Michael J O'Brien

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BACKGROUND The current practice of removing adenomatous polyps of the colon and rectum is based on the belief that this will prevent colorectal cancer. To address the hypothesis that colonoscopic polypectomy reduces the incidence of colorectal cancer, we analyzed the results of the National Polyp Study with reference to other published results. METHODS(More)
Serrated lesions of the colorectum are the precursors of perhaps one-third of colorectal cancers (CRCs). Cancers arising in serrated lesions are usually in the proximal colon, and account for a disproportionate fraction of cancer identified after colonoscopy. We sought to provide guidance for the clinical management of serrated colorectal lesions based on(More)
BACKGROUND In the National Polyp Study (NPS), colorectal cancer was prevented by colonoscopic removal of adenomatous polyps. We evaluated the long-term effect of colonoscopic polypectomy in a study on mortality from colorectal cancer. METHODS We included in this analysis all patients prospectively referred for initial colonoscopy (between 1980 and 1990)(More)
The aim of this study was to compare BRAF and KRAS, CpG island methylator phenotype (CIMP), and microsatellite instability (MSI) status in each of the histologic categories, including end-point carcinomas with residual adenoma, of the serrated polyp neoplasia pathway and the traditional (nonserrated) adenoma-carcinoma sequence. Deoxyribonucleic acid (DNA)(More)
Adenomatous polyps are the most common neoplastic findings discovered in people who undergo colorectal screening or who have a diagnostic work-up for symptoms. It was common practice in the 1970s for these patients to have annual follow-up surveillance examinations to detect additional new adenomas and missed synchronous adenomas. As a result of the(More)
OBJECTIVES Serrated polyps are precursors in an alternative pathway to colon cancer. These polyps are frequently sessile or flat, located in the proximal colon, and may be overlooked during colonoscopy. Histological criteria to classify these polyps have only recently been described. This study assessed the variation of serrated polyp detection among(More)
Colorectal cancer (CRC) is a heterogeneous disorder than arises via multiple distinct pathways, such as the serrated pathway, in which serrated polyps (including variants of hyperplastic polyps) are the precursor lesions. Approximately 15-20% of all CRCs arise via the serrated pathway, and these serrated carcinomas are clinically, morphologically, and(More)
The National Polyp Study (NPS), a randomized clinical trial to evaluate effective surveillance of patients discovered to have one or more colorectal adenomas, was the framework for this statistical analysis which used a multiple logistic model to assess the independent risk factors of patient and polyp characteristics associated with high-grade dysplasia in(More)
Patients with resected colorectal cancer are at risk for recurrent cancer and metachronous neoplasms in the colon. This joint update of guidelines by the American Cancer Society (ACS) and US Multi-Society Task Force on Colorectal Cancer addresses only the use of endoscopy in the surveillance of these patients. Patients with endoscopically resected Stage I(More)