Michael J. O'Brien

Prevention of Colorectal Cancer by Colonoscopic Polypectomy

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 The study cohort consisted of 1418 patients who had a complete colonoscopy during which one or more adenomas of the colon or rectum were removed. The patients subsequently underwent periodic colonoscopy during an average follow-up of 5.9 years, and the incidence of colorectal cancer was ascertained. The incidence rate of colorectal cancer was compared with that in three reference groups, including two cohorts in which colonic polyps were not removed and one general-population registry, after adjustment for sex, age, and polyp size. RESULTS Ninety-seven percent of the patients were followed clinically for a total of 8401 person-years, and 80 percent returned for one or more of their scheduled colonoscopies. Five asymptomatic early-stage colorectal cancers (malignant polyps) were detected by colonoscopy (three at three years, one at six years, and one at seven years). No symptomatic cancers were detected. The numbers of colorectal cancers expected on the basis of the rates in the three reference groups were 48.3, 43.4, and 20.7, for reductions in the incidence of colorectal cancer of 90, 88, and 76 percent, respectively (P < 0.001). CONCLUSIONS Colonoscopic polypectomy resulted in a lower-than-expected incidence of colorectal cancer. These results support the view that colorectal adenomas progress to adenocarcinomas, as well as the current practice of searching for and removing adenomatous polyps to prevent colorectal cancer.

Colonoscopic Polypectomy and Long-Term Prevention of Colorectal-Cancer Deaths

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) at NPS clinical centers who had polyps (adenomas and nonadenomas). The National Death Index was used to identify deaths and to determine the cause of death; follow-up time was as long as 23 years. Mortality from colorectal cancer among patients with adenomas removed was compared with the expected incidence-based mortality from colorectal cancer in the general population, as estimated from the Surveillance Epidemiology and End Results (SEER) Program, and with the observed mortality from colorectal cancer among patients with nonadenomatous polyps (internal control group). RESULTS Among 2602 patients who had adenomas removed during participation in the study, after a median of 15.8 years, 1246 patients had died from any cause and 12 had died from colorectal cancer. Given an estimated 25.4 expected deaths from colorectal cancer in the general population, the standardized incidence-based mortality ratio was 0.47 (95% confidence interval [CI], 0.26 to 0.80) with colonoscopic polypectomy, suggesting a 53% reduction in mortality. Mortality from colorectal cancer was similar among patients with adenomas and those with nonadenomatous polyps during the first 10 years after polypectomy (relative risk, 1.2; 95% CI, 0.1 to 10.6). CONCLUSIONS These findings support the hypothesis that colonoscopic removal of adenomatous polyps prevents death from colorectal cancer. (Funded by the National Cancer Institute and others.).

Randomized Comparison of Surveillance Intervals after Colonoscopic Removal of Newly Diagnosed Adenomatous Polyps

BACKGROUND The identification and removal of adenomatous polyps and post-polypectomy surveillance are considered to be important for the control of colorectal cancer. In current practice, the intervals between colonoscopies after polypectomy are variable, often a year long, and not based on data from randomized clinical trials. We sought to determine whether follow-up colonoscopy at three years would detect important colonic lesions as well as follow-up colonoscopy at both one and three years. METHODS Patients were eligible if they had one or more adenomas, no previous polypectomy, and a complete colonoscopy and all their polyps had been removed. They were randomly assigned to have follow-up colonoscopy at one and three years or at three years only. The two study end points were the detection of any adenoma, and the detection of adenomas with advanced pathological features (defined as those > 1 cm in diameter and those with high-grade dysplasia or invasive cancer). RESULTS Of 2632 eligible patients, 1418 were randomly assigned to the two follow-up groups, 699 to the two-examination group and 719 to the one-examination group. The percentage of patients with adenomas in the group examined at one and three years was 41.7 percent, as compared with 32.0 percent in the group examined at three years (P = 0.006). The percentage of patients with adenomas with advanced pathological features was the same in both groups (3.3 percent). CONCLUSIONS Colonoscopy performed three years after colonoscopic removal of adenomatous polyps detects important colonic lesions as effectively as follow-up colonoscopy after both one and three years. An interval of at least three years is recommended before follow-up colonoscopy after both one and three years. An interval of at least three years is recommended before follow-up examination after colonoscopic removal of newly diagnosed adenomatous polyps. Adoption of this recommendation nationally should reduce the cost of post-polypectomy surveillance and screening.

Serrated Lesions of the Colorectum: Review and Recommendations From an Expert Panel

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 current evidence and expert opinion regarding definitions, classification, and significance of serrated lesions. A consensus conference was held over 2 days reviewing the topic of serrated lesions from the perspectives of histology, molecular biology, epidemiology, clinical aspects, and serrated polyposis. Serrated lesions should be classified pathologically according to the World Health Organization criteria as hyperplastic polyp, sessile serrated adenoma/polyp (SSA/P) with or without cytological dysplasia, or traditional serrated adenoma (TSA). SSA/P and TSA are premalignant lesions, but SSA/P is the principal serrated precursor of CRCs. Serrated lesions have a distinct endoscopic appearance, and several lines of evidence suggest that on average they are more difficult to detect than conventional adenomatous polyps. Effective colonoscopy requires an endoscopist trained in the endoscopic appearance of serrated lesions. We recommend that all serrated lesions proximal to the sigmoid colon and all serrated lesions in the rectosigmoid >5 mm in size, be completely removed. Recommendations are made for post-polypectomy surveillance of serrated lesions and for surveillance of serrated polyposis patients and their relatives.

A comparison of colonoscopy and double-contrast barium enema for surveillance after polypectomy

BACKGROUND After patients have undergone colonoscopic polypectomy, it is uncertain whether colonoscopic examination or a barium enema is the better method of surveillance. METHODS As part of the National Polyp Study, we offered colonoscopic examination and double-contrast barium enema for surveillance to patients with newly diagnosed adenomatous polyps. Although barium enema was performed first, the endoscopist did not know the results. RESULTS A total of 973 patients underwent one or more colonoscopic examinations for surveillance. In the case of 580 of these patients, we performed 862 paired colonoscopic examinations and barium-enema examinations that met the requirements of the protocol. The findings on barium enema were positive in 222 (26 percent) of the paired examinations, including 139 of the 392 colonoscopic examinations in which one or more polyps were detected (rate of detection, 35 percent; 95 percent confidence interval, 31 to 40 percent). The proportion of examinations in which adenomatous polyps were detected by barium enema colonoscopy was significantly related to the size of the adenomas (P=0.009); the rate was 32 percent for colonoscopic examinations in which the largest adenomas detected were 0.5 cm or less, 53 percent for those in which the largest adenomas detected were 0.6 to 1.0 cm, and 48 percent for those in which the largest adenomas detected exceeded 1.0 cm. Among the 139 paired examinations with positive results on barium enema and negative results on colonoscopic examination in the same location, 19 additional polyps, 12 of which were adenomas, were detected on colonoscopic reexamination. CONCLUSIONS In patients who have undergone colonoscopic polypectomy, colonoscopic examination is a more effective method of surveillance than double-contrast barium enema.

Comparison of microsatellite instability, CpG island methylation phenotype, BRAF and KRAS status in serrated polyps and traditional adenomas indicates separate pathways to distinct colorectal carcinoma end points.

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) was extracted from the selected samples and assayed for BRAF(V600E), KRAS2 codon12, 13, CIMP using markers hMLH1, MGMT, MINT1, MINT2, p16, and MSI using an assay for BAT25 and BAT26. A BRAF(V600E) mutation was present in 82% of serrated carcinomas (SCas), 62% of serrated adenomas (SAs), 83% of serrated polyps with abnormal proliferation (SPAPs-syn. sessile serrated adenoma [SSA]), 76% of microvesicular serrated polyps (MVSPs), and was not found in any of the histologic categories of the traditional adenoma-carcinoma sequence. KRAS2 mutations were found in 43% of the goblet cell serrated polyp (GCSP) category, 13% of MVSPs, 7% of SPAPs, and 24% of SAs; in 26% of large traditional adenoma (lTAs) compared with small traditional adenomas (sTAs) (0/30; P<0.005) and in 37.3% of traditional carcinomas (TCa). CIMP-H (>1 marker positive) was significantly more frequent in SPAP, SA, and SCa compared with MVSP (P<0.05); CIMP-H was present in 10% of sTAs but was found more frequently in lTA (44.4%; OR 7.2; P=0.007) and TCa (38.9%; OR 5.8; P=0.007). Higher CIMP levels (4 or more markers positive) were significantly more frequent in advanced categories of the serrated pathway (SAs [31%] and SCas [30%]) compared with lTAs [0%] and TCAs [3.4%] (OR 12.2; P=0.02). MSI-H was identified only in the adenocarcinoma component of SCas (9/11) or in the contiguous SAs (3/7). The findings indicate that a BRAF(V600E) mutation is a specific marker for a serrated polyp pathway that has its origin in a hyperplastic polyp (MVSP) and a potential end point as MSI carcinoma. CIMP-High (CIMP-H) develops early in this sequence and MSI-H develops late. The data provided a less complete picture of a second serrated pathway, identified by a KRAS2 mutation in SAs, but showed that the progressive stages of both iterations of the serrated neoplasia pathway are separate and distinct from those of the traditional adenoma-carcinoma sequence.

The American Society for Gastrointestinal Endoscopy PIVI (Preservation and Incorporation of Valuable Endoscopic Innovations) on real-time endoscopic assessment of the histology of diminutive colorectal polyps

The PIVI (Preservation and Incorporation of Valuable endoscopic Innovations) initiative is an ASGE program whose objectives are to identify important clinical questions related to endoscopy and to establish a priori diagnostic and/or therapeutic thresholds for endoscopic technologies designed to resolve these clinical questions. Additionally, PIVIs may also outline the data and or the research study design required for proving an established threshold is met. Once endoscopic technologies meet an established PIVI threshold, those technologies are appropriate to incorporate into clinical practice presuming the appropriate training in that endoscopic technology has been achieved. The ASGE encourages and supports the appropriate use of technologies that meet its established PIVI thresholds. The PIVI initiative was developed primarily to direct endoscopic technology development toward resolving important clinical issues in endoscopy. The PIVI initiative is also designed to minimize the possibility that potentially valuable innovations are prematurely abandoned due to lack of utilization and to avoid widespread use of an endoscopic technology before clinical studies documenting their effectiveness have been performed. The following document, or PIVI, is one of a series of statements defining the diagnostic or therapeutic threshold that must be met for a technique or device to become considered appropriate for incorporation into clinical practice. It is also meant to serve as a guide for researchers or those seeking to develop technologies that are designed to improve digestive health outcomes. An ad hoc committee under the auspices of the existing ASGE Technology and Standards of Practice Committees Chairs develops PIVIs. An expert in the subject area chairs the PIVI, with additional committee members chosen for their individual expertise. In preparing this document, evidence-based methodology was employed, using a MEDLINE and PubMed literature search to identify pertinent clinical studies on the topic. PIVIs are ultimately submitted to the ASGE Governing Board for approval, as is done for all Technology and Standards of Practice documents. This document is provided solely for educational and informational purposes and to support incorporating these endoscopic technologies into clinical practice. It should not be construed as establishing a legal standard of care.

BRAF and KRAS Mutations in hyperplastic polyps and serrated adenomas of the colorectum: relationship to histology and CpG island methylation status.

The aim of this study was to test the hypothesis that mutations of the oncogenes BRAF or KRAS are early events in the putative serrated polyp neoplasia pathway and more advanced pathology is associated with acquired mutator and suppressor gene inactivation by CpG island methylation of promoter regions. We assayed 79 sporadic hyperplastic polyps (HPs) classified according to the schema of Torlakovic et al and 25 serrated adenomas (SAs) for BRAF and KRAS mutations and related the findings to histologic characteristics and CpG island methylation phenotype (CIMP). Mutations at exon 15, codon 599, of BRAF were assayed using an allele-specific PCR (AS-PCR) technique and confirmed in a sample of AS-PCR- positive cases by direct sequencing of exon 15. AS-PCR-negative HPs and SAs were also sequenced on exon 15 and exon 11 to detect additional mutations. PCR-RFLP was used to assay KRAS codon 12 and 13 mutations, and these mutations were further validated by direct sequencing of the KRAS gene. BRAF599 mutations were identified in a total of 55 HPs (69.6%) and KRAS mutations in a total of 13 (16.5%). BRAF599 mutations occurred with similar frequencies among microvesicular serrated polyp (76.3%) and serrated polyp with abnormal proliferation (82.1%) subtypes but less frequently in goblet cell serrated polyps (23.1%). Conversely, KRAS mutations were most frequent in goblet cell serrated polyp (46.2%) and less frequent in microvesicular serrated polyp (13.2%) and serrated polyp with abnormal proliferation (7.1%). BRAF599 and KRAS mutations were present in 15 (60.0%) and 7 (28.0%) of SAs, respectively. BRAF 599 mutation and KRAS were mutually exclusive findings in the polyps studied and one or the other occurred in 68 of 79 (86.1%) HPs and 22 of 25 (88.0%) SAs. CpG island methylation involving 2 or more genes (CIMP-H) was present in 80.0% of SAs, 75% serrated polyp with abnormal proliferations, 47.4% of microvesicular serrated polyps, and 15.4% of goblet cell serrated polyps. SAs were significantly more likely to be CIMP-H than HPs (odds ratio 3.7; 95% confidence interval, 1.27–10.86; P = 0.017). A similar high frequency of KRAS or BRAF mutations across the histologic spectrum of the serrated polyps assayed suggests that these are early events in the serrated polyp neoplasia pathway. In contrast, the association of higher levels of CpG island methylation with more advanced histologic changes suggests that CpG island methylation plays a role in serrated polyp progression toward colorectal carcinoma.

Variation in the detection of serrated polyps in an average risk colorectal cancer screening cohort.

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 endoscopists and pathologists in an average risk-screening cohort and trends in detection over time.METHODS:Endoscopy and pathology reports were reviewed from all average risk-screening colonoscopies at an urban academic medical center from 2006 through 2008. Polyps were classified as adenoma (tubular, tubulovillous, or villous), serrated polyp (hyperplastic polyp (HP), sessile serrated adenoma (SSA), or dysplastic serrated polyp (DSP)), adenocarcinoma, or other. Differences in polyp detection among endoscopists and pathologists were tested with χ2-tests. Potential predictors of polyp detection were modeled with Poisson regression.RESULTS:Included in the study were 4,335 polyps from 7,192 colonoscopies. Detection prevalence (patients with at least one polyp per 100 colonoscopies) was 22.2 for adenomas, 11.7 for HP, 0.6 for SSA, and 0.2 for DSP. Detection prevalence of proximal SSAs increased from 0.2 in 2006 to 4.4 in 2008 (P<0.001). Detection prevalences among endoscopists differed significantly for adenomas, HP, and SSA. Classification rates among pathologists differed significantly for HP and SSA, but not for adenoma or DSP. On multivariate analysis, endoscopist was a significant predictor of adenoma, HP, and SSA. Pathologist was a significant predictor of HP, SSA, and DSP, but not adenoma.CONCLUSIONS:This study describes the detection of colorectal polyps in an average risk-screening cohort at an urban academic medical center. Detection of proximal SSAs increased during the study period. Detection of adenoma, HP, and SSA differed significantly by endoscopist. Classification of HP and SSA differed significantly by pathologist. Endoscopy and pathology practices should consider educational interventions to improve serrated polyp detection and standardize classification.

Spondylolisthesis, Pelvic Incidence, and Spinopelvic Balance : A Correlation Study

Study Design. A retrospective study of the sagittal alignment in developmental spondylolisthesis. Objectives. To investigate the role of pelvic anatomy and its effect on the global balance of the trunk in developmental spondylolisthesis. Summary of Background Data. Pelvic incidence (PI) is a fundamental anatomic parameter that is specific and constant for each individual, and independent of the three-dimensional orientation of the pelvis. Recent studies have suggested an association between a high PI and patients with isthmic spondylolisthesis. Methods. The lateral standing radiographs of the spine and pelvis of 214 subjects with developmental L5–S1 spondylolisthesis were analyzed with a dedicated software allowing the calculation of the following parameters: pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), lumbar lordosis (LL), thoracic kyphosis (TK), and grade of spondylolisthesis. All measurements were done by the same individual and compared to those of a cohort of 160 normal subjects. Student’s tests were used to compare the parameters between the curve types and Pearson’s correlation coefficients were used to investigate the association between all parameters (&agr; = 0.01). Results. PI, SS, PT, and LL are significantly greater (P < 0.01) in subjects with spondylolisthesis, while TK is significantly decreased. PI has a direct linear correlation (0.41–0.65) with SS, PT, and LL. Furthermore, the differences between the two populations increase in a direct linear fashion as the severity of the spondylolisthesis increases. Conclusions. Since PI is a constant anatomic pelvic variable specific to each individual and strongly determines SS, PT, and LL, which are position-dependent variables, this study suggests that pelvic anatomy has a direct influence on the development of a spondylolisthesis. Study participants with an increased pelvic incidence appear to be at higher risk of presenting a spondylolisthesis, and an increased PI may be an important factor predisposing to progression in developmental spondylolisthesis.