Flexible sigmoidoscopy may be ineffective for secondary prevention of colorectal cancer in asymptomatic, average-risk men

The Association between Distal Findings and Proximal Colorectal Neoplasia: A Systematic Review and Meta-Analysis

OBJECTIVES

Whether screening participants with distal hyperplastic polyps (HPs) detected by flexible sigmoidoscopy (FS) should be followed by subsequent colonoscopy is controversial. We evaluated the association between distal HPs and proximal neoplasia (PN)/advanced proximal neoplasia (APN) in asymptomatic, average-risk patients.

METHODS

We searched Ovid Medline, EMBASE, and the Cochrane Library from inception to 30 June 2016 and included all screening studies that examined the relationship between different distal findings and PN/APN. Data were independently extracted by two reviewers with disagreements resolved by a third reviewer. We pooled absolute risks and odds ratios (ORs) with a random effects meta-analysis. Seven subgroup analyses were performed according to study characteristics. Heterogeneity was characterized with the I² statistics.

RESULTS

We analyzed 28 studies (104,961 subjects). When compared with normal distal findings, distal HP was not associated with PN (OR=1.16, 95% confidence interval (CI)=0.89-1.51, P=0.14, I²=40%) or APN (OR=1.09, 95% CI=0.87-1.36, P=0.39, I²=5%), while subjects with distal non-advanced or advanced adenoma had higher odds of PN/APN. Higher odds of PN/APN were observed for more severe distal lesions. Weaker association between distal and proximal findings was noticed in studies with higher quality, larger sample size, population-based design, and more stringent endoscopy quality-control measures. The Egger's regression tests showed all P>0.05.

CONCLUSIONS

Distal HP is not associated with PN/APN in asymptomatic screening population when compared with normal distal findings. Hence, the presence of distal HP alone detected by FS does not automatically indicate colonoscopy referral for all screening participants, as other risk factors of PN/APN should be considered.

The big picture: does colonoscopy work?

Colonoscopy for average-risk colorectal cancer screening has transformed the practice of gastrointestinal medicine in the United States. However, although the dominant screening strategy, its use is not supported by randomized controlled trials. Observational data do support a protective effect of colonoscopy and polypectomy on colorectal cancer incidence and mortality, but the level of protection in the proximal colon is variable and operator-dependent. Colonoscopy by high-level detectors remains highly effective, and ongoing quality improvement initiatives should consider regulatory factors that motivate changes in physician behavior.

Colonoscopy: the current king of the hill in the USA

Colonoscopy is the dominant colorectal cancer screening strategy in the USA. There are no randomized controlled trials completed of screening colonoscopy, but multiple lines of evidence establish that colonoscopy reduces colorectal cancer incidence in both the proximal and distal colon. Colonoscopy is highly operator dependent, but systematic efforts to measure and improve quality are impacting performance. Colonoscopy holds a substantial advantage over other strategies for detection of serrated lesions, and a recent case-control study suggests that once-only colonoscopy or colonoscopy at 20-year intervals, by a high-level detector, could ensure lifetime protection from colorectal cancer for many patients.

Differences in detection rates of adenomas and serrated polyps in screening versus surveillance colonoscopies, based on the new hampshire colonoscopy registry

BACKGROUND & AIMS

The adenoma detection rate (ADR) is an important quality indicator originally developed for screening colonoscopies. However, it is unclear whether the ADR should be calculated using data from screening and surveillance examinations. The recommended benchmark ADR for screening examinations is 20% (15% for women and 25% for men ≥50 y). There are few data available to compare ADRs from surveillance vs screening colonoscopies. We used a population-based registry to compare ADRs from screening vs surveillance colonoscopies. The serrated polyp detection rate (SDR), a potential new quality indicator, also was examined.

METHODS

By using data from the statewide New Hampshire Colonoscopy Registry, we excluded incomplete and diagnostic colonoscopies, and those performed in patients with inflammatory bowel disease, familial syndromes, or poor bowel preparation. We calculated the ADR and SDR (number of colonoscopies with at least 1 adenoma or serrated polyp detected, respectively, divided by the number of colonoscopies) from 9100 colonoscopies. The ADR and SDR were compared by colonoscopy indication (screening, surveillance), age at colonoscopy (50-64 y, ≥65 y), and sex.

RESULTS

The ADR was significantly higher in surveillance colonoscopies (37%) than screening colonoscopies (25%; P < .001). This difference was observed for both sexes and age groups. There was a smaller difference in the SDR of screening (8%) vs surveillance colonoscopies (10%; P < .001).

CONCLUSIONS

In a population-based study, we found that addition of data from surveillance colonoscopies increased the ADR but had a smaller effect on the SDR. These findings indicate that when calculating ADR as a quality measure, endoscopists should use screening, rather than surveillance colonoscopy, data.

Genetic variation in the base excision repair pathway, environmental risk factors, and colorectal adenoma risk

Cigarette smoking, high alcohol intake, and low dietary folate levels are risk factors for colorectal adenomas. Oxidative damage caused by these three factors can be repaired through the base excision repair pathway (BER). We hypothesized that genetic variation in BER might modify colorectal adenoma risk. In a sigmoidoscopy-based study, we examined associations between 182 haplotype tagging SNPs in 14 BER genes, and colorectal adenoma risk, and examined their potential role as modifiers of the effect cigarette smoking, alcohol intake, and dietary folate levels. Among all individuals, no statistically significant associations between BER SNPs and adenoma risk persisted after correction for multiple comparisons. However, among Asian-Pacific Islanders we observed two SNPs in FEN1 and one in NTHL1, and among African-Americans one SNP in APEX1 that were associated with colorectal adenoma risk. Significant associations were also observed between SNPs in the NEIL2 gene and rectal adenoma risk. Three SNPS modified the effect of smoking (MUTYH interaction p = 0.002; OGG1 interaction p = 0.013); FEN1 interaction p = 0.013)), one SNP in LIG3 modified the effect of alcohol consumption (interaction p = 0.024) and two SNPs in LIG3 modified the effect of dietary folate (interaction p = 0.001 and p = 0.08) on colorectal adenoma risk. These findings support a role for genetic variants in the BER pathway as potential modifiers of colorectal adenoma risk. Our findings strengthen the role of oxidative damage induced by key lifestyle and dietary risk factors in colorectal adenoma formation.

Quality indicators for colorectal cancer screening for colonoscopy

The growing importance of colonoscopy in the prevention of colorectal cancer has stimulated an effort to identify and track quality indicators for this procedure. Several factors have been identified so far which are readily measurable and in many cases have been associated with improved patient outcomes. There is also ample evidence of variations in performance of this procedure. As a result, gathering data about quality indicators may play a vital role in the process of continuous quality improvement. Quality indicators for colonoscopy in colorectal cancer prevention are described along with the evidence that supports their use in benchmarking, quality reporting, and continuous quality improvement.

Efficacy and effectiveness of colonoscopy: how do we bridge the gap?

Colonoscopy is sometimes considered the preferred colorectal cancer screening modality, yet this modality may be subject to variation in operator performance more than any other screening test. Failures of colonoscopy to consistently detect precancerous lesions threaten the effectiveness of this technique for the prevention of colorectal cancer. Studies on high-level adenoma detectors under optimal conditions have begun to establish the true efficacy of colonoscopy and further widen the gap between efficacy and effectiveness. Research is required to establish the component skills, attitudes, and behaviors for high-level mucosal inspection competence necessary for training and assessment. Interventions to bridge the gap between efficacy and effectiveness are lacking, yet they should emphasize quality measurement and operate at various levels within the health system to motivate change in endoscopist behavior.

Improving colonoscopy quality through health-care payment reform

Problems with the quality of colonoscopy are well recognized. Variation in colonoscopist performance is compounded by payment structures that reward volume rather than quality. Payment reform has emerged as one strategy to address these and more systemic problems in the quality of health care. Various forms of value-based purchasing might encourage a realignment of incentives, and allow reimbursement to be directly linked with clinically important goals of colonoscopy. This paper proposes criteria for the selection of quality measures, and three candidate indicators to define quality for the purpose of payment reform in colonoscopy: cecal intubation rate, adenoma detection rate, and recommended post-polypectomy surveillance interval. These measures represent valid, credible, and reliable indicators of the quality of colonoscopy for colorectal cancer screening and surveillance. Payment reform should explicitly link public reporting and performance on these quality measures to payment for colonoscopy.

Colorectal cancer screening coverage in Greece. PACMeR 02.01 study collaboration

BACKGROUND AND AIMS

Colorectal cancer is a major cause of cancer death in European countries and differences in screening implementation may in part explain USA vs European survival differences. Despite the evidence, no study has evaluated the population colorectal cancer screening (CCS) coverage in any European country. We aimed to index the current CCS practices among a large sample of Greek healthy adults.

MATERIALS AND METHODS

The study was designed as a cross-sectional survey. Screening practice habits of 5,259 healthy adults, aged 50-80, were surveyed. Both overall and screening practices of stool occult blood test (SOBT), digital rectal examination (DRE), and colonoscopy or sigmoidoscopy (COL/SIG) were analyzed.

RESULTS

Of the population analyzed, 90.1% declared that they were interested in cancer prevention activities. Overall SOBT practice rate within the last 2 years was 4.77%. When only screening procedures were analyzed, this percentage shrank to 1.73%. Overall and screening COL/SIG rates within the last 10 years were 8.76 and 1.74%, respectively. The respective proportions of individuals who underwent DRE were 14.54 and 5.2%. Evidence-based screening practices were influenced by age, family history of colorectal cancer, profession, and educational level; however, SOBT and colonoscopy/sigmoidoscopy did not overcome 4.1 and 4.6% in any subpopulation analyzed.

CONCLUSION

The level of CCS coverage among the examined sample of Greek adults was discouraging. Surveys among other European countries are encouraged.

Localized depletion: the key to colorectal cancer risk mediated by MTHFR genotype and folate?

Dietary folate has been consistently associated with reduced risk of colorectal cancer (CRC). One of the known biochemical roles of folate is donation of methyl moieties. DNA hypomethylation is an early and almost ubiquitous occurrence in tumor tissue. Therefore, it was originally suggested that adequate folate intake contributed to reduced risk of CRC by facilitating methyl-mediated silencing of oncogenes. Methylene tetrahydrofolate reductase (MTHFR) metabolizes 5,10-MTHF (important in DNA synthesis) to 5-MTHF (contributes to downstream methylation reactions by regeneration of methionine from homocysteine). A common polymorphism in the MTHFR gene (C677T) results in a thermolabile phenotype associated with increased homocysteine levels and DNA hypomethylation. Consistent with the folate/methylation hypothesis, it was originally proposed that C677T may increase risk of CRC due to hypomethylation of oncogenes. However, most subsequent studies have reported a reduced risk associated with this polymorphism. This is inconsistent with methylation as the mechanism by which folate and MTHFR genotype mediate CRC risk. The hypothesis presented here proposes that localized folate depletion combined with the effect of the C677T polymorphism on enzyme stability, impacts on the DNA synthesis pathway and accounts for the observed variation in risk associated with genotype and folate status.

The cost-effectiveness of CT colonography in screening for colorectal neoplasia

BACKGROUND

We examined the cost-effectiveness of 2- and 3-dimensional computerized tomography (CT) colonography as a screening test for colorectal neoplasia.

METHODS

We created a Markov model of the natural history of colorectal cancer. Effectiveness of screening was based upon the diagnostic accuracy of tests in detecting polyps and cancer.

RESULTS

CT colonography every 5 or 10 yr was effective and cost-effective relative to no screening. Optical colonoscopy dominates 2-dimensional CT colonography done every 5 or 10 yr. Optical colonoscopy is weakly dominant over 3-dimensional CT colonography done every 10 yr. 3-D CT colonography done every 5 yr is more effective than optical colonoscopy every 10 yr, but costs an incremental 156,000 dollars per life-year gained. Sensitivity analyses show that test costs, accuracy, and adherence are critical determinants of incremental cost-effectiveness. 3-D CT colonography every 5 yr is a dominant strategy if optical colonoscopy costs 1.6 times more than CT colonography. However, optical colonoscopy is a dominant strategy if the sensitivity of CT colonography for 1 cm adenomas is 83% or lower.

CONCLUSIONS

CT colonography is an effective screening test for colorectal neoplasia. However, it is more expensive and generally less effective than optical colonoscopy. CT colonography can be reasonably cost-effective when the diagnostic accuracy of CT colonography is high, as with primary 3-dimensional technology, and if costs are about 60% of those of optical colonoscopy. Overall, CT colonography technology will need to improve its accuracy and reliability to be a cost-effective screening option.

Cost-effectiveness analysis of colorectal cancer screening with stool DNA testing in intermediate-incidence countries

Background

The aim of this study is to compare the cost-effectiveness of screening with stool DNA testing with that of screening with other tools (annual fecal occult blood testing, flexible sigmoidoscopy every 5 years, and colonoscopy every 10 years) or not screening at all.

Methods

We developed a Markov model to evaluate the above screening strategies in the general population 50 to 75 years of age in Taiwan. Sensitivity analyses were performed to assess the influence of various parameters on the cost-effectiveness of screening. A third-party payer perspective was adopted and the cost of $13,000 per life-year saved (which is roughly the per capita GNP of Taiwan in 2003) was chosen as the ceiling ratio for assessing whether the program is cost-effective.

Results

Stool DNA testing every three, five, and ten years can reduce colorectal cancer mortality by 22%, 15%, and 9%, respectively. The associated incremental costs were $9,794, $9,335, and $7,717, per life-year saved when compared with no screening. Stool DNA testing strategies were the least cost-effective with the cost per stool DNA test, referral rate with diagnostic colonoscopy, prevalence of large adenoma, and discount rate being the most influential parameters.

Conclusion

In countries with a low or intermediate incidence of colorectal cancer, stool DNA testing is less cost-effective than the other currently recommended strategies for population-based screening, particularly targeting at asymptomatic subjects.

Quality assessment of colonoscopic cecal intubation: an analysis of 6 years of continuous practice at a university hospital

BACKGROUND

Despite increased emphasis on endoscopic performance indicators, e.g., cecal intubation rates, limited data from actual clinical practice have been published.

OBJECTIVES

Retrospective database review to determine the rate and documentation of cecal intubation during colonoscopy at the University of Maryland Medical Center.

METHODS

We reviewed 5,477 consecutive colonoscopies performed by 10 faculty gastroenterologists at a University hospital over a 6-yr period (March 1, 1999 to February 28, 2005). Unadjusted cecal intubation rates were analyzed as were rates that were adjusted based on the U.S. Multi-Society Task Force on Colorectal Cancer recommendations. We analyzed trends in overall and individual cecal intubation rates, circumstances that impact these rates, and the quality of documentation of cecal intubation.

RESULTS

The overall adjusted cecal intubation rate for the entire 6 yr was 90.3%, and increased over the study period with the highest adjusted rate (93.7%) in the most recent year studied. There was no correlation between cecal intubation rate and patient age, gastroenterology fellow involvement, or endoscopist experience and number of procedures/year. In contrast, colon cancer screening, male gender, outpatient colonoscopy, and adequate bowel preparation predicted a higher cecal intubation rate. Written and photographic documentation of cecal intubation improved significantly after 2002.

CONCLUSIONS

Our analysis revealed cecal intubation and documentation rates that meet current guidelines, and identified factors that may cause substantial variance in these rates depending on the nature of the practice. The present analysis confirms that computerized databases can be used to assess individual and group cecal intubation and documentation rates on an annual basis, and to make these data available to the public.

A survey of credentialing practices of gastrointestinal endoscopy centers in the United States

BACKGROUND

Competence in gastrointestinal (GI) endoscopy correlates with the number of procedures performed by the endoscopist. For each GI endoscopic procedure, the American Society for Gastrointestinal Endoscopy (ASGE) guidelines recommend minimum numbers needed to assess competence.

METHODS

We conducted an anonymous mail survey to determine whether GI endoscopy centers in the United States follow ASGE or other guidelines for granting and renewing endoscopic privileges.

RESULTS

Completed surveys were received from 479 respondents in 46 states, Puerto Rico, and the District of Columbia. Most respondents were either the physician director (24%) or nurse manager (57%) of the endoscopy center. Most centers have more than 5 endoscopists (62%), and gastroenterologists performed procedures in the majority of the centers (89%). For initial endoscopic credentialing, few centers require a minimum number of procedures and only 10% meet ASGE criteria. To maintain credentials, less than one third require a minimum number and only 2% require more than 25 procedures/year. Although three fourths report periodic review of procedures, less than 5% review them more frequently than every 6 months. Only 20% of centers had ever denied endoscopic privileges (poor skills [80%], no references [27%], poor communication [7%], and excess complications [6%]) for which half faced litigation.

CONCLUSIONS

Most GI endoscopy centers responding to this survey have no minimum standards for determining endoscopic competence and may credential GI endoscopists with suboptimal training. Only 10% adhere to ASGE guidelines. Moreover, there is lack of uniformity to application of these guidelines, and few centers use resulting data to deny or renew credentials. To guarantee high-quality endoscopic practice, more stringent, universal credentialing standards are required.

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.

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.

Screening sigmoidoscopy in persons aged 60 years

OBJECTIVE: To reduce mortality associated with colorectal cancer, an increased interest has focused in recent years on screening of colorectal cancer. No studies of colorectal cancer screening in Finland has been reported. A pilot study of screening sigmoidoscopy was started in 1994 and the results are presented in this paper.SUBJECTS AND METHODS: Between March 1994 and May 2000 all 1224 persons aged 60 years from four communities (population 15 400) were invited to screening sigmoidoscopy; 896 (73%) took part in this study. The screening procedure was flexible sigmoidoscopy to 60 centimetres. All the patients who had adenomas or cancers, were invited to have a double contrast barium enema (DCBE) or colonoscopy to investigate the proximal colon. To study the experience of persons undergoing screening sigmoidoscopy, a questionnaire was sent to 81 consecutive persons after the examination. Sixty persons (74%) returned the filled-in questionnaire.RESULTS: Hyperplastic polyps were found in 136 people (15.2% of the whole material). Hyperplastic polyps were more common in males than females (19.3% and 11.4%, respectively, P=0.0015). People with hyperplastic polyps had the same rate of neoplasia as people without. Neoplastic lesions were found in 65 people. Adenomas were found in 62 patients (6.9%). Twenty-five people (2.8%) had at least one advanced adenoma (>10 mm or villous component). The rate of advanced adenomas in males was 4.9% and in females 0.9% (P=0.0006). Three patients (0.3%) were found to have colorectal cancer. Of 43 diabetic patients, 7 (16.3%) had adenomas whereas 6.5% of the non-diabetic persons had adenomas (P=0.03). The proximal colon was investigated in 34 patients by DCBE and/or colonoscopy and the rate of proximal adenomas in patients with neoplastic findings in screening sigmoidoscopy was 5/34 (14.7%). Concerning the experience of screening sigmoidoscopy, 56 persons (93%) found bowel preparation easy and 4 unpleasant, 55 (92%) experienced either no or mild discomfort during the endoscopy whereas 5 found the examination painful; 59 people (98%) said that they would participate again in screening sigmoidoscopy.CONCLUSIONS: In this study of screening sigmoidosopy, the first published in Finland, adenoma rate was 6.9%, advanced adenoma rate was 2.8% and cancer rate was 0.3%. Males had more hyperplastic polyps and advanced adenomas than females. Diabetic people had more adenomas than non-diabetics. Experiences of the people screened were positive and nearly all said that they would participate again in screening sigmoidoscopy.

Rationale for colonoscopy screening and estimated effectiveness in clinical practice

Colonoscopy screening has the highest anticipated level of effectiveness of the available colorectal cancer screening techniques. Its long-term cost-effectiveness is also comparable with or superior to other modalities. Evidence for the expected reduction in colorectal cancer incidence and mortality varies with colonoscopy screening from 50% to 90%, for reasons that are not fully understood. Maintaining a high standard of performance is critical with regard to achieving the highest level of effectiveness possible.

Which colon cancer screening test? A comparison of costs, effectiveness, and compliance

PURPOSE

Recent media reports have advocated the use of colonoscopy for colorectal cancer screening. However, colonoscopy is expensive compared with other screening modalities, such as fecal occult blood testing and flexible sigmoidoscopy. We sought to determine the cost effectiveness of different screening strategies for colorectal cancer at levels of compliance likely to be achieved in clinical practice.

METHODS

A Markov decision model was used to examine screening strategies, including fecal occult blood testing alone, fecal occult blood testing combined with flexible sigmoidoscopy, flexible sigmoidoscopy alone, and colonoscopy. The timing and frequency of screening was varied to assess optimal screening intervals. Sensitivity analyses were conducted to assess the factors that have the greatest effect on the cost effectiveness of screening.

RESULTS

All strategies are cost effective versus no screening, at less than $20,000 per life-year saved. Direct comparison suggests that the most effective strategies are twice-lifetime colonoscopy and flexible sigmoidoscopy combined with fecal occult blood testing. Assuming perfect compliance, flexible sigmoidoscopy combined with fecal occult blood testing is slightly more effective than twice-lifetime colonoscopy (at ages 50 and 60 years) but is substantially more expensive, with an incremental cost effectiveness of $390,000 per additional life-year saved. However, compliance with primary screening tests and colonoscopic follow-up for polyps affect screening decisions. Colonoscopy at ages 50 and 60 years is the preferred test regardless of compliance with the primary screening test. However, if follow-up colonoscopy for polyps is less than 75%, then even once-lifetime colonoscopy is preferred over most combinations of flexible sigmoidoscopy and fecal occult blood testing. Costs of colonoscopy and proportion of cancer arising from polyps also affect cost effectiveness.

CONCLUSIONS

Colonoscopic screening for colorectal cancer appears preferable to current screening recommendations. Screening recommendations should be tailored to the compliance levels achievable in different practice settings.

The Topography of Colorectal Cancer Varies by Race/Ethnicity and Affects the Utility of Flexible Sigmoidoscopy

Colorectal cancer screening beginning at age 50 is recommended for all Americans considered at “average” risk for the development of colorectal cancer either with flexible sigmoidoscopy and fecal occult blood testing (FOBT) or with colonoscopy. Patients who elect flexible sigmoidoscopy and FOBT undergo full colonoscopy only if left-sided neoplasia is detected or if the FOBT is positive. Unfortunately in blacks and whites most right-sided colorectal lesions are unaccompanied by left-sided sentinel lesions, which leads some to prefer colonoscopic screening in these patients. The topography of colorectal cancer in Asians and Latinos is unavailable. We used 1988–1995 California Cancer Registry data to determine the topography of 105,906 consecutive colorectal cancers among Asian, black, Latino, and white patients. We found that the proportion of colorectal cancer distal to the splenic flexure and therefore detectable by flexible sigmoidoscopy varied by ethnicity: Asian (71%) > Latino (63%) > white (57%) > black (55%); P < 0.001. These differences were significant after adjusting for age and sex. The risk of distal disease relative to whites was 1.61 in Asians, 1.15 in Latinos, and 0.82 in blacks ( P < 0.001). Flexible sigmoidoscopy detects a higher proportion of colorectal cancers in Asians and Latinos than in whites or blacks. Further study is needed to assess whether the topography of benign colorectal neoplasia parallels that of malignant disease. Colorectal screening recommendations may need to incorporate racial and ethnic differences in colorectal neoplasia topography.

The effect of attending a flexible sigmoidoscopic screening program on the prevalence of colorectal adenomas at 13-year follow-up

OBJECTIVES

Understanding the epidemiology of colorectal adenomas is a prerequisite for designing follow-up programs after polypectomy. The aim of the study was to investigate the effect of polypectomy on the long-term prevalence of adenomas.

METHODS

In 1983, a total of 799 men and women aged 50-59 yr were drawn from the general population register. Of these, 400 comprised a screening group and 399 a matched control group. The screenees were invited to undergo a once-only flexible sigmoidoscopy. Persons with polyps had a baseline colonoscopy with follow-ups in 1985 and 1989. In 1996, both the screenees and the controls were invited to a colonoscopic examination.

RESULTS

In 1996, a total of 451 (71%) individuals attended. Adenomas were found in 78 (37%) individuals in the screening group and 103 (43%) in the control group, relative risk (95% confidence interval): 0.9 (0.7-1.1), p = 0.3, and high-risk adenomas (severe dysplasia, adenomas > or = 10 mm, villous components) were found in 16 (8%) and 32 (13%), respectively; relative risk (95% confidence interval): 0.6 (0.3-1.0), p = 0.07.

CONCLUSIONS

There was no significant difference in adenoma prevalence between the group after the screening program and the controls after the usual care. There was a trend toward more high-risk adenomas in the control group. This suggests a very limited effect of one-time screening sigmoidoscopy with surveillance colonoscopy on the prevalence of adenomas, but a preventive effect on the development of high-risk adenomas consistent with the reported effect on cancer prevention.

Racial and ethnic colorectal cancer patterns affect the cost-effectiveness of colorectal cancer screening in the United States

BACKGROUND & AIMS

Colorectal cancer screening beginning at age 50 is recommended for all Americans considered at "average" risk for the development of colorectal cancer.

METHODS

We used 1988-1995 California Cancer Registry data to compare the cost-effectiveness of two 35-year colorectal cancer screening interventions among Asians, blacks, Latinos, and Whites.

RESULTS

Average annual age-specific colorectal cancer incidence rates were highest in blacks and lowest in Latinos. Screening beginning at age 50 was most cost-effective in blacks and least cost-effective in Latinos (measured as dollars spent per year of life saved), using annual fecal occult blood testing (FOBT) combined with flexible sigmoidoscopy every 5 years and using colonoscopy every 10 years. A 35-year screening program beginning in blacks at age 42, whites at age 44, or Asians at age 46 was more cost-effective than screening Latinos beginning at age 50.

CONCLUSIONS

Colorectal cancer screening programs beginning at age 50, using either FOBT and flexible sigmoidoscopy or colonoscopy in each racial or ethnic group, are within the $40,000-$60,000 per year of life saved upper cost limit considered acceptable for preventive strategies. Screening is most cost-effective in blacks because of high age-specific colorectal cancer incidence rates.

Colonic masses: detection with MR colonography

PURPOSE

To assess magnetic resonance (MR) colonography as a method for detection of colorectal masses, with conventional colonoscopy as the reference standard.

MATERIALS AND METHODS

MR colonography was performed in 132 patients referred for colonoscopy because of the possible presence of a mass. After rectal filling with a gadopentetate dimeglumine and water enema, T1-weighted three-dimensional gradient-echo MR studies were acquired with the patient in the prone and supine positions. Water-sensitive single-shot fast spin-echo MR images were also obtained. Surface-rendered virtual endoscopic endoluminal views, orthogonal sections in three planes, and water-sensitive MR images were interactively assessed for presence of colorectal masses by two radiologists.

RESULTS

MR colonography was well tolerated without sedation or analgesia. MR image quality was sufficient for diagnosis in 127 (96%) patients. Most small (</=5-mm-diameter) masses were overlooked at MR colonography, but 19 of 31 6-10-mm lesions and 26 of 27 large (>10-mm) lesions were correctly identified. For these large masses, MR colonography had a sensitivity of 93%, specificity of 99%, positive predictive value of 92%, and negative predictive value of 98% for detection of masses.

CONCLUSION

MR colonography is a promising modality for help in detecting colorectal mass lesions larger than 10 mm in diameter.

Use of colonoscopy to screen asymptomatic adults for colorectal cancer. Veterans Affairs Cooperative Study Group 380

BACKGROUND AND METHODS

The role of colonoscopy in screening for colorectal cancer is uncertain. At 13 Veterans Affairs Medical Centers, we performed colonoscopy to determine the prevalence and location of advanced colonic neoplasms and the risk of advanced proximal neoplasia in asymptomatic patients (age range, 50 to 75 years) with or without distal neoplasia. Advanced colonic neoplasia was defined as an adenoma that was 10 mm or more in diameter, a villous adenoma, an adenoma with high-grade dysplasia, or invasive cancer. In patients with more than one neoplastic lesion, classification was based on the most advanced lesion.

RESULTS

Of 17,732 patients screened for enrollment, 3196 were enrolled; 3121 of the enrolled patients (97.7 percent) underwent complete examination of the colon. The mean age of the patients was 62.9 years, and 96.8 percent were men. Colonoscopic examination showed one or more neoplastic lesions in 37.5 percent of the patients, an adenoma with a diameter of at least 10 mm or a villous adenoma in 7.9 percent, an adenoma with high-grade dysplasia in 1.6 percent, and invasive cancer in 1.0 percent. Of the 1765 patients with no polyps in the portion of the colon that was distal to the splenic flexure, 48 (2.7 percent) had advanced proximal neoplasms. Patients with large adenomas (> or = 10 mm) or small adenomas (< 10 mm) in the distal colon were more likely to have advanced proximal neoplasia than were patients with no distal adenomas (odds ratios, 3.4 [95 percent confidence interval, 1.8 to 6.5] and 2.6 (95 percent confidence interval, 1.7 to 4.1], respectively). However, 52 percent of the 128 patients with advanced proximal neoplasia had no distal adenomas.

CONCLUSIONS

Colonoscopic screening can detect advanced colonic neoplasms in asymptomatic adults. Many of these neoplasms would not be detected with sigmoidoscopy.

Screening colonoscopy in asymptomatic average-risk African Americans

BACKGROUND

Recent data indicate that colorectal cancer incidence and mortality in white Americans have been declining since 1985 at a rate of 2% to 3% per year. In African Americans, however, mortality from colorectal cancer appears to be increasing. We sought to evaluate the prevalence of colonic neoplasia in asymptomatic African Americans.

METHODS

We performed a cross-sectional colonoscopy screening study to determine the prevalence of colonic neoplasia in asymptomatic African Americans older than 50 years of age.

RESULTS

One hundred sixty-six subjects were evaluated for the study of whom 121 (69 women) were deemed to be asymptomatic average-risk persons and completed colonoscopy. Forty-two individuals (35%) had a total of 72 adenomas (67 tubular and 5 tubulovillous); 47 (65.3%) of these were proximal to the splenic flexure. Three subjects had an adenoma 1 cm or greater in diameter and none had severe dysplasia.

CONCLUSIONS

The overall prevalence of adenomas in asymptomatic average-risk African Americans was comparable to that of previously described populations. The predominance of right-sided adenomas in this study confirms previous findings and is an area requiring further study. Until this issue is resolved, we suggest the use of colonoscopy rather than sigmoidoscopy for screening for colorectal neoplasia in asymptomatic, average-risk African Americans.

Cancer screening in the elderly population

This article reviews the current state of knowledge regarding cancer screening in the geriatric population. Care of the elderly requires knowledge of underlying physiologic changes, comorbidities, quality-of-life factors, and life expectancies. There is always the danger that ageism may prevent elderly cancer patients from receiving the proper treatment. On the other hand, overzealous treatment can lead to adverse results if elderly patients are not properly targeted based on current evidence of the benefits and risks of specific screening practices.

AGA technical review on the evaluation and management of occult and obscure gastrointestinal bleeding

This literature review and the recommendations therein were prepared for the American Gastroenterological Association Clinical Practice and Practice Economics committee. The paper was approved by the committee on May 16, 1999, and by the AGA governing board on July 18, 1999.

Frequency of advanced neoplasia in the proximal colon without an index polyp in the rectosigmoid

PURPOSE

Screening endoscopy has the potential to reduce colorectal cancer mortality. However, the efficacy of screening flexible sigmoidoscopy compared with colonoscopy strongly depends on the frequency of advanced proximal neoplasms without an index polyp in the rectosigmoid. We have therefore determined this frequency in our endoscopy population.

METHODS

Endoscopic and histologic data were analyzed from all patients on whom integral colonoscopy was performed between 1980 and 1995. Advanced neoplasia was defined as cancer or adenomas >10 mm in diameter, adenomas with a villous component, or severe dysplasia. Patients with polyposis syndrome or inflammatory bowel disease were excluded.

RESULTS

Colonoscopy was performed on 11,760 patients. 2,272 (19.3 percent) had at least one colorectal neoplasm, of which 39 percent had the neoplasm above the rectosigmoid. Twenty-two percent of all patients with neoplasia had no index polyp in the rectosigmoid and 16 percent of these had no index polyp, but at least one advanced proximal neoplasm.

CONCLUSIONS

Although 39 percent of patients had neoplasms above the rectosigmoid, only 16 percent had an advanced proximal neoplasm without an index polyp in the rectosigmoid. This gives a figure on which to base the evaluation of screening sigmoidoscopy programs against those of screening colonoscopy.

Population-based surveillance by colonoscopy: effect on the incidence of colorectal cancer. Telemark Polyp Study I

BACKGROUND

Most cases of colorectal cancer (CRC) develop from adenomas. Polypectomy is believed to reduce the incidence of CRC, but this effect has never been explored in prospective controlled studies. The aim of the present study was to evaluate the effect of polypectomy on colorectal cancer incidence in a population-based screening program.

METHODS

In 1983, 400 men and women aged 50-59 years were randomly drawn from the population registry of Telemark, Norway. They were offered a flexible sigmoidoscopy and, if polyps were found, a full colonoscopy with polypectomy and follow-up colonoscopies in 1985 and 1989. A control group of 399 individuals was drawn from the same registry. In 1996 both groups (age, 63-72 years) were invited to have a colonoscopic examination. Hospital files and the files of The Norwegian Cancer Registry were searched to register any cases of CRC in the period 1983-96.

RESULTS

At screening endoscopy 324 (81%) individuals attended in 1983 and 451 (71%) in 1996. From 1983 to 1996, altogether 10 individuals in the control group and 2 in the screening group were registered to have developed CRC (relative risk, 0.2; 95% confidence interval (CI), 0.03-0.95; P = 0.02). A higher overall mortality was observed in the screening group, with 55 (14%) deaths, compared with 35 (9%) in the control group (relative risk, 1.57; 95% CI, 1.03-2.4; P = 0.03).

CONCLUSION

Endoscopic screening examination with polypectomy and follow-up was shown to reduce the incidence of CRC in a Norwegian normal population. The possible effect of screening on overall mortality should be addressed in larger studies.

The small polyp at flexible sigmoidoscopy: an historical perspective on why practices still vary

Current practices vary regarding the approach to small polyps discovered during screening flexible sigmoidoscopy. The most common practice is to perform colonoscopy whenever any adenoma is detected, a strategy that generally uses biopsy of polyps < or = 5 mm in size. However, data suggest that tubular adenomas < 1 cm in size in the distal colon have less predictive value than other distal adenomas for advanced adenomas in the proximal colon. Thus, some centers reserve colonoscopy for distal adenomas with tubulovillous or villous histology, > 1 cm in size, or with high-grade dysplasia. At the other end of the spectrum, another school of thought advocates screening colonoscopy, recognizing that most patients with advanced proximal adenomas do not have polyps in their distal colon. Advocates of this approach use any excuse to perform colonoscopy, whether it be a positive fecal occult blood test, minor symptoms, or small polyp at flexible sigmoidoscopy, even if hyperplastic. This review describes the history of the controversy regarding management of findings at flexible sigmoidoscopy, the data pertinent to the controversy, and the basis for the three approaches described above, all of which are currently within the standard of medical care.

Screening for colorectal cancer: present, past and future

Colorectal cancer results in 18,000 deaths annually in England and Wales, with 24,000 new cases diagnosed each year. Despite a better understanding of the genetics, and advancement in surgical and anaesthetic techniques, there has been little reduction in mortality and morbidity from this disease over the past 25 years. Colorectal cancer fits recognized criteria for a disease that should be screened in asymptomatic individuals. The putative duration of the adenoma to carcinoma sequence gives an ample window of opportunity to detect and treat colorectal cancer. In this article we have reviewed the strategies involved in screening for colorectal cancer in an asymptomatic population. We have presented trials and arguments for and against the different screening methods and discussed cost effectiveness of screening. In the USA and Canada, major professional organizations and societies now endorse screening; in the UK it is still far from being accepted. We feel that the available evidence shows that colorectal cancer screening has the potential to reduce the morbidity and mortality from this disease and that funding for a mass screening and public education programme should be sought.

CT and MR colography (virtual colonoscopy): status report

Computed tomography (CT) and magnetic resonance (MR) colography (virtual colonoscopy) are new techniques being developed for the purpose of imaging colorectal polyps and cancer. Limited data are available regarding the performance characteristics of either technique, particularly MR. Initial reports suggest that the sensitivity of CT and MR colography for patients with adenomas > or = 1 cm ranges from 75-90%, and decreases precipitously for smaller polyps. Very early data suggest that the specificity for patient with large adenomas is around 90%, but for patients with adenomas in the 5-9 mm range has been as low as 65%. This review discusses currently available published and abstracted data on CT and MR colography and discusses the real and potential advantages and disadvantages of CT and MR colography compared to current colonic imaging methods. The review discusses problems that must be overcome in order for CT or MR colography to be demonstrated as practical tests, and suggests guidelines for the performance of clinical trials testing the performance characteristics of these methods.

Proliferative patterns of rectal mucosa as predictors of advanced colonic neoplasms in routinely processed rectal biopsies

OBJECTIVES

We sought to determine whether the evaluation of rectal cell proliferation in routinely processed rectal biopsies of apparently normal mucosa can predict the presence of advanced colonic neoplasms.

METHODS

Fifty consecutive patients, who did not meet any of the following exclusion criteria, underwent total colonoscopy. Patients with nonadvanced adenomas, inflammatory bowel disease, hereditary predisposition to colonic cancer, or a history of colonic neoplasms were excluded. Patients with neoplasms in the distal 40 cm of the large bowel were also excluded. An adenoma was considered advanced if it had a diameter > 1 cm, or villous or severe dysplasia histology were present. In 26 of the 50 patients (Group A: 16 men, 10 women; mean age, 65 yr) advanced colonic neoplasms (advanced adenomas or cancer) were detected; in the remaining 24 (Group B: 13 men, 11 women; mean age, 66 yr) the large bowel was free of neoplasms. In all patients the proliferative patterns of apparently normal rectal mucosa were evaluated using the monoclonal antibody MIB-1 to assess the expression of Ki-67 antigen in routinely processed tissues. Proliferation index for the entire crypt, as well as proliferation indices for each of the five equal compartments, into which the crypt had been divided longitudinally, were calculated for each patient.

RESULTS

The mean proliferation indices were similar between the two groups compared. The mean proliferation index for the upper crypt compartments (4 + 5) in the Group A patients was significantly higher than for those of the Group B patients (p < 0.01). Multivariate stepwise logistic regression analysis revealed that among gender, age, and proliferative parameters, the pattern of cell proliferation in the upper rectal crypt (4 + 5) compartment was the only predictor of advanced colonic neoplasms (beta = 11.01, p < 0.001).

CONCLUSIONS

Our data suggest that the evaluation of the upward expansion of the rectal crypt proliferative zone in routinely processed rectal biopsies of apparently normal mucosa appears to predict the presence of advanced colonic neoplasms. These preliminary results should be confirmed in larger studies.

Is colonoscopy needed for the nonadvanced adenoma found on sigmoidoscopy? The Polyp Prevention Trial

BACKGROUND & AIMS

The need for colonoscopy when small tubular adenomas with low-grade dysplasia are found on sigmoidoscopy is uncertain. The aim of this study was to examine the prevalence and characteristics of proximal adenomas in patients with distal adenomas.

METHODS

We studied 981 subjects with distal adenomas found on the index colonoscopy before randomization in the Polyp Prevention Trial.

RESULTS

Four hundred sixty patients (46.9%) had >/=1 distal adenoma that was pathologically advanced (villous component, high-grade dysplasia, or >/=1 cm); 21.5% (211 of 981) had any proximal adenoma; and 4.3% (42 of 981) (95% confidence interval [CI], 3.0-5.5) had an advanced proximal adenoma. A greater percentage of patients with an advanced distal adenoma (5.9%) (95% CI, 3.7-8.0) had an advanced proximal adenoma compared with those with a nonadvanced distal adenoma (2.9%) (95% CI, 1.4-4.3) (OR, 2.1; 95% CI, 1.1-4.3; P = 0.03). Not performing a colonoscopy in patients with a nonadvanced distal adenoma would have missed 36% (15 of 42) of the advanced proximal adenomas.

CONCLUSIONS

Patients with an advanced distal adenoma are twice as likely to have an advanced proximal adenoma as patients with a nonadvanced distal adenoma. However, eschewing a colonoscopy in patients with a nonadvanced distal adenoma would result in not detecting a sizeable percentage of the prevalent advanced proximal adenomas. These data support performance of a colonoscopy in patients with a nonadvanced distal adenoma. Confirmation of these results in asymptomatic subjects undergoing screening sigmoidoscopy is advisable.

Adenoma characteristics at first colonoscopy as predictors of adenoma recurrence and characteristics at follow-up. The Polyp Prevention Study Group

BACKGROUND & AIMS

All patients with colorectal adenomas may not require identical follow-up. We aimed to determine if adenoma characteristics at initial colonoscopy could predict adenoma recurrence or characteristics at follow-up.

METHODS

The number of adenomas and the size, type, and degree of atypia in 479 patients in a polyp prevention trial were evaluated as predictors of the same characteristics at follow-up using odds ratios (ORs) with 95% confidence intervals (CIs). Multiple logistic regression analysis was performed to determine if several baseline characteristics were simultaneously associated with outcome.

RESULTS

Although several characteristics were significant predictors of recurrence univariately, by multivariate analysis, multiple adenomas at follow-up were more likely when patients had > or = 3 baseline adenomas (OR, 2.25; 95% CI, 1.20-4.21) or at least 1 tubulovillous adenoma (OR, 2.12; 95% CI, 1.12-4.02). No specific characteristic was associated with recurrence of high-risk polyps (> or = 1 cm, villous, severe atypia). Seventy percent of patients with 1 or 2 baseline adenomas had no recurrence, and only 3.3% had any adenomas of clinical concern.

CONCLUSIONS

Number and type of baseline adenomas predict recurrent adenomas, but the recurrence is rarely of clinical concern. Patients with 1 or 2 tubular adenomas constitute a low-risk group for whom follow-up might be extended beyond 3 years.

How to screen for colon cancer

The biology of colorectal cancer provides a unique opportunity for early detection and prevention. There is now evidence that screening of asymptomatic average-risk individuals over 50 years of age can reduce mortality resulting from colorectal cancer. New recommendations from the US Preventive Services Task Force endorse screening with fecal occult blood tests or sigmoidoscopy. The best method for population screening remains uncertain. The cost of screening is an important issue in the development of public policy. This review discusses the various screening options, examines the "downstream" effects of screening, and reviews the anticipated costs and effectiveness. Ultimately, the effectiveness of any screening program depends on patient compliance. Further research is needed to determine the best methods of enhancing patient adherence to a screening program.

A sigmoidoscopy-based case-control study of polyps: macronutrients, fiber and meat consumption

We conducted a large, sigmoidoscopy-based case-control study to examine the relation of intake of macronutrients, meat, and fiber to occurrence of adenomas of the large bowel. Cases were subjects diagnosed for the first time with one or more histologically confirmed adenomas. Controls had no polyps of any type at sigmoidoscopy, had no history of polyps, and were individually matched to cases by gender, age, date of sigmoidoscopy, and Kaiser Center. The response rate was 84% for cases and 82% for controls. Complete dietary data for 488 matched pairs were available. All odds ratios are from matched analyses adjusted for energy. We observed positive associations with risk of adenomas for calories, animal fat, saturated fat, red meat, and the ratio of red meat to poultry and fish. Protective effects were observed for vegetable protein, carbohydrates, and dietary fiber. The fiber effects diminished after adjusting for fruits and vegetables. Results after mutually adjusting for the effects of saturated fat, fiber and the ratio of red meat to chicken and fish suggest that each of these variables has an effect on risk of adenomas that is independent of the other 2 exposures.

Endoscopic screening for colorectal cancer

There is strong evidence that colon screening of asymptomatic, average-risk subjects can reduce colorectal cancer mortality. Endoscopic screening with sigmoidoscopy can reduce mortality associated with left-sided cancers due to the discovery of early curable cancers and the detection removal of premalignant adenomas. Screening with colonoscopy is widely accepted for high-risk groups and would likely be effective for the screening of average-risk subjects.