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Colorectal cancer screening: scientific review.

CONTEXT: Screening for colorectal cancer clearly reduces colorectal cancer mortality, yet many eligible adults remain unscreened. Several screening tests are available, and various professional organizations have differing recommendations on which screening test to use. Clinicians are challenged to ensure that eligible patients undergo colorectal cancer screening and to guide patients in choosing what tests to receive. OBJECTIVE: To critically assess the evidence for use of the available colorectal cancer screening tests, including fecal occult blood tests, sigmoidoscopy, colonoscopy, double-contrast barium enema, and newer tests, such as virtual colonoscopy and stool-based molecular screening. DATA SOURCES: All relevant English-language articles were identified using PubMed (January 1966-August 2002), published meta-analyses, reference lists of key articles, and expert consultation. DATA EXTRACTION: Studies that evaluated colorectal cancer screening in healthy individuals and assessed clinical outcomes were included. Evidence from randomized controlled trials was considered to be of highest quality, followed by observational evidence. Diagnostic accuracy studies were evaluated when randomized controlled trials and observational studies were not available or did not provide adequate evidence. Studies were excluded if they did not evaluate colorectal screening tests and if they did not evaluate average-risk individuals. DATA SYNTHESIS: Randomized controlled trials have shown that fecal occult blood testing can reduce colorectal cancer incidence and mortality. Case-control studies have shown that sigmoidoscopy is associated with a reduction in mortality, and observational studies suggest colonoscopy is effective as well. Combining fecal occult blood testing and sigmoidoscopy may decrease mortality and can increase diagnostic yield. CONCLUSION: The recommendation that all men and women aged 50 years or older undergo screening for colorectal cancer is supported by a large body of direct and indirect evidence. At present, the available evidence does not currently support choosing one test over another.

Aged↗

Estimates of costs and effects of screening for colorectal cancer in the United States.

BACKGROUND: In many ways, colorectal cancer might be an excellent candidate for mass screening because of the following: (1) it is the second leading cause of cancer mortality in the United States; (2) it develops slowly from a precursor lesion; and (3) methods of early detection are available. Barriers to screening include unproven efficacy of the procedure and high costs. METHODS: Cost analyses are derived from two mathematic models that estimate screening costs and effects based on expert opinion and data from uncontrolled screening studies. RESULTS: One screening option that follows the guidelines of the American Cancer Society and the National Cancer Institute (annual testing for occult fecal blood and sigmoidoscopy every 5 years) could result in a 40% decrease in colon cancer mortality for American adults between the ages of 50 and 75 years if they comply with screening. This model, developed by David Eddy, projects an average of 44 days of extra life per person screened, at a net cost of $57 per day of life gained. Using assumptions much less favorable to screening, the Office of Technology Assessment modeled this same screening strategy for those aged 65 years and older. This model predicted a similar benefit of extra life per person at a cost of $118 per day of life gained. This doubling of the predicted cost was caused by the inclusion of subsequent colonoscopic surveillance costs for those found to have polyps. Direct costs of screening annually for fecal occult blood and every 5 years by sigmoidoscopy would cost an average of approximately $48 per person per year for screening and follow-up testing of all positive results. Fecal occult blood testing alone, although less effective, costs only $20 per person per year, including follow-up testing of all positive findings. CONCLUSIONS: The results from randomized trials of fecal occult blood screening will be known in the next 5 years, but trials of screening with sigmoidoscopy will not be complete for 10-15 years. Because mass screening programs will be difficult to fund without better data on their efficacy, colorectal cancer screening will continue to be a matter of individual decision making in the clinical setting for years to come. Clearer presentations of costs and benefits that can be understood by both patients and physicians are needed.

Adult↗

A national population-based study of incidence of colorectal cancer and age. Implications for screening in older Americans.

BACKGROUND: Population-based screening programs with flexible sigmoidoscopy have been advocated as a means to reduce the death rate from colorectal cancer. Because other studies have suggested a greater prevalence of lesions inaccessible to sigmoidoscopy in older patients, the expected yield of this procedure may differ in these subgroups. METHODS: A 100% sample of Medicare beneficiaries 65 years or older with a first known diagnosis of colorectal cancer in 1987 was studied. Tumor site was divided into rectum, distal colon (distal to splenic flexure) and proximal colon. The analysis was also stratified by sex, race, and presence or absence metastatic disease, and incidence rates at each site by 5-year age group were calculated. RESULTS: Among the 75,266 patients studied, the incidence of colorectal cancer increased from 1.59 patients/1000 in patients age 65-69 years to 3.87 patients/1000 in patients age 85 years and older. Although the incidence rates at all three sites increased, the increment was greatest for proximal tumors. The incidence trends with age also persisted in an analysis of only metastatic lesions. Moreover, incidence rates were consistently higher in men than in women and higher in whites than in blacks at all sites, though the age-related increase in incidence was consistent among all four groups. CONCLUSIONS: The proportion of tumors beyond the reach of sigmoidoscopy increased with age, as did the actual incidence of accessible lesions. These patterns were also consistent in subgroup analyses. As the age-related increase in incidence was observed for metastatic tumors at all sites in the colon, age-related differences in screening and diagnostic evaluation alone do not adequately explain the findings. These data underscore the need for further studies of the relative benefits of cancer screening and pathogenic factors in tumor development in different subgroups of the older population.

Age Factors↗

Racial disparities in the use of and indications for colorectal procedures in Medicare beneficiaries.

BACKGROUND: African Americans are diagnosed more frequently with colorectal carcinoma at a later stage compared with Caucasians. One potential reason for the disparity is a lower rate of screening examinations. METHODS: Using Outpatient and Physician-Supplier claims for all Medicare beneficiaries age > or = 65 years in 1999, indications for fecal occult blood testing (FOBT), sigmoidoscopy, colonoscopy, and barium enema were divided into diagnostic, surveillance, or screening categories. Annualized rates were calculated based on the number of eligible fee-for-service months. RESULTS: Rates of FOBT (18.24% vs. 11.86%; P < 0.001) and sigmoidoscopy (3.07% vs. 2.17%; P < 0.001) were higher in Caucasians compared with African Americans, whereas rates of barium enema were higher in African Americans (2.26% vs. 1.88%; P < 0.001). Colonoscopy use was more frequent among men only in Caucasians compared with African-Americans (8.00% vs. 6.97%; P < 0.001). For FOBT, sigmoidoscopy, and colonoscopy, the racial differences in procedures performed for diagnostic purposes were of smaller magnitude than for screening; and, for colonoscopy, the use of diagnostic procedures actually was higher for African Americans. CONCLUSIONS: Racial disparities exist not only in the use of colorectal procedures but also in the indications for such testing, with African Americans less likely to undergo screening tests. The differences are consistent with delay in diagnosis until symptoms or signs develop and may contribute to disparities in cancer mortality.

Black or African American↗

Health-related behavior and the use of hormone replacement therapy.

PURPOSE: To study health-related differences between hormone replacement therapy (HRT) users and nonusers among colorectal cases and women without diagnosed cancer. METHODS: Data from the Saskatchewan Health population-based databases were used to ascertain the use of HRT, oral contraceptives (OCs), cardiovascular system (CVS) drugs, central nervous system (CNS) drugs, prescribed NSAIDs and vitamins among 3338 women diagnosed with colorectal cancer and 13025 women without diagnosed cancer. Physician visits and sigmoidoscopy procedures were also determined. RESULTS: Among women without diagnosed cancer, HRT was associated with CVS drugs (OR = 1.23, 95%CI: 1.10-1.37), CNS drugs (OR = 1.96, 95% CI: 1.72-2.23), other hormones (OR = 1.12, 95% CI: 1.01-1.24), prescribed vitamins (OR = 1.37, 95% CI: 1.22-1.55), NSAIDs (OR = 1.41, 95% CI: 1.18-1.68), having had a sigmoidoscopy 3-5 years prior to index dates (OR = 1.33, 95% CI: 1.12-1.59) and 15 or more visits to physicians during the 5th year prior to assigned index date (OR = 2.0, 95% CI: 1.77-2.35). Similar results were observed among women diagnosed with colorectal cancer, but HRT use was not associated with having had a sigmoidoscopy. CONCLUSIONS: Health-related characteristics of HRT users and nonusers are identified and described. Some of these factors may contribute to selection bias in studies examining the health benefits of HRT.

Anti-Inflammatory Agents, Non-Steroidal↗

Diminutive colonic polyps: an indication for colonoscopy.

A prospective study investigated the significance of solitary diminutive colonic polyps discovered during screening flexible sigmoidoscopy. Eighty-two patients with a solitary diminutive polyp (less than or equal to 5 mm) underwent colonoscopy after cold biopsy of the index polyp. Of the patients with adenomatous index polyps, 42.5 percent had proximal neoplastic polyps. Of the patients with hyperplastic index polyps, proximal neoplastic polyps were found in 38.9 percent. These data suggest that diminutive polyps identified during flexible sigmoidoscopy, whether adenomatous or hyperplastic, place the patient in the intermediate risk group for colorectal neoplasia. We recommend that any patient with polyps seen during screening sigmoidoscopy, regardless of histopathology, should undergo colonoscopy.

Biopsy↗

Screening for colorectal neoplasms. A comparison of the fecal occult blood test and endoscopic examination.

Testing for occult blood in stool is used frequently as a screening technique for colorectal carcinomas, but no study has ever shown an improved survival rate for colorectal carcinoma in patients screened by this method. Consequently, the authors have prospectively compared the sensitivity of endoscopy and occult blood testing in finding colorectal neoplasms. During the first year of the Surgical Endoscopy Service, 585 patients underwent sigmoidoscopy or colonoscopy. Seventy-nine patients (13.5 percent) were excluded from the study because their occult blood status was not recorded. Patients averaged 63 + 10 years of age and 98 percent were men. Of the 348 patients with occult blood negative stools 55.5 percent underwent colonoscopy and 44.5 percent underwent sigmoidoscopy. Polyps were found in 25.6 percent of these patients, colorectal carcinomas in 2.6 percent, and diverticulosis 36.2 percent. Of the 158 patients with occult blood positive stool, 76.5 percent underwent colonoscopy and 23.4 percent underwent sigmoidoscopy. Polyps were discovered in 39.0 percent of these patients, colorectal carcinomas in 10.1 percent, and diverticulosis in 43.0 percent. Thus, the occult blood test was negative in 59 percent of patients with polyps and 36 percent with colorectal cancers. These data indicate that lower gastrointestinal endoscopy is superior to occult blood testing in detecting colorectal neoplasms. These results further suggest that using the occult blood test as a screening test for colorectal neoplasms will result in a significant number of these lesions being missed at an early curable stage.

Aged↗

Advanced proximal colon cancer.

BACKGROUND: Two recent studies have documented that sigmoidoscopy as a screening tool for colorectal cancers may miss advanced proximal colonic neoplasms. The purpose of this study was to assess the prevalence of distal synchronous lesions in patients with proximal colon cancer. We sought to determine if screening sigmoidoscopy would have missed these proximal colon cancers. METHODS: Data were collected on all patients (n = 305) diagnosed with colorectal cancer over a 6-year period. Patients were stratified by age, sex, tumor location, presenting complaint, AJCC stage, and TNM classification. The colonoscopy results of patients diagnosed with proximal colon cancer were analyzed to determine the incidence of synchronous distal colon lesions. RESULTS: Proximal colon cancer was diagnosed in 88 patients (29%). Of those studied, 45 (54%) did not have synchronous distal lesions detected by colonoscopy. The patients with proximal colon cancer were elderly (mean age 67), had advanced tumor size [59 patients (67%) T3/T4], and had advanced AJCC stages [37 patients (42%) stage III/IV]. Nearly all patients [84 (95%)] with proximal colon cancer were symptomatic. CONCLUSION: In this study, the majority of patients with proximal colon cancer did not have a synchronous lesion in the distal colon. Current screening methods for colon cancer based on sigmoidoscopy would not have identified these proximal lesions. These findings support the incorporation of screening colonoscopy in protocols designed to identify early colon cancer.

Aged↗

An algorithm for the management of sigmoid colon volvulus and the safety of primary resection: experience with 827 cases.

PURPOSE: This study was designed to review the outcomes of emergent treatment of sigmoid colon volvulus. METHODS: The records of 827 patients were reviewed retrospectively. RESULTS: The mean age was 57.9 years (range, 10 weeks to 98 years), and 688 patients (83.2 percent) were male. Nonoperative reduction was applied in 575 patients (barium enema in 13, rigid sigmoidoscopy in 351, and flexible sigmoidoscopy in 211, with rectal tube placement in all patients). The results were as follows: success of 78.1 percent, mortality of 0.9 percent, complication of 3 percent, and early recurrence of 3.3 percent. Surgical treatment was performed on 393 patients (detorsion in 46, mesosigmoidopexy in 56, exteriorization in 4, resection with Hartmann's procedure in 146, resection with Mikulicz procedure in 14, resection with primary anastomosis in 51, tube cecostomy and colonic cleansing with resection in 75, and laparotomy in 1). The results were as follows: mortality of 15.8 percent, complication of 37.2 percent, early recurrence of 0.8 percent, and late recurrence of 6.7 percent. CONCLUSIONS: Nonoperative reduction is the initial treatment of sigmoid colon volvulus, and flexible sigmoidoscopy with rectal tube placement can be used successfully. Patients in whom bowel gangrene or peritonitis is present or nonoperative treatment is unsuccessful need emergency surgery. In surgical treatment, resection and primary anastomosis is the first choice, and it can be performed with acceptable mortality and morbidity rates if the patient is stable and a tension-free anastomosis is possible. Nondefinitive procedures have high recurrence rates; thus, definitive surgical techniques must be preferred.

Adolescent↗

Effect of workup strategy on the cost-effectiveness of fecal occult blood screening for colorectal cancer.

Physicians respond to a positive fecal occult blood test with a variety of workup strategies. To study the effect of the choice of strategy on the net costs and health benefits of colorectal cancer screening using this test, we used a decision analysis model to compare seven strategies that physicians might choose to examine a positive "screenee." Strategies using rigid or flexible sigmoidoscopy alone are not only insensitive, but also have high cost-effectiveness ratios. The strategy of air contrast barium enema alone had the lowest cost-effectiveness ratio. Rigid sigmoidoscopy combined with barium enema had a lower cost-effectiveness ratio than primary colonoscopy, but the strategy of primary colonoscopy could have an equal or better ratio depending on assumptions about test costs and the benefit of removing benign polyps. The primary colonoscopy strategy is both more effective and less costly than the combination of flexible sigmoidoscopy and barium enema. The optimal strategy will vary with local factors, and with the perspective of the decision-maker.

Aged↗

Cost-effectiveness model for colon cancer screening.

BACKGROUND & AIMS: The relative efficacy and effectiveness of different colon screening programs has not been assessed. The purpose of this analysis was to provide a model for comparing several colon screening programs and to determine the key variables that impact program effectiveness. METHODS: Five screening programs were compared: annual fecal occult blood test (FOBT) alone, flexible sigmoidoscopy, flexible sigmoidoscopy and FOBT combined, one-time colonoscopy, and air-contrast barium enema. Key variables were adjusted for sensitivity analyses. Cost-effectiveness was defined as the cost per cancer death prevented. RESULTS: FOBT alone prevents fewer cancer deaths than the other programs. The addition of flexible sigmoidoscopy to the FOBT increases the rate of cancer prevention. One-time colonoscopy has the greatest impact on colorectal cancer mortality, largely because of assumptions that cancer would be prevented in most patients who undergo polypectomy. FOBT alone is the most cost-effective of the programs, but the cost is sensitive to several key variables. CONCLUSIONS: The model shows key variables that impact the cost-effectiveness of colon screening programs. Compliance is an important determinant of effectiveness of all of the screening programs. Future study should be focused on methods of patient education that improve patient compliance with screening.

Aged↗

Factors associated with colon cancer screening: the role of patient factors and physician counseling.

BACKGROUND: The prevalence of colon cancer screening is nationally low. The relative contribution of patient factors and physician counseling patterns to the low prevalence of screening is unclear. METHODS: We used multivariable analysis to examine the prevalence of colon cancer screening nationally and the reasons for this low prevalence using data from the 2000 National Health Interview Survey, a nationally generalizable survey of US households. RESULTS: Among 11,427 respondents to the Cancer Control Supplement, 16% reported annual fecal occult blood testing (FOBT) and 29% reported having undergone a sigmoidoscopy in the last 5 years or a colonoscopy in the last 10 years. After adjusting for age, sex, body mass index (BMI), healthcare access, and region of the country, Hispanics were less likely to undergo FOBT [OR 0.7 (95% CI 0.6-0.9)] and sigmoidoscopy or colonoscopy [OR 0.8 (95% CI 0.7-0.9)] compared to Whites. Respondents with lower education levels were also less likely to undergo screening. These factors were not associated with being less adherent to physician recommendations for screening. Nevertheless, non-Whites and those less educated were less likely to receive counseling from their health provider about colon cancer screening. Among respondents who did not undergo FOBT, 64% were unaware they needed the test; only 2% cited pain and discomfort as a deterrent, but 94% were not counseled by their physician about the test. Among those who did not undergo sigmoidoscopy or colonoscopy, 72% were unaware that they needed the test and only 1% was deterred by pain and discomfort; 92% were not counseled by their physician. CONCLUSION: The low prevalence of screening for colorectal cancer appears to be due to lack of awareness and inadequate provider counseling rather than poor patient acceptance for screening. Systematic counseling about colorectal cancer screening will likely improve screening rates and reduce disparities by race/ethnicity and education.

Age Distribution↗

Trends in colon cancer screening procedures in the US Medicare and Tricare populations: 1999-2001.

BACKGROUND: This study examined trends in the numbers of double contrast barium enemas, flexible sigmoidoscopies, and colonoscopies and trends in the choices of colorectal cancer screening service providers. METHODS: Descriptive statistics were used to examine Medicare and Tricare data for the years 1999 to 2001. RESULTS: The total volume of procedures increased 5% and 14%, respectively, in Tricare and Medicare. Tricare and Medicare, respectively, saw 32% and 33% reductions in barium enemas and 28% and 41% reductions in flexible sigmoidoscopies. Colonoscopies increased by 45% and 34% in Tricare and Medicare, respectively. Gastroenterologists provided the majority of colonoscopies for both groups each year. CONCLUSIONS: The volume of colonoscopies increased from 1999 to 2001 for both groups while the volumes of barium enemas and flexible sigmoidoscopies decreased. Gastroenterologists appear to be the preferred providers of colonoscopies.

Aged↗

The double contrast enema in ulcerative and Crohn's colitis.

One hundred double contrast enema examinations using a colonic activator (veripaque in the preliminary cleansing enema and 51 conventional barium enema examinations without a preliminary veripaque enema have been performed on 94 patients with either ulcerative colitis or Crohn's disease of the colon. The severity of the disease at barium enema examinations has been graded and compared with the severity of the disease found at sigmoidoscopy. In the double contrast examination, there was agreement between the radiological and sigmoidoscopic findings in 77% of cases and a disagreement of one grade in the remaining 23% of cases. The double contrast enema demonstrated lesions in the colon proximal to the range of the sigmoidoscope of a greater severity than that seen at sigmoidoscopy in 30% of cases. It was not found possible to use the same grading method with the conventional enema, and unless frank ulceration is present, it is considered that the conventional enema is unreliable in assessing the state of the colonic mucosa. It is concluded that the double contrast enema, using a colonic activator in the preliminary cleansing enema, causes no greater risk of complications than either the conventional enema or sigmoidoscopy.

Barium Sulfate↗

The impact of colorectal cancer screening on life expectancy.

METHODS: The purpose of this study was to assess the effect of screening for colorectal cancer on life expectancy and estimate the number of colonoscopies needed per life year saved. The declining exponential approximation of life expectancy was used to calculate the effect of colorectal cancer screening on expected remaining lifetime. The annual number of deaths from colorectal cancer and the size of the population were obtained from the vital statistics of the United States. Published reports were consulted to determine the decrease in mortality from colorectal cancer achieved by fecal occult blood testing, screening sigmoidoscopy or colonoscopy. A Markov chain analysis was used to determine the endoscopic resources required to screen and survey the entire population of U.S. residents age 50 years until death or age 85 years. RESULTS: Colorectal cancer decreases the life expectancy of U.S. residents aged 50 to 54 years by 292 days and those aged 70 to 74 years by 70 days. Screening with fecal occult blood tests extends expected lifetime of the 2 age groups by 51 and 12 days, respectively, whereas screening with sigmoidoscopy leads to increases of 86 and 21 days. Colonoscopic screening increases expected lifetime by 170 and 41 days, respectively. The number of colonoscopies needed to save 1 year of expected life ranges from 2.9 to 6.0, depending on the type of screening regimen used. CONCLUSIONS: The extension of life through screening colonoscopy is two or three times longer than the extension achieved through flexible sigmoidoscopy or fecal occult blood test, respectively. Although a large number of colonoscopies are required to screen the U.S. population, relatively few colonoscopies need to be invested per year of life expectancy saved.

Aged↗

Prospective determination of distal colon findings in average-risk patients with proximal colon cancer.

BACKGROUND: Recent guidelines indicate that colonoscopy and sigmoidoscopy are both acceptable options for screening average-risk patients for colorectal cancer. Retrospective studies have found that a majority of patients with cancer proximal to the splenic flexure have a normal screening flexible sigmoidoscopy. METHODS: This was a multicenter, prospective description of colonoscopic findings and family history in consecutive patients with proximal colon cancer. RESULTS: Among 116 prospectively identified average-risk patients with cancer proximal to the splenic flexure, 40 (34.5%) had neoplasia distal to the splenic flexure. The prevalence of patients with adenomas greater than or equal to 1 cm, with only one tubular adenoma less than 1 cm, and with only hyperplastic polyps were 16.4%, 8.6%, and 6.9%, respectively. CONCLUSIONS: Most average-risk patients with cancer proximal to the splenic flexure will have a normal screening flexible sigmoidoscopy. These patients have an unexpectedly high prevalence of large distal adenomas, but the prevalence of both single small tubular adenomas and hyperplastic polyps alone is similar to that expected during screening of the general population. Clinicians and payers should continue to seek methods to improve the cost-effectiveness and availability of screening colonoscopy in average-risk persons.

Adenocarcinoma↗

Colonic endoscopy in perspective.

Sigmoidoscopy is an easy procedure and should be utilized more frequently. Barium enema examination is incomplete without sigmoidoscopy. Flexible fiberoptic sigmoidoscopy may have a role in the detection of disease of the descending, sigmoid, and rectosigmoid colon. The necessity for its routine usage remains to be determined. The control of colonic polyps by colonoscopy has been the greatest contribution to date by the fiberoptic instrument. Colonoscopy has improved the accuracy of diagnosis of colonic disease and, in certain instances, is helpful in the early detection of cancer of the colon. Colonoscopy complements the use of barium enema examination. Colonoscopy only for the purpose of confirmation of clinical or radiological diagnosis is often unnecessary. While the benefits of endoscopy are obvious, there are definite practical and technological limitations to its use. Complications, although infrequent, are major. Indications for colonoscopy must be clear and findings interpreted with knowledge of the limitations.

Colonic Diseases↗

Colorectal cancer screening.

Colorectal cancer is the second most lethal cancer in the United States. The lifetime risk of developing colorectal cancer in the United States is 5%. Early detection decreases mortality, and involves stratifying individuals by risk factors. Clinicians can use several methods for detection and surveillance of colorectal cancer including the digital rectal exam (DRE), fecal occult-blood test (FOBT), flexible sigmoidoscopy, colonoscopy, and double contrast barium enema. Several groups offer guidelines recommending specific screening techniques and intervals. In general, a combination of an annual FOBT and a flexible sigmoidoscopy every 5 years is recommended for average-risk individuals. Colonoscopy is the gold standard for visualizing the entire colon, and is reserved for abnormal findings on FOBT or flexible sigmoidoscopy or for individuals of greater-than-average risk for colorectal cancer.

Barium Sulfate↗