Sensitivity of fecal hemoccult testing and flexible sigmoidoscopy for colorectal cancer screening

A novel multiplex-protein array for serum diagnostics of colon cancer: a case-control study

BACKGROUND

More than 1.2 million new cases of colorectal cancer are reported each year worldwide. Despite actual screening programs, about 50% of the patients are diagnosed at advanced tumor stages presenting poor prognosis. Innovative screening tools could aid the detection at early stages and allow curative treatment interventions.

METHODS

A nine target multiplex serum protein biochip was generated and evaluated using a training- and validation-set of 317 highly standardized, liquid nitrogen preserved serum samples comprising controls, adenomas, and colon cancers.

RESULTS

Serum levels of CEA, IL-8, VEGF, S100A11, MCSF, C3adesArg, CD26, and CRP showed significant differences between cases and controls. The largest areas under the receiver operating characteristics curve were observed for CEA, IL-8, and CRP. At threshold levels yielding 90% specificity, sensitivities for CEA, IL-8 and CRP were 26%, 22%, and 17%, respectively. The most promising marker combinations were CEA + IL-8 reaching 37% sensitivity at 83% specificity and CEA + CRP with 35% sensitivity at 81% specificity. In an independent validation set CEA + IL-8 reached 47% sensitivity at 86% specificity while CEA + CRP obtained 39% sensitivity at 86% specificity. Early carcinomas were detected with 33% sensitivity for CEA + IL-8 and 28% for CEA + CRP.

CONCLUSIONS

Apart from CEA, IL-8, and CRP, the screening value of additional blood markers and the potential advantage of combining serum biochip testing with fecal occult blood testing needs to be studied. Multiplex biochip array technology utilizing serum samples offers an innovative approach to colorectal cancer screening.

CT colonography: coming of age

OBJECTIVE

The purpose of this article is to highlight key issues in CT colonography (CTC) for radiologists so they can represent the technology accurately to referring physicians and provide a perspective that will hopefully augment best care for their patients.

CONCLUSION

With publication of the National CT Colonography Trial and the endorsement of CTC for screening by a multisociety task force that included the American Cancer Society, American College of Radiology, and U.S. Multisociety Task Force on Colorectal Cancer, the clinical validation of CTC has been completed, and CTC is now ready for widespread clinical application. Radiologists must be skilled in CTC and knowledgeable about colorectal cancer screening issues.

Stool screening for colorectal cancer: molecular approaches

Assay of molecular markers in stool represents a promising noninvasive approach to screen colorectal cancer. Given that neoplasms exfoliate abundantly into the lumen and that DNA recovered from stool can be assayed with sensitive techniques, there is a strong biologic rationale to pursue this emerging technology. A challenge with DNA-based testing relates to the selection of markers. Because of the molecular heterogeneity of cancer, no single marker has yielded perfect sensitivity. Several combinations of markers in early stool assays have produced high detection rates of both colorectal cancer and advanced adenomas in selected patient groups, but observations from large representative populations are lacking at present. Potential expanded applications of stool DNA testing include detection of supracolonic aerodigestive cancers and of dysplasia in inflammatory bowel disease. Further marker discovery and technologic refinements should translate into improved test performance and fuel a continued evolution with this screening approach.

Prospective evaluation of fecal calprotectin as a screening biomarker for colorectal neoplasia

OBJECTIVES

Stool testing is a well established method of screening for colorectal neoplasia. Emerging data suggest that novel biomarkers may offer performance advantages over fecal occult blood. In this large, prospective study, we assessed fecal calprotectin (a leukocyte-derived protein) as a screening biomarker for colorectal neoplasia. Fecal calprotectin was directly compared to fecal hemoglobin (Hb) and colonoscopy as the existing criterion standards for stool screening and structural evaluation, respectively.

METHODS

Subjects included colonoscopy patients with a personal history of colorectal neoplasia, family history of colorectal cancer, or iron deficiency anemia. Stool specimens were collected before purgation, processed appropriately, and quantitatively analyzed for calprotectin (Nycomed Pharma, Oslo, Norway) and for Hb (Mayo Medical Laboratories, Rochester, MN) by masked technicians. Colonoscopies were performed by experienced endoscopists without prior knowledge of the fecal assay results.

RESULTS

Among 412 subjects, 97 (24%) subjects had one or more colorectal neoplasms (including three with adenocarcinomas). Fecal calprotectin levels did not differ significantly between subjects with versus subjects without colorectal neoplasms (p = 0.33). Neither tumor number (p = 0.85) nor tumor size (p = 0.86) significantly influenced the observed fecal calprotectin concentrations. Estimates of the sensitivity, specificity, and positive and negative predictive values of fecal calprotectin for any colorectal neoplasms were 37%, 63%, 23%, and 76%, respectively. Comparable performance estimates for fecal Hb were 3%, 97%, 27%, and 77%, respectively.

CONCLUSIONS

In this cohort of colonoscopy patients at above average risk, fecal calprotectin was a poor screening biomarker for colorectal neoplasia. Further investigation of tumor-derived, rather than blood-based, biomarkers may be a more rewarding approach to stool screening for colorectal neoplasia.

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.

Stool screening for colorectal cancer: evolution from occult blood to molecular markers

BACKGROUND

Colorectal cancer is the second leading cause of malignant death, and better preventive strategies are needed. Participation rates for colorectal cancer screening remain low due, in part, to perceived discomfort, potential harm, and high costs with available tools.

METHODS

Stool testing, unlike other conventional screening approaches, is noninvasive and requires no cathartic preparation. However, widely used fecal blood tests yield frequent false-negative and false-positive results that lower screening effectiveness and raise program costs. There is a compelling biological rationale to target DNA alterations exfoliated from neoplasms into stool, and multiple DNA markers would need to be assayed because of the genetic heterogeneity of colorectal neoplasia. Early clinical studies with this multi-target DNA-based stool assay approach suggest high sensitivity for both colorectal cancer and premalignant adenomatous polyps while maintaining high specificity.

CONCLUSIONS

This apparently accurate and user-friendly new approach holds promise to improve the effectiveness, efficiency, and appeal of colorectal cancer screening. Large-scale clinical studies are clearly warranted to corroborate the early results.

Screening for colorectal cancer: current status in Japan

PURPOSE

Screening for colorectal cancer using a guaiac-based fecal occult blood, or Hemoccult, test has been demonstrated to reduce colorectal cancer mortality. However, the magnitude of effectiveness is relatively low because of poor sensitivity of the Hemoccult test. The immunochemical fecal occult blood test has been shown to be much more sensitive than the Hemoccult test in detecting preclinical colorectal cancer in an asymptomatic population. The purpose of this article is to discuss the validity of the immunochemical fecal occult blood test and the efficacy of a population-based screening program using the test.

METHODS

Relevant articles were primarily identified through MEDLINE search. Review was focused on the studies of population screening programs with the immunochemical fecal occult blood test.

RESULTS

Sensitivities for colorectal cancer calculated in the same population were reported to be 67 to 89 percent and only 33 to 37 percent for the immunochemical test and Hemoccult test, respectively. Case-control studies and other observational studies showed that screening programs using the immunochemical fecal occult blood test by hemagglutination reaction would reduce the risk of dying of colorectal cancer by 60 percent or more for those screened annually compared with those unscreened. It was also shown that a screening strategy using the immunochemical fecal occult blood test had the best cost-effectiveness ratio among the methods available. Nearly 5 million persons are currently screened per year in Japan, yielding 0.15 to 0.2 percent colorectal cancer cases among persons with positive fecal occult blood test results.

CONCLUSIONS

These results strongly suggest that a screening program with immunochemical fecal occult blood test has promising advantages in terms of effectiveness over programs with the Hemoccult test. More stress is warranted on introduction of immunochemical fecal occult blood testing as a screening test in place of the guaiac fecal occult blood test.

A cost-effective analysis of the optimum number of stool specimens collected for immunochemical occult blood screening for colorectal cancer

This study was carried out to assess, from the viewpoint of cost-effectiveness, the optimum number of faecal specimens to collect for use in immunochemical occult blood testing as a means of screening for colorectal cancer. 3300 asymptomatic individuals were subjects of this study. They gave samples for an immunochemical faecal occult blood test, monohaem and colonoscopy was carried out during a medical check-up. For evaluation of the optimum number of sampling specimens, the results of the first day of sampling, those of the first and second days, and those of samples taken for 3 consecutive days were considered as the single-day method, the 2-day method and the 3-day method respectively. The average cost to detect 1 patient with colorectal cancer, the detection rate and the false-positive rate of these three faecal sample collection methods were evaluated. The average costs for one cancer case detected were calculated as $3,630.68 for the single-day method, $3,350.65 for the 2-day method and $4,136.36 for the 3-day method, respectively. The detection rate and the false-positive rate were calculated as 47 and 3.5% for the single-day method, 82 and 4.7% for the 2-day method and 88 and 5.3% for the 3-day method, respectively. This detection rate was significantly different between the single- and the 2-day methods, as well as between the single- and the 3-day methods (P<0. 05). No significant differences in the false-positive rate amongst the three testing methods were observed. This analysis suggests that a 2-day faecal collection method is recommended for immunochemical occult blood screening by Monohaem from the aspects of cost-effectiveness and diagnostic accuracy.

Colorectal cancer screening: a community case-control study of proctosigmoidoscopy, barium enema radiography, and fecal occult blood test efficacy

OBJECTIVE

To examine the effectiveness of screening proctosigmoidoscopy, barium enema radiography, and the fecal occult blood test (FOBT) in decreasing colorectal cancer mortality in a community setting.

PATIENTS AND METHODS

In this population-based case-control study, cases comprised 218 Rochester, Minn, residents who died of colorectal cancer between 1970 and 1993. Controls were 435 age- and sex-matched residents who did not have a diagnosis of colorectal cancer. Screening proctosigmoidoscopy, barium enema radiography, and FOBT results were documented for the 10 years prior to and including the date of diagnosis of fatal colorectal cancer in cases and for the same period in matched controls. History of general medical examinations and hospitalizations was also recorded.

RESULTS

Within the 10 years prior to diagnosis, the percentages of cases vs controls with at least 1 screening proctosigmoidoscopy were 23 (10.6%) of 218 cases vs 43 (9.9%) of 435 controls; at least 1 screening barium enema radiographic study was done in 12 (5.5%) of 218 vs 25 (5.7%) of 435. Within 3 years prior to diagnosis, the percentages of cases vs controls with at least 1 screening FOBT were 27 (12.4%) of 218 vs 44 (10.1%) of 435. Adjusted odds ratios were 1.04 (95% confidence interval [CI], 0.21-5.13) for proctosigmoidoscopy (distal rectosigmoid cancers only), 0.67 (95% CI, 0.31-1.48) for barium enema radiography, and 0.83 (95% CI, 0.45-1.52) for FOBT over the above time periods.

CONCLUSION

In this case-control study within a community setting, a colorectal cancer-specific mortality benefit could not be demonstrated for screening by FOBT, proctosigmoidoscopy, or barium enema radiography. Screening frequency was low, which may have contributed to the lack of measurable effects.

Fecal occult blood tests. A cost-effectiveness analysis

A range of fecal occult blood tests are presently on the market and could potentially be used in population screening programs for the detection of colorectal neoplasms. This paper estimates the relative cost-effectiveness of alternative tests and concludes that the unhydrated Hemoccult II is the most cost-effective. However, the incremental costs per life-year of the HemeSelect test and the rehydrated Hemoccult II test are in line with incremental costs observed in breast cancer and cervical cancer programs.

Review article: faecal occult blood testing for colorectal cancer

Major health organizations recommend colorectal cancer screening using faecal occult blood tests, sigmoidoscopy or both for patients 50 years of age or older who are at average risk for colorectal cancer. However, no specific recommendations have been made regarding choice of test from among the tests currently or soon to be available. Therefore, to aid clinicians in rationally choosing a particular test for faecal occult blood, published data are reviewed regarding the performance characteristics, strengths and weaknesses of the various faecal occult blood tests. New studies suggest that immunochemical tests (e.g. HemeSelect) or a combination of sensitive guaiac tests and immunochemical tests (e.g. Hemoccult Sensa and HemeSelect) are the most sensitive, specific tests for detecting colorectal carcinoma and colorectal polyps > or =1 cm.

Fecal occult blood testing for colorectal cancer. Can we afford to do this?

Fecal blood is an inherently insensitive and nonspecific marker for asymptomatic colorectal neoplasia. As such, use of fecal occult blood tests (FOBTs) necessarily limits the effectiveness and efficiency of a screening application. FOBT screening may result in a modest reduction in colorectal cancer-specific mortality, but it alters neither colorectal cancer incidence nor overall mortality. Costs resulting from FOBT screening are substantial, and the extent to which screen-induced mortality offsets any benefits remains unknown. In the absence of a clearly demonstrated net benefit with FOBT screening, affordability of this expensive effort can be legitimately questioned.

Fecal marker variability in colorectal cancer: calprotectin versus hemoglobin

BACKGROUND

Blood products like hemoglobin are problematic as markers for colorectal neoplasia because bleeding is intermittent. Levels of calprotectin, a leukocyte-derived protein, are increased in stools from colorectal cancer patients. However, this blood constituent may gain luminal access via interstitial leukocyte migration, which could be a less variable mechanism of entry than bleeding.

METHODS

To correlate the levels of and to compare the variability of fecal calprotectin and hemoglobin, quantitative assays were performed independently on multiple serially collected stools from 14 patients with colorectal cancer. Marker level association was estimated with Pearson's correlation coefficient, and variation estimated with an analysis of variance model.

RESULTS

Fecal calprotectin and hemoglobin levels were discordant in 55 (50%) of 110 matched aliquots, and marker levels failed to correlate. The estimated between-subject correlation was -0.10 (95% CI, -0.60 to 0.46), and mean within-subject correlation -0.27 (95% CI, -0.73 to 0.34). The between-stool coefficient of variation was less for calprotectin (22%) than for hemoglobin (80%).

CONCLUSIONS

In patients with colorectal cancer, the mechanism of luminal calprotectin entry appears to be both different from and less erratic than bleeding.

Screening for colorectal cancer by immunochemical fecal occult blood testing

Screening for colorectal cancer using the conventional Hemoccult test has been shown to reduce mortality associated with cancer by 33% through a randomized controlled trial. However, the magnitude of effectiveness is small in terms of cost-effectiveness. The recently developed immunochemical fecal occult blood test (IFOBT) provides a potential replacement for the Hemoccult test as a screening test, due to its superior performance characteristics such as higher sensitivity shown in preliminary studies and the fact that it does not require any dietary restriction. The IFOBT method is reviewed, especially in relation to its specificity. In known colorectal cancer subjects, IFOBTs have shown both higher sensitivity and specificity than the Hemoccult test. Similarly, IFOBT has demonstrated a higher sensitivity than Hemoccult for colorectal cancer in an asymptomatic population. A nationwide screening program in Japan has demonstrated the feasibility of this approach for large population screening. However, the positivity rate varied according to the conditions at each screening facility. Therefore, technical factors that influence the positivity rate of IFOBTs in the screening program are discussed. Case-control studies have strongly suggested that screening using IFOBT would reduce mortality from colorectal cancer by 60% or more. Several observational studies have provided support for this estimate. The feasibility and effectiveness of population-based screening by IFOBT are discussed.

Validity of immunological faecal occult blood screening for colorectal cancer: a follow up study

OBJECTIVES

Immunological faecal occult blood testing has been recognised as a useful method for wide scale screening of colorectal cancer in Japan during the past few years. This study was carried out to evaluate the validity of an immunological faecal occult blood test for colorectal cancer screening.

METHODS

A screening programme for colorectal cancer using an immunological faecal occult blood test was conducted on 3365 residents of regions within Nagano prefecture in 1991, and all the subjects were followed up for three years by verification from cancer registration. Based on the incidence of false negative cases among those who had been evaluated as normal by this screening, but were diagnosed as having colorectal cancer, the sensitivity and the specificity of this test were estimated.

RESULTS

Four false negative cases were found during the subsequent three year follow up period after screening. Among these four cases, one case was within the first follow up year, one case within the second year, and two cases within the third year. Accordingly, the sensitivity of this test was calculated as 90.9% within one year, 83.3% within two years, and 71.4% within three years, while the specificity was found to be 95.6%, indicating a validity higher than that achieved by a chemical occult blood test.

CONCLUSION

These findings suggest that the immunological faecal occult blood test has a high diagnostic accuracy and is a useful strategy for colorectal cancer screening.

Cost-effectiveness analysis of strategies for colorectal cancer screening in Japan

To determine the cost-effectiveness of colorectal cancer screening strategies in Japan and to determine the influence of long-term compliance with screening programs on the selection of strategies, the natural history of a simulated cohort of 40-year-old Japanese of both genders was modeled with and without colorectal cancer screening until age 75 years. Survival, number of complications, and direct medical costs were compared among several combinations of screening examinations. In addition, the age of initiating screening was varied, as was the long-term compliance rate. Strategies using immunological fecal occult blood test were found to be the most cost-effective. Immunological fecal occult blood test followed by colonoscopy, if positive, would save 24.05 (5.88 discounted) days of life and cost 28,420 yen (US $210) per screened person, thus offering a cost-effectiveness ratio of 1.765 million yen (US $13,100) per year of life saved. If long-term compliance is 100%, initiating screening at age 40 years offers more years of life saved and a low incremental cost of screening. However, if more likely dropout rates are considered, initiation at age 40 years is dominated by later initiation of screening.

Tobacco smoking as a risk factor for colon polyps

BACKGROUND

Data from a cancer screening project among pattern makers were used to evaluate the association between tobacco smoking and prevalence of colon polyps.

METHODS

From 1981-1983, 549 White men were examined by flexible sigmoidoscopy and completed self-administered questionnaires including smoking histories.

RESULTS

One or more colon polyps were detected in 76 men. Standardized prevalence rates (SPR) for polyps increased by smoking category (never smoked = 0.094; ex-smokers = 0.118, current smokers = 0.214) and by cigarettes per day, years of smoking, and pack-years among both current and ex-smokers. Both adenomatous and hyperplastic polyps showed an association with smoking while other types of polyps and polyps with unspecified histology did not. The risk associated with smoking was greater for polyps greater than one centimeter in diameter. An interaction with occupational exposures was suggested by a greater increase in the SPR for polyps among current smokers employed as pattern makers for more than 10 years than among current smokers similarly employed for 10 years or less.

CONCLUSIONS

Since at least some colon polyps are considered precursor lesions to colon cancer, one of the most common cancers in the United States, this report suggests that the possible link between colon polyps and smoking deserves further evaluation.

The case for worker notification

There is currently a heated debate about whether the U.S. Congress should enact the High Risk Occupational Disease Notification and Prevention Act. This Act would set up an orderly system for identifying, notifying, and assisting workers at high risk of occupational disease. Significant underpinning for this legislation comes from three pilot projects conducted by the National Institute for Occupational Safety and Health and the Workers' Institute for Safety and Health. These projects demonstrate that notification and intervention for occupational high-risk groups can be implemented feasibly within the existing structures of community health and labor management relations. These projects also suggest that, contrary to the views of opponents of current legislation, it is the absence of systematic programs that leads to massive litigation and high costs. At present, these costs are borne by workers and society.

Colorectal carcinoma and Haemoccult. A study of its value in mass screening using meta-analysis

Meta-analysis has been performed on the world literature relating to Haemoccult screening for colorectal cancer. The analysis indicated a sensitivity of about 50%, specificity of about 97%, positive predictive value of 4.3% and negative predictive value of 99.85%. These figures assume a prevalence of colorectal cancer in the population of 0.3%. A model calculation using these figures together with some additional realistic assumptions suggests no reduction in mortality compared to an unscreened population. It is concluded that many questions about faecal occult blood screening remain and that uncontrolled mass population screening is not justified at this stage.