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Background Thymomas are a group of rare neoplasms of the anterior mediastinum. The objective of this study was to describe the demographics, clinical characteristics and treatment approaches in Latin America. Methods This was a retrospective multicenter cohort study including patients with histologically proven thymomas diagnosed between 1997 and 2018. Demographics, clinicopathological characteristics and therapeutic outcomes were collected locally and analyzed in a centralized manner. Results A total of 135 patients were included. Median age at diagnosis was 53 years old (19–84), 53.3% (n = 72) of patients were female and 87.4% had an ECOG performance score ranging from 0–1. A total of 47 patients (34.8%) had metastatic disease at diagnosis. Concurrent myasthenia gravis occurred in 21.5% of patients. Surgery was performed in 74 patients (54.8%), comprising 27 (20%) tumorectomies and 47 (34.8%) thymectomies. According to the Masaoka‐Koga system, overall survival (OS) at five‐years was 73.4%, 63.8% and 51%, at stages I–II, III–IVA and IVB, respectively (p = 0.005). Furthermore, patients with low lactate dehydrogenase (LDH) (≤373 IU/L) at baseline and myasthenia gravis concurrence showed significantly better OS (p = 0.001 and p = 0.008, respectively). In multivariate analysis, high LDH levels (HR 2.8 [95% confidence interval [CI]: 1.1–7.8]; p = 0.036) at baseline and not performing a surgical resection (HR 4.1 [95% CI: 1.3–12.7]; p = 0.016) were significantly associated with increased risk of death. Conclusions Our data provides the largest insight into the clinical characteristics and outcomes of patients with thymomas in Latin America. Survival in patients with thymomas continues to be very favorable, especially when subjected to adequate local control., Here, we report the largest analysis of clinical characteristics of thymomas and outcomes in Latin American patients. Out of 135 patients included in the study, 21.5% (n = 29) concurrently presented myasthenia gravis. Relapse‐free survival rates at five‐years were 58.5% for stage I–II, and 35.4% for stage III. Five‐year overall survival rates were 73.4%, 63.8% and 51%, at stages I–II, III–IVA and IVB, respectively.

Introduction We analyzed the prevalence of non–small-cell lung cancer (NSCLC) with a programmed cell death ligand 1 (PD-L1) tumor proportion score (TPS) of ≥ 50% and compared the results with the existing data from clinical trials and databases from other countries. Materials and Methods The Latin American Cooperative Oncology Group and Grupo Brasileiro de Oncologia Toracica performed a retrospective, cross-sectional study from August 2017 to April 2018. PD-L1 expression was collected from pathology reports from 5 laboratories in Brazil. All tests were sponsored by the pharmaceutical industry on request from the treating medical oncologist. PD-L1 expression was assessed by immunohistochemistry. The variables were summarized as absolute and relative frequencies or the median and interquartile range. Pearson's χ2 test was used to compare the TPS categories stratified by sex, age, and histologic type. All analyses were performed with SAS, version 9.4, and were deemed statistically significant at P Results A total of 1512 patients were included in the present study. Their median age was 66 years. Most patients were men (56.02%), and the most common histologic type was adenocarcinoma (58.04%); 109 tumors (11.31%) had EGFR mutations and 34 (3.64%) had ALK gene rearrangements. Overall, 56.54% had a PD-L1 TPS Conclusion The prevalence of high PD-L1 expression among the Brazilian NSCLC samples was lower than previously described in other countries, which could affect the number of patients who might be candidates for immunotherapy alone.

Background Intestinal and diffuse gastric adenocarcinomas differ in clinical, epidemiological and molecular features. However, most of the concepts related to the intestinal-type are translated to gastric adenocarcinoma in general; thus, the peculiarities of the diffuse-type are underappreciated. Results Besides its growing importance, there are many gaps about the diffuse-type carcinogenesis and, as a result, its epidemiologic and pathogenetic features remain poorly understood. Conclusions Alternative hypotheses to explain these features are discussed, including the role of the gastric microbiota, medical therapies, and modifications in the stomach’s microenvironment.

The development of immune checkpoint inhibitors initiated a new era of anti-cancer therapies with very promising results. Although effective for many patients, others are primarily refractory to this treatment. Identifying systemic immune cell subpopulations associated with treatment success or failure can reveal mechanisms behind therapeutic failure and offer potential predictive markers of clinical use. Here, for the first time, we performed a prospective non-interventional study and evaluated the pretreatment systemic immunological status of 33 patients with stage IV non-small cell lung cancer treated with anti-PD-1 combined with chemotherapy by flow cytometry. Treatment outcome was evaluated 9 weeks after treatment to define patients as Responders and Non-responders. Patients were reevaluated 6 months after therapy. Responders presented a higher frequency of activated CD4+ CD69+ T lymphocytes and non-classical monocytes before treatment began, which acted as predictive biomarkers for response measured at nine weeks. Conversely, CTLA-4+CD4+ T lymphocytes were more frequent in Non-responders and may contribute to an immunosuppressive milieu impairing the control of the tumor. Patients with durable responses (³ 6 months) also had higher frequency of activated CD4+ T lymphocytes before treatment started, compared with non-responders. In contrast, non-classical monocytes did not predict a durable response. However, patients with a higher frequency of both immune populations had longer median progression free survival. Our results suggest that higher frequency of peripheral activated CD4+CD69+, CD4+CTLA-4+ T cells may be useful biomarkers of therapeutic success or failure in NSCLC and point to mechanisms underlying therapeutic outcome. Studies are underway to further characterize the functional potential and activation status these systemic immune subpopulations. Citation Format: Amanda B Figueiredo, Stephanie M Iasbeke Ferreira, Guilherme FB Evangelista, Iasmim P Santos, Larissa M Kuil, Clara M Cavalcanti, Kátia LP Morais, Nayane AL Galdino, Ananda D Lopes, Helano C Freitas, Jefferson L Gross, Clóvis A Lopes Pinto, Rubens Chojniak, Vladmir C Cordeiro de Lima, Kenneth J Gollob. Increased systemic activated CD4+ T cells and non-classical monocytes are associated with improved immunotherapy response and progression-free survival in non-small cell lung cancer patients [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy; 2022 Oct 21-24; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(12 Suppl):Abstract nr A58.

Aim: Osimertinib is a third-generation, irreversible, oral EGFR tyrosine kinase inhibitor. We report real-world effectiveness and safety data. Patients & methods: EGFR T790M positive advanced non-small-cell lung cancer adults, who received ≥1 prior EGFR tyrosine kinase inhibitor, received osimertinib 80 mg daily. Primary effectiveness outcome: overall survival. Secondary effectiveness outcomes included: investigator-assessed clinical response, progression-free survival, time-to-treatment discontinuation. Results: At data cutoff, 3015 patients had enrolled: 57.1% had investigator-assessed response (95% CI: 55.2–58.9). Median progression-free survival: 11.1 months (95% CI: 11.0–12.0) and median time-to-treatment discontinuation: 13.5 months (95% CI: 12.6–13.9). Interstitial lung disease/pneumonitis-like events reported in 28 (1%) patients. Conclusion: Osimertinib demonstrated clinical effectiveness similar to efficacy observed in the clinical trial program with no new safety signals.

The participation of patients in precision oncology trials needs to fulfill molecular-based selection criteria. This strongly limits accrual, and as a consequence, screening successes have decreased, costs have increased, and fewer subjects are enrolled. To achieve narrowed targets, studies have been forced to be multicenter and multinational to reach a larger pool of candidates. However, this globalization faces many challenges, as, for example, in the case of precision oncology trials. These trials have a complex structure that is dependent upon a high-tech infrastructure and knowledge in a dynamic environment. Given the movement of precision clinical cancer research to regions other than Europe and the U.S., it is important to evaluate the feasibility of performing such trials in lower-middle- and low-income countries. Here we critically discuss the advantages of conducting precision oncology clinical trials in Latin America and make suggestions on how to overcome the main challenges involved. IMPLICATIONS FOR PRACTICE: Precision clinical trials in oncology are studies that require candidates to have tumors with specific molecular alterations, which are considered the target for the trial experimental therapy. Because many molecular alterations are rare, fewer patients are enrolled. This has led to trials being forced to be multicenter and multinational, including trials in Latin America. This article discusses the challenges and opportunities to conduct precision oncology trials in Latin America, aiming to help sponsors and investigators to solve complex issues that ultimately lead to more of such trials being run in the region, potentially benefiting more Latin American patients with cancer.

IntroductionTherapies that target activatingEgfr, Alk, Ros1and other mutations have become first-line treatments that improve NSCLC patient’s life expectancy. Latin-American patients are poorly represented in clinical trials and in genomic databases, thus little is known about the prevalence of actionable mutations in this population. This study characterizes, for the first time, the somatic mutations found in 52 actionable genes, and describe a novel set of potentially actionable mutations, in NSCLC patients from Chile, Brazil and Peru, while correlating these genomic occurrences with relevant clinical, demographic and pathology aspects.Methods1732 subjects diagnosed with NSCLC were analyzed. DNA and RNA were sequenced using a 52 genes NGS panel. Mutations were annotated using the Variant Effect Predictor, COSMIC, OncoKB and the Cancer Genome Interpreter to categorize somatic mutations.ResultsWe found a total of 1713 mutations with 626 (36.5%) novel, potentially driver mutations. 66.1% of these novel mutations were predicted as Tier 1 driver mutations. Actionable mutations forRet and Alkwere more prevalent in Brazil than in Chile, whereasMetexon-14 skipping was significantly enriched in Chile. In Peru,Egfris higher whileKrasis lower. A high number of novels potentially driver mutations in know NSCLC actionable genes, such asAlk, Erbb2, Ret, Met, andRos1, was found.ConclusionsThe analysis of many Latin America subjects revealed a significant number of clinically actionable but also novel somatic mutations in cancer genes highlighting the importance of including less-represented populations in clinical trials and molecular studies.

The world currently faces a pandemic due to SARS-CoV-2. Relevant information has emerged regarding the higher risk of poor outcomes in lung cancer patients. As such, lung cancer patients must be prioritized in terms of prevention, detection and treatment. On May 7th, 45 experts in thoracic cancers from 11 different countries were invited to participate. A core panel of experts regarding thoracic oncology care amidst the pandemic gathered virtually, and a total of 60 initial recommendations were drafted based on available evidence, 2 questions were deleted due to conflicting evidence. By May 16th, 44 experts had agreed to participate, and voted on each of the 58 recommendation using a Delphi panel on a live voting event. Consensus was reached regarding the recommendations (>66 % strongly agree/agree) for 56 questions. Strong consensus (>80 % strongly agree/agree) was reached for 44 questions. Patients with lung cancer represent a particularly vulnerable population during this time. Special care must be taken to maintain treatment while avoiding exposure.

DNA mismatch repair deficiency (dMMR) leads to increased mutation load, which in turn may impact anti-tumor immune responses and treatment effectiveness. Currently, there are different mutational signatures described in primary cancers that are associated with dMMR. Whether the somatic and epigenetic changes in MMR genes precede one or more dMMR signatures, and if so by which mechanism remains unknown. To investigate the relationship between these changes and dMMR signatures, we performed a de novo extraction of mutational signatures in a large cohort of 787 gastric cancer patients. We detected three dMMR-related signatures, one of which clearly discriminates tumors with MLH1 gene silencing caused by hyper-methylation within its promoter (AUC = 98%). We then demonstrate that samples with the highest exposures to signature share features related to better prognosis, encompassing clinical and molecular aspects, as well as altered immune infiltrate composition, predictive of a better response to immune checkpoint inhibitors. Overall, our analysis explored the impact of modifications in MMR-related genes on shaping specific mutational signatures and we provide evidence that patient classification based on mutational signature exposure can identify a group of patients with a good prognosis and who are potentially good candidates for immunotherapy.

Hyaluronan (HA) is the mainly component of extracelular matrix and shows promise for detecting cancerous change in pleural effusion and urine. Because cell-extracellular matrix interactions participate in several steps required for tumor cell invasion and formation of metastases, a group of glycosaminoglycans as hyaluronan has been targeted as a potentially useful tumor marker.Sputum can be readily and easily collected from almost any individual and could function as in non-invasive lung cancer screening strategies.The aim of this study is to determine HA levels in the sputum of patient with non-small cell lung cancer (NSCLC) compared with that observed in healthy individuals and in patients diagnosed with chronic obstructive pulmonary disease (COPD) .HA was examined in sputum samples of 64 NSCLC, 14 COPD patients and 18 healthy controls. We observed significantly higher concentration of HA in the sputum of NSCLC patients when compared with healthy individuals (median: 29,9 ng/µg x 14,1 ng/µg; p Median HA concentration in COPD patients was 20,1 ng/µg and also significantly lower than that observed in NSCLC patients (p The results hereby presented suggest a promising role of HA concentration determination in the sputum as a tool to differentiate NSCLC patients from healthy individuals, as well as a predictor of therapeutic response.

About 4% to 7% of the non–small-cell lung cancer patients have anaplastic lymphoma kinase (ALK) rearrangements, and specific targeted therapies improve patients' outcomes significantly. ALK gene fusions are detected by immunohistochemistry or fluorescent in situ hybridization as gold standards in South America. Next-generation sequencing–based assays are a reliable alternative, able to perform simultaneous detection of multiple events from a single sample. We analyzed 4240 non–small-cell lung cancer samples collected in 37 hospitals from Chile, Brazil, and Peru, where ALK rearrangements were determined as part of their standard of care (SofC) using either immunohistochemistry or fluorescent in situ hybridization. A subset of 1450 samples was sequenced with the Oncomine Focus Assay (OFA), and the concordance with the SofC tests was measured. An orthogonal analysis was performed using a real-time quantitative PCR echinoderm microtubule-associated protein-like 4-ALK fusion detection kit. ALK fusion prevalence is similar for Chile (3.67%; N = 2142), Brazil (4.05%; N = 1013), and Peru (4.59%; N = 675). Although a comparison between OFA and SofC assays showed similar sensitivity, OFA had significantly higher specificity and higher positive predictive value, which opens new opportunities for a more specific determination of ALK gene rearrangements.

Objectives: Approximately 60% of lung adenocarcinomas (LAs) carry mutations that can guide treatment with tyrosine-kinase inhibitors (TKI) and other targeted therapies. Data on activating mutations in EGFR and other tyrosine-kinase receptor (TKR) genes in highly admixed populations, such as that of Brazil, are scarce. In this study, we comprehensively analyzed the actionable alteration profile of LA in Brazilian patients. Materials and Methods: EGFR driver mutation data were collected from a large Brazilian LA cohort covering an 8-year period of molecular testing in a single institution. Tests were performed using three distinct methods, and demographic and histopathological data were analyzed. For a subset of patients, driver mutations in KRAS, NRAS, and BRAF and gene fusions involving TKR genes (before TKI treatment) and EGFR T790M (after TKI treatment) were assessed. Results: EGFR mutations were detected in 25% of 1,316 LAs evaluated, with exon 19 deletions and exon 21 L858R TKI sensitizing mutations representing 72.5% of all mutations. Mutation rates were higher in women and non-smokers (p < 0.001). Next-generation sequencing was very sensitive, with a lower rate of inconclusive results compared with Sanger sequencing and pyrosequencing. EGFR/RAS/BRAF hotspot gene panels were applied in 495 LA cases and detected oncogenic mutations in 51.3% of samples, most frequently in EGFR (22.4%) and KRAS (26.9%). In subgroups of 36 and 35 patients, gene fusions were detected in 11.1% of tumors and EGFR T790M resistance mutations were detected in 59% of plasma samples from patients previously treated with TKI, respectively. Conclusion: This report provides the first comprehensive actionable alteration portrait of LA in Brazil. The high rate of actionable alterations in EGFR and other driver genes in LA reinforces the need to incorporate TKI guided by molecular diagnostics into clinical routines for patients in both public and private healthcare systems.

Gastric cancer (GC) is the fifth most common type of cancer worldwide with high incidences in Asia, Central, and South American countries. This patchy distribution means that GC studies are neglected by large research centers from developed countries. The need for further understanding of this complex disease, including the local importance of epidemiological factors and the rich ancestral admixture found in Brazil, stimulated the implementation of the GE4GAC project. GE4GAC aims to embrace epidemiological, clinical, molecular and microbiological data from Brazilian controls and patients with malignant and pre-malignant gastric disease. In this letter, we summarize the main goals of the project, including subject and sample accrual and current findings.

Simple Summary Mutational signatures due to DNA mismatch repair deficiency (dMMR) is common in many cancers. However, the prognostic value of dMMR-associated mutational signatures remains to be assessed. Here, we performed a de novo extraction of mutational signatures in a cohort of 787 patients with gastric cancer. We detected three dMMR-related signatures, one of which clearly discriminates tumors with MLH1 gene silencing through hypermethylation of its promoter. We showed evidence that classification based on mutational signature exposure can be used to identify groups of patients with common clinical, immunological, and mutational features related directly to better prognosis. Abstract DNA mismatch repair deficiency (dMMR) is associated with the microsatellite instability (MSI) phenotype and leads to increased mutation load, which in turn may impact anti-tumor immune responses and treatment effectiveness. Various mutational signatures directly linked to dMMR have been described for primary cancers. To investigate which mutational signatures are associated with prognosis in gastric cancer, we performed a de novo extraction of mutational signatures in a cohort of 787 patients. We detected three dMMR-related signatures, one of which clearly discriminates tumors with MLH1 gene silencing caused by promoter hypermethylation (area under the curve = 98%). We then demonstrated that samples with the highest exposure of this signature share features related to better prognosis, encompassing clinical and molecular aspects and altered immune infiltrate composition. Overall, the assessment of the prognostic value and of the impact of modifications in MMR-related genes on shaping specific dMMR mutational signatures provides evidence that classification based on mutational signature exposure enables prognosis stratification.

Mechanisms of viral oncogenesis are diverse and include the off-target activity of enzymes expressed by the infected cells, which evolved to target viral genomes for controlling their infection. Among these enzymes, the single-strand DNA editing capability of APOBECs represent a well-conserved viral infection response that can also cause untoward mutations in host DNA. Here we show, after evaluating somatic single-nucleotide variations and transcriptome data in 240 gastric cancer samples, a positive correlation between APOBEC3s mRNA-expression and the APOBEC-mutation signature, both increased in EBV+ tumors. The correlation was reinforced by the observation of APOBEC-mutations preferentially occuring in transcriptionally-active loci. The EBV-infection and APOBEC3 mutation-signature axis was confirmed in a validation cohort of 112 gastric cancer patients. Our findings suggest that APOBEC3 upregulation in EBV+ cancer may boost the mutation load, providing further clues to the mechanisms of EBV-induced gastric carcinogenesis. After further validation, this EBV-APOBEC axis may prove to be a secondary driving force in the mutational evolution of EBV+ gastric tumors, whose consequences in terms of prognosis and treatment implications should be vetted.

Whereas cancer patients have benefited from liquid biopsies, the scenario for gastric adenocarcinoma (GAC) is still dismal. We used next-generation deep sequencing of TP53-a highly mutated and informative gene in GAC-to assess mutations in tumor biopsies, plasma (PL) and stomach fluids (gastric wash-GW). We evaluated their potential to reveal tumor-derived mutations, useful for monitoring mutational dynamics at diagnosis, progression and treatment. Exon-capture libraries were constructed from 46 patients including tumor biopsies, GW and PL pre and post-treatment (196 samples), with high vertical coverage >8,000×. At diagnosis, we detected TP53 mutations in 15/46 biopsies (32.6%), 7/46 GW- (15.2%) and 6/46 PL-samples (13%). Biopsies and GW were concordant in 38/46 cases (82.6%) for the presence/absence of mutations and, furthermore, four GW-exclusive mutations were identified, suggesting tumor heterogeneity. Considering the combined analysis of GW and PL, TP53 mutations found in biopsies were also identified in 9/15 (60%) of cases, the highest detection level reported for GAC. Our study indicates that GW could be useful to track DNA alterations, especially if anchored to a comprehensive gene-panel designed for this malignancy.

Objectives Contrasting other EGFR mutations (EGFRm) in lung adenocarcinomas, insertions in exon 20 (exon20ins) are generally associated with resistance to targeted therapy, limiting therapeutic options and impoverishing the prognosis compared to other EGFRm. We sought to extensively characterize exon20ins from a large cohort of lung adenocarcinomas in Hispanic patients. Materials and methods This was a region-wide, observational longitudinal cohort study to evaluate characteristics and outcomes of patients with exon20ins in lung adenocarcinoma, based on a secondary analysis of electronic records from the Geno1.2-CLICaP Platform and extended genotype testing. Patients from six Latin-American countries were included (Argentina, Colombia, Costa Rica, Ecuador, Panama, and Mexico). Data obtained included the molecular spectrum (extended genotyping for mutations in BRAF, NRAS, PIK3CA, Her2 and MEK1, as well as for EGFR amplification, ALK and PD-L1 protein expression), clinic-pathologic characteristics, prevalence and outcomes to therapeutic approach. Results and conclusions 4.005 patients diagnosed with stage III/IV lung adenocarcinoma from 2011 to 2016 were initially screened. Among these, 88 patients had a confirmed exon20 in. and were included; median age was 66-years, 62.5% were females, 64% were never smokers and 39% presented with brain metastases. The H773insH variant was the most frequent, making up 21.6% of cases. A common EGFRm was concomitantly found in 36.4% (del19/L858R), and 8% (G719X/L861Q/S768I) of cases. Five cases had additional mutations in PI3K, KRAS and MEK1, 26% had EGFR amplification and 81.7% had PD-L1 expression 1–50%. Overall response rate to first-line therapy was 28% and overall survival was 16.4 months. Prognosis was positively influenced by the concomitant presence of common EGFRm and response to first-line. Our results suggest that patients with EGFR exon20ins have similar clinical characteristics to those with common EGFRm but a poorer prognosis. Last, the mean PD-L1 expression in this population seems higher than for patients with common EGFRm.

Background and Purpose Intestinal mucositis is a common side-effect of irinotecan-based cancer chemotherapy regimens. This mucositis is associated with cytokine activation and NO synthesis. Production of IL-18 is up-regulated in patients suffering from inflammatory bowel disease. Therefore, we have investigated the role of IL-18 in the pathogenesis of irinotecan-induced intestinal mucositis. Experimental Approach Wild type (WT), IL-18 or caspase-1 knockout mice were treated with either saline or irinotecan (60 mg·kg−1 per 4 days, i.p.) or the IL-18 binding protein (IL-18bp, 10 mg·kg−1) before irinotecan. On day 5, diarrhoea was monitored and proximal intestinal strips were obtained for histopathology, in vitro gut contractility, myeloperoxidase (MPO) and inducible NOS (iNOS) activity, and detection of IL-18 expression. Key Results Irinotecan induced severe diarrhoea accompanied by intestinal injury (villi shortening and increased crypt depth). Additionally, irinotecan treatment increased MPO and iNOS activity, iNOS immunostaining and IL-18 expression in WT mice compared with saline treatment. The IL-18 production was associated with macrophages. In vitro, intestinal smooth muscle strips were hyperresponsive to ACh after irinotecan treatment. Increases in MPO and iNOS activity, intestinal contractility and diarrhoea were prevented in caspase-1 knockout and IL-18 knockout mice, and in IL-18bp-treated WT mice. Furthermore, the Survival of irinotecan-treated mice was increased and iNOS immunoexpression and IL-18 production prevented in IL-18 knockout mice. Conclusions and Implications Targeting IL-18 function may be a promising therapeutic approach to decreasing the severity of intestinal mucositis during irinotecan treatment regimens.

e15585 Background: Loss of expression of ARID1A, a tumor suppressor gene involved in chromatin remodeling and transcription activation, has been associated with worse prognosis in Asian GC patients (Yang et al. 2016). Mutations in ARID1A have been found in 8-27% of GC, usually leading to gene/protein inactivation. Here we evaluated the possible involvement of ARID1A mutations and clinical characteristics, while considering genomic ancestry and survival, in a cohort of Brazilian GC patients. Methods: We included 112 pts diagnosed with GC and treated at AC Camargo Cancer Center before 2013. The study was approved by local IRB. Genomic DNA was used for capture-based enrichment of a customized gene panel including 99 genes. Libraries were sequenced in the NextSeq 500 platform (Illumina), using paired-end reads (2x75bp). For ancestry inference we used a set of ancestry informative markers, covered by target and off-target reads, described by Elhaik et al. (2014). Results: Median age was 64y (37-91), 63% were male, M:F ratio was 1.73. Most cases were classified as Diffuse (47.3%) followed by Intestinal (41.1%), Mixed (2.7%) and 8.9% were deemed unclassifiable by Lauren´s classification. 22.3% were stage I, 20.5% stage II, 42.9% stage III and 14.3% stage IV. 11.6% were in the GEJ and 80.4% were in corpus/antrum. Five patients were EBV positive (4.5%). Genomic ancestry was as follows: 55.4% European, 27.7% Asian, 8.9% African and 8% were highly admixed ( < 50% of any ancestry). ARID1A was mutated in 19% of cases and showed no association with age at diagnosis (p = 0.21), gender (p = 0.76), tumor location (p = 0.55), staging (p = 0.42), Lauren (p = 0.14) or EBV (p = 0.42). ARID1A had no impact on overall survival (OS) (HR 1.17; 95%CI 0.59-2.31; p = 0.6) or disease-free survival (DFS) (HR 1.24; 95%CI 0.66-2.32; p = 0.5), including the subgroup with Asian genomic background: OS-Asia (HR 1.08; 95%CI 0.31-3.81; p = 0.9), DFS-Asia (HR 1.15; 95%CI 0.32-4.12; p = 0.8). Conclusions: ARID1A is a common driver in GC among Brazilian patients. Unlike in Asians, ARID1A was not prognostic in this Brazilian cohort even in the subgroup with a predominant ( > 50%) Asian genomic ancestry.

e15588 Background: Clinical characteristics, treatment response and overall survival of GC patients differ between Asian and non-Asian countries. Here we evaluated the possible associations between PGA, clinical characteristics and survival in an admixed GC Brazilian cohort. Methods: We included 112 GC pts diagnosed and treated at AC Camargo Cancer Center (São Paulo, Brazil) before 2013. The study was approved by local IRB. Genomic DNA was used for capture-based enrichment of a customized gene panel including 99 genes. Libraries were sequenced in the NextSeq 500 platform (Illumina), using paired-end reads (2x75bp). Ancestries were determined through a set of ancestry informative markers (AIMs), covered by target and off-target reads, described by Elhaik et al. (2014). Results: An average of 406 AIMs were recovered from the available samples, revealing average ancestries was as follows: 55.4% European, 27.7% Asian, 8.9% African; 8% of subjects were highly admixed (HA; < 50% of any ancestry). We found no association between PGA and age at diagnosis (p = 0.58), tumor location (p = 0.34), Lauren (p = 0.24) and staging (p = 0.68). There was an association between PGA and gender (p = 0.04) and a marginal association between PGA and EBV (p = 0.056). BRCA2 was the only gene enriched in the Asian subgroup, compared to the other groups combined (p = 0.009). The median follow-up time was 95 months. We found no differences in median overall survival (OS) (p = 0.4) or disease-free survival (DFS) (p = 0.6) according to PGA. The HA subgroup presented worst survival outcomes compared to the other groups aggregated (mOS 34m; 95%CI 5-80 x mOS 71m; 95% CI 44-85, respectively), but the difference was not statistically significant (HR 1,73; 95% CI 0.74-4.05; p = 0.2). Even for patients with > 75% AIMs for any given ancestry, we found no differences in OS between Europeans (n = 25; mOS 86m; 95%CI 80-NA), Asians (n = 22; mOS 83m; 95%CI 51-NA) and Africans (n = 5; mOS 67m; 95%CI 22-NA), p = 0.4. Conclusions: The most prevalent ancestries in this Brazilian GC cohort were European, followed by Asian and African. Although we found associations between ancestry and a few clinical aspects, PGA was not associated with survival.

527 Background: Sidedness alongside with RAS status in colorectal adenocarcinoma has been proved to correlate with survival and response to systemic therapy. There are few data reporting how these clinical characteristics can predict the dissemination of metastasis. We hypothesize that lung metastasis were more common among those with RAS mutations and left colon primary cancers. Methods: In this study, 609 patients with stage I to IV colorectal adenocarcinoma were enrolled retrospectively. Patients were divided by sidedness, right and left and were also classified according to KRAS and NRAS status. The frequencies of lung metastasis were analyzed among the different groups. Results: Of the 609 patients analyzed, 129 (21.1%) had recurrent disease and 206 (33.8%) had synchronous metastasis. RAS status was available in 311 (92.8%) of the metastatic patients and 138(44.4%) were wild type. We found that 60 (34.7%) of the patients with RAS mutated tumors presented with metachronic or synchronous lung metastasis compared with 31 (22.5%) of the wild-type population (p = 0.019). Focusing only on sidedness, excluding rectal cancer since its already described increased incidence of lung metastasis, 47 (29.7%) of the patients with left sided colon cancer had lung metastasis compared with 8 (11.1%) of the right sided primary population (p = 0,002). It was observed similar frequencies of RAS mutations among patients with left (54.1%) and right (57.6%) sided tumor. Conclusions: RAS mutated colorectal adenocarcinoma is associated with an increased incidence of lung metastasis as well as left sided tumors where this finding seems to be independent of RAS status.

In the last module of this consensus, controversial topics were discussed. Management of the disease after progression during first line chemotherapy was the first discussion. Next, the benefits of liver resection in the presence of extra-hepatic disease were debated, as soon as, the best sequence of treatment. Conversion chemotherapy in the presence of unresectable liver disease was also discussed in this module. Lastly, the approach to the unresectable disease was also discussed, focusing in the best chemotherapy regimens and hole of chemo-embolization. RESUMO Neste último módulo do consenso, abordou-se alguns temas controversos. O primeiro tópico discutido foi o manejo da doença após progressão na primeira linha de quimioterapia, com foco em se ainda haveria indicação cirúrgica neste cenário. A seguir, o painel debruçou-se sobre as situações de ressecção da doença hepática na presença de doença extra-hepática, assim como, qual a melhor sequência de tratamento. O tratamento de conversão para doença inicialmente irressecável também foi abordado neste módulo, incluindo as importantes definições de quando se pode esperar que a doença se torne ressecável e quais esquemas terapêuticos seriam mais efetivos à luz dos conhecimentos atuais sobre a biologia tumoral e taxas de resposta objetiva. Por último, o tratamento da doença não passível de ressecção foi discutida, focando-se nos melhores esquemas a serem empregados e seu sequenciamento, bem como o papel da quimioembolização no manejo destes pacientes.

We investigated whether interleukin-4 (IL-4) is present and capable of reducing inflammatory changes seen in ifosfamide-induced hemorrhagic cystitis. Male Swiss mice were treated with saline or ifosfamide alone or ifosfamide with the classical protocol with mesna and analyzed by changes in bladder wet weight (BWW), macroscopic and microscopic parameters, exudate, and hemoglobin quantification. In other groups, IL-4 was administered intraperitoneally 1 h before ifosfamide. In other experimental groups, C57BL/6 WT (wild type) and C57BL/6 WT IL-4 (-/-) knockout animals were treated with ifosfamide and analyzed for changes in BWW. Quantification of bladder IL-4 protein by ELISA in control, ifosfamide-, and mesna-treated groups was performed. Immunohistochemistry to tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) as well as protein identification by Western blot assay for inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) was carried out on ifosfamide- and IL-4-treated animals. In other experimental groups, antiserum against IL-4 was given 30 min before ifosfamide. In IL-4-treated animals, the severity of hemorrhagic cystitis was significantly milder than in animals treated with ifosfamide only, an effect that was reverted with serum anti-IL-4. Moreover, knockout animals for IL-4 (-/-) exhibit a worse degree of inflammation when compared to C57BL/6 wild type. Exogenous IL-4 also attenuated TNF-α, IL-1β, iNOS, and COX-2 expressions in ifosfamide-treated bladders. IL-4, an anti-inflammatory cytokine, attenuates the inflammation seen in ifosfamide-induced hemorrhagic cystitis.