The National Polyp Study

The adenoma carcinoma sequence: an indoctrinated model for tumorigenesis, but is it always a clinical reality?

OBJECTIVE

Evidence exists to support alternative pathways to the adenoma carcinoma sequence. Some mutations in key onco-suppressor genes relate to the anatomical site of the tumour. This link is typified by microsatellite instability and proximal neoplasia. However, rectal tumours are rarely considered separately. We hypothesized that tumour behaviour in the rectum may differ in terms of pathogenesis and malignant propensity. Therefore, we aimed to look for an association between the histopathological features of adenomas and their anatomical location as compared with the distribution of cancers.

METHODS

A single centre prospective study was undertaken over a four-year period. Patients referred to a colorectal assessment clinic with bowel symptoms underwent a minimum investigation of flexible sigmiodoscopy. Neoplastic lesions were either biopsied or removed after noting distance from the anal margin. Adenomas, differentiated by size, villous architecture and degree of dysplasia were compared to both early and advanced carcinomas.

RESULTS

Of 4089 patients, polyps were identified in 8.0% and cancer in 4.2%. There was a clear difference between the distribution of cancer and adenomas > 1 cm, P < 0.001. All degrees of dysplasia in large adenomas were more prevalent in the sigmoid colon as compared to cancer, P < 0.001. Seventy-five percent of high risk diminutive adenomas were rectal in origin.

CONCLUSION

Our data provides indirect evidence to support the concept that a significant proportion of rectal cancers may arise via an alternative pathway to the Vogelstein model. Polyp behaviour along with malignant propensity may actually be site dependent, with rectal polyps harbouring a more aggressive phenotype.

Colonoscopy in the elderly: low risk, low yield in asymptomatic patients

PURPOSE

Current colonoscopy guidelines do not address the issue of when to stop performing screening and surveillance colonoscopy in the elderly. We reviewed our experience and results of colonoscopy in patients aged 80 years and older to assess the risks and diagnostic yield in this population.

METHODS

We reviewed retrospectively the endoscopic and pathologic reports from consecutive colonoscopies performed on patients aged 80 years and older at a single, high-volume endoscopy center between August 1999 and May 2003. Patient characteristics, indications for examination, findings at colonoscopy, and complications were recorded and analyzed.

RESULTS

A total of1,199 colonoscopic examinations were performed on 1,112 patients. Average age was 83.1 (range, 80-100) years. Male:female distribution was 1:1.7. Leading exclusive indications for colonoscopy included: polyp surveillance, 227 (19 percent); altered bowel habits, 168 (14 percent); iron-deficiency anemia, 132 (11 percent); and cancer follow-up, 108 (9 percent). Eighty-six examinations (7 percent) were performed solely for an indication of colorectal cancer screening. Twenty-two percent of patients had more than one indication for colonoscopy. Forty-five malignancies were found (3.7 percent). No cancers were found in the screening group, and two malignancies (0.7 percent) were detected in patients undergoing colonoscopy for polyp surveillance. There were eight (0.6 percent) reported major complications.

CONCLUSIONS

Colonoscopy can be performed safely in patients aged 80 years and older. However, the diagnostic yield is low, particularly in patients undergoing routine screening or surveillance examinations. Colonoscopy should for the most part be limited to elderly patients with symptoms or specific clinical findings.

Effects of cyclooxygenase-2 inhibition on serum and tumor gastrins and expression of apoptosis-related proteins in colorectal cancer

The objective of the present study was to determine the influence of cyclooxygenase-2 (COX-2) inhibition by Celecoxib (CLX) in humans with distal colorectal adenocarcinoma (CRC) on serum and tumor levels of progastrin and gastrin and serum levels of proinflammatory cytokines (IL-8, TNF-alpha). In addition, the effects of this CLX treatment on tumor and adjacent mucosa expression of gastrin, its receptors (CCK2), and COX-1 and COX-2, as well as protein expression of the active form of nuclear factor kappa B (NFkappa B) and the apoptotic-related proteins Bcl-2 and survivin, have been examined. Ten distal CRC patients were examined twice, once before and then after 14-day treatment with CLX (200 mg bid). Large biopsy samples were taken from the tumor and intact mucosa 10 cm above the tumor. For comparison, 20 age- and sex-matched healthy controls were enrolled and treated with CLX as CRC patients. Serum levels of IL-8 and TNF-alpha were measured by enzyme-linked immunosorbent assay, and serum levels of amidated gastrins and progastrin, by specific radioimmunoassay. The gene or protein expressions of progastrin, gastrin, CCK2, COX-1, COX-2, Bcl-2, and survivin as well as NFkappa B were determined by RT-PCR or Western blot in biopsy samples of tumor and intact mucosa of CRC patients. Serum IL-8 and TNF-alpha values were severalfold higher in CRC patients than in controls. The increase in serum proinflammatory cytokines was accompanied by increased expression of the active form of NFkappa B. Serum progastrin levels were also found to be significantly higher in CRC than in controls. Treatment of CRC with CLX resulted in a significant decrease in serum levels of progastrin and this was accompanied by an increment in tumor expression of COX-2 with a concomitant reduction in gastrin, Bcl-2, survivin, and NFkappa B expression. We conclude that (1) distal CRC patients show significantly higher serum progastrin levels than matched healthy controls, confirming that this hormone may be implicated in rectal carcinogenesis; (2) CRC patients exhibit significantly higher serum levels of IL-8 and TNF-alpha than healthy controls, probably reflecting more widespread inflammatory reaction in the colonic mucosa in CRC; (3) gastrin, COX-2, Bcl-2, survivin, and NFkappa B were overexpressed in CRC tumor compared to intact mucosa, but treatment with CLX significantly reduced serum levels of progastrin and IL-8 and TNF-alpha, which could mediate the up-regulation of COX-2 in CRC; and (4) CLX also enhanced expression of COX-2, while inhibiting the expression of gastrin, Bcl-2, survivin, and NFkappa B, suggesting that COX-2 inhibition might be useful in chemoprevention against CRC, possibly due to suppression of the antiapoptotic proteins and reduction in progastrin-induced and NFkappa B-promoted tumor growth.

Reduction of false positives by internal features for polyp detection in CT-based virtual colonoscopy

In this paper, we present a computer-aided detection (CAD) method to extract and use internal features to reduce false positive (FP) rate generated by surface-based measures on the inner colon wall in computed tomographic (CT) colonography. Firstly, a new shape description global curvature, which can provide an overall shape description of the colon wall, is introduced to improve the detection of suspicious patches on the colon wall whose geometrical features are similar to that of the colonic polyps. By a ray-driven edge finder, the volume of each detected patch is extracted as a fitted ellipsoid model. Within the ellipsoid model, CT image density distribution is analyzed. Three types of (geometrical, morphological, and textural) internal features are extracted and applied to eliminate the FPs from the detected patches. The presented CAD method was tested by a total of 153 patient datasets in which 45 patients were found with 61 polyps of sizes 4-30 mm by optical colonoscopy. For a 100% detection sensitivity (on polyps), the presented CAD method had an average FPs of 2.68 per patient dataset and eliminated 93.1% of FPs generated by the surface-based measures. The presented CAD method was also evaluated by different polyp sizes. For polyp sizes of 10-30 mm, the method achieved mean number of FPs per dataset of 2.0 with 100% sensitivity. For polyp sizes of 4-10 mm, the method achieved 3.44 FP per dataset with 100% sensitivity.

Local recurrence after transanal endoscopic microsurgery for rectal polyps and early cancers

BACKGROUND

Transanal endoscopic microsurgery (TEM) allows for local excision of rectal neoplasms with greater exposure than transanal excision and less morbidity than transabdominal approaches. This study examines the implications of the procedure with respect to predictors of recurrence.

METHODS

We performed a retrospective analysis of 144 consecutive TEMs from 1993 to 2004.

RESULTS

The study comprises 107 patients presenting for TEM with benign disease and 32 patients with cancer. Patients had a mean age of 64+/-14 (SD) years. TEM was performed for recurrent lesions in 17% of cases. Pathologic classification of the lesions after TEM was benign adenoma in 45%, adenoma with high-grade dysplasia (HGD) in 17%, cancer in 33%, and other in 4%. Complications occurred in 10%, and local recurrence occurred in 15% of patients. Median follow-up was 44 months, with a median time to recurrence of 14 months. Positive margins did not influence lesion recurrence. Recurrence of cancers correlated with the depth of tumor invasion (P<.05). On multivariate analysis, independent predictors of recurrence were lesion size and the presence of HGD within adenomas (P<.05). Five-year neoplastic recurrence probabilities were 11% for benign adenomas, 35% for adenomas with HGD, and 20% for cancers (P=.31); invasive recurrence probabilities were 0% for benign adenomas, 15% for adenomas with HGD, and 13% for cancers (P<.05).

CONCLUSIONS

Close endoscopic follow-up is warranted after TEM for both benign and malignant disease, with special attention to lesions with HGD. TEM can be performed safely for early rectal cancer with careful patient selection.

Screening of colorectal cancer

Cost-effectiveness analyses have shown that the cost per year of life saved by screening with any of the tests recommended is reasonable by US standards. Although the specific results vary among analyses, in general the marginal cost-effectiveness of this screening is less than $25,000 per year of life saved. Screening for CRC was among the highest ranked services in an analysis of the value of preventive services based on the burden of disease prevented and cost-effectiveness. Although the up-front costs vary by screening modality, the long-term cost-effectiveness is similar across screening tests, so that decisions about which options to include--in the long run and from the perspective of society--do not need to be affected heavily by costs. Costs increase out of proportion to benefits with shorter intervals between screening examinations. Screening has provided great opportunities. Screening can prevent CRC by polypectomy and find early-stage cancers for treatment with less morbidity. Screening can reduce the burden of treating advanced cancers and can identify families at increased risk. Screening also has provided a better understanding of the biology of CRC. Screening for CRC should be part of a complete prevention program that includes a healthy lifestyle and familial risk assessment. Individuals with increased familial risk require special screening approaches, whereas individuals with average risk can have more standard screening. The average-risk individuals can be stratified further into persons who require intensive follow-up and persons who require less intensive or no follow-up at all. We are beginning to learn how to apply screening and surveillance approaches based on risk stratification for a more cost-effective approach to conserve resources and reduce complications and costs. Chemoprevention can be added to the program when substantial benefit of agents has been demonstrated. We have a better understanding of the biology of CRC and the technology to intervene in that biology to make a difference in the lives of many people. We have the concepts and technology to reduce substantially the mortality for CRC and even prevent it entirely. Newer screening tests or others yet to be developed may, with time, replace the modern options. Screening should take place with the tests currently available and not wait until something better comes along. In this way, needless suffering and loss of life can be avoided for this leading cause of cancer death. Screening may become even more successful if the promise of new technologies is confirmed and they enter clinical practice. In the last analysis, the best test is the one that gets done and gets done immediately.

DNA repair polymorphisms and risk of colorectal adenomatous or hyperplastic polyps

Genetic variability in DNA repair genes may contribute to differences in DNA repair capacity and susceptibility to cancer, especially in the presence of exposures such as smoking. In a Minnesota-based case-control study of cases with only adenomatous polyps (n = 384), only hyperplastic polyps (n = 191), or both types of polyps (n = 119) versus polyp-free controls (n = 601), we investigated the role of polymorphisms in the DNA repair genes O(6)-methylguanine methyltransferase (MGMT; p.L84F and p.I143V), XPD (p.D312N and p.K751Q), and XPG (p.D1104H). MGMT polymorphisms were not associated with polyp risk. Overall, a homozygous variant XPD-combined genotype was associated with an increased risk of adenomatous polyps [odds ratio (OR), 1.57; 95% confidence interval (95% CI), 1.04-2.38] and an XPGHH1104 genotype with a decreased risk of hyperplastic polyps (OR, 0.36; 95% CI, 0.13-0.98). However, age stratification showed that the XPD association was present only in subjects >/=60 years old (OR, 3.77; 95% CI, 1.94-7.35), whereas the XPG association was observed largely in subjects <60 years old (OR, 0.20; 95% CI, 0.05-0.91). Smokers did not have a significantly increased risk of adenomatous polyps in the absence of synchronous hyperplastic polyps, except for subjects with a homozygous variant XPD genotype or a homozygous wild-type XPG genotype (OR, 3.93; 95% CI, 1.68-9.21 and OR, 1.59; 95% CI, 1.01-2.50, respectively). Smoking was associated with a statistically significant 2.5- to 6-fold increased risk of hyperplastic polyps for individuals with most of the DNA repair genotypes. However, no substantial increase was observed among individuals who were homozygous variant for XPG (1104HH; OR, 1.38; 95% CI, 0.25-7.65). Our data suggest that polymorphisms in DNA repair genes may be risk factors for colorectal neoplasia and that they may exacerbate the effects of exposures to carcinogens.

Screening of colorectal cancer: progress and problems

Considerable progress has been made in the past three decades in our understanding of the biology and prevention of colorectal cancer. The long natural history of colorectal cancer as it evolves from adenomatous polyps in the majority of cases provides opportunities for detection of early stage cancer and for prevention of cancer by removal of adenomas. Strong evidence of the effectiveness of screening has resulted in a worldwide consensus, as reported in evidence-based guidelines, that screening should be offered to all men and women age 50 and older, younger in the presence of factors that increase risk. Several options are now available for screening, and the emerging technology of stool DNA testing and virtual colonoscopy shows promise. However, many problems remain to be addressed. Screening rates are low. Successful strategies need to be implemented to overcome patient and system barriers. Resources, especially endoscopic capacity, may be inadequate to handle the burden of screening, diagnosis, and follow-up surveillances. There are quality-control issues at every step. Stratification of people by risk, a two-stage screening approach and less intensive surveillance following polypectomy can be helpful. Colorectal cancer screening is cost-effective and could save many lives each year if it were widely implemented.

Colorectal Cancer: Epidemiology and Health Services Research

The causes of colorectal carcinoma are multifactorial. Numerous lines of epidemiologic evidence support the role of dietary factors, with strong associations revealed for folate and calcium, more equivocal evidence exists for dietary antioxidants. Lifestyle factors such as physical activity, alcohol in-take, and tobacco use are also positively correlated with the risk of colorectal carcinoma. Health services research examines epidemiologic issues,clinical evidence regarding prevention and treatment, patient preferences,and other factors with the goal of improving the quality of care. Observations based on epidemiologic studies and health services research will in the future provide the basis for reducing personal and social burdens caused by colorectal carcinoma.

Computed tomography colonography: current issues

OBJECTIVE

Direct and indirect evidence supports the concept of screening for adenomas and early stage colorectal cancer in reducing the incidence and disease-specific mortality. Controversy remains as to the appropriateness of and preferred methods for screening an asymptomatic population.

METHODS

Review of computed tomography (CT) colonography based on the literature and personal experience.

RESULTS AND CONCLUSIONS

Current discrepancies in the data on accuracy and patient acceptance of CT colonography reflect differences in the performance and evaluation of this examination. Before CT colonography can be implemented in colorectal cancer screening, factors that cause this variability must be elucidated. Studies in which high-resolution scanning, three-dimensional review methods and an enhanced colonoscopic reference are used achieve an accuracy that is similar to colonoscopy. At the same time the evidence that ultra-low radiation dose CT colonography is feasible is mounting, a development that dramatically reduces one of the largest obstacles for large-scale application of this technique.

DNA end binding activity and Ku70/80 heterodimer expression in human colorectal tumor

AIM: To determine the DNA binding activity and protein levels of the Ku70/80 heterodimer, the functional mediator of the NHEJ activity, in human colorectal carcinogenesis.

METHODS: The Ku70/80 DNA-binding activity was determined by electrophoretic mobility shift assays in 20 colon adenoma and 15 colorectal cancer samples as well as matched normal colonic tissues. Nuclear and cytoplasmic protein expression was determined by immunohistochemistry and Western blot analysis.

RESULTS: A statistically significant difference was found in both adenomas and carcinomas as compared to matched normal colonic mucosa (P<0.00). However, changes in binding activity were not homogenous with approximately 50% of the tumors showing a clear increase in the binding activity, 30% displaying a modest increase and 15% showing a decrease of the activity. Tumors, with increased DNA-binding activity, also showed a statistically significant increase in Ku70 and Ku86 nuclear expression, as determined by Western blot and immunohistochemical analyses (P<0.001). Cytoplasmic protein expression was found in pathological samples, but not in normal tissues either from tumor patients or from healthy subjects.

CONCLUSION: Overall, our DNA-binding activity and protein level are consistent with a substantial activation of the NHEJ pathway in colorectal tumors. Since the NHEJ is an error prone mechanism, its abnormal activation can result in chromosomal instability and ultimately lead to tumorigenesis.

Incident rates of colonic neoplasia according to age and gender: implications for surveillance colonoscopy intervals

INTRODUCTION

Current guidelines endorse surveillance colonoscopy at 3 to 5 years following initial detection of neoplasia. However, individual patients' risks may vary according to age and gender. This study aimed to characterize neoplasia recurrence in a large patient cohort undergoing surveillance colonoscopy.

METHODS

All patients undergoing two colonoscopies at least 12 months apart between 1996 and 2000, with detection and removal of a polyp on the index colonoscopy, were identified using our endoscopic database to determine the incidence of colonic neoplasia. Patients were classified according to age (<50, 50-64, 65-74, > or =75 years) and gender.

RESULTS

Overall, 1803 patients underwent two colonoscopies at least 12 months apart (median interval, 140 weeks) with removal of a polyp on initial examination. Polyps > or =5 mm were detected in 334 (19%) patients and polyps > or =10 mm in 105 (6%) on subsequent endoscopy. All age and gender groups were well matched with respect to size of polyp detected on initial colonoscopy (P = 0.2). Kaplan-Meier curves and a Cox proportional hazards model demonstrated similar rates of neoplasia recurrence for all patients irrespective of age and gender.

CONCLUSIONS

Similar rates of neoplasia recurrence were observed among patients of different gender and age groups on surveillance colonoscopy. From a health resource utilization perspective, these findings support current recommendations for similar surveillance intervals for patients regardless of age and gender.

Virtual colonoscopy by MRI: state-of-the-art and future directions

MR colonography has been shown to be an appropriate diagnostic tool for the detection of colorectal lesions. The technique is based on the acquisition of T1-weighted sequences after the administration of water enema and the intravenous administration of paramagnetic contrast. This article describes the technical requirements for MR colonoscopy and the procedures of data acquisition and image interpretation. The advantages and drawbacks of MR colonoscopy also are outlined.

Association between adenomas of rectosigmoid colon and metabolic syndrome features in a Chinese population

BACKGROUND AND AIMS

Metabolic syndrome (MS) consists of a cluster of diseases, including obesity, dyslipidemia, hyperglycemia and high blood pressure. The purpose of the present study was to assess the association of MS with adenomas of the rectosigmoid colon, a well-established precancerous lesion.

METHODS

A total of 4938 Taiwanese patients (2891 men and 2047 women with a mean age of 50.1 years), who had a physical examination at our hospital between January 2001 and October 2002, were enrolled in this study. All patients underwent a sigmoidoscopic examination to 60 cm from the anus. A modified National Cholesterol Education Program (NCEP) definition of MS was used in this study, in which body mass index (BMI) was substituted for the waist circumference measurement.

RESULTS

Overall, 14% of patients had an elevated fasting glucose, 27% had high blood pressure, 14% had an increased triglyceride (TG) level, 8% had low high density lipoprotein (HDL) cholesterol, and 18% were obese. Rectosigmoid polyps were present in 17% of patients, among whom 568 received polypectomy. Pathological findings were hyperplastic in 138 subjects, adenomas in 341, carcinomas in 10, and other benign lesions in 79. In patients without polyps, the adjusted mean TG level and calculated BMI level were lower than those in patients with adenomas. No such difference existed, however, between patients without polyps and those with hyperplastic polyps. The odds ratio of adenomas in situ as compared to either a polyp-free state or the presence of hyperplastic polyps increased significantly with the number of MS diagnostic criteria the patient exhibited.

CONCLUSION

Our study shows that MS is associated with rectosigmoid adenomas in a Chinese population. In patients with rectosigmoid polyps, the coexistence of MS may portend an increased risk of adenomas.

Vitamin D receptor gene Tru9I polymorphism and risk for incidental sporadic colorectal adenomas

AIM: Recent laboratory and epidemiological studies suggest that vitamin D is a potential agent for colorectal cancer prevention. Its function is partially mediated by the vitamin D receptor (VDR). The aim of this study was to investigate whether a novel G (allele ‘U’)>A (allele ‘u’) polymorphism (Tru9I) in the VDR intron 8 region is associated with risk for colorectal adenoma in a colonoscopy-based case-control study.

METHODS: Genotyping for a total of 391 subjects was carried out through PCR and restriction fragment length polymorphism.

RESULTS: The frequencies of ‘U’ and ‘u’ alleles were 89.3% and 10.7%, respectively. The ‘Uu’ and ‘uu’ genotypes were associated with decreased risk for adenoma (OR, 0.71; 95%CI, 0.40-1.25). The inverse association was more pronounced for multiple adenomas and adenomas that were larger had moderate or greater dysplasia, or were sessile: the odds ratios (ORs) were, 0.51 (95%CI, 0.21-1.24), 0.37 (95%CI, 0.11-1.28), 0.68 (95%CI, 0.33-1.41), and 0.36 (95%CI, 0.13-0.97) respectively. In joint/combined analyses, inverse associations were more obvious among those who had at least one ‘u’ allele and also were younger (OR, 0.60; 95%CI, 0.26-1.37), women (OR, 0.38; 95%CI, 0.17-0.88), did not smoke (OR, 0.39; 95%CI, 0.13-1.23), or took NSAID (OR, 0.38; 95%CI, 0.12-1.25), but no evidence existed for interactions with calcium or vitamin D intake.

CONCLUSION: Our findings suggest that the VDR Tru9I polymorphism may be associated with lower risk for colorectal adenoma, particularly in interaction with various risk factors, but not with calcium or vitamin D.

A new path planning algorithm for maximizing visibility in computed tomography colonography

In virtual colonoscopy, minimizing the blind areas is important for accurate diagnosis of colonic polyps. Although useful for describing the shape of an object, the centerline is not always the optimal camera path for observing the object. Hence, conventional methods in which the centerline is directly used as a path produce considerable blind areas, especially in areas of high curvature. Our proposed algorithm first approximates the surface of the object by estimating the overall shape and cross-sectional thicknesses. View positions and their corresponding view directions are then jointly determined to enable us to maximally observe the approximated surface. Moreover, by adopting bidirectional navigations, we may reduce the blind area blocked by haustral folds. For comfortable navigation, we carefully smoothen the obtained path and minimize the amount of rotation between consecutive rendered images. For the evaluation, we quantified the overall observable area on the basis of the temporal visibility that reflects the minimum interpretation time of a human observer. The experimental results show that our algorithm improves visibility coverage and also significantly reduces the number of blind areas that have a clinically meaningful size. A sequence of rendered images shows that our algorithm can provide a sequence of centered and comfortable views of colonography.

Colonography by magnetic resonance imaging

Dark-lumen magnetic resonance colonography has been shown to be an appropriate diagnostic tool for the detection of colorectal pathologies. This review describes the underlying techniques of dark-lumen magnetic resonance colonography concerning data acquisition, image interpretation and diagnostic accuracy for the detection of colorectal pathologies. In addition, techniques to improve patients' acceptance are discussed.

Magnetic resonance colonography without bowel cleansing using oral and rectal stool softeners (fecal cracking)—a feasibility study

The aim of our study was to assess the effect of oral and rectal stool softeners on dark-lumen magnetic resonance (MR) colonography without bowel cleansing. Ten volunteers underwent MR colonography without colonic cleansing. A baseline examination was performed without oral or rectal administration of stool softeners. In a second set, volunteers ingested 60 ml of lactulose 24 h prior to MR examination. In a third examination, water as a rectal enema was replaced by a solution of 0.5%-docusate sodium (DS). A fourth MR examination was performed, in conjunction with both oral administration of lactulose and rectal application of DS. A T1-weighted data set was acquired at scanning times of 0, 5 and 10 min after colonic filling. A fourth data set was acquired 75 s after i.v. injection of contrast agent. Signal intensity of stool was calculated for all colonic segments. Without oral ingestion of lactulose or rectal enema with DS stool signal intensity was high and did not decrease over time. However, lactulose and DS caused a decrease in stool signal intensity. Both substances together led to a decreasing signal intensity of feces. Combination of lactulose and DS provided the lowest signal intensity of stool. Thus, feces could hardly be distinguished from dark rectal enema allowing for the assessment of the colonic wall.

Do forceps biopsies truthfully reflect the nature of endoscopically uncovered polypoid lesions of the colon?

BACKGROUND

Total excision of colonic polyps is not always attainable and in some patients it is clinically contraindicated. Also, a resected polyp may be lost at any step between its endoscopic removal and its embedding in paraffin. The aim of this study was to compare the histological features of colonic polyps as analysed by the study of biopsy-forceps obtained samples with those assessed on scrutinizing the totally resected growths.

PATIENTS AND METHODS

This prospective study included a cohort of 59 patients in whom, in the course of an elective colonoscopy, a total excision of a 6 mm-sized or larger polyp was called for. Sizeable biopsies were obtained by means of an Olympus Multibyte forceps prior to the total polypectomy. Subsequent to the study of the polypectomy specimens, the forceps biopsy samples were submitted for histological examination. The pathologists were blinded as to the source of the tissue they were studying. The diagnoses rendered by evaluating the biopsy samples and polypectomy specimens of each patient were contrasted with each other.

RESULTS

Major discrepancies between the histological features of the fragments captured by the biopsy-forceps and the factual nature of the totally removed polyps were uncovered in 11 (18.6%) of 59 cases. Intriguingly, the grade of the tumours was underrated in all the 11 cases, as judged by contrasting the tentative diagnoses of the forceps-biopsies with the decisive diagnoses of the polypectomies. Importantly, 2 adenocarcinomas would have been missed by just looking at the forceps-retrieved sample.

CONCLUSIONS

In our experience, a discordance of 18.6% is to be expected between the diagnoses rendered after examining forceps-biopsies of and totally excised colonic polyps. Nevertheless, it is advisable to procure biopsies prior to the excision of the growths, because on those occasions in which patients' growths cannot be removed or have not been retrieved for one reason or another, a small forceps-captured tissue sample correctly reflects the characteristics of the polyp in 81.4% of the cases. Finally, the biopsies may be discarded in the event that total removal was successful.

[Early diagnosis of colorectal tumors]

Colorectal cancer (CRC) is one of the most common causes of cancer mortality in Western countries. Approximately six percent of the population will develop colorectal cancer during life. Individuals older than 50 years or with a family history for colorectal tumors as well as patients with an inflammatory bowel disease have an increased risk for CRC. A significant reduction of colorectal cancer mortality can be achieved by screening of asymptomatic patients and removal of premalignant adenomatous polyp precursors. Colonoscopy is recognized as the gold standard, but in future virtual colonoscopy might be a reasonable addition. Asymptomatic individuals with an average risk for CRC should be screened from the age of 50 and then every 10 years if the examination showed no pathological findings. When the individual or family history indicate a higher risk for a colorectal neoplasia, screening should begin at the age of 40 or 10 years before the earliest tumor occurrence in the family. Families with hereditary CRC require a special surveillance.

Region-based supine-prone correspondence for the reduction of false-positive CAD polyp candidates in CT colonography

RATIONALE AND OBJECTIVES

Radiologists often compare the supine and prone data sets of a patient to confirm potential polyp findings in computed tomographic (CT) colonography (CTC). We developed a new automated method that uses region-based supine-prone correspondence for the reduction of false-positive (FP) polyp candidates in computer-aided detection (CAD) for CTC.

MATERIALS AND METHODS

Up to six anatomic landmarks are established by use of the extracted region of the colonic lumen. A region-growing scheme with distance calculations is used to divide the colonic lumen into overlapping segments that match in the supine and prone data sets. Polyp candidates detected by means of a CAD scheme are eliminated in colonic segments that have sufficient diagnostic quality and contain polyp candidates in only one of the data sets of a patient. The method was evaluated with 121 CTC cases, including 42 polyps of 5 mm or greater in 28 patients, obtained by use of single- and multidetector CT scanners with standard pre-colonoscopy cleansing.

RESULTS

Complete or partial correspondence was established in 71% of cases. Based on a leave-one-patient-out evaluation, application of the method reduced 19% of FP results reported by our CAD scheme at a 90.5% by-polyp detection sensitivity, without loss of any true-positive results. The resulting CAD scheme yielded 2.4 FP results per patient, on average, with the use of the correspondence method, whereas it yielded 3.0 FP results per patient without the use of the method.

CONCLUSION

The correspondence method is potentially useful for improving the specificity of CAD in CTC.

Prevalence and predictors of multiple behavioral risk factors for colon cancer

OBJECTIVES

This paper examines the prevalence of behavioral risk factors for colorectal cancer (CRC) (e.g., red meat consumption, fruit and vegetable intake, multivitamin intake, alcohol, smoking, and physical inactivity), co-occurrence among these behaviors, and motivation for change among patients at increased risk.

METHODS

The study sample included 1,247 patients with recent diagnosis of adenomatous colorectal polyps. Within 4 weeks following the polypectomy, participants completed a baseline survey by telephone.

RESULTS

Sixty-six percent of participants had not been diagnosed with polyps before. Fifty-eight percent of the sample had red meat as a risk factor, 63% had fruit and vegetable consumption as a risk factor, 54% did not take a daily multivitamin, and 44% had physical activity as a risk factor. In contrast, only 9% of the sample had alcohol consumption as a risk factor and only 14% were current smokers. The prevalence of the six individual risk factors was combined into an overall multiple risk factor score (MRF). The average number of risk factors was 2.43. Men, those with a high school education or below, those reporting fair or poor health status, and those with less self-efficacy about risk factor change had more risk factors.

CONCLUSIONS

There is a need for multiple risk factor interventions that capitalize on natural intersections among intra- and interpersonal factors that maintain them.

The risk of metachronous neoplasia in patients with serrated adenoma

Serrated adenomas are the precursors of at least 5.8% of colorectal cancers; otherwise little is known of their clinical significance in comparison with conventional adenomas and hyperplastic polyps. We compared the risk of metachronous lesions in colorectal serrated adenomas, conventional adenomas, and hyperplastic polyps. A consecutive series of patients with colorectal polyps first diagnosed from January 1978 to December 1982 and follow-up specimens to the end of 2000 was reviewed, and 239 polyps fulfilling the selection criteria were chosen as index polyps. The type of polyp seen in follow-up correlated significantly with the type of the initial lesion. Serrated adenomas were estimated to grow faster than conventional adenomas, but the incidence of colorectal cancer did not differ significantly between serrated (2/38 [5%]) and conventional adenomas (2.2%). The results indicate that serrated adenomas are lesions with a significant risk of metachronous serrated adenomas and the development of cancer. We emphasize the need for the proper recognition and management of serrated adenomas.

Efficacy of magnifying chromoendoscopy for the differential diagnosis of colorectal lesions

Magnifying chromoendoscopy is an exciting new tool and offers detailed analysis of the morphological architecture of mucosal crypt orifices. In this review, we principally show the efficacy of magnifying chromoendoscopy for the differential diagnosis of colorectal lesions such as prediction between non‐neoplastic lesions and neoplastic ones, and distinction between endoscopically treatable early invasive cancers and untreatable cancers based on a review of the literature and our experience at two National Cancer Centers in Japan. Overall diagnostic accuracy by conventional view, chromoendoscopy and chromoendoscopy with magnification ranged from 68% to 83%, 82% to 92%, and 80% to 96%, respectively, and diagnostic accuracy of accessing the stage of early colorectal cancer using magnifying colonoscopy was over 85%. Although the reliability depends on the skill in magnifying observation, widespread applications of the magnification technique could influence the indications for biopsy sampling during colonoscopy and the indication for mucosectomy. Moreover, the new detailed images seen with magnifying chromoendoscopy are the beginning of a new period in which new optical developments, such as narrow band imaging system, endocytoscopy system, and laser‐scanning confocal microscopy, will allow a unique look at glandular and cellular structures.

Dark lumen MR colonography based on fecal tagging for detection of colorectal masses: accuracy and patient acceptance

BACKGROUND

Magnetic resonance colonography (MRC) with fecal tagging has recently been investigated in clinical studies for the detection of polyps. We assessed fecal tagging MRC in a field trial.

METHODS

Forty-two patients in a private gastroenterologic practice underwent MRC with barium-based fecal tagging (150 mL of 100% barium at each of 6 main meals before MRC) and conventional colonoscopy. Diagnostic accuracy of MRC and patient acceptance were assessed and compared with the respective results of conventional colonoscopy.

RESULTS

Eighteen percent of all MRC examinations showed a remaining high stool signal in the colon that impeded a reliable inclusion or exclusion of polyps. On a lesion-by-lesion basis, sensitivities for polyp detection were 100% for polyps larger than 2 cm (n = 1), 40% for polyps between 10 and 19 mm, 16.7% for polyps between 6 and 9 mm, and 9.1% for polyps smaller than 6 mm. The main reason for the low acceptance of MRC was the barium preparation, which was rated worse than the bowel cleaning procedure with conventional colonoscopy.

CONCLUSION

MRC with fecal tagging must be further optimized. The large amount of barium resulted in poor patient acceptance, and barium according to this protocol did not provide sufficient stool darkening. Other strategies, such as increasing the hydration of stool, must be developed.

Colorectal cancer screening: prospects for molecular stool analysis

Colorectal cancer is common. As many patients present with advanced disease, an effective screening test would have substantial clinical benefits. Recent progress in understanding the biology of colorectal cancer (and of cancer cells in general) has led to possible new approaches to screening. In particular, there are prospects of developing tests based on analysis of stool, which promise improved accuracy, safety, affordability and patient compliance.

Bipolar electrocoagulation vs conventional monopolar hot biopsy forceps in the endoscopic treatment of diminutive rectal adenomas

OBJECTIVE

To assess whether a cold biopsy from a diminutive rectal adenoma followed by destruction with bipolar (gold probe) electrocoagulation using large probes and high power setting would be a safe and efficient alternative to conventional monopolar hot biopsy forceps (MHBF).

PATIENTS AND METHODS

Eligible patients were those undergoing colonoscopy, fulfilling the criteria of additional clearing colonoscopy and having at least one suspected rectal adenoma < or = 5 mm. At the time of endoscopy patients were randomized to receive treatment for their diminutive rectal adenomas either with cold biopsy followed by repeated gold probe electrocoagulation (Group A) using a 10 Fr catheter with setting 8 (40 W) for 1 second or with MHBF (Group B). These patients were followed up with a colonoscopy at 2-4 months.

RESULTS

A total number of 24 (15 males, 9 females; mean age 56 years) patients were included in group A and 26 (14 males, 12 females; mean age 58 years) in group B. A total number of 38 and 37 diminutive rectal adenomas was detected in patients of Group A and Group B, respectively. At follow up colonoscopy residual adenoma tissue was found in 2 (5.2%) adenomas of 38 in Group A and in 4 (10.8%) of 37 in Group B (P > 0.3). No complications related to colonoscopy or endoscopic treatments in both groups occurred.

CONCLUSIONS

Our data suggest that the use of cold biopsy followed by bipolar electrocoagulation using large probes and high power setting for destroying diminutive rectal adenoma seems to be equally effective and safe as MHBF.

MR colonography: baseline appearance of the unprepared rectosigmoid

A retrospective review of 100 routine pelvic MR examinations was conducted to evaluate the appearance of the unprepared rectosigmoid colon, with the aim of informing future strategies for minimal preparation MR colonography. All examinations were reviewed by two observers in consensus, and included matched-location axial T1 weighted and T2 weighted fat suppressed fast spin echo (FSFSE) images. Analysis revealed that the overall appearance of the faecal material in the colon could simulate tumour in 80% of T1 weighted and 17% of T2 weighted images. By matching the images from the two sequences for each patient the faeces had an overall appearance that would mimic tumour in only 7% of cases. However, luminal tumour-mimicking foci of signal occurred frequently, present in 91% of T1 weighted and 85% of T2 weighted studies. The results indicate that if bowel-cleansing regimens are to be avoided for MR colonography, effective strategies such as dietary restriction and use of oral contrast agents will be required to reduce luminal signal on T2 weighting and eliminate polyp-mimicking foci. The results also suggest that T2 weighted strategies should be further investigated and that combination with T1 weighted imaging may improve discrimination of lesions from normal faecal material.

Risk of colorectal adenomas in a multiethnic Asian patient population: race does not matter

BACKGROUND

Ethnic differences have been reported for colorectal polyps and large bowel cancer; although the supporting data is weak and insufficient to draw firm conclusions.

AIM

We undertook this study to determine whether such racial disparity in colorectal adenomas exists in an ethnically mixed non-migrant population. The prevalence, histology and distribution of colonic polyps were documented as well as other known risk factors for colorectal malignancy.

METHODS

In this prospective cross-sectional study, 311 consecutive referred and self-referred multiracial patients attending for colonoscopy over a 41-month period in a private endoscopy center were recruited. The mean age of the study population was 51.8 +/- 14 years (range 16-91). The male to female ratio was 1.1 and an ethnic breakdown as follows: 87 Malays, 115 Chinese and 109 Indians.

RESULTS

Sixty-three adenomas were recorded in 36 patients: six Malays, 19 Chinese and 11 Indians. Of these adenomas, 59 were polypoid, three flat and one depressed. The majority of adenomas 42/63 (67%) were distal to the splenic flexure as were all (10/10) the Duke's A carcinomas and 6/8 (75%) of the advanced cancers. Patients with adenoma(s) compared with those without (controls) were significantly older (P = 0.005), more likely to have a family history of colorectal cancer (P = 0.005), and showed a trend towards significance for ethnic group (P = 0.09) on univariate analysis. Using logistic regression analysis, only family history (P = 0.05) and age > or = 50 years (P = 0.011) were found to be significantly associated with adenomas.

CONCLUSION

Risk factors for colonic adenoma(s) in our cohort of symptomatic multiethnic patients attending for colonoscopy do not seem to differ from those reported elsewhere and, in particular, race does not appear to be a factor.

Recent developments in CT colonography

CT colonography allows reliable, non-invasive, rapid, high resolution imaging of the whole large bowel. Recent advances in technology such as computer-aided detection (CAD), scanning with or without bowel preparation, and low radiation are continually developing to improve the efficacy of this technique. This review will update the reader as to ongoing developments while presenting current thinking from the gastroenterological perspective.

Dark Lumen Magnetic Resonance Colonography in a Rodent Polyp Model

PURPOSE

We sought to assess dark lumen magnetic resonance (MR) colonography for the detection of colon polyps in a rodent model with histology as the gold standard.

MATERIAL AND METHODS

Fourteen male Wistar rats were subjected to carcinogenic N-methyl-N'-nitro-N-nitrosoguanidine at the age of 4 months to induce colon neoplasms. MR imaging was performed after a time interval of 1 year. Preparation and data acquisition was performed with the animals under full anesthesia. After a body-warm saline enema images were acquired on a clinical 1.5-T whole-body MR system using a standard extremity coil. Plain and contrast-enhanced (0.3 mmol/kg; Gd-DOTA; Dotarem, Guerbet, France) 3-dimensional T1-weighted gradient recall echo images were acquired. Two radiologists analyzed the MR data sets in consensus for lesion depiction. Contrast uptake in colonic wall and polyps was quantitatively assessed by signal-to-noise ratio and contrast-to-noise ratio measurements and compared using a Wilcoxon-Mann-Whitney U test with statistical significance at a P value < 0.05. Finally, all animals were killed, and the MR imaging results were compared with pathologic findings. Sensitivity and specificity were calculated.

RESULTS

By pathology, a total of 15 polyps were found in 9 of 14 rats. MR colonography detected 13 of 15 polyps measuring between 4 and 11 mm (mean 7 +/- 0.6 mm) in 8 of 9 animals, resulting in a sensitivity and specificity of 0.87 and 1.0, respectively. Compared with the precontrast data, all polyps showed a statistically significant increase in signal-to-noise ratio (78.2 +/- 6.3 to 167.4 +/- 17.7) and contrast-to-noise ratio (45.4 +/- 5.2 to 124.6 +/- 11.2).

CONCLUSION

MR colonography with a dark colon lumen and a bright, contrast-enhanced colon wall appears well suited for the detection of colonic lesions in a rodent model.

Computerized detection of colorectal masses in CT colonography based on fuzzy merging and wall-thickening analysis

In recent years, several computer-aided detection (CAD) schemes have been developed for the detection of polyps in CT colonography (CTC). However, few studies have addressed the problem of computerized detection of colorectal masses in CTC. This is mostly because masses are considered to be well visualized by a radiologist because of their size and invasiveness. Nevertheless, the automated detection of masses would naturally complement the automated detection of polyps in CTC and would produce a more comprehensive computer aid to radiologists. Therefore, in this study, we identified some of the problems involved with the computerized detection of masses, and we developed a scheme for the computerized detection of masses that can be integrated into a CAD scheme for the detection of polyps. The performance of the mass detection scheme was evaluated by application to clinical CTC data sets. CTC was performed on 82 patients with helical CT scanners and reconstruction intervals of 1.0-5.0 mm in the supine and prone positions. Fourteen patients (17%) had a total of 14 masses of 30-50 mm, and sixteen patients (20%) had a total of 30 polyps 5-25 mm in diameter. Four patients had both polyps and masses. Fifty-six of the patients (68%) were normal. The CTC data were interpolated linearly to yield isotropic data sets, and the colon was extracted by use of a knowledge-guided segmentation technique. Two methods, fuzzy merging and wall-thickening analysis, were developed for the detection of masses. The fuzzy merging method detected masses with a significant intraluminal component by separating the initial CAD detections of locally cap-like shapes within the colonic wall into mass candidates and polyp candidates. The wall-thickening analysis detected nonintraluminal masses by searching the colonic wall for abnormal thickening. The final regions of the mass candidates were extracted by use of a level set method based on a fast marching algorithm. False-positive (FP) detections were reduced by a quadratic discriminant classifier. The performance of the scheme was evaluated by use of a leave-one-out (round-robin) method with by-patient elimination. All but one of the 14 masses, which was partially cut off from the CTC data set in both supine and prone positions, were detected. The fuzzy merging method detected 11 of the masses, and the wall-thickening analysis detected 3 of the masses including all nonintraluminal masses. In combination, the two methods detected 13 of the 14 masses with 0.21 FPs per patient on average based on the leave-one-out evaluation. Most FPs were generated by extrinsic compression of the colonic wall that would be recognized easily and quickly by a radiologist. The mass detection methods did not affect the result of the polyp detection. The results indicate that the scheme is potentially useful in providing a high-performance CAD scheme for the detection of colorectal neoplasms in CTC.

Morphologically distinct patterns of apoptosis correlate with size and high-grade dysplasia in colonic adenomas

AIMS

To examine the relationship of morphological patterns of apoptosis in colonic adenomas to standard pathological variables.

METHODS AND RESULTS

Apoptosis patterns were evaluated in 184 consecutive colonic adenomas and 14 adenocarcinomas, using haematoxylin and eosin sections. Apoptosis identification was selectively validated by electron microscopy. There were three patterns of apoptosis: (i) confluent basal apoptosis; (ii) crypt lumen apoptosis, both assessed semiquantitatively; and (iii) scattered apoptosis (not quantified). Adenoma site, size, type, mitoses, and grade of dysplasia were also assessed. MIB-1 immunostaining was performed in 20 cases. In 142 adenomas (77%) confluent basal apoptosis (n = 124) and/or crypt lumen apoptosis (n = 69) were identified; 42 (23%) had scattered apoptosis only. Significant correlations were: (i) extensive confluent basal apoptosis with small adenomas < or =5 mm (P < 0.0001); (ii) crypt lumen apoptosis with large adenomas >5 mm (P < 0.0001) and (iii) with high-grade dysplasia (P < 0.0003); and (iv) coexistence of both patterns (n = 51) with large adenomas >5 mm (P < 0.0001). Neither apoptosis pattern correlated with other variables. Adenocarcinomas had minimal confluent basal apoptosis (5/14), conspicuous crypt lumen apoptosis (14/14), intraglandular coagulative necrosis, and scattered apoptotic tumour cells.

CONCLUSIONS

Confluent basal apoptosis is maximal early in colonic tumorigenesis. The 'switch' to a predominant crypt lumen apoptosis pattern suggests that a different apoptosis induction mechanism might be associated with the transition to adenocarcinoma.

Phenotypic characteristics and risk of cancer development in hyperplastic polyposis: case series and literature review

OBJECTIVES

Hyperplastic polyposis (HP) is a poorly understood condition. The aim of this study is to describe the phenotype and the risk of cancer in HP.

METHODS

Patients with HP, as defined by the WHO International Classification, were identified through the University of Utah and the Huntsman Cancer Institute databases. Family history was retrieved when possible.

RESULTS

Fifteen patients were identified (10 M, 5 F) with a mean age at diagnosis of 52.6 +/- 16.4 yr (18-71). Sixty-five colonoscopies were performed (2-11 per person). A median of 90 polyps (16-210) per person and 15 polyps (range, 0-100) per procedure were reported. The median follow-up was 33 months (3-133); no cancer occurred during this period. Polyps were more frequent in the distal than the proximal colon (74%vs 26%; p < 0.001). The median polyp size was 4 mm (1-40 mm). Fifty-one hyperplastic polyps >10 mm were identified in 10 patients (38 proximal, 13 distal; p= 0.089). Forty-eight adenomas were found in 11 patients and were uniformly distributed. Serrated adenomas (n = 3) were found in one patient. A unique patient had 20 large hyperplastic polyps, 24 adenomas, 3 serrated adenomas, and 118 hyperplastic polyps. None of the patients had a first-degree relative with colon cancer.

CONCLUSIONS

In HP, hyperplastic polyps are more frequently distal colonic, and vary greatly in size and number. Most patients also develop adenomas that are distributed throughout the colon. No cancers developed within 3 yr of follow-up. Colonoscopic surveillance at intervals of 1-3 yr, depending upon the number and size of both adenomatous and hyperplastic polyps, appears prudent.

Evaluation of polyp detection in relation to procedure time of screening or surveillance colonoscopy

BACKGROUND AND OBJECTIVES

Multiple factors influence the yield of colonoscopy for the detection of neoplasia. Few studies have addressed the impact of colonoscopy duration on procedure yield. The aim of our study was to determine whether endoscopist-specific procedure times correlate with the number and clinical significance of polyps detected at screening or surveillance colonoscopy.

METHODS

Procedural data from screening or surveillance colonoscopies performed at Mayo Clinic, Rochester MN, between January 1, 1996 and June 30, 2000, were reviewed. Individual endoscopists were characterized by their personal endoscopist procedure mean time (EPMT) to perform a negative colonoscopy. Procedure time included patient's consent and sedation. EPMT was then correlated with individual polyp detection rates.

RESULTS

Overall, 10,159 colonoscopies were reviewed of which 4,312 (42.4%) yielded polyps. Polyp detection varied among endoscopists between 19.0% and 62.3%. There was a close correlation between EPMT and polyp yield (all sizes), r = 0.64, although correlation was weaker for polyps >10 mm (r = 0.42) and polyps >20 mm (r = 0.20). On multivariate analysis, longer mean endoscopist time was associated with colonic lesion detection, OR = 1.54 (95% CI 1.37-1.62). Longer mean procedure duration demonstrated a looser association with identification of polyps >10 mm, OR = 1.40 (1.19-1.64) and polyps >20 mm, OR = 1.03 (0.74-1.43).

CONCLUSIONS

There is a direct correlation between colonoscopy procedure time and yield, with a three-fold variation of polyp detection rates. These results should prompt future prospective studies assessing the impact of colonoscopic withdrawal time on lesion detection.

AGA future trends report: CT colonography

BACKGROUND & AIMS

Computed tomographic colonography (CTC) was first described more than a decade ago. Recent advances in imaging hardware and software and results of clinical trials based on new methods for performing and interpreting images suggest that CTC may now be assessed as a method for colorectal cancer screening.

METHODS

The Research Policy Committee of the American Gastroenterological Association assembled a task force to review the results of recent clinical trials and quantitative mathematical models pertaining to CTC. The goal of the task force was to assess the current knowledge about CTC and to evaluate the issues that will define its impact.

RESULTS

Limitations in evaluating the current state of CTC technology include a wide variation in results of clinical trials. There are as yet insufficient data on the use of CTC in routine clinical practice. Limitations in the use of quantitative mathematical models make predictions based on such models of limited value. The cancer risk and therefore clinical importance of small colorectal polyps detected by CTC and/or nonpolypoid neoplasia not detected by CTC remains largely unknown.

CONCLUSIONS

CTC is attractive as a colon imaging modality. It is therefore anticipated that CTC will have a significant impact on the practice of gastroenterology. However, the magnitude of the impact is currently unknown. Whether the ongoing implementation of CTC will increase or decrease the number of referrals for colonoscopy or shift the procedure from colorectal cancer screening to therapeutic interventions (e.g., polypectomy) is unknown at the present time. Multidisciplinary collaboration between gastroenterology and radiology to promote effective implementation and ongoing quality assurance will be important.

Colon cancer-associated DNA mutations: marker selection for the detection of proximal colon cancer

This study evaluates the potential ability of a specific panel of DNA mutations to identify right-sided colorectal carcinomas (CRCs) that would be missed by a flexible sigmoidoscopy (FS) screening program. This panel could then be applied to stool DNA analysis for noninvasive proximal CRC detection. A series of resected right-sided CRCs from 101 patients who had no left-sided advanced colonic neoplasms distal to the splenic flexure were analyzed. Tumor DNA was isolated from microdissected tumor sections. Deletions in the BAT-26 locus, a marker of microsatellite instability, and mutations at 19 loci spread among the p53, K-ras, and Apc genes were detected following PCR amplification. Mutations were identified in 83% of successfully amplified samples and were variably present in each of the target sites: p53 (42%), Apc (37%), K-ras (28%), and BAT-26 (24%). Mutations were identified across all Dukes stages (CIS/A 6/8 [75%], B 41/51[80%], C 30/32 (94%), and D 6/9 [67%]). Our data suggest that this 20-marker mutation panel may be associated with more than 80% of cancers undetectable by FS. The adjunctive use of stool DNA mutation analysis using this marker panel in FS CRC screening programs may significantly increase the detection of proximal CRC.

The relationship between cyclooxygenase-2 expression and characteristics of malignant transformation in human colorectal adenomas

BACKGROUND AND AIMS

Cyclooxygenase 2 (COX-2) is a target of aspirin and other non-steroidal anti-inflammatory drugs and is implicated in the pathogenesis of colorectal cancer. The objective of this study was to evaluate the extent of COX-2 in pre-malignant colorectal polyps and to assess the relationship between COX-2 and the level of dysplasia in these lesions.

METHODS

Whole polypectomy specimens were retrieved from 123 patients by endoscopic or surgical resection. Following formalin fixation and paraffin embedding, the polyps were evaluated histologically for size, type and grade of dysplasia. The extent of COX-2 expression was measured by the avidin-biotin immunohistochemical technique using a monoclonal COX-2 antibody. The extent of COX-2 expression was graded according to percentage epithelial COX-2 expression.

RESULTS

The polyps were of the following histological types: 10 hyperplastic, 35 tubular adenomas, 61 tubulovillous adenomas and 17 villous adenomas. Twenty showed mild dysplasia, 65 moderate dysplasia, and 28 focal or severe dysplasia (including eight with focal invasion). The average polyp size was 1.7 cm. Nine hyperplastic polyps were COX-2-negative and one was COX-2-positive. COX-2 expression was more extensive in larger polyps and in polyps with a higher villous component. There was a significant increase in the extent of COX-2 protein with increasing severity of dysplasia. Within a polyp, there was a focal corresponding increase in COX-2 expression within epithelium showing a higher grade of dysplasia.

CONCLUSIONS

COX-2 expression is related directly to colorectal adenomatous polyp size, type and grade of dysplasia. This suggests that the role of COX-2 in colorectal cancer may be at an early stage in the adenoma-to-carcinoma sequence and supports the suggestion that inhibition of COX-2 may be useful chemoprevention for this disease.

Diagnostic value of distal colonic polyps for prediction of advanced proximal neoplasia in an average-risk population undergoing screening colonoscopy

BACKGROUND

For colorectal cancer screening, the predictive value of distal findings in the ascertainment of proximal lesions is not fully established. The aims of this study were to assess distal findings as predictors of advanced proximal neoplasia and to compare the predictive value of endoscopy alone vs. combined endoscopic and histopathologic data.

METHODS

Primary colonoscopy screening was performed in 2210 consecutive, average-risk adults. Age, gender, endoscopic (size, number of polyps), and histopathologic distal findings were used as potential predictors of advanced proximal neoplasms (i.e., any adenoma > or =1 cm in size, and/or with villous histology, and/or with severe dysplasia or invasive cancer). Polyps were defined as distal if located in the descending colon, the sigmoid colon, or the rectum. Those in other locations were designated proximal.

RESULTS

Neoplastic lesions, including 11 invasive cancers, were found in 617 (27.9%) patients. Advanced proximal neoplasms without any distal adenoma were present in 1.3% of patients. Of the advanced proximal lesions, 39% were not associated with any distal polyp. Older age, male gender, and distal adenoma were independent predictors of advanced proximal neoplasms. The predictive ability of a model with endoscopic data alone did not improve after inclusion of histopathologic data. In multivariate logistic regression analysis, the predictive ability of models that use age, gender, and any combination of distal findings was relatively low. The proportion of advanced proximal neoplasms identified if any distal polyp was an indication for colonoscopy was only 62%.

CONCLUSIONS

A strategy in which colonoscopy is performed solely in patients with distal colonic findings is not effective screening for the detection of advanced proximal neoplasms in an average-risk population.

Gene mutations in advanced colonic polyps: potential marker selection for stool-based mutated human DNA assays for colon cancer screening

The detection and removal of advanced colonic polyps (ACPs) can help prevent the development of colorectal cancer. A set of DNA mutations known to be associated with colorectal carcinoma was tested against resected ACPs to determine the set s potential utility as a marker panel for ACPs. A sensitive mutation marker panel could be used by stool-based assays that look for mutated human DNA to detect the presence of ACPs. DNA from 32 ACPs = 1.0 cm in diameter was amplified and tested for 19 colorectal cancer associated DNA mutations and for deletions in BAT-26 (microsatellite instability). One or more mutations were identified by microsequencing in 28 of the 32 ACPs (88%). Mutations were identified in k-ras (59%), APC (33%), and p53 (22%). BAT-26 mutation, a marker for microsatellite instability, was not identified. Stool DNA based assays that can identify these mutations may significantly increase the identification of patients with potentially premalignant ACPs for evaluation and treatment by colonoscopy.

Colorectal adenoma characteristics as predictors of recurrence

PURPOSE

The identification of groups with a high risk of colorectal adenoma recurrence remains a controversial issue for clinicians. This study was designed to assess the predictive value of initial patient and adenoma characteristics of the three-year recurrence.

METHODS

The study population was composed of 552 patients with resected colorectal adenomas who completed the European Fiber-Calcium Intervention trial. At both baseline and three-year examinations, the characteristics of adenomas were recorded according to a standardized protocol. The main outcomes measured were the three-year overall recurrence, recurrence of multiple adenomas, recurrence of advanced adenomas (size > or = 1 cm or tubulovillous/villous architecture or moderate/severe dysplasia), and proximal and distal recurrence.

RESULTS

A three-year recurrence was observed in 122 patients (22.1 percent), and more than one-half of them had recurrent adenomas on the proximal colon. After adjustment for patient characteristics and treatment allocation, the number of adenomas and their proximal location at baseline were the main predictors of recurrence. In comparison with patients who had one or two adenomas on the distal colon, patients with three or more adenomas with at least one of them located on the proximal colon had a much higher risk of overall recurrence (5.3; 95 percent confidence interval, 2.7-10.3), proximal recurrence (8.5; 95 percent confidence interval, 4.1-18), and advanced adenoma recurrence (5.5; 95 percent confidence interval, 2.4-12.6).

CONCLUSIONS

Follow-up colonoscopies in patients with adenomas should include careful examination of the proximal colon. The time interval between follow-up examinations could probably be extended beyond three years in patients who have only one or two distal adenomas.

Prevalence of proximal adenomas after an adenoma is found on flexible sigmoidoscopy

BACKGROUND

Adenomatous polyps are a precursor of colorectal cancer and a frequent finding on screening flexible sigmoidoscopy (FS). Performance of colonoscopy when a diminutive (<6mm) adenoma is found on FS has been the subject of considerable debate.

METHODS

We retrospectively reviewed the data from our colorectal cancer screening program for patients with adenoma(s) found on FS. Patients were divided into three groups based on FS findings: (1) an adenoma <6mm in size, (2) multiple non-advanced adenomas or an adenoma 6-10mm in size, or (3) advanced adenoma defined as an adenoma >10mm or with villous histology or high-grade dysplasia or cancer. A comparison of the proximal findings was then made.

RESULTS

5291 FS reports were reviewed with 606 (12%) patients having at least one adenoma. Colonoscopy reports were available in 550 patients. Of the 258 patients with a diminutive distal adenoma, 69 (27%) had a proximal adenoma and 13 (5%) had an advanced proximal adenoma on colonoscopy. Of the 164 patients with an adenoma 6-10mm or multiple non-advanced adenomas, 59 (36%) had a proximal adenoma and 13 (8%) had an advanced proximal adenoma. Of the 128 patients with a distal advanced adenoma, 58 (45%) had a proximal adenoma and 15 (12%) had an advanced proximal adenoma. The increase in proximal adenomas across the three groups was significant (P=0.001), and there was a trend for increased prevalence of advanced adenomas (P=0.061).

CONCLUSIONS

The prevalence of proximal adenomas increased significantly with more advanced lesions found distally at FS, and there was a trend towards a higher prevalence of advanced proximal adenomas. Based on current guidelines, flexible sigmoidoscopy is a screening option that can be used to identify average-risk patients at increased risk of proximal neoplasia.

Use of colonoscopy as a primary screening test for colorectal cancer in average risk people

OBJECTIVE

The use of colonoscopy as a primary screening test for colorectal cancer (CRC) in average risk adults is a subject of controversy. Our primary objective was to build a predictive model based on a few simple variables that could be used as a guide for identifying average risk adults more suitable for examination with colonoscopy as a primary screening test.

METHODS

The prevalence of advanced adenomas was assessed by primary screening colonoscopy in 2210 consecutive adults at least 40 yr old, without known risk factors for CRC. Age, gender, and clinical and biochemical data were compared among people without adenomas, those with non-advanced adenomas, and those with any advanced neoplasm. A combined score to assess the risk of advanced adenomas was built with the variables selected by multiple logistic regression analysis.

RESULTS

Neoplastic lesions were found in 617 subjects (27.9%), including 259 with at least one neoplasm that was 10 mm or larger, villous, or with moderate-to-severe dysplasia, and 11 with invasive cancers. Advanced lesions were more frequent among men, older people, and those with a higher body mass index (BMI). These three variables were independent predictors of advanced adenomas in multivariate analysis. A score combining age, sex, and BMI was developed as a guide for identifying individuals more suitable for screening colonoscopy.

CONCLUSIONS

Age, gender, and BMI can be used to build a simple score to select those average risk adults who might be candidates for primary screening colonoscopy.