Institutional Research Board and application of Informed Consent Form related to a clinical trial entitled “Treatment of Patients with Ewing Sarcoma Family of Tumors: A study of the Brazilian Cooperative Group”. METHODS: Retrospective cross-sectional study. Through patient records were performed an analysis of the regulatory proceeding and the signing of the Informed Consent Form by 180 patients from 16 institutions. RESULTS: Ten of the sixteen centers submitted the Protocol to the local Institutional Review Board. Regarding the Informed Consent Form, 161 of 180 patients and/or their legal representatives consented and signed the Form applied by the researcher. Of these, 123 signed the consent form specific to the protocol and 38 signed an institutional form. Regarding the date the consent form was signed, 141 of 161 patients signed it after receiving information about the trial and before starting treatment. CONCLUSION: Most of the participating institutions had a structure adapted to welfare and were not familiar with the ethical, legal and regulatory systems involved in a project like this.
37

Délais diagnostiques des cancers de l’enfant : distribution, déterminants et conséquences / DIAGNOSIS DELAYS OF CANCER IN CHILDREN : DISTRIBUTION, CAUSES AND CONSEQUENCES

Brasme, Jean-François 28 November 2014 (has links)
L’objectif de cette thèse était d’étudier la distribution, les déterminants et les conséquences des délais diagnostiques des cancers de l’enfant, par une revue systématique de la littérature, une analyse des plaintes déposées en France et au Canada et par des études ad hoc en population sur les tumeurs ayant des délais particulièrement longs : le médulloblastome et le sarcome d’Ewing.La revue systématique n’a pas retrouvé de diminution significative de la longueur des délais au cours du temps. Les délais longs étaient associés à un âge élevé, au type histologique et à la localisation de la tumeur. Les relations entre délai et gravité de la maladie étaient variables. Seul un tiers des conclusions des expertises judiciaires (n = 56) étaient concordantes avec les données de la littérature.Le délai diagnostique médian des enfants atteints de médulloblastome en Ile-de-France (n = 166) était de 65 jours. Les délais longs étaient associés paradoxalement à des métastases moins fréquentes et à une histologie favorable, mais pas à la survie ni aux séquelles.Le délai diagnostique médian des enfants atteints de sarcome d’Ewing en France (n = 436) était de 70 jours. Les délais longs, liés à un âge élevé et à la localisation de la tumeur, n’étaient pas associés au volume tumoral, à la présence de métastases, à l’opérabilité ni à la survie.Pour certaines tumeurs, une association entre délais diagnostiques et gravité est établie (rétinoblastome) ou hautement probable. Pour d’autres, l’absence d’association démontrée permettrait de dédramatiser la perception de leurs conséquences, sans dispenser d’essayer de réduire ces délais, notamment pour en atténuer les conséquences psychologiques. / The aim of this thesis was to study the distribution, determinants and consequences of time to diagnosis of cancer in children, through a systematic review of the literature and an analysis of lawsuits in France and Canada, and two population-based studies of tumors with particularly long diagnosis delays: medulloblastoma and Ewing sarcoma.The systematic review did not identify any significant decreases in time to diagnosis during the studies. Long times to diagnosis were associated with older age, histological type and location of the tumor. Associations between time to diagnosis and severity of the disease varied. Only a third of the court-appointed experts (n = 56) provided testimony concordant with the available medical literature.The median time to diagnosis of children with medulloblastoma in the area of Paris (n = 166) was 65 days. Diagnosis delays were paradoxically associated with less frequent metastasis and favorable histology, but not with survival, or sequelae.The median time to diagnosis of children with Ewing sarcoma in France (n = 436) was 70 days. Diagnosis delays, related with older age and tumor location, were not associated with tumor size, presence of metastasis, surgical outcome, or survival.For some tumors, an association between time to diagnosis and severity of the disease is well established (e.g. retinoblastoma), or highly probable. For others, the lack of demonstrated associations could tone down the perception of the supposed consequences of diagnosis delays - but does not exempt from trying to reduce them, in order to alleviate their psychological consequences.

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