Assessment of polygenic architecture and risk prediction based on common variants across fourteen cancers

Abstract: Genome-wide association studies (GWAS) have led to the identification of hundreds of susceptibility loci across cancers, but the impact of further studies remains uncertain. Here we analyse summary-level data from GWAS of European ancestry across fourteen cancer sites to estimate the number of common susceptibility variants (polygenicity) and underlying effect-size distribution. All cancers show a high degree of polygenicity, involving at a minimum of thousands of loci. We project that sample sizes required to explain 80% of GWAS heritability vary from 60,000 cases for testicular to over 1,000,000 cases for lung cancer. The maximum relative risk achievable for subjects at the 99th risk percentile of underlying polygenic risk scores (PRS), compared to average risk, ranges from 12 for testicular to 2.5 for ovarian cancer. We show that PRS have potential for risk stratification for cancers of breast, colon and prostate, but less so for others because of modest heritability and lower incidence

AGA Clinical Practice Update on New Technology and Innovation for Surveillance and Screening in Barrett’s Esophagus: Expert Review

DescriptionThe purpose of this best practice advice (BPA) article from the Clinical Practice Update Committee of the American Gastroenterological Association is to provide an update on advances and innovation regarding the screening and surveillance of Barrett's esophagus.MethodsThe BPA statements presented here were developed from expert review of existing literature combined with discussion and expert opinion to provide practical advice. Formal rating of the quality of evidence or strength of BPAs was not the intent of this clinical practice update. This expert review was commissioned and approved by the AGA Institute Clinical Practice Updates Committee (CPUC) and the AGA Governing Board to provide timely guidance on a topic of high clinical importance to the AGA membership, and underwent internal peer review by the CPUC and external peer review through standard procedures of Clinical Gastroenterology and Hepatology. BEST PRACTICE ADVICE 1: Screening with standard upper endoscopy may be considered in individuals with at least 3 established risk factors for Barrett's esophagus (BE) and esophageal adenocarcinoma, including individuals who are male, non-Hispanic white, age >50 years, have a history of smoking, chronic gastroesophageal reflux disease, obesity, or a family history of BE or esophageal adenocarcinoma. BEST PRACTICE ADVICE 2: Nonendoscopic cell-collection devices may be considered as an option to screen for BE. BEST PRACTICE ADVICE 3: Screening and surveillance endoscopic examination should be performed using high-definition white light endoscopy and virtual chromoendoscopy, with endoscopists spending adequate time inspecting the Barrett's segment. BEST PRACTICE ADVICE 4: Screening and surveillance exams should define the extent of BE using a standardized grading system documenting the circumferential and maximal extent of the columnar lined esophagus (Prague classification) with a clear description of landmarks and the location and characteristics of visible lesions (nodularity, ulceration), when present. BEST PRACTICE ADVICE 5: Advanced imaging technologies such as endomicroscopy may be used as adjunctive techniques to identify dysplasia. BEST PRACTICE ADVICE 6: Sampling during screening and surveillance exams should be performed using the Seattle biopsy protocol (4-quadrant biopsies every 1-2 cm and target biopsies from any visible lesion). BEST PRACTICE ADVICE 7: Wide-area transepithelial sampling may be used as an adjunctive technique to sample the suspected or established Barrett's segment (in addition to the Seattle biopsy protocol). BEST PRACTICE ADVICE 8: Patients with erosive esophagitis should be biopsied when concern of dysplasia or malignancy exists. A repeat endoscopy should be performed after 8 weeks of twice a day proton pump inhibitor therapy. BEST PRACTICE ADVICE 9: Tissue systems pathology-based prediction assay may be utilized for risk stratification of patients with nondysplastic BE. BEST PRACTICE ADVICE 10: Risk stratification models may be utilized to selectively identify individuals at risk for Barrett's associated neoplasia. BEST PRACTICE ADVICE 11: Given the significant interobserver variability among pathologists, the diagnosis of BE-related neoplasia should be confirmed by an expert pathology review. BEST PRACTICE ADVICE 12: Patients with BE-related neoplasia should be referred to endoscopists with expertise in advanced imaging, resection, and ablation. BEST PRACTICE ADVICE 13: All patients with BE should be placed on at least daily proton pump inhibitor therapy. BEST PRACTICE ADVICE 14: Patients with nondysplastic BE should undergo surveillance endoscopy in 3 to 5 years. BEST PRACTICE ADVICE 15: In patients undergoing surveillance after endoscopic eradication therapy, random biopsies should be taken of the esophagogastric junction, gastric cardia, and the distal 2 cm of the neosquamous epithelium as well as from all visible lesions, independent of the length of the original BE segment

Assessment of polygenic architecture and risk prediction based on common variants across fourteen cancers.

Genome-wide association studies (GWAS) have led to the identification of hundreds of susceptibility loci across cancers, but the impact of further studies remains uncertain. Here we analyse summary-level data from GWAS of European ancestry across fourteen cancer sites to estimate the number of common susceptibility variants (polygenicity) and underlying effect-size distribution. All cancers show a high degree of polygenicity, involving at a minimum of thousands of loci. We project that sample sizes required to explain 80% of GWAS heritability vary from 60,000 cases for testicular to over 1,000,000 cases for lung cancer. The maximum relative risk achievable for subjects at the 99th risk percentile of underlying polygenic risk scores (PRS), compared to average risk, ranges from 12 for testicular to 2.5 for ovarian cancer. We show that PRS have potential for risk stratification for cancers of breast, colon and prostate, but less so for others because of modest heritability and lower incidence

Large scale meta-analysis identifies new genetic risk loci for esophageal adenocarcinoma (EA) and the first EA risk locus independent of Barrett’s esophagus

SUMMARY Background: Esophageal adenocarcinoma (EA) represents one of the fastest rising oncological diseases in western countries. Barrett’s Esophagus (BE) is the premalignant precursor of EA. However, only a subset of BE patients develop EA, which complicates the clinical management in the absence of valid predictors. Methods: Within an international consortium of groups involved in the genetics of BE/EA, we performed the first meta-analysis of all genome-wide association studies (GWAS) available (>10,000 BE/EA patients, >17,000 controls, all of European descent). The entire GWAS-data set was also analyzed using bioinformatics approaches in order to identify pathophysiologically relevant cellular pathways. Findings: We identified nine new disease loci for BE/EA (P<5×10-8) and thereby doubled the number of known risk loci. The strongest new risk locus implicates CFTR as BE/EA risk gene. Mutations in CFTR cause cystic fibrosis (CF), the most common recessive disorder in Europeans. Gastroesophageal reflux (GER) belongs to the phenotypic CF-spectrum and represents the main risk factor for BE/EA. Thus, the CFTR locus may trigger a common GER-mediated pathophysiology. The strongest disease pathways identified (P<10-6) belong to muscle cell differentiation and to mesenchyme development/differentiation, which fit with current pathophysiological BE/EA concepts. Furthermore, for the first time we identified an EA-specific association (P=1·6×10-8) near HTR3C/ABCC5 which is independent of BE development (P=0·45). Interpretation: The identified disease loci and pathways reveal new insights into the etiology of BE and EA. Furthermore, the EA-specific association at HTR3C/ABCC5 may constitute a novel genetic marker for the prediction of transition from BE to EA. Funding: US National Cancer Institute, US National Institutes of Health, National Health and Medical Research Council of Australia, Swedish Cancer Society, Medical Research Council of UK, Cambridge NIHR biomedical research centre, Cambridge Experimental Cancer - 5 - Medicine Centre, Else Kröner Fresenius Stiftung, Wellcome Trust, Cancer Research UK, AstraZeneca UK, University Hospitals of Leicester, University of Oxford