The use of Hilbert space theory became an important tool for ergodic theoreticians ever since John von Neumann proved the fundamental Mean Ergodic theorem in Hilbert space. Recurrence is one of the corner stones in the study of dynamical systems. In this dissertation some extended ideas besides those of the basic, well-known recurrence results are investigated. Hilbert space theory proves to be a very useful approach towards the solution of multiple recurrence problems in ergodic theory. Another very important use of Hilbert space theory became evident only relatively recently, when it was realized that non-commutative dynamical systems become accessible to the ergodic theorist through the important Gelfand-Naimark-Segal (GNS) representation of C*-algebras as Hilbert spaces. Through this construction we are enabled to invoke the rich catalogue of Hilbert space ergodic results to approach the more general, and usually more involved, non-commutative extensions of classical ergodic-theoretical results. In order to make this text self-contained, the basic, standard, ergodic-theoretical results are included in this text. In many instances Hilbert space counterparts of these basic results are also stated and proved. Chapters 1 and 2 are devoted to the introduction of these basic ergodic-theoretical results such as an introduction to the idea of measure-theoretic dynamical systems, citing some basic examples, Poincairé’s recurrence, the ergodic theorems of Von Neumann and Birkhoff, ergodicity, mixing and weakly mixing. In Chapter 2 several rudimentary results, which are the basic tools used in proofs, are also given. In Chapter 3 we show how a Hilbert space result, i.e. a variant of a result by Van der Corput for uniformly distributed sequences modulo 1, is used to simplify the proofs of some multiple recurrence problems. First we use it to simplify and clarify the proof of a multiple recurrence result by Furstenberg, and also to extend that result to a more general case, using the same Van der Corput lemma. This may be considered the main result of this thesis, since it supplies an original proof of this result. The Van der Corput lemma helps to simplify many of the tedious terms that are found in Furstenberg’s proof. In Chapter 4 we list and discuss a few important results where classical (commutative) ergodic results were extended to the non-commutative case. As stated before, these extensions are mainly due to the accessibility of Hilbert space theory through the GNS construction. The main result in this section is a result proved by Niculescu, Ströh and Zsidó, which is proved here using a similar Van der Corput lemma as in the commutative case. Although we prove a special case of the theorem by Niculescu, Ströh and Zsidó, the same method (Van der Corput) can be used to prove the generalized result. Copyright 2004, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Beters, FJC 2004, A Hilbert space approach to multiple recurrence in ergodic theory, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-02222006-104936 / > / Dissertation (MSc (Applied Mathematics))--University of Pretoria, 2007. / Mathematics and Applied Mathematics / unrestricted

In this thesis we study lower ramification numbers of power series tan- gent to the identity that are defined over fields of positive characteristics. Let f be such a series, then f has a fixed point at the origin and the corresponding lower ramification numbers of f are then, up to a constant, the multiplicity of zero as a fixed point of iterates of f. In this thesis we classify power series having ‘small’ ramification numbers. The results are then used to study ramification numbers of polynomials not tangent to the identity. We also state a few conjectures motivated by computer experiments that we performed.

Background: Colorectal adenocarcinoma is the third commonest cancer in Sweden, with 6100 new cases every year. Several factors have been identified as contributors in the development of colorectal adenocarcinoma, amongst them is inflammation inducing angiogenesis, cell migration and mutations. C-reactive protein (CRP) is an acute phase protein that is produced by the liver in response to inflammation. Method: CRP was measured at diagnosis and six weeks after surgery in 271 patients with stage II and III colorectal adenocarcinoma. The concentration of CRP in plasma was compared to parameters and outcomes as registered in the Swedish Colorectal Cancer Registry. Results: Age over 70, co-morbidities, acute operation and mortality were significantly correlated with CRP concentrations over 5 mg/l. Using Cox-regressions univariate hazard ratios (HR) were calculated. CRP (HR 1.19-7.22, p&lt;0.05), age (HR 6.02 p=0.0001), ASA-classification (HR 5.47, p=0.000), acute operation (HR 3.25, p=0.004), positive lymph nodes (HR 4.45-5.71, p=0.006), postoperative complications (HR 3.03, p=0.005) of which ICU-care (HR 13.86, p=0.000) and re- operation (HR 5.48, p=0.000) were the best predictors of mortality using the univariate model. In the multivariate model age over 70 (HR 4.792, p=0.006), postoperative complications (HR 3.645, p=0.012), N1- or N2-stage (HR 5.490 and 16.397, p=0.003 and 0.000 respectively) and preoperative CRP over 5 mg/l (HR 3.227, p=0.045) were significant predictors of mortality. Including only elective patients, N2-stage (HR 12.829, p= 0.000), age over 70 (HR 5.240, p= 0.017) and ASA-classification III and IV (HR 4.465, p= 0.012) were correlated to excess mortality.Discussion: The results confirm previous studies and adds to the evidence in support of CRP as a predictor of mortality in patients with colorectal adenocarcinoma. In the future these results might be valuable in predicting mortality and tailoring the care for patients with colorectal adenocarcinoma. / Bakgrund: Tjock- och ändtarmscancer är ett folkhälsoproblem som drabbar cirka 6 100 personer årligen, vilket gör sjukdomen till den tredje vanligaste cancerformen. Det finns flera teorier om tjock- och ändtarmscancers uppkomstmekanism. En faktor som identifierats som grundläggande för all cancer är inflammation. Kroppen reagerar vid inflammation genom att bland annat uttrycka mer av vissa äggviteämnen. Ett sådant äggviteämne är C-reaktivt protein (CRP). Denna studies syfte är att undersöka om det finns någon korrelation mellan CRP och hur allvarlig cancern är, ålder, samsjuklighet, överlevnad och prognos hos patienter med tjock- och ändtarmscancer. Metod: Journaler från 525 patienter som inkluderats i ett lokalt kvalitetsregister för tjock- och ändtarmscancer användes för att jämföra hur nivån av CRP i plasma före och efter operation påverkar cancerutfallet för patienterna. En grupp på 271 patienter valdes ut baserat på tumörstadie och analyserades med statistiska metoder. Resultat: Pre- och postoperativt CRP är korrelerar till hög ålder (över 70 år), samsjuklighet, akut operation och överlevnad hos patienterna. Patienter äldre än 70 år, de som hade CRP över 5 mg/l, lymfkörtelmetastaser eller som drabbats av en komplikation efter operationen var överrepresenterade bland de avlidna. Delades patienterna in i två grupper baserat på CRP- koncentrationen i blodet sågs en ökad dödlighet hos de med CRP över 5 mg/l före operationen. Diskussion: Tidigare studier som gjorts på området visar liknande resultat. Fortsatta studier bör göras på patientgruppen då uppföljningstiden och antalet patienter i registret ökar. I framtiden kan man använda resultaten för att hitta de patienter som löper större risk att avlida och anpassa deras behandling för att minska risken.

Countries emerging out of armed conflicts face immense challenges in their efforts to build electoral democracies. Contrary to our intuition that elections can transform violent competition to peaceful political contests, past research suggests that holding post-conflict elections only increases the chance of renewed violence. Why are elections unable to build sustainable democracies as expected? In this dissertation, I examine the question by focusing on two levels of analysis. First, I study the effects of violence on political behavior of mass publics at the individual level using the World Values survey Dataset. I argue that citizens are more inclined to support undemocratic leaders, when they are faced with threats from armed violence. Empirically, I find that presence of pre-election violence in post-conflict elections leads voters to prefer parties that are stronger in terms of their violence-wielding capacities over more moderate and peaceful parties. Second, I investigate how such an outcome might influence the risk of renewed conflicts in a country emerging out of armed conflict. The hypothesized mechanism can only be described as tragic. At individual level, fearful voters support violent parties mainly to maintain the status quo, fearing that parties with a violent reputation are likely to renew conflict if they lose the election. Tragically, however, placing undemocratic and violent parties in power only increases the likelihood of renewed conflicts. I test this expectation using an event history model to analyze all post-conflict countries from 1950 to 2010 and find that the presence of pre-election violence in a country increases its risk of renewed armed conflicts. The study has important implication for policymakers and election monitoring bodies. Rather than the current practice of observing only a single event Election Day, this study emphasizes the importance of creating a secure environment during the pre-election phase, about six months prior to the first election, in order to achieve a sustainable peace in post-conflict countries.

Les troubles dépressifs représentent aujourd’hui l’une des causes de handicap et de mortalité précoce les plus fréquentes dans le monde. Les projections établies par l’Organisation Mondiale de la Sante à l’horizon 2020 prévoient qu’ils seront classés second, juste après les maladies cardiovasculaires. De nombreuses études ont montré l’efficacité des antidépresseurs dans la prévention des rechutes, cependant la situation semble moins claire s’agissant de la prévention des récidives. Un certain nombre de travaux de recherche ont été menés visant à évaluer l’impact médico-économique des stratégies thérapeutiques préventives, en recourant à la construction de modèles de simulation, ceux-ci permettant une représentation schématique de l’évolution de la pathologie au cours du temps. Cependant, afin d’être en mesure d’évaluer l’impact économique des stratégies de prévention des troubles dépressifs, un certain nombre de facteurs doivent être pris en considération dans l’élaboration du modèle représentatif de la pathologie. Nous montrons que l’intégration de l’ensemble des facteurs déterminants des récidives, tout en considérant un horizon temporel suffisamment large afin de capter les bénéfices thérapeutiques et (éventuellement) économiques sur le long terme, n’est pas sans poser problème. Nous montrons que les modèles disponibles dans la littérature sont seulement en mesure de proposer une forme partielle d’abstraction de la pathologie dépressive, généralement réduite à un ou deux facteurs de risque principaux, parmi lesquels l’observance du traitement, l’histoire médicale ou encore les caractéristiques sociodémographiques du patient. Nous proposons alors d’envisager les modèles de simulation à événements discrets en tant que réponse possible pour la représentation des facteurs de risque des troubles dépressifs récurrents, et détaillons les principes de la méthode. Nous tentons ensuite de développer un modèle ≪ princeps ≫ à partir de données épidémiologiques. Nous montrons alors que la flexibilité associée à ce type de modélisation permet de proposer un cadre d’analyse au plus près de la réalité de la pathologie dépressive / Depressive disorders represent today one of the most frequent causes of disability and premature death worldwide. Research on the natural history of depressive disorders has shown that it is indeed a chronic rather than an acute disease. Many studies have shown the effectiveness of antidepressants in preventing relapse; however, the situation seems less clear with regard to the prevention of recurrence. A number of research activities have been conducted to evaluate the pharmaco-economic impact of preventive strategies with the help of simulation models. These techniques represent a convenient tool enabling the schematic representation of disease progression over time. However, in order to be able to assess the economic impact of prevention strategies for depressive disorders, a number of factors must be taken into account when developing the model structure. We show that the integration of all determining factors, especially on a wide-enough time horizon in order to capture the therapeutic and possible economic benefits in the long term can be somewhat problematic. We show that the models available in the literature only present a partial framework aiming at depicting disease’s risk factors (medical history, treatment compliance or socio-demographic characteristics) and progression over time. We propose then to consider the use of discrete event simulation models as a possible tool for modelling recurrent depressive disorders, and we provide a detailed description of the principles of this methodology. We then try to develop a core model based on epidemiological evidence. We show that the flexibility associated with this type of modelling method can provide an analytical framework that depicts the characteristics of the depressive pathology in a more realistic fashion

While the role of youth in post-conflict settings has increasingly gained policy attention, systematic academic studies on this topic remain scarce. This research adds to existing literature by the youth bulge theory of conflict onset to a post-conflict setting. It hypothesizes that large youth bulges at the time conflict episodes end increase the feasibility for rebel groups to relaunch their insurgence and are therefore associated with a higher risk of conflict recurrence. A global quantitative analysis revealed a statistically significant positive correlation between youth bulges and conflict recurrence. Three conditional hypotheses which focus on elements of economic, political and social exclusion that are argued to interact with youth bulges to influence the risk of conflict recurrence found no empirical support. However, the combination of findings for Hypothesis 1 and non-findings for Hypotheses 2 may indicate that the underlying cause for the relationship between youth bulges and conflict recurrence may not be based on young people’s individual grievances and motives to join a rebel group. Instead, other factors may be at play which could not be tested within the scope of this study. Despite its shortcomings, this study therefore confirms the necessity of continuing to investigate the relationship between the age distribution of a population and the risk of conflict recurrence.

INTRODUÇÃO: O carcinoma papilífero é o tumor maligno mais comum da tireoide e sua incidência vem aumentando em todo o mundo nas últimas décadas. A maioria dos pacientes com carcinoma papilífero apresenta bom prognóstico, com uma taxa de sobrevida em 10 anos de 90 a 95%, porém, as taxas de recorrência e a necessidade de continuar o tratamento continuam a ser um problema significativo para 5 a 40% dos pacientes. Embora sejam utilizadas diversas classificações de risco baseadas em diferentes fatores prognósticos, nenhuma é capaz de predizer quais pacientes terão maior chance de recorrência e desfecho desfavorável. Este estudo tem como objetivo analisar a expressão de marcadores imunoistoquímicos (Citoqueratina-19, Galectina- 3, EGFR, Ki-67, NF-kB) como marcadores preditivos de recorrência no carcinoma papilífero de tireoide. MÉTODOS: Estudo retrospectivo caso-controle, que incluiu 42 casos de pacientes com carcinoma papilífero de tireoide tratados cirurgicamente no A.C. Camargo Cancer Center entre janeiro de 2000 e julho de 2010 que apresentaram recorrência diagnosticada durante o período de seguimento. Pacientes do grupo controle foram pareados por gênero, idade, estadiamento patológico T e N. Os casos selecionados tiveram suas características clínicas registradas e variáveis anatomopatológicas revistas por um patologista com experiência em patologia tireoideana. As lâminas foram confeccionadas pelo sistema de tissue microarray e foram submetidos a reação de imunoistoquímica. Análise de sobrevida multivariada pelo método de Cox foi aplicada para identificar fatores de risco independentes para recorrência. RESULTADOS: Dos 42 casos selecionados, 30 pacientes (71,4%) eram do gênero feminino e 12 (28,6%) do gênero masculino, com a idade variando entre 10 e 80 anos (mediana de 39 anos). A maioria dos pacientes (64,3%) tinha tumores com estadiamento T inicial (T1-T2). Metade da casuística foi classificada como baixo risco, segundo a estratificação de risco da American Thyroid Association (ATA). Dezessete pacientes (40,5%) apresentava risco intermediário e quatro pacientes (9,5%) foram classificados como de alto risco. O tempo de seguimento variou de 46 a 196 meses, com tempo até a recorrência de 2 a 106 meses (mediana de 30 meses). Entre os marcadores analisados, o CK-19 e Ki-67 apresentaram associação estatisticamente significativa com o risco de recorrência (p=0,029 e p=0,007 respectivamente). Na análise multivariada, a imunoexpressão para os marcadores CK-19 e Ki-67 foram identificados como fatores independentes significativos para predição do risco recorrência loco-regional (IC-1,14-81,01 e 1,32- 7,94, respectivamente). Galectina-3, EGFR e NF-kB não apresentaram associação estatisticamente significante. Não observamos associação entre a imunoexpressão dos marcadores imunoistoquímicos e as variáveis clinico-patológicas estudadas. CONCLUSÃO: A análise imunoistoquímica dos marcadores de Ki-67 e CK-19 mostrou-se significativa para predizer recorrência tumoral em pacientes com carcinoma papilífero de tireoide / INTRODUCTION: Papillary carcinoma is the most common malignant thyroid tumor and its incidence has been increasing around the world in recent decades. Most papillary carcinoma have a good prognosis, with a 10-year survival rate of 90-95%, however, as rates of recurrence and salvage treatment remain a significant problem for 5-40% of patients. Although several risk classifications based on prognostic factors are in use, no one is able to predict precisely higher risk os recurrence and unfavorable outcome. The aim os this study is to analyse the immunohistochemical expression of selected markers (Cytokeratin-19, Galectin-3, EGFR, Ki 67, NF-kB) as predictors of thyroid papillary carcinoma recurrence. METHODS: Retrospective case-control study, which included 42 cases of patients with papillary thyroid carcinoma surgically treated at the A.C.Camargo Cancer Center between January 2000 and July 2010. The control group was matched by gender, age, pathological staging T and N stages. Clinical data was registered and pathological characteristics were reviwed by a single pathologist specialized in thyroid diseases. The slides were prepared for microarray tissue system and were submitted to an immunohistochemical reactions. Multivariate Cox method was used to identify the independent risk factors for recurrence. RESULTS: Of the 42 selected cases, 30 patients (71.4%) were female and 12 (28.6%) were male, ranging in age from 10 to 80 years (median of 39 years). Most patients (64.3%) had tumors at initial T staging (T1-T2). Half of the sample was classified as low risk according to the American Thyroid Association (ATA) risk stratification. Seventeen patients (40.5%) presented intermediate risk and four patients (9.5%) were classified as high risk. Follow-up ranged from 46 to 196 months, with time to recurrence from 2 to 106 months (median of 30 months). Among the markers analyzed, CK-19 and Ki-67 had a statistically significant association with the risk of recurrence (p = 0.029 and p = 0.007, respectively). In the multivariate logistic regression analysis, immunoexpression for the CK-19 and Ki-67 markers was independent risk factors for locoregional recurrence (CI-1.14-81.01 and 1.32-7.94, respectively) . Galectin-3, EGFR and NF-kB did not present a statistically significant association in this study. We did not observe an association between the immunoexpression of the immunohistochemical markers and the clinical-pathological variables studied. CONCLUSION: The immunohistochemical analysis of the Ki-67 and CK-19 markers are significant predictors of tumor recurrence in patients with papillary thyroid carcinoma

O tabagismo tem sido considerado um problema de saúde pública mundial pela Organização Mundial da Saúde. São previstas, para 2020, mais de dez milhões de mortes no mundo por doenças tabaco-relacionadas. Torna-se, portanto, importante aprimorar formas de tratamento aos fumantes que queiram parar de fumar e busquem ajuda por não se sentirem capazes de conseguí-lo sozinhos. O objetivo da presente proposta foi investigar se a efetividade de um programa de tratamento com base na terapia cognitivo-comportamental, associada à medicação, seria mais efetivo do que a literatura reporta para a abstinência/recaída. O critério de efetividade foi a cessação do tabagismo auto-referida pelos participantes em seis meses de tratamento. Foram avaliados 61 fumantes, com idades variando entre 18 a 60 anos, de ambos os sexos. Estes fumantes foram divididos em três grupos: pacientes que não pararam de fumar (grupo 1 ), abstinentes (grupo 2) e que recaíram (grupo 3). Os resultados demonstraram que, desta população, 78,7% estavam abstinentes ao final de seis meses de tratamento. Antes, eles fumavam, em média, por 24,6 anos, 22,6 cigarros por dia; 62,3% estavam no estágio de contemplação de acordo com Prochaska. Os motivos mais freqüentes citados para a recaída foram estresse (61,9%) e ansiedade (19%). A média geral do Fagerström foi de 4,18 (tolerância baixa), sendo que o grupo 1 apresentou o grau de tolerância menor da amostra. 77,4% dos fumantes manifestaram estar satisfeitos com o tratamento, sendo que os motivos maiores de satisfação foram o apoio psicológico e a interação com o grupo. O índice de Saúde Geral da amostra é compatível com a população geral; o Inventário Beck de Depressão (BDI) mostrou níveis maiores de depressão nos grupos 1 e 3. Foram propostos indicadores de maior risco de recaída: número de anos que o participante fuma (maior), número de cigarros fumados por dia (menor), ter fumado sempre a mesma quantidade de cigarros por dia, morar com outros fumantes, teores baixos de nicotina no cigarro em relação ao médio e alto, ausência de tentativas anteriores para cessar de fumar, freqüência baixa de participação nas sessões de tratamento, utilizar o cigarro como estimulante, fumar quando entusiasmado, quando não consegue permanecer em locais onde o fumo é proibido, quando refere ter dó de si próprio, quando manifesta pouca satisfação em relação ao trabalho e à vida. A Curva de sobrevida de Kaplan-Meier demonstrou que 49,7% desta amostra devem permanecer em abstinência por um ano, índice maior do que reporta a literatura revisada. Propõe-se a realização de estudo randomizado, com uma população maior, para validar os indicadores propostos e a efetividade comparativa do programa. / Tobaccoism has been considered as a World Public Health problem according to the World Health Organization. More than 10 million deaths in the world caused by problems related to tobacco is the prevision for 2020. Therefore, it is important to improve ways of treatment for smokers who would like to quit smoking and search for help for not being able to do so by themselves. The purpose of this present proposal was to check whether the effectiveness of a treatment based on Cognitive-Behavior Therapy associated with medication was better than the literature reported to abstinence/relapse. The effectiveness criterion was the self- mentioned smoking cessation by the participants in 6 months of the treatment. 61 smokers aged 18-60 years both male and female were evaluated. These smokers were divided into three groups: patients who did not give up smoking (group 1), the abstinence smokers (group 2) and the relapse ones (group 3). The results showed that by the end of 6 months of treatment 78,7% of this population had become abstainers. At first, as an average they smoked for 24,6 years, 22,6 cigarettes a day; 62,3% was on contemplation stage according to Prochaska. The most frequent mentioned causes for the relapse were stress (61,9%) and anxiety (19%). Fagerström general average was 4,18 (low tolerance) so that group 1 showed a lower degree of tolerance of the sample. 77,4% of the smokers mentioned to be happy with the treatment due to the psychological support and group interaction as main reasons. The General Health Index of the sample is compatible with general population and the Beck Depression Inventory (BDI) showed higher levels of depression in groups 1 and 3. Indicators of higher relapse risk were suggested: the participant smoking time (higher), how many cigarettes a day (lower), having always smoked the same quantity of cigarettes a day, living with another smokers, low nicotine in the cigarette in relation to the medium and high ones, absence of previous attempts to stop smoking, low frequency of participation in the meetings for treatment, using the cigarette as a stimulant, smoking when the smoker is excited, when he can\'t help remaining where smoking is forbidden, when the smoker mention to be sorry for himself, when the smoker presents no pleasure in relation to work and life. The Kaplan-Meier survival curve showed that 49,7% of this sample must continue in abstinence for one year, a higher index than the reported revised literature. It is suggested to perform randomized studies, with a bigger population, to validate the appointed indicators and the comparative effectiveness of the program.

O objetivo deste estudo foi avaliar retrospectivamente, em longo-prazo, os preditores de recorrência de fibrilação atrial paroxística (FA) em 139 pacientes submetidos à ablação por radiofreqüência, através das técnicas ostial ou extraostial de abordagem do átrio esquerdo, associadas ou não à ablação do istmo cavo-tricuspídeo (ICT). Variáveis pré, intra e pós-ablação foram avaliadas por análise uni e multivariada, para determinar os preditores de recorrência da FA após um procedimento. Observou-se que maior tempo de história de FA, uso de mais antiarrítmicos e recorrência de FA dentro de 60 dias pós-procedimento, aumentaram o risco de recorrência de FA a longo-prazo. Por outro lado, a associação de flutter atrial e a ablação concomitante do ICT, reduziram o risco de recorrência ao final de 33 ±12 meses. / The objective of this study was to evaluate in retrospect, in long-term, the predictors of late recurrence of atrial fibrillation (AF) in 139 patients submitted to the ablation by radiofrequency, through the techniques ostial or extra-ostial of approach of the atrium left, associated or not to the ablation of the cavotricuspid isthmus(ICT). Variables pre, intra and post-ablation were appraised for analysis uni and multivariated, to determine the predictors of recurrence of AF after one procedure. It was observed that larger time of history of AF, use of more drugs and recurrence of AF within 60 days after procedure; they increased the risk of recurrence of AF in long-term. On the other hand, the association of atrial flutter and the concomitant ablation of ICT, they reduced the recurrence risk at the end of 33 ±12 months.

INTRODUÇÃO: O transplante (TX) de fígado corresponde ao tratamento de escolha em pacientes com cirrose e carcinoma hepatocelular (CHC) precoce irressecável. A recidiva do CHC pós-transplante, entretanto, ainda apresenta impacto na sobrevida dos pacientes transplantados com este tumor. As taxas de recidiva, nos estudos mais recentes, variam de 8 a 20%. O tamanho e número de nódulos, a presença de invasão vascular e de nódulos satélites no explante, são fatores de risco relacionados à recidiva tumoral pós-transplante. No Brasil, observamos um crescimento importante do número de transplantes de fígado, inclusive por CHC. Entretanto, existem poucos estudos nacionais analisando os resultados do transplante hepático por CHC. Os objetivos do nosso estudo foram analisar as características demográficas, clínicas e a evolução dos pacientes submetidos a transplante hepático com CHC no Brasil, avaliando os fatores prognósticos relacionados com a recidiva do CHC pós-transplante e sobrevida e estudar o desempenho dos critérios de seleção para transplante utilizados no nosso país, os \"Critérios de Milão Brasil\" (CMB). MÉTODOS: Estudo de coorte retrospectivo, multicêntrico, para analisar os resultados do transplante de fígado em pacientes com CHC, após a implantação do sistema MELD. Foram incluídos 1.119 pacientes transplantados com CHC, de 07/2006 até 07/2015, em 13 centros de transplante, no Brasil. Características clínicas, demográficas, exames laboratoriais e de imagem e dados anatomopatológicos, foram retrospectivamente analisados e correlacionados com a sobrevida e recidiva do CHC pós-transplante. RESULTADOS: A maioria dos pacientes era do sexo masculino (81%), com uma idade média no TX de 58 anos. A etiologia mais associada ao tumor foi a Hepatite C (VHC), presente em 60% dos casos. O tempo médio de espera em lista foi de 9,8 meses. Setenta e oito pacientes (8%) foram incluídos por \"Down-staging\". Nos exames de imagem do diagnóstico, a maioria dos casos (67%) apresentava um nódulo, com tamanho médio de 30 mm; 85% estavam dentro dos Critérios de Milão (CM), 8% fora dos CM, mas dentro dos \"Critérios de Milão Brasil\" (CMB) e 7% fora de ambos os critérios. O tratamento do CHC em lista foi realizado em 67% dos pacientes. Na análise do explante, 44% apresentavam tumor uninodular, com tamanho médio de 26 mm e a maioria (71%) tinha CHC moderadamente diferenciado. A invasão vascular foi observada em 26% dos casos e nódulos satélites em 22%. No explante, 70% dos pacientes estavam dentro dos CM, 20,5% fora dos CM, mas dentro dos CMB e 9,5%fora de ambos os critérios. A sobrevida global foi de 79% em 1 ano, 72,5% em 3 anos e 63%, em 5 anos, com um tempo médio de seguimento de 28 meses. Excluindo os pacientes que foram a óbito no pós-operatório ( < 30 dias pós-transplante), a sobrevida global foi de 89% em 1 ano e 75%, em 5 anos. A recidiva do CHC pós-TX ocorreu em 8% (86/1.119) dos casos, em um tempo médio de 12 meses. A sobrevida livre de recidiva (SLR) foi de 94,4% em 1 ano e 88,3%, em 5 anos. A recidiva do CHC foi extra-hepática em 55% dos casos, hepática em 27% e hepática e extra-hepática em 18%. Os pacientes transplantados que evoluíram com recidiva tumoral apresentaram alta mortalidade, com uma sobrevida em 1 ano de 34% e em 5 anos de 13%. Em relação aos fatores prognósticos, os pacientes transplantados dentro dos Critérios de Milão apresentaram melhor sobrevida e SLR quando comparados aos pacientes transplantados fora dos CM, mas dentro dos CMB, tanto quando analisamos os dados do diagnóstico, quanto através da análise do explante. Os pacientes transplantados após realização de \"Down-staging\" apresentaram taxas de recidiva e sobrevida semelhantes aos pacientes transplantados sem \"Down-staging\". Os níveis séricos elevados de alfa-fetoproteína (AFP) foram um fator prognóstico importante de sobrevida e recidiva tumoral. Os melhores pontos de corte de AFP encontrados para avaliação do risco de recidiva e sobrevida foram: AFP > 400 ng/ml, no momento do diagnóstico e AFP > 200 ng/ml pré-transplante. Realizamos, também, uma comparação dos \"Critérios de Milão Brasil\" com os Critérios de Milão, através do índice IDI (Integrated Discrimination Index) e os CMB apresentaram performance inferior aos CM, na capacidade de classificar corretamente os pacientes em relação ao risco de recidiva tumoral. Os níveis séricos elevados de AFP, o estádio fora dos Critérios de Milão no momento do diagnóstico e no explante e a presença e invasão vascular no explante, foram fatores de risco independentes de recidiva do CHC pós-transplante e pior sobrevida. A idade > 60 anos e a etiologia da hepatopatia (VHC), também foram fatores prognósticos negativos de sobrevida. CONCLUSÕES: A presença de recidiva tumoral teve grande impacto na sobrevida do paciente transplantado com CHC. O estadiamento tumoral no diagnóstico e no explante, avaliado através dos Critérios de Milão, os níveis séricos elevados de AFP e a presença de invasão vascular no explante foram fatores prognósticos importantes de recidiva do CHC pós-transplante e sobrevida. Os pacientes transplantados após \"Down-staging\" apresentaram evolução pós-transplante semelhante a dos pacientes transplantados sem \"Down-staging\". Os pacientes transplantados fora dos CM, mas dentro dos CMB, apresentaram pior sobrevida, quando comparados aos pacientes dentro dos CM. Os CMB apresentaram desempenho inferior aos CM na capacidade de classificar corretamente os pacientes em relação ao risco de recidiva tumoral / INTRODUCTION: Liver transplantation (LT) is the treatment of choice for patients with cirrhosis and unresectable early hepatocellular carcinoma (HCC). HCC post-transplant recurrence, however, still has an impact on survival. In recent studies, the incidence of HCC recurrence after transplantation ranged from 8% to 20%. Tumor number, size, vascular invasion and satellite nodules have emerged as risk factors for HCC recurrence. In Brazil, in the last decade, we observed a significant increase in the number of liver transplants performed, including in patients with HCC. However, there are few national studies analyzing the results of liver transplantation for HCC. The aim of this multicentric study was to analyze the demographic characteristics, clinical features and outcomes of patients submitted to liver transplantation with HCC in Brazil, evaluate prognostic factors related to HCC post-transplant recurrence and survival, and study the performance of the national selection criteria for liver transplantation, the \"Brazilian Milan Criteria\" (BMC). METHODS: We conducted a national, multicentric, retrospective study to analyze the results of liver transplantation in patients with HCC, in \"MELD era\". Medical records of 1,119 transplanted patients with HCC between 07/2006 and 07/2015, from 13 transplant centers in Brazil, were collected. Patient and tumor characteristics, radiologic and pathologic data were retrospectively analyzed and correlated with post-transplant HCC recurrence and survival. RESULTS: Of the 1,119 HCC transplanted patients, median age was 57 years and 81% were male. Etiology of liver disease was HCV in 60%. Median time on transplant list was 9.8 months. Seventy-eight patients (8%) were included after \"Down-staging\". At diagnosis, most patients had uninodular HCC (67%) and median tumor burden was 30 mm. At diagnosis, in imaging studies, 85% of patients were within the Milan criteria (MC), 8% out of the MC but within the \"Brazilian Milan Criteria\" (BMC) and 6% out of both criteria. During the waiting list period, HCC treatment was performed in 67%. In explant analysis, tumor was uninodular in 46% and moderately differentiated in the majority of cases (71%). Median HCC size was 26 mm. Vascular invasion and satellite nodules were observed in 26% and 22% of patients, respectively. In explant, 70% of patients were within Milan Criteria, 20.5% outside MC but within BMC and 9.5% out of both criteria. Mean follow-up was 28 months, an overall survival was 79% in 1 year, 72.5% in 3 years and 63% in 5 years. Excluding patients who died within 30 days after surgery, overall survival was 89% in 1 year and 75% in 5 years. HCC post-transplant recurrence occurred in 86/1,119 (8%) cases, at a mean time of 12 months. Recurrence-free survival (RFS) was 94.4% in 1 year and 88.3% in 5 years. Sites of recurrence were extrahepatic in 55%, hepatic in 27% and both hepatic and extrahepatic in 18%. Transplanted patients with tumor recurrence presented high mortality, with 1-year survival rate of 34% and 5-year survival rate of 13%. Analyzing the prognostic factors, patients transplanted under Milan Criteria, in radiologic or explant analysis, presented better survival and RFS when compared to patients transplanted outside MC, but within BMC. Patients submitted to liver transplantation after \"Down-staging\" present long-term survival and RFS similar to patients transplanted without \"Down-staging\". Alpha-fetoprotein (AFP) levels were an important pre-transplant prognostic factor for tumor survival and recurrence. The best AFP cut off points found for relapse risk and survival assessment were: AFP at diagnosis > 400 ng / ml and AFP pre-transplant > 200 ng / ml. We also performed a comparison of the \"Brazilian Milan Criteria\" with the Milan Criteria through the Integrated Discrimination Index (IDI). The BMC presented a lower performance than the MC, in the ability to correctly classify patients in relation to the risk of relapse. Elevated AFP levels before liver transplantation, tumor outside Milan Criteria at diagnosis and in explant, and vascular invasion, were independent risk factors for post-transplant HCC recurrence and worse survival. Age > 60 years and etiology of liver disease (HCV), were also negative prognostic factors for survival. CONCLUSIONS: The presence of tumor recurrence had a major impact on survival of transplanted patients with HCC. Tumor staging, evaluated by Milan Criteria on imaging studies or explant analysis, high serum AFP levels and presence of vascular invasion in explant were important prognostic factors for post-transplant HCC recurrence and survival. Patients transplanted after Down-staging presented long-term outcomes similar to patients transplanted under conventional criteria. Patients transplanted outside Milan Criteria, but within \"Brazilian Milan Criteria\" presented worse survival, when compared to patients within MC. The BMC showed lower performance than MC in the ability to correctly classify patients in relation to the risk of tumor recurrence