Sigmoidoscopy and mortality from colorectal cancer: the Kaiser Permanente Multiphasic Evaluation Study

General health checks in adults for reducing morbidity and mortality from disease

BACKGROUND

General health checks are common elements of health care in some countries. They aim to detect disease and risk factors for disease with the purpose of reducing morbidity and mortality. Most of the commonly used individual screening tests offered in general health checks have been incompletely studied. Also, screening leads to increased use of diagnostic and therapeutic interventions, which can be harmful as well as beneficial. It is therefore important to assess whether general health checks do more good than harm. This is the first update of the review published in 2012.

OBJECTIVES

To quantify the benefits and harms of general health checks.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, two other databases and two trials registers on 31 January 2018. Two review authors independently screened titles and abstracts, assessed papers for eligibility and read reference lists. One review author used citation tracking (Web of Knowledge) and asked trial authors about additional studies.

SELECTION CRITERIA

We included randomised trials comparing health checks with no health checks in adults unselected for disease or risk factors. We did not include geriatric trials. We defined health checks as screening for more than one disease or risk factor in more than one organ system.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the risk of bias in the trials. We contacted trial authors for additional outcomes or trial details when necessary. When possible, we analysed the results with a random-effects model meta-analysis; otherwise, we did a narrative synthesis.

MAIN RESULTS

We included 17 trials, 15 of which reported outcome data (251,891 participants). Risk of bias was generally low for our primary outcomes. Health checks have little or no effect on total mortality (risk ratio (RR) 1.00, 95% confidence interval (CI) 0.97 to 1.03; 11 trials; 233,298 participants and 21,535 deaths; high-certainty evidence, I² = 0%), or cancer mortality (RR 1.01, 95% CI 0.92 to 1.12; 8 trials; 139,290 participants and 3663 deaths; high-certainty evidence, I² = 33%), and probably have little or no effect on cardiovascular mortality (RR 1.05, 95% CI 0.94 to 1.16; 9 trials; 170,227 participants and 6237 deaths; moderate-certainty evidence; I² = 65%). Health checks have little or no effect on fatal and non-fatal ischaemic heart disease (RR 0.98, 95% CI 0.94 to 1.03; 4 trials; 164,881 persons, 10,325 events; high-certainty evidence; I² = 11%), and probably have little or no effect on fatal and non-fatal stroke (RR 1.05 95% CI 0.95 to 1.17; 3 trials; 107,421 persons, 4543 events; moderate-certainty evidence, I² = 53%).

AUTHORS' CONCLUSIONS

General health checks are unlikely to be beneficial.

Impact of sigmoidoscopy and colonoscopy on colorectal cancer incidence and mortality: an evidence-based review of published prospective and retrospective studies

Screening for colorectal cancer (CRC) using sigmoidoscopy or colonoscopy is now common in many developed countries. This concise, evidence-based review looks at the impact of sigmoidoscopy or colonoscopy screening on CRC incidence, CRC mortality and overall mortality. Data from controlled retrospective and prospective (observational or randomized) studies have generally shown that sigmoidoscopy and colonoscopy, whether for diagnostic, screening or surveillance purposes, are associated with a significant reduction in CRC incidence and CRC mortality. The data on their impact on overall mortality is much more limited, with most studies unable to report a reduction in overall mortality. The results of three meta-analyses have confirmed these conclusions. As expected, sigmoidoscopy has a predominant effect on left-sided CRC, although some studies have shown modest effects on right-sided colon cancer as well. Most studies on colonoscopy have demonstrated that the protective effect applies to both right and left-sided cancer, although the protection seemed better on the left side. Despite the introduction of other screening and diagnostic modalities for the colon, such as computed tomography colonography and colonic capsule endoscopy, lower endoscopy will continue to be an important mode of screening for CRC and evaluating the colon.

A comparison of colorectal cancer screening uptake among average-risk insured American Indian/Alaska Native and white women

INTRODUCTION

American Indian and Alaska Native (AI/AN) women have among the lowest rates of colorectal cancer (CRC) screening. Whether screening disparities persist with equal access to health care is unknown.

METHODS

Using administrative data from 1996-2007, we compared CRC screening events for 286 AI/AN and 14,042 White women aged 50 years and older from a health maintenance organization in the Pacific Northwest of the U.S.

RESULTS

The proportion of AI/AN and White women screened for CRC at age 50 was similar (13.3% vs. 14.0%, p =.74). No differences were seen in the type of screening test. Time elapsed to first screening among AI/AN women who were not screened at age 50 did not differ from White women (hazard ratio 1.0, 95% confidence interval 0.8-1.3).

CONCLUSIONS

Uptake for CRC screening was similar among insured AI/AN and White women, suggesting that when access to care is equal, racial disparities in screening diminish.

Flexible sigmoidoscopy versus faecal occult blood testing for colorectal cancer screening in asymptomatic individuals

BACKGROUND

Colorectal cancer is the third most frequent cancer in the world. As the sojourn time for this cancer is several years and a good prognosis is associated with early stage diagnosis, screening has been implemented in a number of countries. Both screening with faecal occult blood test and flexible sigmoidoscopy have been shown to reduce mortality from colorectal cancer in randomised controlled trials. The comparative effectiveness of these tests on colorectal cancer mortality has, however, never been evaluated, and controversies exist over which test to choose.

OBJECTIVES

To compare the effectiveness of screening for colorectal cancer with flexible sigmoidoscopy to faecal occult blood testing.

SEARCH METHODS

We searched MEDLINE and EMBASE (November 16, 2012), the Cochrane Central Register of Controlled Trials (CENTRAL) (2012, Issue 11) and reference lists for eligible studies.

SELECTION CRITERIA

Randomised controlled trials comparing screening with flexible sigmoidoscopy or faecal occult blood testing to each other or to no screening. Only studies reporting mortality from colorectal cancer were included. Faecal occult blood testing had to be repeated (annually or biennially).

DATA COLLECTION AND ANALYSIS

Data retrieval and assessment of risk of bias were performed independently by two review authors. Standard meta-analyses using a random-effects model were conducted for flexible sigmoidoscopy and faecal occult blood testing (FOBT) separately and we calculated relative risks with 95% confidence intervals (CI). We used a Bayesian approach (a contrast-based network meta-analysis method) for indirect analyses and presented the results as posterior median relative risk with 95% credibility intervals. We assessed the quality of evidence using GRADE.

MAIN RESULTS

We identified nine studies comprising 338,467 individuals randomised to screening and 405,919 individuals to the control groups. Five studies compared flexible sigmoidoscopy to no screening and four studies compared repetitive guaiac-based FOBT (annually and biennially) to no screening. We did not consider that study risk of bias reduced our confidence in our results. We did not identify any studies comparing the two screening methods directly. When compared with no screening, colorectal cancer mortality was lower with flexible sigmoidoscopy (relative risk 0.72; 95% CI 0.65 to 0.79, high quality evidence) and FOBT (relative risk 0.86; 95% CI 0.80 to 0.92, high quality evidence). In the analyses based on indirect comparison of the two screening methods, the relative risk of dying from colorectal cancer was 0.85 (95% credibility interval 0.72 to 1.01, low quality evidence) for flexible sigmoidoscopy screening compared to FOBT. No complications occurred after the FOBT test itself, but 0.03% of participants suffered a major complication after follow-up. Among more than 60,000 flexible sigmoidoscopy screening procedures and almost 6000 work-up colonoscopies, a major complication was recorded in 0.08% of participants. Adverse event data should be interpreted with caution as the reporting of adverse effects was incomplete.

AUTHORS' CONCLUSIONS

There is high quality evidence that both flexible sigmoidoscopy and faecal occult blood testing reduce colorectal cancer mortality when applied as screening tools. There is low quality indirect evidence that screening with either approach reduces colorectal cancer deaths more than the other. Major complications associated with screening require validation from studies with more complete reporting of harms

General health checks in adults for reducing morbidity and mortality from disease

BACKGROUND

General health checks are common elements of health care in some countries. These aim to detect disease and risk factors for disease with the purpose of reducing morbidity and mortality. Most of the commonly used screening tests offered in general health checks have been incompletely studied. Also, screening leads to increased use of diagnostic and therapeutic interventions, which can be harmful as well as beneficial. It is, therefore, important to assess whether general health checks do more good than harm.

OBJECTIVES

We aimed to quantify the benefits and harms of general health checks with an emphasis on patient-relevant outcomes such as morbidity and mortality rather than on surrogate outcomes such as blood pressure and serum cholesterol levels.

SEARCH METHODS

We searched The Cochrane Library, the Cochrane Central Register of Controlled Trials (CENTRAL), the Cochrane Effective Practice and Organisation of Care (EPOC) Trials Register, MEDLINE, EMBASE, Healthstar, CINAHL, ClinicalTrials.gov and WHO International Clinical Trials Registry Platform (ICTRP) to July 2012. Two authors screened titles and abstracts, assessed papers for eligibility and read reference lists. One author used citation tracking (Web of Knowledge) and asked trialists about additional studies.

SELECTION CRITERIA

We included randomised trials comparing health checks with no health checks in adults unselected for disease or risk factors. We did not include geriatric trials. We defined health checks as screening general populations for more than one disease or risk factor in more than one organ system.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed the risk of bias in the trials. We contacted authors for additional outcomes or trial details when necessary. For mortality outcomes we analysed the results with random-effects model meta-analysis, and for other outcomes we did a qualitative synthesis as meta-analysis was not feasible.

MAIN RESULTS

We included 16 trials, 14 of which had available outcome data (182,880 participants). Nine trials provided data on total mortality (155,899 participants, 11,940 deaths), median follow-up time nine years, giving a risk ratio of 0.99 (95% confidence interval (CI) 0.95 to 1.03). Eight trials provided data on cardiovascular mortality (152,435 participants, 4567 deaths), risk ratio 1.03 (95% CI 0.91 to 1.17) and eight trials on cancer mortality (139,290 participants, 3663 deaths), risk ratio 1.01 (95% CI 0.92 to 1.12). Subgroup and sensitivity analyses did not alter these findings.We did not find an effect on clinical events or other measures of morbidity but one trial found an increased occurrence of hypertension and hypercholesterolaemia with screening and one trial found an increased occurence of self-reported chronic disease. One trial found a 20% increase in the total number of new diagnoses per participant over six years compared to the control group. No trials compared the total number of prescriptions, but two out of four trials found an increased number of people using antihypertensive drugs. Two out of four trials found small beneficial effects on self-reported health, but this could be due to reporting bias as the trials were not blinded. We did not find an effect on admission to hospital, disability, worry, additional visits to the physician, or absence from work, but most of these outcomes were poorly studied. We did not find useful results on the number of referrals to specialists, the number of follow-up tests after positive screening results, or the amount of surgery.

AUTHORS' CONCLUSIONS

General health checks did not reduce morbidity or mortality, neither overall nor for cardiovascular or cancer causes, although the number of new diagnoses was increased. Important harmful outcomes, such as the number of follow-up diagnostic procedures or short term psychological effects, were often not studied or reported and many trials had methodological problems. With the large number of participants and deaths included, the long follow-up periods used, and considering that cardiovascular and cancer mortality were not reduced, general health checks are unlikely to be beneficial.

Organized colorectal cancer screening in integrated health care systems

Colorectal cancer (CRC) is an ideal target for early detection and prevention through screening. Noninvasive screening options are the guaiac fecal occult blood test and the fecal immunochemical test. Organized screening offers the promise of uniformly delivering screening to all members of a population who are eligible and due. Organized screening is defined as an explicit policy with defined age categories, method, and interval for screening in a defined target population with a defined implementation and quality assurance structure, and tracking of cancer in the population. The UK National Health Service; the Ontario, Canada Ministry of Health and Long-Term Care; and the US Veteran's Health Administration have used varied organized approaches to deliver guaiac fecal occult blood test screening to their populations. Kaiser Permanente Northern California began CRC screening in the 1960s, initially using flexible sigmoidoscopy. Implementation of organized fecal immunochemical test outreach was associated with improved Healthcare Effectiveness Data and Information Set CRC screening rates between 2005 and 2010 from 37% to 69% and from 41% to 78% in the commercial and Medicare populations, respectively. Organized fecal immunochemical test screening has been associated with an increase in annually detected CRCs, almost entirely because of increased detection of localized-stage cancers.

Potential risk factors for cutaneous squamous cell carcinoma include oral contraceptives: results of a nested case-control study

Recently, a population-based case-control study observed a 60% increased odds ratio (OR) for cutaneous squamous cell carcinoma (SCC) among women who had ever used oral contraceptives (OCs) compared with non users (95% confidence interval (CI) = 1.0-2.5). To further characterize the putative association between OC use and SCC risk, we conducted a nested case-control study using a large retrospective cohort of 111,521 Kaiser Permanente Northern California members. Multivariable conditional logistic regression was used to estimate ORs and CIs adjusting for known and hypothesized SCC risk factors. Pre-diagnostic OC use was associated with a statistically significant increased OR for SCC in univariate analysis (OR = 2.4, CI = 1.2-4.8), with borderline statistical significance in multivariable analysis (CI = 2.0, CI = 0.91-4.5). Given the high incidence of SCC in the general population and the prevalent use of OCs among women in the United States, there is a need for more large, carefully designed epidemiologic studies to determine whether the observed association between OC use and SCC can be replicated and to better understand the etiologic basis of an association if one exists.

Association of prediagnostic serum vitamin D levels with the development of basal cell carcinoma

We investigated the association between serum 25-hydroxyvitamin D (25(OH)D) levels and basal cell carcinoma (BCC) risk in a nested case-control study at Kaiser Permanente Northern California (KPNC). A total of 220 case patients with BCC diagnosed after serum collection were matched to 220 control subjects. We estimated odds ratios (ORs) and 95% confidence intervals (CIs) using conditional logistic regression. Fully adjusted models included body mass index (BMI), smoking, education, sun-exposure variables, X-ray exposure, and personal history of cancer. For each measure of serum 25(OH)D (continuous, clinically relevant tertiles, quintiles), we found an increased risk of BCC in unadjusted models (OR=1.03, 95% CI 1.00-1.05, P<0.05; OR=3.98, 95% CI: 1.31-12.31, deficient vs. sufficient, test for trend P-value <0.01; OR=2.32, 95% CI: 1.20-4.50, 1st vs. 5th quintile, test for trend P-value 0.03). In fully adjusted models, the values attenuated slightly (OR=1.02, 95% CI 1.00-1.05, P<0.05; OR=3.61, 95% CI: 1.00-13.10, deficient vs. sufficient, t-trend P=0.03; OR=2.09 1st vs. 5th quintile, 95% CI: 0.95-4.58, t-trend P=0.11). Our findings suggest that higher prediagnostic serum 25(OH)D levels may be associated with increased risk of subsequent BCC. Further studies to evaluate the effect of sun exposure on BCC and serum 25(OH)D levels may be warranted.

Abdominal obesity and the risk of esophageal and gastric cardia carcinomas

BACKGROUND

Esophageal adenocarcinoma is rapidly increasing in incidence. Body mass index (BMI) is a risk factor, but its distribution does not reflect the demographic distribution of the cancer (which is highest among White men). Abdominal obesity patterns may explain this discordance, but no studies exist to date.

METHODS

Nested case-control study within 206,974 members of the Kaiser Permanente multiphasic health checkup cohort; subjects received detailed questionnaires, a standardized examination including BMI and anthropometric measurements, and follow-up of esophageal and cardia cancers using registry data.

RESULTS

101 incident esophageal adenocarcinomas, 105 cardia adenocarcinomas, and 144 esophageal squamous cell carcinomas were detected (BMI data available for all cases; abdominal measurements for a subset). Increasing abdominal diameter was strongly associated with an increased risk of esophageal adenocarcinoma [odds ratio (OR), 3.47; 95% confidence interval (95% CI), 1.29-9.33; abdominal diameter, > or =25 versus <20 cm]. Adjustment for BMI did not diminish this association (BMI-adjusted OR, 4.78; 95% CI, 1.14-20.11). The association was also not diminished by adjustment for gastroesophageal reflux-type symptoms, although reflux-type symptoms were separately associated with both abdominal diameter and cancer risk. Abdominal diameter was not associated with the risk of cardia adenocarcinomas (OR, 1.28; 95% CI, 0.38-4.25; diameter, > or =25 versus <20 cm) or esophageal squamous cell carcinomas (OR, 0.78; 95% CI, 0.32-1.92).

CONCLUSIONS

Increasing abdominal diameter was associated with an increased risk of esophageal adenocarcinoma, independent of BMI. Cancer risk was not substantially mediated through gastroesophageal reflux-type symptoms, although symptoms may imperfectly measure reflux severity. Given abdominal obesity is more common among males, these findings suggest that increases in obesity may disproportionately increase the risk of esophageal adenocarcinoma in males.

Telephone outreach to increase colorectal cancer screening in an urban minority population

OBJECTIVES

We compared the effectiveness of a telephone outreach approach versus a direct mail approach in improving rates of colorectal cancer (CRC) screening in a predominantly Black population.

METHODS

A randomized trial was conducted between 2000 and 2003 that followed 456 participants in the New York metropolitan area who had not had recent CRC screening. The intervention group received tailored telephone outreach, and the control group received mailed printed materials. The primary outcome was medically documented CRC screening 6 months or less after randomization.

RESULTS

CRC screening was documented in 61 of 226 (27.0%) intervention participants and in 14 of 230 (6.1%) controls (prevalence rate difference=20.9%; 95% CI = 14.34, 27.46). Compared with the control group, the intervention group was 4.4 times more likely to receive CRC screening within 6 months of randomization.

CONCLUSIONS

Tailored telephone outreach can increase CRC screening in an urban minority population.

Screening for colon cancer

Colorectal cancer screening reduces mortality in individuals 50 years and older. Each of the screening tests currently available has advantages and limitations, and there is no consensus as to which test or combination of tests is best. What is clear, however, is that the rates of colorectal cancer screening remain low. This review summarizes the clinical evidence supporting colorectal cancer screening in the average risk population and in high risk groups, discusses the advantages and disadvantages of the available screening tests, outlines the currently recommended guidelines for screening based on risk category, and discusses new and emerging technologies for colorectal cancer screening.

Comparing risks and benefits of colorectal cancer screening in elderly patients

BACKGROUND & AIMS

In patients with limited life expectancy, the risks of colorectal cancer screening may outweigh the benefits. The aim of this study was to quantify risks and benefits of different screening strategies in elderly patients with varying life expectancies.

METHODS

We examined risks and benefits of screening in patients aged 70-94 years with differing health status using 3 strategies: annual fecal occult blood tests, flexible sigmoidoscopy every 5 years, or colonoscopy every 10 years. We compared the number needed to screen to prevent one cancer-related death and the number needed to encounter one screening-related complication for different strategies.

RESULTS

The potential benefit from screening varied widely with age, life expectancy, and screening modality. One cancer-related death would be prevented by screening 42 healthy men aged 70-74 years with colonoscopy, 178 healthy women aged 70-74 years with fecal occult blood tests, 431 women aged 75-79 years in poor health with colonoscopy, or 945 men aged 80-84 years in average health with fecal occult blood tests. Colonoscopy screening had the greatest benefit but the highest risk of complications. The potential for screening-related complications was greater than estimated benefit in some population subgroups aged 70 years and older. At all ages and life expectancies, the potential reduction in mortality from screening outweighed the risk of colonoscopy-related death.

CONCLUSIONS

The potential benefits and risks of screening vary in elderly patients of different life expectancies. For any individual patient, the potential for harm from screening must be weighed against the likelihood of benefit, especially with shorter life expectancy.

[Population screening for colorectal cancer: a systematic review]

INTRODUCTION

Colorectal cancer (CRC) is a serious public health problem due to its high frequency and the mortality it provokes. This disease presents a series of characteristics that make it an ideal candidate for population screening. The aim of the present study was to analyze current knowledge on the efficacy/effectiveness of CRC screening through the fecal occult blood test (FOBT), rectosigmoidoscopy and colonoscopy in individuals without symptoms of this disease.

METHOD

We performed a systematic review of the literature on each of the methods of early detection. The databases consulted were MEDLINE and PREMEDLINE (1966-2002), Embase (1980-2002), HTA and Cochrane, among others. Articles were selected using explicit criteria and were classified according to their level of scientific evidence.

RESULTS

The best validated test is the FOBT, with the greatest number of randomized controlled trials. The results on the sensitivity and specificity of this test and reduction in mortality from CRC varied widely, depending on the technique used. The decrease in mortality from CRC in groups that underwent screening through FOBT was between 15% and 33%. The number and quality of the studies performed to evaluate flexible sigmoidoscopy and colonoscopy as methods of early detection were much lower. Although the rate of detection of polyps is greater than with the FOBT, the value of these tests as screening techniques has not been analyzed through randomized controlled trials.

CONCLUSION

Population screening for CRC reduces mortality from this disease. However, consensus is lacking on the screening method of choice and on the frequency with which screening should be performed. The method best supported by the evidence as a primary detection test is the FOBT. To date, sigmoidoscopy and colonoscopy should be used as diagnostic tests only, mainly because of their invasiveness.

Options for screening for colorectal cancer

Unlike other types of cancer, there are several options for screening for colorectal cancer (CRC). The most extensively examined method, faecal occult blood testing (FOBT), has been shown, in three large randomized trials, to reduce mortality from CRC by up to 20% if offered biennally and possibly more if offered every year. Recently published data from the US trial suggest that CRC incidence rates are also reduced by up to 20%, but only after 18 years. In this study, the number of positive slides was associated with the positive predictive value both for CRC and adenomas larger than 1 cm, suggesting that the reduction in CRC incidence was caused by the identification and removal of large adenomas. In this respect, this study supports the concept that removing adenomas prevents CRC. More efficient methods of detecting adenomas include the use of colonoscopy or flexible sigmoidoscopy (FS). Considerable evidence exists from case-control and uncontrolled cohort studies to suggest that endoscopic screening by sigmoidoscopy reduces incidence of distal colorectal cancer. However, in the absence of evidence from a randomized trial, several countries have been reluctant to introduce endoscopic screening. Three trialsare currently in progress (in the UK, Italy and the US) to address this issue. Two of these trials are examining the hypothesis that a single FS screen at around age 55-64 might be a cost-effective and acceptable method for reducing CRC incidence rates. Recruitment and screening are now complete in both studies and the first analysis of results on incidence rates is expected in 2004. Colonoscopy screening at 10-year intervals has recently been endorsed in the US on the basis that the reductions in incidence observed with distal CRC screening can be extrapolated to the proximal colon. However, data are lacking and a pilot study for a trial of the acceptability and efficacy of colonoscopy screening is in progress in the US. It has also been suggested that FOBT testing should be used to detect proximal CRC missed by sigmoidoscopy screening, but the small amount of published data suggest that supplementing FS with FOBT offers very little advantage over FS alone. Other forms of CRC screening are under investigation and represent exciting options for the future. Extraction of DNA from stool is now feasible and a number of research groups have shown high sensitivity for CRC using a panel of DNA markers including mutations in k-ras, APC, p53 and BAT26. Data so far indicate that, with the exception of k-ras, these markers are highly specific and therefore represent a significant improvement over FOBT. Whether these tests will replace or supplement existing methods of screening has yet to be determined. It has been suggested that BAT26, which is a marker of microsatellite instability, a feature of proximal sporadic CRC, might be a useful adjunct to sigmoidoscopy screening. Others have suggested that a test for occult blood should be included with the DNA markers to further increase sensitivity. It is not yet known how sensitive these markers are for adenomas--it is only by detecting adenomas that CRC incidence rates can be reduced. A final exciting new option for screening is virtual colonoscopy (VC), which by screening out people without neoplasia allows colonoscopy to be reserved for patients requiring a therapeutic intervention. The sensitivity of VC for large adenomas and CRC appears to be high, although results vary by centre and there is a steep learning curve. Sensitivity for small adenomas is low, but perhaps it is less essential to find such lesions. Some groups have suggested that virtual colonoscopy might be a useful option for investigating patients who test positive with stool-based screening tests. Whichever CRC screening method is finally chosen (and there is no reason why several methods should not ultimately be available), high quality endoscopy resources will always be required to investigate and treat neoplastic lesions detected.

Computerized tomographic colonography: performance evaluation in a retrospective multicenter setting

BACKGROUND & AIMS

No multicenter study has been reported evaluating the performance and interobserver variability of computerized tomographic colonography. The aim of this study was to assess the accuracy of computerized tomographic colonography for detecting clinically important colorectal neoplasia (polyps >or=10 mm in diameter) in a multi-institutional study.

METHODS

A retrospective study was developed from 341 patients who had computerized tomographic colonography and colonoscopy among 8 medical centers. Colonoscopy and pathology reports provided the standard. A random sample of 117 patients, stratified by criterion standard, was requested. Ninety-three patients were included (47% with polyps >or=10 mm; mean age, 62 years; 56% men; 84% white; 40% reported colorectal symptoms; 74% at increased risk for colorectal cancer). Eighteen radiologists blinded to the criterion standard interpreted computerized tomography colonography examinations, each using 2 of 3 different software display platforms.

RESULTS

The average area under the receiver operating characteristic curve for identifying patients with at least 1 lesion >or=10 mm was 0.80 (95% lower confidence bound, 0.74). The average sensitivity and specificity were 75% (95% lower confidence bound, 68%) and 73% (95% lower confidence bound, 66%), respectively. Per-polyp sensitivity was 75%. A trend was observed for better performance with more observer experience. There was no difference in performance across software display platforms.

CONCLUSIONS

Computerized tomographic colonography performance compared favorably with reported performance of fecal occult blood testing, flexible sigmoidoscopy, and barium enema. A prospective study evaluating the performance of computerized tomography colonography in a screening population is indicated.

Barriers to screening for colorectal cancer

Rapidly growing interest in colon cancer screening is a crucial first step to identifying and reducing many of the barriers that impede population screening for this common disease. Promoting screening demands health care policy change to increase the percentage of Americans with insurance coverage that includes a colon cancer screening benefit. A systematic approach to screening with invitations that come from a clinician are likely to be the most effective way to prompt more individuals to be screened. Awareness campaigns and patient educational aids, including decision tools, implemented in multiple sites, such as worksites, community centers, health care systems, and physician offices, increase the percent of eligible Americans who understand their personal risk, the need for screening, and the options available to them.

Design of the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial

The objectives of the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial are to determine in screenees ages 55-74 at entry whether screening with flexible sigmoidoscopy (60-cm sigmoidoscope) can reduce mortality from colorectal cancer, whether screening with chest X-ray can reduce mortality from lung cancer, whether screening men with digital rectal examination (DRE) plus serum prostate-specific antigen (PSA) can reduce mortality from prostate cancer, and whether screening women with CA125 and transvaginal ultrasound (TVU) can reduce mortality from ovarian cancer. Secondary objectives are to assess screening variables other than mortality for each of the interventions including sensitivity, specificity, and positive predictive value; to assess incidence, stage, and survival of cancer cases; and to investigate biologic and/or prognostic characterizations of tumor tissue and biochemical products as intermediate endpoints. The design is a multicenter, two-armed, randomized trial with 37,000 females and 37,000 males in each of the two arms. In the intervention arm, the PSA and CA125 tests are performed at entry, then annually for 5 years. The DRE, TVU, and chest X-ray exams are performed at entry and then annually for 3 years. Sigmoidoscopy is performed at entry and then at the 5-year point. Participants in the control arm follow their usual medical care practices. Participants will be followed for at least 13 years from randomization to ascertain all cancers of the prostate, lung, colorectum, and ovary, as well as deaths from all causes. A pilot phase was undertaken to assess the randomization, screening, and data collection procedures of the trial and to estimate design parameters such as compliance and contamination levels. This paper describes eligibility, consent, and other design features of the trial, randomization and screening procedures, and an outline of the follow-up procedures. Sample-size calculations are reported, and a data analysis plan is presented.

Screening for colorectal cancer

Colorectal cancer is the third most commonly diagnosed cancer and the second leading cause of cancer deaths in the United States. Fortunately, both the incidence and mortality associated with the disease have declined during the past 2 decades. This is likely due, at least in part, to improved efforts at screening and more aggressive removal of adenomatous polyps. However, colorectal cancer screening is still generally underutilized. This article reviews the current status and future outlook for colorectal cancer screening, including a discussion of risk factors for the disease, its anatomic distribution, proposed mechanisms of development from adenomatous polyps, rationale for screening, and screening options. Published literature concerning the cost-effectiveness of colorectal cancer screening is also summarized. The article concludes with a discussion of the emerging consensus regarding the importance of and approaches to screening.

Survival and treatment for colorectal cancer Medicare patients in two group/staff health maintenance organizations and the fee-for-service setting

The current study compares treatment use and long-term survival in colorectal cancer patients between Medicare beneficiaries enrolled in two large prepaid group/staff health maintenance organizations (HMOs) and the fee-for-service (FFS) setting. The study is based on 15,352 colorectal cancer cases diagnosed between 1985 and 1992 and followed through 1995. Survival differences between the HMO and FFS cases were assessed using Cox regression. Treatment differences were evaluated using logistic regression. HMO cases had a lower overall mortality than did FFS cases but not a significantly lower colorectal cancer-specific mortality. Use of surgical resection was similar between HMO and FFS cases. However, rectal cancer cases in the HMOs were more likely to receive postsurgical radiation therapy than FFS cases. Superior overall survival in the HMOs may be the result of increased colorectal cancer screening, greater use of adjuvant therapies, and selection of healthier individuals.

Screening for colorectal cancer

Randomized, controlled trials have shown with certainty that screening for colorectal cancer reduces morbidity and is cost-effective. Factors that increase the risk of colorectal cancer include a personal or family history of adenomatous polyps or colorectal cancer, certain genetic syndromes and chronic inflammatory bowel disease.

Colorectal cancer in women: an underappreciated but preventable risk

Colorectal cancer is the third most common non-skin malignancy in women, after breast and lung cancer. Although approximately 40% of the 65,000 women diagnosed each year eventually die of the disease, colon cancer is highly curable when diagnosed at an early stage. Moreover, because the majority of colon cancers arise in previously benign colonic polyps, there is a substantial period, up to several years, in which removal of polyps can reduce the risk of colon cancer. Recently, the United States Preventive Task Force recommended universal screening for colon cancer after age 50. Strong evidence from randomized controlled trials and case-control studies supports use of annual testing for occult blood in stool and flexible sigmoidoscopy every 5-7 years. Although the risk of colon cancer is similar in men and women, women frequently have the perception that colorectal cancer is a man's disease. Partially in consequence, women are less likely than men to undergo screening sigmoidoscopy. Further barriers include primary care providers' lack of awareness of updated guidelines and patients' lack of compliance with multiple screening tests and their fear of discomfort. Because the risk of colorectal cancer can be reduced by up to 75% in those who undergo screening and subsequent surveillance to remove further polyps, it is crucial that women be targeted to undergo screening tests for colorectal cancer.

Participation in colorectal cancer screening: a review

The purpose of this review is to evaluate the published literature on adherence to colorectal cancer (CRC) screening with fecal occult blood testing (FOBT) and sigmoidoscopy. Specifically, the review addresses the following: 1) prevalence of FOBT and sigmoidoscopy; 2) interventions to increase adherence to FOBT and sigmoidoscopy; 3) correlates or predictors of adherence to FOBT and sigmoidoscopy; and 4) reasons for nonadherence. Other objectives are to put the literature on CRC screening adherence in the context of recently reported findings from experimental interventions to change prevention and early detection behaviors and to suggest directions for future research on CRC screening adherence. CRC screening offers the potential both for primary and for secondary prevention. Data from the 1992 National Health Interview Survey show that 26% of the population more than 49 years of age report FOBT within the past 3 years and 33% report ever having had sigmoidoscopy. The Year 2000 goals set forth in Healthy People 2000 are for 50% of the population more than 49 years of age to report FOBT within the past 2 years and for 40% to report that they ever had sigmoidoscopy. Thus, systematic efforts to increase CRC screening are warranted. To date, attempts to promote CRC screening have used both a public health model that targets entire communities, e.g., mass media campaigns, and a medical model that targets individuals, e.g., general practice patients. Most of these efforts, however, did not include systematic evaluation of strategies to increase adherence. The data on FOBT show that the median adherence rate to programmatic offers of FOBT is between 40% and 50%, depending on the type of population offered the test, e.g., patients or employees. Approximately, 50% of those initially offered testing in unselected populations will respond to minimal prompts or interventions. A salient issue for FOBT, however, is whether or not the behavior can be sustained over time. Fewer studies examined adherence to sigmoidoscopy. Adherence was highest in relatives of CRC cases and in employer-sponsored programs offered to workers at increased risk of CRC. At present, we know very little about the determinants of CRC screening behaviors, particularly as they relate to rescreening.

Detection rate of immunochemical fecal occult blood test for colorectal adenomatous polyps with severe dysplasia

This study was conducted to assess the accuracy of an immunochemical occult blood test for detecting colorectal adenomas with severe dysplasia, and to determine the relationship between the grading of adenomatous dysplasia and the results of this test. Sixteen colorectal adenomas under 1 cm with severe dysplasia, 65 adenomas under 1 cm with mild-to-moderate dysplasia, 65 adenomas 1 cm or larger with mild-to-moderate dysplasia, 65 colorectal cancers and 130 healthy controls were investigated. Each subject was tested with an immunochemical fecal occult blood test on 3 consecutive days, and the accuracy of the test was evaluated. The detection rate of this test was 13% for severe dysplasia under 1 cm, 45% for severe dysplasia 1 cm or more, 17% for mild-to-moderate dysplasia under 1 cm, 40% for mild-to-moderate dysplasia 1 cm or more, and 89% for colorectal cancers, and the false positive rate was 5%, showing a significant difference in the detection rate between severe dysplasias 1 cm or more and those under 1 cm (P < 0.05) as well as significant difference between severe dysplasias 1 cm or more and mild-to-moderate dysplasia under 1 cm (P < 0.01), and between cancers and adenomas (P < 0.001), whereas there was no significant difference between the detection rates for severe dysplasia 1 cm or more and mild-to-moderate dysplasia 1 cm or more. These results indicate that there is no association between the detection rate of this immunochemical occult blood test for adenomas and the grade of adenomatous dysplasia.

An epidemiological perspective on cancer screening

OBJECTIVE

To provide an epidemiological perspective on cancer screening.

METHODS AND RESULTS

For screening to be applicable as public health policy, the disease has to be an important health problem, there has to be evidence that early detection results in improved outcome, that adequate facilities for diagnosis, therapy, and subsequent management of true and false positives are available, that screening is acceptable to the target groups, and that programs are cost effective in the population. Although it is relatively easy to demonstrate that screening results in earlier detection of cancer, survival is a biassed measure of its effectiveness. The only valid design to study the efficacy of screening is the randomized trial. Cervical cancer screening was introduced before these requirements were recognized. There is, however, good evidence of its effectiveness; the challenge is to make programs cost effective. For breast cancer, studies show little or no evidence of effectiveness of mammography screening in women age 40-49. For women age 50-69, there is good evidence of effectiveness in trials comparing screening with no screening. These support the introduction of population-based programs for this age group. The challenge is to put the research results into practice to ensure cost-effective programs. For colo-rectal cancer, there is some evidence that both screening sigmoidoscopy and the fecal occult blood test will reduce mortality. It is not clear, however, whether programs using either or both these tests will be cost effective. For lung cancer, there is good evidence of no benefit for screening. For ovarian, prostate, mouth, and skin cancer, although early detection has been demonstrated, there is no evidence of reduction in mortality in the target groups; indeed, prostate screening could result in lowering the overall quality of life.

CONCLUSION

Screening, which offers a fairly rapid return from appropriate investment, should remain part of our armamentarium for cancer control.

Colorectal tumourigenesis

Colorectal cancer is significant because of its lethality and high incidence in the Western world. Furthermore, it is a particularly suitable model for studying the events involved in the progression from normal tissue to invasive cancer. There is a great deal of epidemiological and histopathologic evidence to implicate the adenomatous polyp as the precursor to colorectal cancer. Moreover in recent years investigators have uncovered some of the molecular genetic events that underlie the progression from normal epithelium to polyp to cancer. It is hoped that an increased understanding of the molecular changes will afford opportunities for new diagnostic, prognostic and therapeutic strategies in the management of this disease.

Prevention of colorectal cancer by once-only sigmoidoscopy

There is no national screening programme for colorectal cancer in the UK despite the fact that the annual death toll from this disease exceeds that of breast and cervical cancer. Faecal occult blood testing (FOBT) is under evaluation for screening, but screening by sigmoidoscopy is not considered viable. This situation contrasts with the USA where both annual FOBT and screening by flexible sigmoidoscopy every 3 to 5 years are recommended from 50 years old. We seek to demonstrate that most of the benefit from the US screening policy would accrue from a single flexible sigmoidoscopy examination at age 55 to 60 years with appropriate colonoscopic surveillance for the 3% to 5% found to have high-risk adenomas (> or = 1 cm or villous histology). If applied nationally, this screening regimen could prevent about 5500 colorectal cancer cases and 3500 deaths in the UK each year, thus saving 40,000 years of life. We estimate that there would be little net cost to the National Health Service because savings obtained from treating fewer patients would largely offset the cost of screening. We recommend that a randomised trial to evaluate screening by single flexible sigmoidoscopy should start without delay. Such a trial would involve about 120,000 participants, and 15 years of follow-up would be required to obtain a clear answer on mortality, although information on incidence reduction would be available sooner.

Screening strategies for colorectal cancer

The efficacy of screening for colorectal cancer has not been established. Policy-making organizations differ in recommendations for asymptomatic and high-risk groups because of the inadequacy of current evidence. A critical appraisal of the current evidence for screening for colorectal cancer and a discussion of the aims and pitfalls of screening programs are presented.

Colon cancer overview

The scope of current prevention research support by the National Cancer Institute includes the clinical assessment of dietary modifications and cancer screening trials, epidemiologic studies, development of new chemopreventive therapies, and the use of advanced molecular biologic technologies to probe the genetic determinants of colorectal adenomas. Colorectal cancer frequently has been associated with high-fat low-fiber diets in epidemiologic and experimental studies. A recently initiated Phase III Dietary Intervention Study of Recurrence of Large Bowel Adenomatous Polyps will investigate the potential benefits of a low-fat high-fiber fruit-and-vegetable-enriched eating pattern to decrease the polyp recurrence rate. The Chemoprevention Program currently is supporting four Phase III controlled clinical intervention trials investigating the cancer-inhibiting effects on colorectal cancer of beta-carotene, piroxicam, calcium, and calcium plus fiber in persons with previous adenomas. A proposed early detection trial will screen for colorectal, prostate, lung, and ovarian cancers. A comparison of incidence and mortality trends indicates progress in colorectal cancer detection and therapy.

Gastrointestinal endoscopy: an accurate and safe primary diagnostic and therapeutic modality

OBJECTIVE

To review the place of gastrointestinal endoscopy in the management of upper and lower gastrointestinal disorders.

DATA SOURCES

We reviewed articles on endoscopy reported over two decades. A Medline search complementing our experience and knowledge of the literature was used to identify the articles.

STUDY SELECTION

Papers were selected which focused on indications, comparison with radiology, including clinical outcome measures, and complications. One hundred papers, including those from radiology journals, were reviewed.

DATA EXTRACTION

Results of studies are referenced as appropriate.

DATA SYNTHESIS AND CONCLUSIONS

Endoscopy allows direct visualisation of the mucosa of the upper gastrointestinal tract, colon and terminal ileum. Subtleties of colour change, vascular pattern abnormalities and scarring are easily detected at endoscopy and are often of diagnostic importance. Endoscopy also provides access for tissue biopsy and allows a wide variety of therapeutic interventions. Traditionally barium studies have been the first step in the evaluation of many gastrointestinal symptoms and still retain cost advantages over endoscopy. However, endoscopy is frequently more sensitive and specific than barium studies. Costs associated with incorrect diagnoses may undermine the apparent cost benefits of barium studies. Advances in endoscopic design have allowed wider therapeutic options and increased safety. Gastrointestinal endoscopy should now be the first line of investigation where diagnostic precision is required or where therapeutic intervention is likely.

Screening for large bowel neoplasms in individuals with a family history of colorectal cancer

Logistical problems associated with population screening for colorectal cancer are identified and the possibility of targeting screening to those with a familial predisposition to the disease is discussed. Evidence for a substantial genetic effect on the overall incidence of colorectal cancer is reviewed. The screening detection rate of colorectal neoplasms in relatives of patients with colorectal cancer has been shown to be higher than that expected in a non-selected population; the evidence that polypectomy will reduce future colorectal cancer risk in such individuals is explored. Recent advances in the molecular genetics of colorectal cancer susceptibility are reviewed; it is possible that a genetic test might be developed in the future which could identify at least a proportion of those at risk. Excluding financial considerations, the risk-benefit ratio of colonoscopy in a screened population is intimately related to the remaining risk of colorectal cancer in those who undergo the examination. At present, patients undergoing colonoscopy to investigate a positive faecal occult blood (FOB) test as part of a population-based screening programme include individuals with a familial predisposition as well as those without. About 20 per cent of all cases of colorectal cancer are associated with an obvious genetic predisposition, and the risk of cancer in their relatives is high. Because false positives occur with Haemoccult, the residual risk to the population who are FOB positive but do not have a familial trait may be sufficiently low that the dangers of colonoscopy could outweigh the potential benefits. Scotland has a high incidence of colorectal cancer, and analysis of recent Scottish incidence data shows an actuarial lifetime risk of developing this disease of one in 23 for men and one in 33 for women. As a family history of the disease increases that risk by two to four times and the neoplasms arise throughout the colon in such a group, there may be a case for offering colonoscopy to all first-degree relatives of those under 50 years of age at diagnosis, if not of all index cases of colorectal cancer.

Quality of care for colorectal cancer in a fee-for-service and health maintenance organization practice

This study assessed the effectiveness of two types of health plans, offered by the same health care provider, in the diagnosis and treatment of colorectal cancer. Data on 330 cases diagnosed from 1984 through 1989 were abstracted from medical records. Of these, 205 (62%) used fee-for-service (FFS) and 125 (38%) used health maintenance organization (HMO) plans. Overall, there were no differences between FFS and HMO cases for duration of symptoms before diagnosis, training of physician who diagnosed the tumor, anatomic location of the tumor, type of primary treatment, Dukes' stage at final diagnosis, or survival. There were differences between the groups for age, presence of symptoms at diagnosis, time from detection to treatment, and method of detection. Cox regression analysis showed no difference in survival by type of health plan before or after adjusting for age and stage at diagnosis. The findings from this study are consistent with those from studies reporting little or no difference in the process or outcome of care for patients with different types of medical insurance coverage.

Screening guidelines for colorectal cancer

A review is given of methods and results of screening for colorectal cancer in average-risk and high-risk groups. Possible methods are digital rectal exploration, endoscopic examination, barium enemas, faecal occult blood tests, tumour markers like carcinoembryonic antigen, Ca-19-9, and others, and gene markers. Final results of large randomized population studies with faecal occult blood tests are expected within the next few years, but it will probably be necessary to add flexible sigmoidoscopy to achieve a major reduction in mortality from colorectal cancer in average-risk persons. Recommendations for screening in high-risk groups are proposed, but strong support for these guidelines are still missing, an exception being first-degree relatives of individuals with familial adenomatous polyposis; the other high-risk groups include members of hereditary non-polyposis colorectal cancer families, relatives of patients with sporadic colorectal cancer, patients with colorectal adenomas, patients with previous colorectal cancer, and patients with inflammatory bowel disease.

Colon cancer incidence: recent trends in the United States

Between 1976-78 and 1985-87, the age-adjusted incidence rates of invasive colon cancer in the United States rose by 15 percent, 3 percent, 21 percent, and 16 percent among White males, White females, Black males, and Black females, respectively. The increases in incidence occurred in all age groups over age 54 and affected each of the major subsites of the colon nearly equally. The larger rates of increase have resulted in higher incidence among Blacks than Whites by the mid-1980s and an increasingly greater excess of this cancer in males. Trends toward earlier diagnosis of invasive colon cancer were found, with increasing rates for localized and regional diseases coupled with stable or decreasing distant-stage disease-rates. The incidence of in situ colon cancer also rose substantially. The findings suggest that changes in diagnostic trends and risk-factor prevalence may be contributing to these patterns, and that the era when colon cancer predominated among White females is clearly over.

Population screening for colorectal cancer, the goals and means

The causes of colorectal cancer are complex and in most cases obscure, making primary prevention impossible at present. Secondary prevention by finding and treating early asymptomatic cancers may possibly reduce mortality from this very common cancer. Results from conventional treatment have changed little during recent decades and are unsatisfactory, with more than half of the patients dying from the disease. The incidence has increased during recent years in many countries, making it vital to evaluate possible benefits from screening. This review considers different methods of screening for colorectal cancer and includes an overview of continuing European controlled randomised trials with the faecal occult blood test, Haemoccult-II. No final evaluation is possible, but advantages and drawbacks of different strategies are discussed. Assuming that the goal of reducing mortality is achieved, several other problems remain unsolved: the organisation of screening, the training of doctors in endoscopy, cost benefit and cost effectiveness all of which will have to be solved before a population screening can be recommended. Present screening tools are not ideal and we have to continue the search for better markers of early colorectal cancers and even possible precursors like adenomas.

Cost-effective management of colon and rectal cancer

Health care costs in the United States of America continue to rise. Legislators, economists and third party payers are becoming increasingly concerned with intervention outcomes and the distribution of resources. It is the responsibility of the medical profession to assume a leading role in assessing the cost-effectiveness of health care interventions. Although many physicians perform informal cost-effectiveness analyses on a daily basis, health economists employ a variety of more complex methodologies. This article will attempt to provide physicians with an understanding of the value and limitations of the tools used in formal cost-effectiveness analyses and demonstrate how these tools may be applied to the management of colon and rectal cancer.

Colorectal cancer: have we identified an effective screening strategy?

Three currently used screening methods are aimed at detecting colorectal cancer when it is asymptomatic and curable, and at detecting polyps so that they can be removed before they can progress to cancer. Digital rectal examinations are relatively cheap and easy but can detect only a small fraction of large-bowel cancers. Sigmoidoscopy is more sensitive, but its low acceptability to patients has been only partially mitigated by the introduction of the 35-cm flexible instrument. Fecal occult blood testing has limited sensitivity because blood from cancers and polyps is neither continuously shed nor uniformly distributed in feces; specificity and positive predictive value are also low because of other sources of blood in the stool. Prudent judgment suggests that all of these screening tests may prevent death from colorectal cancer in some patients. However, none has been proven effective in general use by well-controlled studies. Case-control studies can provide timely and valuable new evidence in this regard; the authors' investigations in progress are described. The current lack of strong evidence in support of these screening tests should not be interpreted as evidence against their use.

Natural history of colorectal polyps and the effect of polypectomy on occurrence of subsequent cancer

To elucidate the natural history of colorectal polyps and to observe the influence of endoscopic polypectomy on the incidence of colorectal cancer, we conducted a retrospective cohort study of all patients who had undergone colonoscopic examination at the Center for Adult Diseases, Osaka, between April 1974 and December 1985. The study subjects consisted of a control group (760 non-polyp patients) and a polyp group (648 polyp patients, including 136 treated by polypectomy at the initial examination). These subjects were followed up until the end of 1987 by record linkage with the Osaka Cancer Registry's file to observe the occurrence of colorectal cancer. The O/E (observed/expected numbers derived from the general population) was 5.1 (95% confidence interval = 2.5-9.4) and 1.0 (0.1-3.6) for the polyp and control group, respectively. When subjects in the polyp group were categorized into polypectomy and non-polypectomy sub-groups, the O/E was 2.3 (0.1-12.6) and 8.0 (3.4-15.8) respectively. The relative risk of undergoing polypectomy to developing subsequent cancer was estimated at 0.3 (0.1-2.1). These results suggest an increased risk of developing cancer among polyp patients and the possibility of prophylactic effect of polypectomy against subsequent cancer. A large-scale and long-term follow-up study is required to confirm these findings.

Does screening proctosigmoidoscopy result in reduced mortality from colorectal cancer? A critical review of the literature

OBJECTIVE

To determine the strength of the evidence in the literature that screening proctosigmoidoscopy reduces colorectal cancer mortality.

DESIGN

All English-language studies reporting mortality or survival from screening proctosigmoidoscopy published since 1960 were critically reviewed.

DATA EXTRACTION

Fifteen references reported on five studies of screening proctosigmoidoscopy. Two authors independently reviewed each reference using explicit methodologic criteria, particularly for potential sources of bias.

MEASUREMENTS AND MAIN RESULTS

Of the five studies, four used historical controls and were susceptible to bias, especially self-selection and lead-time bias. Only the Kaiser-Permanente Multiphasic Health Check-up study collected a representative patient sample from a defined population, had randomly allocated controls, and avoided multiple sources of bias. There was a reduction in mortality from a group of seven potentially postponable causes of mortality, including colorectal cancer, although no difference in overall mortality between screened and control groups was found. This study was not designed to determine specifically the impact of screening proctosigmoidoscopy on mortality from colorectal cancer, and suggested that most of the reduction in colorectal cancer deaths was due to a lower incidence in the screened group, which could not be attributed to polypectomy. The benefit of screening proctosigmoidoscopy in this study, if any, was small.

CONCLUSIONS

The evidence in the literature is inadequate to determine whether or not screening proctosigmoidoscopy has an impact on colorectal cancer mortality, but the best available data suggest that the benefit is small, at best.