No description available.

Suspeita-se da Síndrome de Lynch (SL) a partir da história pessoal e familial do indivíduo. Posteriormente, os dados histopatológicos, imuno-histoquímicos e moleculares podem ser utilizados para aprimorar o diagnóstico da doença. Entretanto, um grande desafio no diagnóstico da Síndrome de Lynch é a baixa acurácia dos critérios clínicos utilizados. OBJETIVOS: Avaliar a frequência de SL em pacientes submetidos a tratamento cirúrgico por câncer colorretal e com história familial de câncer. Avaliar quais dos critérios clínicos e/ou moleculares seriam mais informativos no diagnóstico desta Síndrome na população brasileira. PACIENTES E MÉTODOS: Estudaram-se 458 casos de câncer colorretal (CCR), do Serviço de Coloproctologia do Departamento de Gastroenterologia do Hospital das Clínicas - FMUSP, de janeiro de 2005 a dezembro de 2008. História familial (HF) positiva para CCR ocorreu em 118 pacientes. Promoveu-se a revisão das lâminas para critérios histopatológicos de MSI (diretrizes de Bethesda), avaliação imuno-histoquímica (IHC) para as proteínas MLH1, MSH2, MSH6, PMS2, através do complexo avidina-biotina-peroxidase e instabilidade de microssatélites (MSI) (BAT-25, BAT-26, NR-21, NR-24 e MONO-27). Realizada a análise da mutação somática para o BRAF em todos os casos com MSI positiva. RESULTADOS: Dos 118 pacientes com HF, 61 (51,69%) preencheram pelo menos um dos critérios de Bethesda revisados. 36 eram do sexo feminino (59%), média de idade de 53,2 anos. Nove (14,7%) pacientes apresentaram todos os critérios de Amsterdam I. Cinquenta e dois tumores localizaram-se no cólon esquerdo. Os componentes histopatológicos de MSI incluíram: linfócitos intratumoral (47,5%), característica expansiva do tumor (29,5%) e o componente mucinoso (27,8%) (componentes histopatológicos de MSI instável) em 44 (72%). A IHC estava alterada em oito (13%) e a MSI em 12 pacientes (20%). Houve associação entre os critérios de Amsterdam I e MSI e na IHC com MLH1 e PMS2. Houve associação entre os critérios de Bethesda revisados com o sexo, na histopatologia com o componente mucinoso e a reação Crohn like; com a MSI e na IHC com o MLH1 e PMS2. O BRAF foi realizado nos 12 casos com MSI positiva e em todos os casos foram negativos. Os indivíduos que apresentaram o critério 4 de Bethesda revisado (CCR ou câncer associado a SL, diagnosticado em um ou mais parentes de primeiro grau, desde que uma das neoplasias tenha ocorrido antes dos 50 anos de idade), tiveram uma chance 10,6 vezes maior de apresentar MSI positiva. Propôs-se um escore para caracterizar pacientes com SL baseado nas variáveis estudadas nesta pesquisa. CONCLUSÕES: A frequência de Síndrome de Lynch nos pacientes submetidos a ressecção por câncer e com história familial foi de 20%. O critério 4 de Bethesda revisado associou-se mais fortemente à presença de instabilidade de microssatélites na população estudada. O escore desenvolvido neste estudo contribui como uma ferramenta prática na ampliação diagnóstica da Síndrome de Lynch / Lynch Syndrome is suspected due to the personal and familial history of the individual. Subsequently, histopathological, immunohistochemical and molecular data can be used to improve diagnosis of the disease. However, a major challenge in the diagnosis of Lynch Syndrome is the low accuracy of clinical criteria. OBJECTIVES: To assess the frequency of Lynch Syndrome in patients with familial cancer history submitted to colorectal cancer resection. To assess what clinical and / or molecular criteria would be the most informative in the diagnosis of this syndrome in Brazilian population. PATIENTS AND METHODS: 458 colorectal cancer (CRC) cases were studied, from the Coloproctology Unit of the Department of Gastroenterology, Hospital das Clinicas - USP, from January 2005 to December 2008. Positive family history (FH) for CRC occurred in 118 patients. The pathologic slides were reviewed for histological criteria for MSI (Bethesda guidelines), immunohistochemical analysis (IHC) for MLH1, MSH2, MSH6, PMS2 proteins, through the avidin-biotin-peroxidase complex, and microsatellite instability (MSI) (BAT-25, BAT-26, NR-21, NR-24 and MONO-27). BRAF somatic mutation was analyzed in all cases with positive MSI. RESULTS: Of the 118 patients with HF, 61 (51.69%) met at least one of the revised Bethesda criteria. Thirty-six were female (59%), and the mean age was 53.2 years. Nine (14.7%) patients presented all Amsterdam criteria I. Fifty-two tumors were located in the left colon. MSI histopathological components included: intratumoral lymphocytes (47.5%), expansive characteristics of the tumor (29.5%) and mucinous component (27.8%) (Histological unstable components of MSI) in 44 (72%). IHC was abnormal in eight (13%) and MSI in 12 patients (20%). There was an association between the Amsterdam criteria I and MSI; and between IHC with MLH1 and PMS2. There was an association with the revised Bethesda criteria with: sex, mucinous histology and Crohn\'s like reaction; with MSI and IHC with PMS2 and MLH1. BRAF was performed in 12 patients with MSI positive, and all were negative. Patients who presented the revised Bethesda criteria 4 (CRC or cancer associated with SL, diagnosed in one or more first-degree relatives, with one of the neoplasms occurred before 50 years of age), had a 10.6 increased chance to display positive MSI. Based on the studied variables, we proposed a score to characterize the Lynch Syndrome. CONCLUSIONS: The frequence of Lynch Syndrome in patients who were submitted to cancer resection, and had a cancer familial history was 20%. The criterion 4 Revised Bethesda was associated more strongly with the presence of microsatellite instability in the studied population. The developed score contributes as a practical tool in the diagnosis of Lynch Syndrome

INTRODUÇÃO: O câncer colorretal metastático (CCRm) é uma doença clinicamente e molecularmente heterogênea. Os pacientes apresentam diferentes prognósticos e respostas variáveis às terapias direcionadas contra o tumor. Alterações na função do sistema de reparo do DNA (deficiency mismatch repair - dMMR) estão associadas com o fenótipo de instabilidade de microssatélites e bom prognóstico em tumores de estádio inicial. No entanto, dMMR é raro no CCRm e pouco se sabe sobre sua influência na taxa de resposta (TR) ao tratamento. Nosso objetivo primário foi comparar a TR, de acordo com o status dMMR, nos pacientes com CCRm. Os desfechos secundários foram TR, conforme RAS e BRAF mutados, e a sobrevida global (SG), de acordo com dMMR. MÉTODOS: Estudo retrospectivo com grupo controle que comparou a TR por RECIST 1.1 em pacientes com CCRm, tratados com quimioterapia (QT) sistêmica, de acordo com o status dMMR. Os dados clínicos foram coletados, retrospectivamente, dos prontuários médicos. Todas as imagens foram digitais e recuperadas para avaliação de resposta por um único radiologista, cego quanto ao status dMMR. dMMR foi definido como a perda de expressão imuno-histoquímica em pelo menos um dos genes MMR (MLH1, MSH2, MSH6 e PMS2). Mutações em RAS e BRAF foram investigadas por meio de sequenciamento gênico. Os casos foram os pacientes com dMMR, e os controles, com MMR proficiente (pMMR), selecionados de forma consecutiva, em proporção de 1:2. Com base em características clínicas e moleculares, os indivíduos dMMR foram classificados como provável Lynch ou dMMR esporádico. Estatística descritiva foi usada para resumir os resultados. A associação entre dMMR e os resultados específicos de cada grupo foram analisados pelo teste do qui-quadrado, e para a avaliação de SG mediana, curvas de Kaplan-Meier e teste log-rank foram utilizados. Valores bicaudados de p < 0.05 foram considerados significativos. RESULTADOS: Entre janeiro de 2009 e janeiro de 2013, de 1270 pacientes, 762 foram elegíveis e rastreados para dMMR: N = 27 (3,5%) tiveram dMMR e N = 735 (96,5%) tiveram pMMR. Dada a raridade, foram incluídos 14 indivíduos com dMMR fora do período de inclusão, totalizando 41 casos (pacientes dMMR) e 84 controles (pacientes pMMR). Em análise por intenção de tratamento, considerando os pacientes que receberam pelo menos uma dose de QT baseada em oxaliplatina (N dMMR = 34), aqueles com dMMR apresentaram TR numericamente menor, comparados aos pMMR (11.7% vs 28.6%, OR: 0.33, IC 95%: 0.08-1.40, p = 0.088). Em análise por protocolo, incluindo apenas os pacientes que preencheram os critérios de inclusão (N dMMR = 33), aqueles com dMMR mantiveram TR menor à QT baseada em oxaliplatina em primeira linha, em comparação aos doentes pMMR, embora estatisticamente não significante (12.1% vs 28.6 %, OR: 0.34, IC 95%: 0.09-1.18, p = 0.102). Ainda neste contexto, os pacientes com possível Lynch apresentaram maior TR do que os indivíduos com provável dMMR esporádico (16% vs 0). Mutações em RAS ou BRAF não influenciaram na TR ou sobrevida. O status \"provável dMMR esporádico\" foi fator de pior prognóstico, quando todos os pacientes da amostra (N dMMR = 41) foram considerados. CONCLUSÃO: Este estudo sugere que dMMR é preditivo de resistência à quimioterapia baseada em oxaliplatina, como mostrado por outros estudos. Aparentemente, essa resistência é mais acentuada nos pacientes dMMR esporádicos, sugerindo heterogeneidade biológica nos doentes com CCRm e dMMR / BACKGROUND: Metastatic colorectal cancer (mCRC) is a clinically and molecularly heterogeneous disease, where patients present different prognosis and variable responses to cancer-directed therapies. Alterations in the function of DNA deficiency mismatch repair (dMMR) genes are associated with microsatellite instability and good prognosis in early stage tumors. However dMMR dysfunction is rare in mCRC and little is known about its influence on treatment response rate (RR). Our primary endpoint was to compare the RR of mCRC patients according to dMMR status and to explore differences between patients with likely sporadic versus likely Lynch-related tumors. Secondary endpoints were RR according to RAS and BRAF mutation status, and survival times as per dMMR status. METHODS: Retrospective study with control group that compared the RR by RECIST 1.1 in patients with mCRC treated with systemic chemotherapy according to dMMR status. Clinical data were collected retrospectively from medical charts. All images were digital and were retrieved for response evaluation by a single radiologist blinded to dMMR results. dMMR status was defined as loss of immunohistochemistry expression in at least one of the MMR genes (MLH1, MSH2, MSH6 e PMS2). RAS and BRAF mutations were investigated through next generation sequencing. Cases were defined as dMMR and controls, as proficient MMR (pMMR) patients, in a 1:2 fashion. Based on clinical and molecular features, dMMR patients were classified as likely Lynch or sporadic. Descriptive statistics was used to summarize the results. The association between dMMR and outcomes of each group were analyzed by chi-square test; estimates of median overall survival were done by the Kaplan-Meier method and comparisons, by the log-rank test. Two-tailed p values < 0.05 were considered significant. RESULTS: From January 2009 to January 2013, out of 1270 patients, 762 were eligible and screened for dMMR: N = 27 (3.5%) had dMMR and N = 735 (96.5%) had pMMR. Given the rarity, 14 dMMR cases outside the inclusion period were included, with a total of 41 cases (dMMR patients) and 84 controls (pMMR patients). By intention-to-treat analysis, considering all patients who received at least one dose of oxaliplatin-based chemotherapy (N dMMR = 34), those with dMMR had numerically lower RR, compared with pMMR (RR = 11.7% vs 28.6%, OR: 0.33, 95% CI: 0.08-1.40, p = 0.088). As per protocol analysis, considering only the patients who met inclusion criteria (N dMMR = 33), those with dMMR status persisted with numerically, but non-significant, lower RR to first-line oxaliplatin-based chemotherapy compared with pMMR (12.1% vs 28.6%, OR: 0.34, 95% CI: 0.09-1.18, p = 0.102); also, patients with likely Lynch-related mCRC presented higher RR than subjects with probable sporadic dMMR (16% vs 0). Either survival or RR was influenced by RAS or BRAF mutations. Probable sporadic dMMR status was a poor prognostic factor when all patients in the sample (N dMMR = 41) were analyzed. CONCLUSION: This study suggests that the dMMR phenotype is predictive of resistance to oxaliplatin-based chemotherapy, as shown by other studies. Apparently, such resistance is more pronounced in the sporadic dMMR patients, suggesting biological heterogeinity within the dMMR mCRC patients

Suspeita-se da Síndrome de Lynch (SL) a partir da história pessoal e familial do indivíduo. Posteriormente, os dados histopatológicos, imuno-histoquímicos e moleculares podem ser utilizados para aprimorar o diagnóstico da doença. Entretanto, um grande desafio no diagnóstico da Síndrome de Lynch é a baixa acurácia dos critérios clínicos utilizados. OBJETIVOS: Avaliar a frequência de SL em pacientes submetidos a tratamento cirúrgico por câncer colorretal e com história familial de câncer. Avaliar quais dos critérios clínicos e/ou moleculares seriam mais informativos no diagnóstico desta Síndrome na população brasileira. PACIENTES E MÉTODOS: Estudaram-se 458 casos de câncer colorretal (CCR), do Serviço de Coloproctologia do Departamento de Gastroenterologia do Hospital das Clínicas - FMUSP, de janeiro de 2005 a dezembro de 2008. História familial (HF) positiva para CCR ocorreu em 118 pacientes. Promoveu-se a revisão das lâminas para critérios histopatológicos de MSI (diretrizes de Bethesda), avaliação imuno-histoquímica (IHC) para as proteínas MLH1, MSH2, MSH6, PMS2, através do complexo avidina-biotina-peroxidase e instabilidade de microssatélites (MSI) (BAT-25, BAT-26, NR-21, NR-24 e MONO-27). Realizada a análise da mutação somática para o BRAF em todos os casos com MSI positiva. RESULTADOS: Dos 118 pacientes com HF, 61 (51,69%) preencheram pelo menos um dos critérios de Bethesda revisados. 36 eram do sexo feminino (59%), média de idade de 53,2 anos. Nove (14,7%) pacientes apresentaram todos os critérios de Amsterdam I. Cinquenta e dois tumores localizaram-se no cólon esquerdo. Os componentes histopatológicos de MSI incluíram: linfócitos intratumoral (47,5%), característica expansiva do tumor (29,5%) e o componente mucinoso (27,8%) (componentes histopatológicos de MSI instável) em 44 (72%). A IHC estava alterada em oito (13%) e a MSI em 12 pacientes (20%). Houve associação entre os critérios de Amsterdam I e MSI e na IHC com MLH1 e PMS2. Houve associação entre os critérios de Bethesda revisados com o sexo, na histopatologia com o componente mucinoso e a reação Crohn like; com a MSI e na IHC com o MLH1 e PMS2. O BRAF foi realizado nos 12 casos com MSI positiva e em todos os casos foram negativos. Os indivíduos que apresentaram o critério 4 de Bethesda revisado (CCR ou câncer associado a SL, diagnosticado em um ou mais parentes de primeiro grau, desde que uma das neoplasias tenha ocorrido antes dos 50 anos de idade), tiveram uma chance 10,6 vezes maior de apresentar MSI positiva. Propôs-se um escore para caracterizar pacientes com SL baseado nas variáveis estudadas nesta pesquisa. CONCLUSÕES: A frequência de Síndrome de Lynch nos pacientes submetidos a ressecção por câncer e com história familial foi de 20%. O critério 4 de Bethesda revisado associou-se mais fortemente à presença de instabilidade de microssatélites na população estudada. O escore desenvolvido neste estudo contribui como uma ferramenta prática na ampliação diagnóstica da Síndrome de Lynch / Lynch Syndrome is suspected due to the personal and familial history of the individual. Subsequently, histopathological, immunohistochemical and molecular data can be used to improve diagnosis of the disease. However, a major challenge in the diagnosis of Lynch Syndrome is the low accuracy of clinical criteria. OBJECTIVES: To assess the frequency of Lynch Syndrome in patients with familial cancer history submitted to colorectal cancer resection. To assess what clinical and / or molecular criteria would be the most informative in the diagnosis of this syndrome in Brazilian population. PATIENTS AND METHODS: 458 colorectal cancer (CRC) cases were studied, from the Coloproctology Unit of the Department of Gastroenterology, Hospital das Clinicas - USP, from January 2005 to December 2008. Positive family history (FH) for CRC occurred in 118 patients. The pathologic slides were reviewed for histological criteria for MSI (Bethesda guidelines), immunohistochemical analysis (IHC) for MLH1, MSH2, MSH6, PMS2 proteins, through the avidin-biotin-peroxidase complex, and microsatellite instability (MSI) (BAT-25, BAT-26, NR-21, NR-24 and MONO-27). BRAF somatic mutation was analyzed in all cases with positive MSI. RESULTS: Of the 118 patients with HF, 61 (51.69%) met at least one of the revised Bethesda criteria. Thirty-six were female (59%), and the mean age was 53.2 years. Nine (14.7%) patients presented all Amsterdam criteria I. Fifty-two tumors were located in the left colon. MSI histopathological components included: intratumoral lymphocytes (47.5%), expansive characteristics of the tumor (29.5%) and mucinous component (27.8%) (Histological unstable components of MSI) in 44 (72%). IHC was abnormal in eight (13%) and MSI in 12 patients (20%). There was an association between the Amsterdam criteria I and MSI; and between IHC with MLH1 and PMS2. There was an association with the revised Bethesda criteria with: sex, mucinous histology and Crohn\'s like reaction; with MSI and IHC with PMS2 and MLH1. BRAF was performed in 12 patients with MSI positive, and all were negative. Patients who presented the revised Bethesda criteria 4 (CRC or cancer associated with SL, diagnosed in one or more first-degree relatives, with one of the neoplasms occurred before 50 years of age), had a 10.6 increased chance to display positive MSI. Based on the studied variables, we proposed a score to characterize the Lynch Syndrome. CONCLUSIONS: The frequence of Lynch Syndrome in patients who were submitted to cancer resection, and had a cancer familial history was 20%. The criterion 4 Revised Bethesda was associated more strongly with the presence of microsatellite instability in the studied population. The developed score contributes as a practical tool in the diagnosis of Lynch Syndrome

No description available.

INTRODUÇÃO: O câncer colorretal metastático (CCRm) é uma doença clinicamente e molecularmente heterogênea. Os pacientes apresentam diferentes prognósticos e respostas variáveis às terapias direcionadas contra o tumor. Alterações na função do sistema de reparo do DNA (deficiency mismatch repair - dMMR) estão associadas com o fenótipo de instabilidade de microssatélites e bom prognóstico em tumores de estádio inicial. No entanto, dMMR é raro no CCRm e pouco se sabe sobre sua influência na taxa de resposta (TR) ao tratamento. Nosso objetivo primário foi comparar a TR, de acordo com o status dMMR, nos pacientes com CCRm. Os desfechos secundários foram TR, conforme RAS e BRAF mutados, e a sobrevida global (SG), de acordo com dMMR. MÉTODOS: Estudo retrospectivo com grupo controle que comparou a TR por RECIST 1.1 em pacientes com CCRm, tratados com quimioterapia (QT) sistêmica, de acordo com o status dMMR. Os dados clínicos foram coletados, retrospectivamente, dos prontuários médicos. Todas as imagens foram digitais e recuperadas para avaliação de resposta por um único radiologista, cego quanto ao status dMMR. dMMR foi definido como a perda de expressão imuno-histoquímica em pelo menos um dos genes MMR (MLH1, MSH2, MSH6 e PMS2). Mutações em RAS e BRAF foram investigadas por meio de sequenciamento gênico. Os casos foram os pacientes com dMMR, e os controles, com MMR proficiente (pMMR), selecionados de forma consecutiva, em proporção de 1:2. Com base em características clínicas e moleculares, os indivíduos dMMR foram classificados como provável Lynch ou dMMR esporádico. Estatística descritiva foi usada para resumir os resultados. A associação entre dMMR e os resultados específicos de cada grupo foram analisados pelo teste do qui-quadrado, e para a avaliação de SG mediana, curvas de Kaplan-Meier e teste log-rank foram utilizados. Valores bicaudados de p < 0.05 foram considerados significativos. RESULTADOS: Entre janeiro de 2009 e janeiro de 2013, de 1270 pacientes, 762 foram elegíveis e rastreados para dMMR: N = 27 (3,5%) tiveram dMMR e N = 735 (96,5%) tiveram pMMR. Dada a raridade, foram incluídos 14 indivíduos com dMMR fora do período de inclusão, totalizando 41 casos (pacientes dMMR) e 84 controles (pacientes pMMR). Em análise por intenção de tratamento, considerando os pacientes que receberam pelo menos uma dose de QT baseada em oxaliplatina (N dMMR = 34), aqueles com dMMR apresentaram TR numericamente menor, comparados aos pMMR (11.7% vs 28.6%, OR: 0.33, IC 95%: 0.08-1.40, p = 0.088). Em análise por protocolo, incluindo apenas os pacientes que preencheram os critérios de inclusão (N dMMR = 33), aqueles com dMMR mantiveram TR menor à QT baseada em oxaliplatina em primeira linha, em comparação aos doentes pMMR, embora estatisticamente não significante (12.1% vs 28.6 %, OR: 0.34, IC 95%: 0.09-1.18, p = 0.102). Ainda neste contexto, os pacientes com possível Lynch apresentaram maior TR do que os indivíduos com provável dMMR esporádico (16% vs 0). Mutações em RAS ou BRAF não influenciaram na TR ou sobrevida. O status \"provável dMMR esporádico\" foi fator de pior prognóstico, quando todos os pacientes da amostra (N dMMR = 41) foram considerados. CONCLUSÃO: Este estudo sugere que dMMR é preditivo de resistência à quimioterapia baseada em oxaliplatina, como mostrado por outros estudos. Aparentemente, essa resistência é mais acentuada nos pacientes dMMR esporádicos, sugerindo heterogeneidade biológica nos doentes com CCRm e dMMR / BACKGROUND: Metastatic colorectal cancer (mCRC) is a clinically and molecularly heterogeneous disease, where patients present different prognosis and variable responses to cancer-directed therapies. Alterations in the function of DNA deficiency mismatch repair (dMMR) genes are associated with microsatellite instability and good prognosis in early stage tumors. However dMMR dysfunction is rare in mCRC and little is known about its influence on treatment response rate (RR). Our primary endpoint was to compare the RR of mCRC patients according to dMMR status and to explore differences between patients with likely sporadic versus likely Lynch-related tumors. Secondary endpoints were RR according to RAS and BRAF mutation status, and survival times as per dMMR status. METHODS: Retrospective study with control group that compared the RR by RECIST 1.1 in patients with mCRC treated with systemic chemotherapy according to dMMR status. Clinical data were collected retrospectively from medical charts. All images were digital and were retrieved for response evaluation by a single radiologist blinded to dMMR results. dMMR status was defined as loss of immunohistochemistry expression in at least one of the MMR genes (MLH1, MSH2, MSH6 e PMS2). RAS and BRAF mutations were investigated through next generation sequencing. Cases were defined as dMMR and controls, as proficient MMR (pMMR) patients, in a 1:2 fashion. Based on clinical and molecular features, dMMR patients were classified as likely Lynch or sporadic. Descriptive statistics was used to summarize the results. The association between dMMR and outcomes of each group were analyzed by chi-square test; estimates of median overall survival were done by the Kaplan-Meier method and comparisons, by the log-rank test. Two-tailed p values < 0.05 were considered significant. RESULTS: From January 2009 to January 2013, out of 1270 patients, 762 were eligible and screened for dMMR: N = 27 (3.5%) had dMMR and N = 735 (96.5%) had pMMR. Given the rarity, 14 dMMR cases outside the inclusion period were included, with a total of 41 cases (dMMR patients) and 84 controls (pMMR patients). By intention-to-treat analysis, considering all patients who received at least one dose of oxaliplatin-based chemotherapy (N dMMR = 34), those with dMMR had numerically lower RR, compared with pMMR (RR = 11.7% vs 28.6%, OR: 0.33, 95% CI: 0.08-1.40, p = 0.088). As per protocol analysis, considering only the patients who met inclusion criteria (N dMMR = 33), those with dMMR status persisted with numerically, but non-significant, lower RR to first-line oxaliplatin-based chemotherapy compared with pMMR (12.1% vs 28.6%, OR: 0.34, 95% CI: 0.09-1.18, p = 0.102); also, patients with likely Lynch-related mCRC presented higher RR than subjects with probable sporadic dMMR (16% vs 0). Either survival or RR was influenced by RAS or BRAF mutations. Probable sporadic dMMR status was a poor prognostic factor when all patients in the sample (N dMMR = 41) were analyzed. CONCLUSION: This study suggests that the dMMR phenotype is predictive of resistance to oxaliplatin-based chemotherapy, as shown by other studies. Apparently, such resistance is more pronounced in the sporadic dMMR patients, suggesting biological heterogeinity within the dMMR mCRC patients

Abstract Colorectal cancer is the third most common cancer in the developed countries. Originally, development of CRC was thought to proceed by a sequence of steps known as an adenoma-carcinoma sequence. At present CRC is recognized as a disease developing through diverse pathways. Serrated adenocarcinoma represents an endpoint of tumors developing from serrated pathway. This thesis focuses on studying the molecular alterations in serrated adenocarcinoma. Microsatellite instability, hypermethylation of promoter region in DNA repair genes hMLH1 and MGMT, frequency of KRAS and BRAF mutations and mutation spectrum of PTCH1 was determined in serrated adenocarcinomas (n=42) and compared to non-serrated adenocarcinomas (n=75). MSI, particularly low level of MSI (p=0.02) and methylation of both hMLH1 and MGMT promoters (p=0.004, p=0.026) were found to be more prevalent for serrated CRC. BRAF mutation was frequent and specific to serrated adenocarcinomas (p&lt;0.001) and KRAS mutations were more frequent in serrated adenocarcinomas than in non-serrated cancers (p=0.002). A significant association between BRAF mutation, hMLH1 and MGMT methylation and MSI-H phenotype was found in serrated carcinomas. KRAS mutation was seen in association with MSS/MSI-L phenotype; in fact, if serrated adenocarcinoma presents with MSI-L there always seems to be a KRAS mutation as well. Negative immunohistochemical staining of the hMLH1 enzyme was in association with methylation of the gene and proved reliable in the detection of MSI-H phenotype (p&lt;0.0001). Sequencing analysis of the whole coding regions of the PTCH1 gene did not reveal any truncating mutation to explain the previously detected downregulation of the gene in serrated CRCs. In conclusion, serrated adenocarcinomas proved to be an independent, but heterogeneous subtype of CRCs. High combined mutation rate (79–82%) of KRAS and <I>BRAF</I> in serrated adenomas and adenocarcinomas indicates that MAPK activation is a crucial part of the serrated pathway. BRAF mutations are specific for serrated adenocarcinoma, and identify a subset of serrated adenocarcinomas with gene methylation and a tendency for MSI-H. High frequency of KRAS mutations in serrated adenocarcinomas suggests that a significant proportion of KRAS-mutated CRCs originate from serrated precursors. / Tiivistelmä Paksu- ja peräsuolisyöpä eli kolorektaalisyöpä on Suomessa kolmanneksi yleisin syöpätyyppi. Syöpää edeltävien muutosten tunnistaminen on tärkeää, jotta sen ehkäisy ja seuranta olisi tehokasta. Tavallisia adenoomapolyyppeja on pidetty tärkeimpinä kolorektaalisyövän esiastemuutoksina. 2000-luvulla on havaittu, että nk. sahalaitapolyypit edustavat tärkeää osaa esiastemuutoksista, ja näistä kehittyvää syöpää kutsutaan sahalaitaiseksi syöväksi. Sahalaitaisen syövän kehittymismekanismit eroavat huomattavasti tavallisesta kolorektaalisyövästä. Tässä väitöskirjassa keskityttiin tutkimaan sahalaitaiselle syövälle tyypillisiä morfologisia piirteitä sekä geneettisiä muutoksia. Työssä selvitettiin DNA mikrosatelliitti-instabiliteetin sekä DNA korjausgeenien hMLH1 ja MGMT promoottorialueiden hypermetylaation esiintyminen, nk. MAPK –signaalinsiirtoreitin komponenttien, KRAS ja BRAF -geenien, mutaatioiden yleisyys sekä PTCH1 geenin mutaatiokirjo sahalaitaisissa (n=42) ja tavallisissa kolorektaalisyövissä (n=75). DNA:n mikrosatelliitti-instabiliteetti, erityisesti matala-asteisena (MSI-L) (p=0.02) sekä <I>MLH1</I> ja hMGMT -geenien metylaatio (p=0.004, p=0.026) olivat yleisempiä sahalaitaisissa syövissä. <I>BRAF</I> mutaatio oli yleinen sekä spesifinen sahalaitasyöville (p&lt;0.001). Myös KRAS -mutaatiot olivat yleisempiä sahalaitaisissa syövissä (p=0.002). BRAF mutaatio, hMLH1 sekä MGMT metylaatio ja korkea-asteinen mikrosatelliitti-instabiliteetti (MSI-H) esiintyivät hyvin usein yhdessä sahalaitaisissa syövissä. Sahalaitaisissa syövissä KRAS –mutaatiot liittyivät MSI-L fenotyyppiin. hMLH1 geenin ilmentyminen tutkittiin myös immunohistokemiallisesti. Sahalaitaisissa syövissä MLH1 –proteiinin häviäiminen oli yhteydessä metylaatioon ja liittyi spesifisesti MSI-H:n esiintymiseen (p &lt; 0.0001). PTCH1 geenin sekvensointi ei paljastanut proteiinin toimintaa vahingoittavia muutoksia, eikä tuloksen perusteella pystytä selittämään aikaisemmin havaittua geenin ilmentymisen häviämistä sahalaitaisessa syövässä. Tulosten perusteella sahalaitainen syöpä on oma, mutta heterogeeninen kolorektaalisyövän alatyyppi. KRAS ja BRAF –geenien aktivoivien mutaatioiden yleisyys (79–82%) osoittaa, että MAPK -reitin aktivaatio on tärkeää sahalaitaisen syövän kehityksessä. BRAF -mutaatiot ovat spesifisiä sahalaitaisille syöville, ja yhdessä metylaation sekä MSI-H:n kanssa identifioi osan sahalaitasyövistä omaksi ryhmäkseen. <I>KRAS</I> –mutaatioiden yleisyys sahalaitaisissa syövissä antaa aiheen epäillä, että merkittävä osa KRAS –mutaation sisältävistä kolorektaalisyövistä kehittyy sahalaitapolyypeista.