TTP3.12 Stenting For Colorectal Cancer – An Evaluation of Outcomes from a District General Hospital

Background: African Americans (AAs) have the highest incidence and mortality rates of colorectal cancer (CRC) cases in the United States, with higher levels of early-onset and right-sided CRC, yet there are little data on carcinogenesis in AA CRC. Copy number variations (CNVs) affect large portions of the cancer genome, and they provide information about mechanisms of cancer initiation and progression. Given the unique clinical-pathological features of AA CRC, we hypothesized that different mechanisms operate in colorectal carcinogenesis in AAs. To test this hypothesis, we evaluated CNVs in AA CRC as compared to publically available data on CRC from the TCGA. Methods: Tumor DNA samples from 46 AA CRC cases were available through the Chicago Colorectal Cancer Consortium. Determinations of CNVs were performed using the Affymetrix Cytoscan HD platform, which provides data from 2.67 million copy number probes and 750,000 genotype probes for analysis of loss of heterozygosity (LOH) with and without copy number change. Whole chromosome-arm gains and losses were defined as the gain or loss of >50% of probes on an arm. Gains and losses were tabulated and compared to data from the TCGA. Statistical analyses of arm losses and gains were performed with Fisher exact tests, adjusting for multiple testing using a Bonferroni correction. Statistical analysis of total chromosome number alterations was performed with the chi-square test. Results: Overall, significantly fewer chromosome-arm gains and losses occurred in AA CRC cases than in TCGA CRC cases with 10% of gains and losses in AA and 34% of gains and losses from TCGA (p < 0.0001). More specifically, we found chromosome-arm gains occurred significantly less frequently for 8p (28% to 0%), 13q (56% to 26%), and 20 p and q (58% to 17% and 72% to 39%, respectively). Similarly, we found chromosome-arm losses occurred significantly less frequently for 1p (19% to 0%), 5q (17% to 0%), 8p (50% to 20%), 14q (30% to 0%), 17p (56% to 24%), 18p and q (61% to 26% and 66% to 28%, respectively), 20p (32% to 7%), and 21q (22% to 2%). All adjusted p values were less than 0.05 for these comparisons. No chromosome-arm gains or losses were significantly more frequent in AA CRC cases than in TCGA cases. The difference in chromosome-arm gain and loss was not the result of segmental gain or loss. However, analysis of genotype data revealed that copy-number neutral LOH in AA CRC cases substantially compensates for the lower frequency of chromosome-arm losses and focal amplifications for the lower frequency of gains. For example, in AAs, for chromosomal region 17p where TP53 localizes, 24% of cases exhibited 17p loss and 26% exhibited copy-number neutral LOH, for a total of 50% TP53 loss. For chromosomal region 13q where CDK8 localizes, 26% of cases exhibited 13q gain and 28% exhibited focal gains around CDK8, for a total of 54% CDK8 gain. The total frequency of tumor-suppressor gene losses and oncogene gains was similar in AA CRC and TCGA cases. Conclusion: These data show that, although the major carcinogenesis genes (as identified by LOH and gene amplification) appear to be similar in AA and TCGA CRC cases, the mechanisms of genomic instability that generate these genetic changes are different. Chromosome-arm losses are more frequent in TCGA CRC cases whereas AA CRC is driven by homologous recombination and segregation resulting in copy-number neutral LOH. Chromosome-arm gains are more frequent in TCGA CRC cases whereas AA CRC is driven by focal amplification, which could result from unequal sister chromatid exchange. Thus, these CNV differences could reflect variation in the regulation of fundamental genomic integrity mechanisms in AAs. More studies are needed to confirm these results and elucidate the mechanisms of carcinogenesis in AA CRC. This abstract is also presented as Poster A62. Citation Format: Gaius J. Augustus, Rosa Xicola, Arthur R. Brothman, Xavier Llor, Nathan A. Ellis. Homologous recombination drives African American colorectal carcinogenesis. [abstract]. In: Proceedings of the Eighth AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 13-16, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2016;25(3 Suppl):Abstract nr PR02.

e n t ; C : t r a n s a n a l decompression tube; O:technicla success rate, c l i n i c a l s u c c e s s r a t e , p ro c e d u re -re l a t e d complications, postoperative adverse events; S:RCT or non-randomized controlled studies. Condition being studiedColorectal cancer is a common malignant tumor, and about 7%-28% of patients have intestinal obstruction as the initial symptom.Emergency surgery is the main treatment, but the risk of first-stage anastomotic leakage, prophylactic stoma rate, postoperative complications and mortality of emergency surgery are high.In recent years, with the development of endoscopy and interventional medicine, intestinal stent implantation can be used as an effective treatment for colorectal cancer complicated with acute intestinal obstruction.Because of its advantages of small trauma and exact effect, it is now used as a preoperative bridging therapy, and the emergency surgery is converted to elective surgery to reduce the risk of surgery. METHODSSearch strategy We search the datebase CochraneEmbasePubmedScopusWeb of scienceclinicaltrials.Terms"Colorectal Neoplasms""Colorectal Neoplasm""Neoplasm, Colorectal""Neoplasm, Colorectal""Colorectal Tumors""Colorectal Tu m o r " " Tu m o r, C o l o r e c t a l " " Tu m o r s , C o l o r e c t a l " " N e o p l a s m s , C o l o r e c t a l " "Colorectal Cancer""Cancer, Colorectal" "Cancers, Colorectal""Colorectal Cancers" " C o l o r e c t a l C a r c i n o m a " " C a r c i n o m a , C o l o re c t a l " " C a r c i n o m a s , C o l o r e c t a l " "Carcinomas, Colorectal""Self Expandable Metallic Stents""Self Expandable Metallic Stents""Self Expandable Metallic Stent""Self Expandable Metal Stent""colonic stent" INPLASY 1 International Platform of Registered Systematic Review and Meta-analysis Protocols INPLASY Short-term outcomes of self-expandable metallic stent compared with transanal decompression tube for obstructive colorectal cancer: a systematic review and meta-analysis

A growing number of patients with obstructive colorectal cancer are being treated with self-expanding metallic stents (SEMS) followed by laparoscopic resection. The aim of this study was to assess the feasibility of stent insertion and laparoscopic surgery for obstructive colorectal cancer and to compare these outcomes to regular laparoscopic surgery for non-obstructive colorectal cancer. We retrospectively analyzed the outcomes of patients with a malignant colonic obstruction who underwent SEMS placement followed by elective laparoscopic resection. The comparison was made between stent-laparoscopy and laparoscopy alone for non-obstructive colorectal cancer. Colonic stenting as a bridge to surgery was successful in 97.1% of all cases. Fifteen patients underwent an elective laparoscopic surgery for left-sided colon and rectal cancer after SEMS. The mean interval from SEMS insertion to laparoscopic surgery was 21.5 days. There was no conversion to open surgery and no need for a diverting stoma. One patient (6.7%) experienced paralytic ileus. Our comparison of stent-laparoscopy to regular laparoscopy for non-obstructive colorectal cancer treatment showed comparable short-term postoperative outcomes with the exception of blood loss, which was greater in the stent-laparoscopy group. Elective laparoscopic surgery after colonic stenting is a safe and feasible strategy for the treatment of an acute malignant colonic obstruction.

IntroductionColonic stenting for malignant obstruction is now established as the preferred treatment for patients without curative intent, and provides a lower rate of stoma formation. Guidelines in the UK (NICE)...

BackgroundThere is already evidence that the faecal immunochemical test (FIT) is a useful tool for the diagnosis of colorectal cancer (CRC) that helps to identify symptomatic patients requiring early colonoscopy. Although the recommendation to use FIT is widely accepted, there are no data concerning whether this strategy improves patient survival.The objective was to assess whether the survival is higher if CRC patients have been first diagnosed by FIT (as compared with the rest of patients with CRC).MethodsWe identified all cases of CRC diagnosed between 2009 and 2016 in Donostialdea (Spain), excluding all the CRC detected in population screening. We focused on symptomatic patients. One thousand five hundred twenty-seven cases of CRC were divided into two groups based on the route to diagnosis: group 1: individuals who tested positive in a FIT during the year before diagnosis, and group 2: others.Survival was assessed by Kaplan-Meier estimation, and with the log-rank test. A Cox regression model was used to adjust for differences between groups due to other variables associated with survival.ResultsOne thousand nine hundred sixty-seven cases of invasive CRC were identified, of which 22.4% were detected in population screening. Of the 1527 cases diagnosed in symptomatic patients, 317 patients had undergone a FIT in the year before the diagnosis of CRC. In 279 cases(18.3%), the result had been positive and this was the first step towards their CRC diagnosis (group 1). Group 2 was composed of the 1248 cases of CRC (81.7%). Considering these cases, 1210 patients with CRC did not undergo any FIT while 38 patients presented a negative result in the year before the diagnosis. The rate of early-stage disease (stage I or II) was higher in group 1 (51.3% vs 45.5% in group 2) (p = 0.04). Furthermore, the 3-year survival was longer in group 1 (72% vs 59% in group 2) (HR 1.50; 95% CI 1.22–1.84).The variables independently associated with worse survival were: group 2, age > 70 years and stage at the moment of diagnosis.ConclusionsThe use of FIT as a diagnostic strategy in symptomatic patients may improve survival in CRC. Nonetheless,FIT is still not widely used in our region.

Summary Carcinomas of the colon and rectum are the third most common in the world in men and second in women. About 60% of cases occur in developed countries. Colorectal carcinomas are observed more frequently in men than women. In Poland most cases of colorectal cancers occur after the age of 50 – about 94%, with more than 75% of cases in both sexes falls on the population of the elderly over 60 years. Approximately 20% of patients with colorectal cancer have distant metastasis at time of diagnosis. Up to 29% patients with colorectal cancer present symptoms of bowel obstruction such as: vomiting and abdominal pain. Due to age, serious multiple comorbidities and metastatic disease, colonic stenting is safe and effective alternative approach for palliation. The authors of this article presented a case of a 76-year-old Caucasian man who was admitted to the Department of Surgical Oncology because of colorectal carcinoma which was located in descending colon. Due to age and serious multiple comorbidities, doctors with the patient decided to palliative treatment by using self-expanding metallic stent. The authors performed a literature review on enteral metallic stents for the management of malignant colorectal cancers.

<h3>Introduction</h3> FIT (faecal immunochemical test) is recommended by NICE in the assessment of symptomatic patients who do not meet criteria for urgent suspected cancer referral. It can be a useful tool where there is a lower suspicion of cancer and may avoid unnecessary colonoscopies in select cases. However, previous studies report a cancer miss rate of 7-13%.^{1 2} The aim of this audit was to identify the number of FIT-negative new colorectal cancer (CRC) cases in a single centre. <h3>Methods</h3> This was a single centre, retrospective audit. New CRC cases between June and December 2021 were identified. Bowel cancer screening programme patients were excluded. Where histology was available, adenocarcinomas and polyps with high grade dysplasia were included. If only a radiological diagnosis was available, patients were included if the diagnosis was presumed to be CRC. Neuroendocrine tumours, cancers of non-colorectal primary, lymphomas and anal squamous cell carcinomas were excluded. Data was collected on symptoms, tumour location, histology, metastases and FIT level. A FIT cut off of &lt;10ug/g was used as recommended by NICE. <h3>Results</h3> 122 patients were included. 67 of these had FIT tests prior to diagnosis, of which 5 were negative (7.5%). of the FIT negative cases, age ranged from 56-82 and cancer location varied (rectum, splenic flexure, hepatic flexure, ascending colon and caecum). Two patients presented with iron deficiency anaemia and one each with rectal bleeding, weight loss and diarrhoea with weight loss. <h3>Conclusions</h3> 7.5% of CRC cases had a negative FIT, which is consistent with previous literature. This adds to the existing body of evidence that a negative FIT does not rule out CRC in symptomatic patients and urgent referral should be offered if red flag features are present. In our series, one patient did not meet NICE criteria for suspected CRC and therefore referral would not have been indicated with a negative FIT. Clinicians must bear this in mind, thoroughly assess risk factors and use clinical judgement when considering whether to refer or investigate. This was a small, single centre audit and further studies with larger data sets are required to accurately assess FIT’s sensitivity and specificity. <h3>References</h3> Laszlo H.E, <i>et al.</i> Faecal immunochemical test for patients with ‘high-risk’ bowel symptoms: a large prospective cohort study and updated literature review.<i>Br J Cancer</i> 2021. Farrugia A, <i>et al.</i> Faecal immunochemical testing (FIT) in symptomatic patients: what are we missing?<i>Frontline Gastroenterology</i> 2020.

Colon Cancer Screening Models: Lessons and Challenges

IntroductionColonic stenting of proximal Colorectal Cancers (CRC) (lesions at splenic flexure or beyond) is technically challenging and currently out-favour as surgical techniques allow safe primary anastomosis on unprepared dilated colon....

Introduction: Some patient with metastatic colorectal cancer present colonic obstruction by their primary tumor. Palliative colonic stenting is associated with risks of colonic perforation, death and risk is probably increased with anti-VEGF. We reviewed our procedures and complications to confirm benefit with acceptable risks in our local population. Methods: We reviewed the files of all patients with colonic stenting with self-expandable metal stent (SEMS) between January 2005 and March 2014. Stenting of benign stenosis or bridge to surgery were excluded. Results: Colonic stents were used as palliation in 128 patients; 127 had metastatic colorectal cancer and 1 had locally advanced non-resectable sigmoid cancer. Our population comprise 89 women and 39 men (70|30%) with mean age of 76 (43 to 93 year-old). 31 (24%) patients were on chemotherapy before the procedure. Bevacizumab was utilised in a total of 8 patients.The procedure was considered technically successful in 120 (94%). Early major complications (≤ 7 days) were stent dysfunction 1/120, stent migration 3/120 and perforation 4/120. Within those, 3 patients recovered with medical treatment and, one developed overt haemorrhage and died in the week following urgent hemicolectomy. The one patient with early stent dysfunction had balloon dilatation and perforation ensued. The three patients with early stent migration had balloon dilation and deployment of a second stent, colonic perforation was recorded in all three with subsequent death. Total early complication rate was 7% (8/120) and early death rate was 4% (5/128). Reported late complications (> 7 days) were stent dysfunction 13/120 (11%) and no migration or perforation occurred. The perforation risk associated with stricture dilatation was 44% (4 early perforations in 9 balloon dilatations, all were fatal). The perforation rate with anti-VEGF was 63% (5 perforations in 8 patients on anti-VEGF) with 50% mortality (4/8). The perforation in anti-VEGF plus balloon dilatation is 100%(4/4) and is always fatal. Conclusion: The early major complication rate is 7% with a 4% death. The perforation and mortality of stent installation are marked in the group of bevacizumab, with balloon dilation and when these two factors were associated; with a 100% perforation and mortality. This outlines the importance of patient selection and appropriate intervention for optimal quality of care.

Purpose: The association between Human Papillomavirus (HPV) infection and the development of cervical cancer and anogenital cancer has been established. Moreover, molecular studies have detected HPV DNA in tumor tissues of head and neck cancer, esophageal cancer, and some skin cancers. Viral genes expression and multiplication occur exclusively in the nuclei of the infected cells and are tightly linked to the state of differentiation of the cells. Integration of viral DNA into host genome is essential for carcinogenesis since it promotes disruption of HPV E2 gene, leading to abnormal expression of E6 and E7 oncoproteins. Both E6 and E7 can form specific complexes with tumor suppressor gene p53 and pRB respectively. However, the role of HPV infection in colorectal cancer (CRC) and its mechanisms of carcinogenesis have not been properly elucidated. Our objectives were to evaluate the presence of HPV infection in patients with CRC; to probe the viral integrations status of HPV 16 in CRC and its adjacent normal colonic mucosa, and to determine the mRNA expression levels of the viral oncogenes HPV-16 E6 and HPV-16 E7. Experimental Designs: To determine the association of HPV and CRC, we conducted an age-and-gender matched case-control study using tumor and tumor-adjacent colorectal tissues from patients with CRC (cases) and without CRC (controls). Presence of L1, E2, and E6 genes was analyzed to determine whether a full-length HPV genome existed in tumor and normal tissue samples. Head-to-tail junctions of HPV-16 genomes were analyzed to determine the integration the HPV-16 genome in the HPV-16 (+) cases. Moreover, we determined the mRNA expression levels of E6 and E7 in the HPV-16 (+) cases. Hypothesis testing was performed using Pearson Chi-square analysis of proportions using SPSS 17. Results: A total of 45 (ß-actin+) CRC patients (mean age 61 ±11 years, 24 males) and 47 controls (mean age was 60 ± 9 years, 18 males) were evaluated. Tumors were located in proximal colon (n=7) and distal colon (n=38). HPV DNA was identified in 19 of 45 (42.2%) patients with CRC and in 2 of 47 (4.3%) controls (OR = 16.4; 95% CI 3.5-76.3, p &amp;lt; 0.001). HPV-16 was identified in 12 of 19 (63.2%) HPV (+) CRC patients and in none (0%) HPV(+) controls. The twelve HPV-16 CRC cases showed integration of HPV-16. Three of 12 (25%) HPV16 (+) cases expressed E6 and E7 mRNA. Among the 12 CRC cases where both tumor and adjacent tissue was available, 2 of 9 (16.7%) exhibited HPV-16 DNA in both tumor and tumor-adjacent tissues.Conclusion: These results suggest that colorectal HPV infection is common among patients with CRC. The presence of HPV in tumors located proximal to the rectum suggests that this infection might not result from direct spread from anogenital sites. Moreover, our finding of highly frequent integration of viral DNA and the active expression of E6 and E7 viral oncogenes in the host strongly suggests that HPV oncoproteins may play a role in the pathogenesis of colorectal carcinogenesis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 552. doi:1538-7445.AM2012-552

Methylenetetrahydrofolate reductase (MTHFR) is involved in DNA synthesis and repair. We here aimed to investigate two common polymorphisms, C677T and A1298C, with genotype and haplotype frequencies in colorectal cancer (CRC) cases among Jordanian. 131 CRC cases were studied for MTHFR C677T and A1298C polymorphisms, compared to 117 controls taken from the general population, employing the PCR-RFLP technique. We found the frequency of the three different genotypes of MTHFR C677T among Jordanians to be CC: 61.7%, CT: 35.2%, and TT 3.1% among CRC cases and 50.9%, 38.8% and 10.3% among controls. Carriers of the TT genotype were less likely to have CRC (OR=0.25; 95%CI: 0.076-0.811; p=0.021) as compared to those with the CC genotype. Genotype analysis of MTHFR A12987C revealed AA: 38.9%, AC: 45%, and CC 16% among CRC cases and 37.4%, 50.4% and 12.2% among controls. There was no significant association between genetic polymorphism at this site and CRC. Haplotype analysis of MTHFR polymorphism at the two loci showed differential distribution of the TA haplotype (677T-1298A) between cases and controls. The TA haplotype was associated with a decreased risk for colorectal cancer (OR=0.6; 95% CI: 0.4-0.9, p=0.03). The genetic polymorphism of MTHFR at 677 and the TA haplotype may modulate the risk for CRC development among the Jordanian population. Our findings may reflect an importance of genes involved in folate metabolism in cancer risk.

e18136 Background: Colombia has gone to great lengths to provide nearly universal health care insurance for its patients, as 96.6% of its constituents now have health insurance as of 2014 compared to 23.5% in 1993. Most Colombians are associated with either contributive insurance (CI) in which employees and employers contribute to the insurance or subsidized insurance (SI) in which government funds cover the insurance cost. Colorectal cancer (CRC) has the 5th highest incidence of all malignancies in Colombia. This abstract aims to compare CRC care delivery metrics between CI and SI. Methods: We used the Colombian National Administrative Cancer Registry (NACR) data compiled from the Department of Health Ministry from January 2, 2016- January 1, 2017 consisting of 32 departments and 1122 municipalities. CRC cases were investigated by incidence, mortality, percentage of cases with early stage detection, stage I-III with curative surgery intent, nutritional support, and TNM staging, and days between suspicion to diagnosis, diagnosis to first treatment, neoadjuvant therapy to surgery, and surgery to adjuvant therapy. Results: There were 2605 new CRC cases in the NACR in 2017, with 1691 CI cases and 823 SI cases. There was a noticeably higher incidence in CI (7.2 new cases per 100,000 people) than in SI (3.7 new cases per 100,000), and a higher mortality rate (5.0 deaths per 100,000) in CI compared with SI cases (2.6 deaths per 100,000). There was a significant increase in average wait time for SI CRC cases from diagnosis to first treatment (77.7 days vs. 57.3 days, p = .027) and in average time to neoadjuvant therapy to surgery in CI cases (123.1 days vs. 92.5 days, p = .054) with longer but statistically insignificant wait times in SI cases in average time to adjuvant therapy (83.6 days vs. 73.9 days, p = .0168) and suspicion to diagnosis (56.1 days vs. 46.9 days, p = .811). Similar percentages of CI and SI cases had early stage detection (37.2% in SI vs. 34.3% in CI, p = 0.311), TNM staging (50.7% in CI vs. 49.3% in SI, p = 0.146), stage I-III cases with curative surgery intent (23.3% in CI vs. 21.8% in SI, p = 0.833), and nutritional support (10.5% in CI vs. 8.5% in SI, p = 0.942). Conclusions: The NACR represents a model for developing countries to improve cancer care delivery efficiently. As evidenced by higher incidence and mortality in CI cases and longer wait times before treatment in SI cases, there are differences in cancer care delivery between major modes of healthcare delivery in Colombia. More investigation needs to be done with a goal of streamlining cancer care delivery.

Purpose. Self-expandable metallic stents (SEMS) have been widely used in obstructive lesions. They are an alternative treatment for obstructive colorectal tumors. In this article, we retrospectively review our experience with placement of colonic stents for palliative treatment of obstructive metastatic colorectal cancers and inoperable colorectal cancers. Methods. From March 2004 to March 2007, we inserted SEMS in 15 patients. A retrospective chart review was undertaken at the China Medical University Hospital. For all patients, surgical treatment was not considered initially or the patients refused surgery. We analyzed the technical and clinical success rates of stent placement. All patients were characterized in terms of age, localization of tumor, complications, morbidity and mortality, and the necessity for further interventions. Results. Our subjects included eight males and seven females, with a mean age of 66 years (range 42-94 years). Sites of the lesion included six upper rectum, four rectosigmoid junction, three sigmoid colon , one descending colon , and one splenic flexure of colon. The stents were successfully implanted in 12 of the 15 patients and bowel obstruction relieved in all patients; the technical success rate was 80% and clinical success rate was 60%. Two patients with stent related perforations required emergency operation on the 4th or 18th day after stent implantation. The mean survival time (stent implantation to death) of the ten stage IV patients (n=10) was 7 months (range 1-16months). Four patients had complications. In general, there was no stent-related mortality. Conclusions. Self-expandable metallic stents in patients with malignancy- induced colorectal obstruction is technically feasible, but it has higher morbidity rate in our study. Colonic stent is an alternative option in treatment of obstructed colorectal malignancy, but is not encouraged for every patient. When use of SEMS, surgeon or gastroenterologist should evaluate the clinical benefits and cost effectiveness for the patient.

Introduction: Colorectal cancer (CRC) is one of the most common cancers worldwide, with higher incidence among more developed countries. However, mortality rates are higher and increasing in less-developed regions, including Colombia. Incidence and mortality rates of CRC vary across the country, with the lowest rates among populations with increased concentration of Native Americans. Our group previously reported that increased European and African ancestry was associated with higher adenomatous polyps (AP) and CRC risk in Colombians. Based on this observation we hypothesize that genetic contribution to the observed regional variation on CRC development in Colombia might be partly explained by the influence of genetic variants with different frequency distribution in the European, Amerindian, and African ancestral components. Objective: To test our hypothesis we performed a genome-wide association study (GWAS) of colorectal tumors in Colombian CRC and AP cases and controls. Materials and Methods: We conducted a GWAS of Colombians from different regions of the country that included 162 CRC cases, 122 AP cases, and 131 controls. Only SNPs with MAF ≥ 0.05 were included. The role of these common variants was assessed by logistic regression models adjusted for age, sex, and the first 10 principal components (PCs) of the genetic variation. Analyses were performed for a total of 606410 SNPs. The P value threshold for genome-wide significant SNPs was set at the traditional value of ≤ 5 × 10−8. Results: We replicated some of the previously reported associations (8 out of 44 SNPs, P ≤ 0.05) of which 7 had directionally concordant ORs. Regarding the remaining 36 published risk variants, 25 had directionally concordant ORs, even though neither of them was significant at nominal P ≤ 0.05. None of the SNPs analyzed passed the threshold for genome-wide significance. However, we found multiple suggestive associations. One novel SNP within the region 2q11.2-q12 near the gene MAP4K4 was associated with the risk of AP (rs4280476-G; OR 0.36; 95% CI 0.23-0.56; P = 8.7 x 10-6). We also found four novel SNPs across three regions with suggestive CRC risk associations: rs10514122-A located in the locus 5q14 near the TBCA gene (OR 0.30; 95% CI 0.18-0.49; P = 3.6 x 10-6), rs10746883-G (OR 0.37; 95% CI 0.25-0.56; P = 3.2 x 10-6) and the rs10781032-A (OR 0.35; 95% CI 0.22-0.53; P = 1.7 x 10-6), in high LD with each other (R2 = 0.81), located in the locus 9q21.1-q21.2 near the genes TRPM3 and TMEM2 and the SNP rs2800641-G located in the region 6q25.2 near the MYCT1 gene (OR 2.96; 95% CI 1.83-4.77; P = 8.9 x 10-6). The inflation factors (λ), when comparing AP or CRC cases vs controls, were 1.05 and 1.04, respectively, indicating appropriate control for population stratification. Finally, it is of note that the MAF reported for the 5 novel SNPs identified in our study shows important differences between European, Asian, and African reference populations from the public database 1,000 genomes. Conclusions: In this GWAS of AP and CRC in individuals from Colombia, we replicated some of the previously reported associations and identified suggestive signals for 5 novel risk alleles located at four loci (2q11.2-q12, 5q14, 9q21.1-q21.2, and 6q25.2). Further work is needed to replicate our findings in other Latin American populations. Citation Format: Maria Carolina Sanabria-Salas, Laura Fejerman, Konrad Rawlik, Albert Tenesa, Martha L. Serrano-Lopez, Jovanny Zabaleta, Gustavo A. Hernandez-Suarez. Genome-wide association study of colorectal tumors in Latin American individuals from Colombia [abstract]. In: Proceedings of the Tenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2017 Sep 25-28; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2018;27(7 Suppl):Abstract nr A37.