Screening for colorectal cancer with fecal occult blood testing and sigmoidoscopy

CT and MR colography (virtual colonoscopy): status report

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

Outcome states of colorectal cancer: identification and description using patient focus groups

OBJECTIVE

Utilities for the outcome states of colorectal cancer must be measured to evaluate the cost-utility of screening and surveillance strategies for this disease. We sought to identify these outcome states, define their associated areas of morbidity, and construct representative descriptions of them for use in a utilities assessment instrument.

METHODS

We identified candidate colorectal cancer outcome states based on a review of the literature and interviews with health care professionals. We organized patient focus groups from each of the candidate outcome states to examine their homogeneity and define their associated areas of morbidity. After analyzing the focus group transcripts, we identified and described outcome states of colorectal cancer for future incorporation into a utilities assessment instrument.

RESULTS

Six candidate outcome states of colorectal cancer were identified based on disease stage and location at diagnosis. Thirty-eight patients then participated in six focus groups. Analysis of the focus group transcripts revealed seven areas of morbidity associated with colorectal cancer. These areas included problems with social interaction and cognition, fear of cancer recurrence, pain, fatigue, changes in bowel habits, and sexual dysfunction. Based on differences in the intensity and frequency of the symptoms reported in each of these areas, seven distinct outcome states of colorectal cancer were identified and described.

CONCLUSION

Clinically distinct outcome states of colorectal cancer are determined by the stage and location of the cancer at the time of diagnosis. Descriptions of these outcome states were created using data collected from patient focus groups. These descriptions can be incorporated into a utilities assessment instrument.

A systematic review of the effects of screening for colorectal cancer using the faecal occult blood test, hemoccult

OBJECTIVE

To review effectiveness of screening for colorectal cancer with faecal occult blood test, Hemoccult, and to consider benefits and harms of screening.

DESIGN

Systematic review of trials of Hemoccult screening, with meta-analysis of results from the randomised controlled trials.

SUBJECTS

Four randomised controlled trials and two non-randomised trials of about 330 000 and 113 000 people respectively aged >=40 years in five countries.

MAIN OUTCOME MEASURES

Meta-analysis of effects of screening on mortality from colorectal cancer.

RESULTS

Quality of trial design was generally high, and screening resulted in a favourable shift in the stage distribution of colorectal cancers in the screening groups. Meta-analysis of mortality results from the four randomised controlled trials showed that those allocated to screening had a reduction in mortality from colorectal cancer of 16% (relative risk 0.84 (95% confidence interval 0.77 to 0.93)). When adjusted for attendance for screening, this reduction was 23% (relative risk 0.77 (0.57 to 0.89)) for people actually screened. If a biennial Hemoccult screening programme were offered to 10 000 people and about two thirds attended for at least one Hemoccult test, 8.5 (3.6 to 13.5) deaths from colorectal cancer would be prevented over a period of 10 years.

CONCLUSION

Although benefits of screening are likely to outweigh harms for populations at high risk of colorectal cancer, more information is needed about the harmful effects of screening, the community's responses to screening, and costs of screening for different healthcare systems before widespread screening can be recommended.

Part II. Evidence-based medicine: a passing fancy or the future of primary care?

Reliable experimental evidence provides a firm scientific foundation for only a minority of the clinical decisions primary care practitioners must make each day. Thus clinicians' experience and judgment must complement and supplement their knowledge of published research studies. This presents a dynamic and difficult challenge to the practitioner--one that is magnified when combined with the never ending influx of medical information, with patients' and physicians' uneasiness with clinical uncertainty, and with new external pressures to standardize care. With these factors in mind, this article will review evidence-based medicine, a process and philosophy for the practice and teaching of clinical medicine that has sparked much controversy in recent years. Clinical scenarios commonly encountered in adult primary care--acute low back pain, hypertension, and screening for vascular disease--illustrate some strengths and limitations of evidence-based medicine.

Predictors of fecal occult blood screening among older socioeconomically disadvantaged Americans: a replication study

Socioeconomically disadvantaged elderly are less likely to participate in fecal occult blood testing (FOBT). A quasi-experimental design was used in this operational replication study to determine predictors at baseline of subsequent participation in FOBT. Sixty-five percent of the 211 participants in the replication study participated in FOBT, and 47% of the 171 participants in the original study participated in FOBT. Predictors for FOBT in the replication study were male gender, age of 65-75 years old, ability to go places without assistance, history of having had a digital rectal examination and FOBT. This replication study supports targeting socioeconomically disadvantaged populations for FOBT as well as females, persons 85 years and older, persons who need assistance in travel, and person who have not had FOBT before. The results show that socioeconomically disadvantaged persons will participate in FOBT when effective educational interventions that include adaptation for aging changes are used.

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.

What's new in colorectal cancer screening?

There is now good evidence from case control studies and randomized controlled trials that screening average-risk subjects for colorectal cancer using faecal occult blood tests reduces mortality. There is limited data indicating that screening sigmoidoscopy can also achieve this. There is no evidence yet that screening by colonoscopy or double contrast barium enema can reduce mortality. Calculations of cost-effectiveness suggest that all of the above strategies should be economically worthwhile but there is no convincing evidence to suggest that one strategy is markedly more cost-effective than the others. Further data on several aspects of screening are required before any decisions are made on which form(s) of screening should be offered nationwide.

How to screen for colon cancer

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

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.

Effect of faecal occult blood testing on colorectal mortality: results of a population-based case-control study in the district of Florence, Italy

The aim of our case-control study was to estimate the effect on mortality from colorectal cancer (CRC) of a population-based screening with a faecal occult blood test started in 1982 in a rural area of the district of Florence. We examined the relationship between mortality and the interval since the most recent screening. The cases in the study were 206 individuals who had died from CRC after the age of 41 years. Five controls were selected randomly from the list of individuals alive at the time of diagnosis of the corresponding case and were matched by sex, age and place and length of residence. After adjustment for potentially confounding factors, the odds ratio (OR) for death from CRC for screened persons vs. those not screened was 0.60 [95% confidence interval (CI), 0.4-0.9]. The OR was lowest in the first 3 years after the most recent test (OR = 0.54; 95% CI, 0.3-0.9) and increased towards unity subsequently. Our results suggest that screening for CRC by biennial faecal occult blood testing can reduce mortality from the disease.

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.

Screening and surveillance for colorectal carcinoma

Screening and surveillance examinations are effective in lowering colorectal cancer risk. Screening tests have been demonstrated to reduce colorectal cancer mortality. Colonoscopic removal of adenomatous polyps has been determined to reduce colorectal cancer incidence. High-risk individuals and their family members should be identified and offered more aggressive recommendations for appropriate screening and surveillance guidelines. Colorectal cancer screening strategies are in an acceptable range of cost effectiveness.

Preventive medicine and screening in older adults

PURPOSE

To review important current issues, studies, recommendations and controversies relating to preventive medicine and screening in older people. STUDY SELECTION/DATA ABSTRACTION: MEDLINE searches for literature on prevention and screening with regard to older adults as well as each individual condition reviewed; bibliographical reviews of textbooks, journal articles, government and advocacy organization task force reports, and recommendations. Important information synthesized and discussed qualitatively.

DATA SYNTHESIS

Data and recommendations are presented for most common preventive services, including primary prevention and screening for cardiovascular diseases and risk factors, common malignancies, endocrine and infectious diseases, osteoporosis, sensory deficits, and dementia.

CONCLUSIONS

The goal of preventive medicine in older people should be not only reduction of premature morbidity and mortality but preservation of function and quality of life. Attempts to prevent diseases of old age should start in youth; the older the patient, the less likely the possibility or value of primary and secondary prevention, and the greater the stress must be on tertiary prevention. Age 85 is proposed as a general cutoff range beyond which conventional screening tests are unlikely to be of continued benefit; however, care must always be individualized. Emphasis should be on offering the best proven and most effective interventions to the individuals at highest risk of important problems such as cardiovascular diseases, malignancies, infectious and endocrine diseases, and other important threats to function in older people. Breast cancer screening, smoking cessation, hypertension treatment, and vaccination for infectious diseases are thus far among the most firmly proven and well accepted specific preventive measures, with physical exercise also being particularly promising. Although more research is needed, a current working approach is necessary and possible. A summary table of recommendations and information tools such as reminders or flowsheets may be valuable in helping the physician carry out prevention and screening programs.

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.

Psychological opportunities and hazards in predictive genetic testing for cancer risk

Although the availability of genetic tests seems like an unequivocally favorable turn of events, they are, in fact, not without controversy. At the center of the controversy is a question regarding the risks and benefits of genetic testing. Many geneticists, ethicists, psychologists, and persons at risk for cancer are concerned about the potentially adverse psychological effects of genetic testing on tested persons and their families. In addition, the screening and interventions that are useful in the general population remain to be shown effective in those with high genetic cancer risk. Consequently, there have been calls for caution in moving genetic testing out of research laboratories and into commercial laboratories until their impact and the effectiveness of cancer prevention strategies can be studied. This article examines the arguments and data for and against this caution, citing examples related to hereditary nonpolyposis colon cancer and drawing upon literature on testing for other genetic diseases.

Fecal occult blood testing for colorectal cancer. Can we afford not to do this?

Current practice guidelines recommend annual fecal occult blood test screening for colorectal cancer in the average-risk population over the age of 50. Efficacy of fecal occult blood test screening is supported by several controlled prospective trials and case-control studies. Implementation of this recommendation, in combination with periodic flexible sigmoidoscopy every 5 years, is feasible, affordable, highly effective, and has the potential for reducing colorectal cancer mortality by at least 50%. With over 50,000 Americans dying of this malignancy each year, we cannot afford not to do this.

A survey of screening compliance among first degree relatives of people with colon cancer in New South Wales

OBJECTIVE

To survey screening practices, knowledge, and attitudes towards screening among first degree relatives of people with colon cancer.

SETTING

A random sample of people with colon cancer listed on the New South Wales (NSW) Cancer Registry were mailed a questionnaire to be passed on to an appropriate first degree relative.

METHODS

Two hundred and twenty five first degree relatives completed a self administered questionnaire.

RESULTS

Although there were high levels of awareness about colorectal cancer, and attitudes towards colorectal cancer were generally positive, screening rates were low, and only three relatives had been screened in accordance with current Australian recommendations. Factors associated with previous participation in any type of screening test (usually once) included receiving a medical recommendation to screen, having more than one relative with colorectal cancer, being a sibling of the relative with colon cancer, the relative with cancer being female, and perceiving screening as messy, but not painful.

CONCLUSIONS

Strategies to enhance screening awareness and participation among relatives need to be considered. This study provides some insight into factors to be considered in developing awareness programmes. Further research is required to explore these factors, and to identify ways to overcome barriers.

Randomised study of screening for colorectal cancer with faecal-occult-blood test

BACKGROUND

Case-control studies and a voluntary-based follow-up study have suggested that repeated screening with faecal-occult-blood (FOB) tests can lead to a reduction in mortality from colorectal cancer (CRC). The aim of this randomised study was to compare mortality rates after FOB tests every 2 years during a 10-year period with those of unscreened similar controls.

METHODS

140,000 people aged 45-75 years lived in Funen, Denmark, in August, 1985, and were considered for inclusion in our study. Before randomisation we excluded individuals who had CRC or precursor adenomas and those who had taken part in a previous pilot study. Randomisation of 137,485 people in blocks of 14 allocated three per 14 to the screening group (30,967), three per 14 to the control group (30,966), and eight not to be enrolled in the study (75,552). Controls were not told about the study and continued to use health-care facilities as normal. Hemoccult-II blood tests (with dietary restrictions but without rehydration) were sent to screening-group participants. Only those participants who completed the first screening round were invited for further screening--five rounds of screening during a 10-year period. Participants with positive tests were asked to attend to full examination and were offered colonoscopy whenever possible. The primary endpoint was death from CRC.

FINDINGS

Of the 30,967 screening-group participants, 20,672 (67%) completed the first screening round and were invited for further screening; more than 90% accepted repeated screenings. During the 10-year study, 481 people in the screening group had a diagnosis of CRC, compared with 483 unscreened controls. There were 205 deaths attributable to CRC in the screening group, compared with 249 deaths in controls. CRC mortality, including deaths attributable to complications from CRC treatment, was significantly lower in the screening group than in controls (mortality ratio 0.82 [95% CI 0.68-0.99]) p = 0.03).

INTERPRETATION

Our findings indicate that biennial screening by FOB tests can reduce CRC mortality. This study is being continued to improve its statistical power and to assess the effect of the removal of more precursor adenomas in the screening-group participants than in controls on CRC incidence.

Screening for colorectal cancer, 1996

Screening average-risk people aged 55 to 70 years for colorectal cancer is now a public health priority in Australia. Pilot studies of faecal occult blood testing are required to find ways of achieving optimal compliance and cost efficiency in the Australian health care setting. Flexible sigmoidoscopy probably should be used as complementary screening but further trials are needed. High-risk groups (family history of colorectal cancer, or previous ulcerative colitis, adenomas or cancer) should already be in surveillance programs.

Screening for colorectal cancer by once only sigmoidoscopy: a feasibility study in Turin, Italy

OBJECTIVES

To assess the impact on compliance of three invitation methods, as well as the acceptability and efficacy of two bowel preparation regimens, for endoscopic screening in the general population.

METHODS

1170 subjects (men and women aged 55 to 59, in the rosters of a sample of general practitioners (GPs) in Turin), were randomly allocated to one of three invitation groups (A: personal letter, signed by GP, with a pre-fixed appointment; B: same as for A + letter supporting the study by a well known scientist; C: letter signed by the study coordinator, NS) and two preparation regimens (i: one enema, self administered at home two hours before the test; ii: two enemas, administered the night before and two hours before the test). A postal reminder was mailed to non-attenders. A sample of non-responders was contacted for a telephone interview by a trained nurse. Written consent was obtained from all subjects undergoing the test.

RESULTS

A total of 278 subjects attended for sigmoidoscopic screening. An invitation from the GP alone produced the highest response rate (compliance: A = 29.3%; B = 24.9%; C = 26.8%). A single enema was as effective as two enemas in achieving satisfactory preparation for the test: the proportion of subjects invited to repeat the test was 8.1% in the single enema group, and 9.6% in the group receiving two enemas.

CONCLUSIONS

Compliance with this screening procedure tends to be low. One enema, self administered two hours before sigmoidoscopy, can ensure a satisfactory bowel preparation.

Cost-effectiveness analysis of screening by faecal occult blood testing for colorectal cancer in Australia

The incremental costs and effects of annual faecal occult blood test screening in Australia were modelled for a hypothetical cohort of 1000 persons offered screening or not offered screening. Incremental costs and effects were estimated as the differences in direct health care costs (Australian costs) and years of life remaining between the annual-screen group and the control (no screen) group, based on the published results of the Minnesota randomised controlled trial. The cost per life year saved was $24,660. The greatest source of variability in the cost-effectiveness ratio is the effectiveness of screening. The 95 percent confidence interval for cumulative mortality in the annual-screen group is 3.86 to 7.9 per 1000, assuming the control rate is fixed at 8.83 per 1000. With this confidence interval, the cost per life year saved ranges from $12,695 to $67,848. The cost-effectiveness ratio increases to $48,000 if no mortality benefit is assumed beyond the end of the trial follow-up period, 13 years. The results are sensitive to the cost of colonoscopy (at $400 per colonoscopy, the cost per life year saved is $12,319) and the false-positive rate. The cost-effectiveness of colorectal cancer screening is comparable with that of other screening programs but further evidence is needed on the efficacy of screening. Whether the benefits of colorectal cancer screening outweigh the harm and costs needs to be more certain before more resources are committed to mass screening. Health policy planners should initiate planning for Australian pilot projects in the event that the efficacy of screening is confirmed by two current studies.

Screening for melanoma by primary health care physicians: a cost-effectiveness analysis

BACKGROUND AND DESIGN - Australia has the highest rates of skin cancer in the world, and the incidence is estimated to be doubling every 10 years. Despite advances in the early detection and treatment of melanoma about 800 people still die nationally of the disease each year. A possible strategy for further reducing the mortality from melanoma is an organised programme of population screening for unsuspected lesions in asymptomatic people. Arguments against introducing melanoma screening have been based on cost and the lack of reliable data on the efficacy of any screening tests. To date, however, there has been no systematic economic assessment of the cost effectiveness of melanoma screening. The purpose of this research was to determine whether screening may be potentially cost effective and, therefore, warrants further investigation. A computer was used to simulate the effects of a hypothetical melanoma screening programme that was in operation for 20 years, using cohorts of Australians aged 50 at the start of the programme. Based on this simulation, cost-effectiveness estimates of melanoma screening were calculated. RESULTS - Under the standard assumptions used in the model, and setting the sensitivity of the screening test (visual inspection of the skin) at 60%, cost effectiveness ranged from Aust$6853 per life year saved for men if screening was undertaken five yearly to $12 137 if screening was two yearly. For women, it ranged from $11 102 for five yearly screening to $20 877 for two yearly screening. CONCLUSION - The analysis suggests that a melanoma screening programme could be cost effective, particularly if five yearly screening is implemented by family practitioners for men over the age of 50.

A comparison of fecal occult-blood tests for colorectal-cancer screening

BACKGROUND

Hemoccult II, a widely used guaiac test for fecal occult blood, has a low sensitivity for detecting colorectal neoplasms in asymptomatic patients at average risk. In such patients, the performance characteristics of screening tests developed to improve on Hemoccult II are not known.

METHODS

A set of three fecal occult-blood tests--Hemoccult II; Hemoccult II Sensa, a more sensitive guaiac test; and HemeSelect, an immunochemical test for human hemoglobin--was mailed to all patients 50 years of age or older who were scheduled for personal health appraisals at the Kaiser Permanente Medical Center in Oakland, California. The performance of each test and of a combination test (HemeSelect to confirm positive Hemoccult II Sensa results) was evaluated by identifying screened patients who had colorectal neoplasma (carcinoma or a polyp > or = 1 cm in diameter) in the two years after screening.

RESULTS

Of the 10,702 eligible patients, 8104 (75.7 percent) had at least one interpretable sample and were screened on the basis of at least one test; 96 percent of these patients had complete two-year follow-up. The sensitivity of the tests for detecting carcinoma was lowest with Hemoccult II (37.1 percent; 95 percent confidence interval, 19.7 to 54.6 percent), intermediate with the combination test (65.6 percent; 95 percent confidence interval, 47.6 to 83.6 percent) and with HemeSelect (68.8 percent; 95 percent confidence interval, 51.1 to 86.4 percent), and highest with Hemoccult II Sensa (79.4 percent; 95 percent confidence interval, 64.3 to 94.5 percent). The specificity for detecting carcinoma was 86.7 percent with Hemoccult II Sensa, 94.4 percent with HemeSelect, 97.3 percent with the combination test, and 97.7 percent with Hemoccult II. HemeSelect and the combination test detected more colorectal carcinomas and polyps than Hemoccult II, with only slight increases in the number of colonoscopies needed.

CONCLUSIONS

HemeSelect and a combination test in which HemeSelect is used to confirm positive Hemoccult II Sensa results improve on Hemoccult II in screening patients for colorectal carcinoma.

Cost benefit of early diagnosis of colorectal cancer

In most Western countries, colorectal cancer is an important disease in terms of morbidity and mortality. As it has a premalignant asymptomatic stage in the form of benign adenomas that might be detected by screening, and as screening leads to detection of colorectal cancer at an earlier stage, there is potential for improved and better quality survival. Most cost-effective analyses rank the various screening strategies at less than an accepted benchmark value of approximately $40,000 per added year of life. Periodic colorectal screening is therefore a cost-effective intervention and the Office of Technology Assessment of the Congress of the United States has concluded that colorectal cancer screening in average-risk adults beginning at age 50 is a relatively good investment for society. Flexible sigmoidoscopy and double contrast barium enema are the most cost-effective strategies but they both require colonoscopy if a lesion is identified. Colonoscopy at 10-yearly intervals is of comparable cost to flexible sigmoidoscopy every 5 years and less costly than FSIG every 3 years. Combination strategies, using faecal occult blood testing with periodic flexible sigmoidoscopy or double contrast barium enema are as costly as colonoscopy. The choice of screening strategies needs to be tailored to the individual, and a process of community education is an essential prerequisite to the success of any programme.

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.

Flexible sigmoidoscopy plus air-contrast barium enema versus colonoscopy for evaluation of symptomatic patients without evidence of bleeding

One hundred forty-nine patients aged 40 years or more with symptoms suggestive of colonic disease but without evidence of gastrointestinal bleeding (absence of hematochezia, normal serum levels of hemoglobin, and at least one test negative for fecal occult blood) were randomized to undergo either initial colonoscopy or initial flexible sigmoidoscopy plus air-contrast barium enema. Patients with incomplete initial colonoscopy and certain patients with polyps seen on flexible sigmoidoscopy plus barium enema underwent the alternative procedure (barium enema or colonoscopy). The main results were as follows: First, the overall prevalence of cancer in the study was very low (0.67%). Second, initial flexible sigmoidoscopy plus barium enema detected more patients with diverticulosis than did initial colonoscopy (46% versus 31%; p = .01). Initial colonoscopy detected more persons with adenomas (p = .06) than did initial flexible sigmoidoscopy plus barium enema. Patients undergoing initial flexible sigmoidoscopy plus barium enema require the alternative procedure (24%) than were patients undergoing initial colonoscopy (6%; p = .002). Third, sensitivity analyses suggested that for most areas in the United States, initial colonoscopy would be more cost-effective for the outcomes of detection of adenomas and detection of large adenomas, although very few patients in the study had large adenomas. We conclude that the prevalence of colorectal cancer in persons with colonic symptoms but no evidence of bleeding is low and is comparable with the prevalence in an asymptomatic population. Cost-effective selection of imaging strategies in this population can be based on demographic factors such as age and sex, which are better predictors of the presence of adenomas than are symptoms.

A case-control study to evaluate efficacy of screening for faecal occult blood

OBJECTIVES

Faecal occult blood testing is routinely used for early detection of colorectal cancer, but evidence of its efficacy in preventing death from colorectal cancer is limited. A case-control study was carried out to evaluate whether screening for faecal occult blood is associated with a reduced risk of fatal colorectal cancer.

SETTING

A health maintenance organisation in western Washington State, which has offered its members faecal occult blood testing every two years since 1983.

METHODS

Cases (n = 248) were members of the health maintenance organisation who died from colorectal cancer between 1986 and 1991. For each case, two control subjects, who did not die from colorectal cancer and who were similar to each case in age, gender, and year of enrollment at the health maintenance organisation, were randomly selected from the membership list of the year in which the case was diagnosed (n = 496). Information about episodes of faecal occult blood testing (including the location and reason for the test, and the evaluation of positive tests) and potential confounders was obtained from medical records.

RESULTS

Cases were less likely than controls to have ever been screened (odds ratio (OR) = 0.7, 95% confidence interval (CI) 0.5 to 1.0), consistent with a beneficial impact of screening. There was little difference, however, for screening that had taken place within a three year period before diagnosis (OR = 0.9, 95% CI 0.6 to 1.2), the maximum interval during which most tumours ought to have been detectable by faecal occult blood testing. A reduction in risk was seen for home testing but not for office testing, and in individuals aged less than 75 but not in those aged 75 or older. Although most of the 21 controls with a positive faecal occult blood test underwent some additional testing, only five (24%) were evaluated with colonoscopy or air contrast barium enema.

CONCLUSIONS

While there can be uncertainty as to whether specific faecal occult blood tests were performed as screening or diagnostic tests, those performed at home and in younger persons may be relatively less likely to be diagnostic tests that were misclassified as screening. Thus the modest reduced risk associated with faecal occult blood testing in these settings/persons may reflect genuine benefit. However, the presence of a reduced risk associated with a screening faecal occult blood test received in the past, well before a tumour or polyp might bleed enough to allow detection, is compatible with uncontrolled confounding. Interpretation is further complicated by the fact that a number of individuals in the study group who had positive test results underwent limited or no diagnostic testing. Thus our results should be interpreted with considerable caution.

Prevention and early detection of cancer in women

Cancer remains a significant problem for women. When detected early, cancer is more easily treated and the possibility of long-term cure is greatest. Nurses play an important role in the prevention and early detection of cancer in women. Nurses can serve as role models to women by incorporating cancer prevention and detection practices into their personal health behaviors. Nurses also have many opportunities to incorporate primary, secondary, and tertiary prevention methods into their practice, regardless of the setting. The impact on quality of life and decreased mortality as a result of implementation of prevention and early detection practices is significant.

Screening for colorectal cancer

In the past few years, knowledge of the clinical, biologic, and molecular genetic characteristics of colorectal cancer has greatly increased. Although the most cost-effective approach remains to be identified, screening for colorectal cancer can decrease mortality due to this disease by detecting cancers at earlier stages and allowing the removal of adenomas, thus preventing the subsequent development of cancer. Molecular studies that have helped define the genetic basis for this disease hold great promise for the development of better and more powerful methods to identify populations at risk. Individually, these technological, clinical, and basic-science advances are exciting; together, they promise to move us closer to the goal of substantially reducing mortality due to colorectal cancer.

The potential benefits and harms of screening for colorectal cancer

Australian guidelines for colorectal cancer screening for average-risk populations vary from recommendations for annual screening by faecal occult blood testing for those over 40 years to recommendations that screening may be appropriate if requested by an informed patient aged 50 to 75 years. There are five large screening trials, of which three have published mortality data. A meta-analysis of the mortality data suggests a 19 per cent reduction in colorectal cancer mortality (95 per cent confidence intervals 0.68 to 0.96) with Hemoccult screening. Because of the width of the confidence interval, decisions about the magnitude of the effect of screening should await further trial results, which should be available in the next few years. In the interim, we should examine issues of harm and costs in Australia. For example, in the major trials, over 80 per cent of positive results have been falsely positive and have required invasive investigation. Estimates of the cost-effectiveness of screening for the Australian health system are not yet available and are essential. If the benefits of screening outweight the harms and costs, a successful screening program would require provision of screening infrastructure and appropriate information to target populations, quality control for screening tests and investigations, recall mechanisms to ensure appropriate follow-up of persons with positive results and the active participation of the Australian public and health practitioners.

Laboratory study on occult gastrointestinal bleedings: differential diagnostic method for the parallel study of intact and fragmented hemoglobin

The authors produced various degradation products of human hemoglobin. With the aid of immune sera raised against native hemoglobin and their fragments, we examined the antigenicity of the intact molecule and fragments as well as the specificity and reactivity of the immune sera used. Since conventional guaiac-type reactions make no distinction between the different hemoglobin molecules and the methods described in recent years' publications only with immune sera raised against native intact hemoglobin, the demonstration of occult fecal blood has not reached the desired rate of efficacy in clinical practice. The authors recommend the introduction of a simple differential diagnostic methods suitable for the parallel examination of intact and fragmented hemoglobin.

Screening for colorectal cancer using an immunochemical test for faecal occult blood: results of the first 2 years of a South Australian programme

This paper reports an evaluation of the first 2 years of a South Australian screening programme for colorectal cancer which was established in 1988 by the Institute of Medical and Veterinary Science. The programme uses an immunochemical test for faecal occult blood. Based on 1 year of follow-up, over the period of this analysis there were 24 cancers and 99 adenomas detected in 6208 participants, and the estimated sensitivity and specificity of the test (for colorectal cancer) were 82.8 and 95.9%, respectively. In many cases the test was used to detect recurrence of disease in individuals with a previous diagnosis of colorectal cancer. The estimated predictive value of a positive test for colorectal cancer in this population was 7.5%. Results suggest that participants belonged to higher-than-average socio-economic groups and were more likely than the general population to have a family history of colorectal cancer. Almost one-third had suffered from bowel symptoms in the 6 months before taking the test. These unique characteristics of participants, which limit the generalizability of results to the wider population, may result from the programme's reliance on self-recruitment methods. Consistent evidence for improvements in mortality in populations screened for colorectal cancer is still required before a recommendation for widespread screening in Australia can be made.

Prevention of colorectal cancer by colonoscopic polypectomy. The National Polyp Study Workgroup

BACKGROUND

The current practice of removing adenomatous polyps of the colon and rectum is based on the belief that this will prevent colorectal cancer. To address the hypothesis that colonoscopic polypectomy reduces the incidence of colorectal cancer, we analyzed the results of the National Polyp Study with reference to other published results.

METHODS

The study cohort consisted of 1418 patients who had a complete colonoscopy during which one or more adenomas of the colon or rectum were removed. The patients subsequently underwent periodic colonoscopy during an average follow-up of 5.9 years, and the incidence of colorectal cancer was ascertained. The incidence rate of colorectal cancer was compared with that in three reference groups, including two cohorts in which colonic polyps were not removed and one general-population registry, after adjustment for sex, age, and polyp size.

RESULTS

Ninety-seven percent of the patients were followed clinically for a total of 8401 person-years, and 80 percent returned for one or more of their scheduled colonoscopies. Five asymptomatic early-stage colorectal cancers (malignant polyps) were detected by colonoscopy (three at three years, one at six years, and one at seven years). No symptomatic cancers were detected. The numbers of colorectal cancers expected on the basis of the rates in the three reference groups were 48.3, 43.4, and 20.7, for reductions in the incidence of colorectal cancer of 90, 88, and 76 percent, respectively (P < 0.001).

CONCLUSIONS

Colonoscopic polypectomy resulted in a lower-than-expected incidence of colorectal cancer. These results support the view that colorectal adenomas progress to adenocarcinomas, as well as the current practice of searching for and removing adenomatous polyps to prevent colorectal cancer.