Randomised controlled trial of faecal-occult-blood screening for colorectal cancer

Screening for colorectal cancer: present, past and future

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

Colorectal cancer prevention. An approach to increasing compliance in a faecal occult blood test screening programme

STUDY OBJECTIVE

The assessment of the uptake of colorectal cancer screening offered in a workplace setting.

DESIGN

Employees were offered a free faecal occult blood test (Haemoccult). A repeat letter was sent two months later to non-responders. Those with positive tests were invited for colonoscopy. Compliance was measured according to age, sex, and occupational group and the effects of reinviting non-compliers investigated.

SETTING

Leicester General Hospital, a large university teaching hospital.

PARTICIPANTS

990 employees aged 41 to 65 years.

MAIN RESULTS

Total compliance was 46% with women participating more than men (49% v 34%, chi 2 = 12.2, p < 0.001). The difference was mostly because of women aged 41 to 50 years complying more than their male counterparts (48% v 24%, chi 2 = 15.5, p < 0.0001). Participation was highest in clinical support staff (56%), nurses (52%), and clerical workers (46%). Uptake by doctors (26%) and managers (26%) was significantly lower than by clinical support staff and nurses (chi 2 > 5.5, p < 0.02). Remailing raised compliance slightly from 43.6% to 46.3%. Four employees (1%) had positive faecal occult blood tests but three were negative on repeat testing with dietary restrictions.

CONCLUSIONS

The government favours the development of health promotion programmes as stated in its document "Health at work in the NHS". The response in this study, showed methods to increase compliance must be developed if such programmes are to be successful. As uptake was similar to that in several community based programmes in general practice, workplace based programmes could offer a complementary method of delivering screening.

Colorectal cancer screening and follow-up

Cancer of the colon and rectum is a significant health problem in the United States. Nearly 50% of the 186,000 patients diagnosed annually with colorectal cancer will eventually die of their disease. Because development of a colorectal carcinoma is most frequently preceded by the development of a well-recognized pre-malignant lesion, screening modalities can significantly impact the incidence and mortality rate of this disease. Population screening employing digital rectal examination, fecal occult blood testing and endoscopic examination of the rectum and colon has been demonstrated to reduce the risk of death from colorectal cancer. Screening regimens should be instituted at an earlier age and with increased frequency for patients in the highest risk categories. Patients who have been treated for a cancer of the colon or rectum should undergo surveillance at regular intervals in an attempt to identify recurrences of disease both in the residual colon and rectum and at distant sites. Most physicians and patients believe that intensive follow-up strategies will afford improved survival and quality of life, however few randomized studies examining the utility of intensive follow-up programs have been performed and the quality of cancer-related follow-up literature is generally poor. Good-quality clinical trials are needed to sort out which tests make a difference in the patient's long-term outcome. The algorithm for surveillance for recurrence in the future may be altered as newer testing modalities are developed.

Effectiveness and cost-effectiveness of colorectal cancer screening: Selecting the ideal strategy

Colorectal cancer is the second most common cancer killer of Americans. Recently developed and tested methods of screening and surveillance can effectively diagnose and treat the disease in most patients before symptoms develop when the chance of cure is high. It is also possible to prevent colorectal cancer by detecting and resecting premalignant adenomatous polyps. Evidence-based guidelines recommend that the average-risk population greater than age 50 be screened with annual faecal occult blood tests plus periodic flexible sigmoidoscopy. This approach is feasible, efficacious, affordable and cost-effective in a high-risk country such as the US. Widespread compliance with these recommendations could reduce the mortality from this malignancy by more than 50%.

Primary colorectal cancers detected with PET

Positron emission tomography (PET) using 18F-fluorodeoxyglucose can sensitively detect cancers of increased glucose metabolism. We describe three asymptomatic individuals who were found to have colorectal cancer and underwent potentially curative surgery. On the PET images, lesions were easily discernible. Our experience and the experience of others suggest that primary colorectal cancer can be detected with PET in a resectable stage. Our three cases are presented and the potential utility of PET is discussed.

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.

Serum ferritin. Screening test for colorectal cancer?

PURPOSE

There is increasing evidence that screening for colorectal cancer may save lives, and consequently, both professional and public interest in screening for colorectal cancer is increasing. As yet, however, there is no perfect screening test. Insidious blood loss is a common feature of colorectal cancer and may lead to a fall in serum ferritin before the patient becomes anemic. Measurement of serum ferritin, which is widely available and easily and inexpensively performed, has, therefore, been postulated as a potential screening test for colorectal cancer.

METHOD

This study used samples of serum collected from 148 patients recruited to a screening study for colorectal cancer. All patients were thoroughly investigated by double-contrast barium enema and/or colonoscopy. Patients were selected randomly from each of three clinical diagnostic groups: 50 patients with proven colorectal cancer, 49 patients without colon disease, and patients with adenomas of the colon. Serum ferritin was assayed by immunoradiometry. The expected adult reference ranged is 25 to 350 milligrams, and results were reported without patient identification.

RESULTS

There were no significant differences in serum ferritin levels among any of the three groups.

CONCLUSION

Serum ferritin is unlikely to be of value as a screening test for colorectal cancer.

Relative frequency of upper gastrointestinal and colonic lesions in patients with positive fecal occult-blood tests

BACKGROUND

Although bleeding lesions anywhere in the gastrointestinal tract can cause a positive reaction on guaiac-based fecal occult-blood tests, the relative frequency of upper gastrointestinal and colonic lesions is unknown.

METHODS

During a period of 30 months, we prospectively studied all patients with at least one stool specimen containing fecal occult blood who were referred for further evaluation. Fecal occult blood was detected by standard guaiac-based tests of stool specimens obtained as part of routine screening or of stool obtained by digital rectal examination. Patients with documented iron-deficiency anemia or active gastrointestinal bleeding were excluded from the study. All participants had a detailed history taken and underwent colonoscopy, followed by esophagogastroduodenoscopy.

RESULTS

Of the 409 patients with fecal occult blood who were referred, 310 were potentially eligible to participate, and 248 (mean age, 61 years; range, 40 to 89) were studied; 40 percent were women. We identified lesions consistent with occult bleeding in 119 patients (48 percent); in 71 bleeding lesions were found in the upper gastrointestinal tract, and in 54 they were identified in the colon. Six patients had abnormalities in both areas. The most common upper gastrointestinal lesions were esophagitis (23 patients), gastric ulcer (14), gastritis (12), and duodenal ulcer (10). Thirty patients with lesions in the upper gastrointestinal tract were long-term users of aspirin, ethanol, nonsteroidal antiinflammatory drugs, or a combination of these substances. The most common colonic lesions were adenomas more than 1.0 cm in diameter (29 patients), carcinoma (13), colitis (5), and vascular ectasia (5). Although the overall sensitivity of symptoms for the detection of gastrointestinal lesions was low, logistic-regression analysis demonstrated that the presence of symptoms in the upper gastrointestinal tract was associated with the detection of lesions in the upper gastrointestinal tract (odds ratio, 2.6; 95 percent confidence interval, 1.4 to 4.7). In both patients with symptoms and those without symptoms, the prevalence of lesions in the upper gastrointestinal tract was greater than or equal to that of colonic lesions.

CONCLUSIONS

In a group of patients with positive fecal occult-blood tests who were referred for further evaluation, from which those with iron-deficiency anemia and active bleeding had been excluded, upper gastrointestinal lesions were identified more frequently than colonic lesions.

Colorectal cancer: a survey of community beliefs and behaviours in Victoria

OBJECTIVE

To document self-reported beliefs and behaviours in relation to colorectal cancer (CRC) and screening for CRC.

DATA COLLECTION

A stratified random sample was selected from the telephone directory, and structured telephone interviews were conducted using a computer-assisted telephone interviewing system.

PARTICIPANTS

500 men and 500 women aged 40-60 years, 70% randomly selected from the Melbourne metropolitan area and 30% from rural Victoria. The response rate to the initial telephone invitation of 1569 eligible people was 63.7%.

OUTCOME MEASURES

Awareness of and experience with CRC; knowledge of CRC risk, risk reduction behaviour, and screening tests for CRC; willingness to have screening tests for CRC; and test preferences.

RESULTS

The people surveyed were relatively unaware of their personal risk of CRC, despite 61% (95% CI, 57%-65%) knowing someone who had CRC. Although 51% (95% CI, 48%-54%) could not name any CRC screening test, 68% (95% CI, 65%-71%) knew of the value of a high fibre diet in prevention. However, 67% (95% CI, 64%-70%) thought it was unlikely they would have a screening test for CRC in the next two years, but 64% (95% CI, 61%-67%) considered that some person could influence their decision to have a test, 60% (95% CI, 56%-64%) stating that they would be influenced by a doctor. Faecal occult blood testing and sigmoidoscopy were equally acceptable. In general, women were more knowledgeable than men. There were no systematic age or urban/rural differences.

CONCLUSIONS

There is a variable understanding of CRC in the community. Although prevention is well understood, this is not true of screening. General practitioners are likely to be influential in the uptake of any screening programs.

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.

Community (mis)understanding of colorectal cancer treatment

BACKGROUND

A study was undertaken to assess community understanding of colorectal cancer symptoms and colorectal cancer treatment.

METHODS

A computer-assisted telephone survey was undertaken to interview 1000 men and women aged 40-60 years.

RESULTS

Overall there was a considerable lack of information in the community about colorectal cancer symptoms and treatment. Men were less knowledgeable than women, and 28% of men were unable to name any symptoms of bowel cancer. Although surgery was mentioned by 53% of the sample, a third could not name any treatments. Most responses to questions about the effects of treatment related to chemotherapy-related disturbances and the possibility of having a colostomy bag postoperatively.

CONCLUSIONS

There is inaccurate information in the community about colorectal cancer symptoms and treatment. This may inhibit involvement in screening programmes or delay presentation for therapy, as a result of undue concern about the prospects of treatment.

Nested consent design for clinical trials

BACKGROUND

Since random treatment allocation is hardly understood by the majority of patients, a new 'nested consent design' for clinical trials is proposed.

PROPOSED DESIGN

The design consists of a two-step enrollment of study subjects. The first step is the enrollment of participants into a follow-up study, where consent to be subjects involved in the follow-up is obtained. The second step is the enrollment of randomly sampled eligible participants into a new treatment group. After the explanation of (1) treatment mode, (2) additional burdens associated with the proposed treatment and (3) expected effects and possible adverse events, written informed consent is obtained. Those who reject participation and those who are not allocated into the new treatment are treated by standard care. Endpoints are set to be the same for all follow-up study participants whether allocated into the new treatment or not, and follow-up is carried out in the same manner. Analyses are performed between those allocated to the new treatment and those non-allocated on an intent-to-treat basis.

EXAMPLE

Although not a clinical trial, this design was applied in a smoking cessation program at Aichi Cancer Center Hospital for first-visit patients who answered in a questionnaire survey that they were smokers. Out of 1330 necessary participants, 324 were enrolled in the follow-up study during the first three months of enrollment.

CONCLUSIONS

The design was found to be feasible for prevention trials, and possibly for clinical trials to compare a new treatment with a standard treatment. There seems to be no ethical difference between this design and the one-arm study design.

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.

Community screening for colorectal cancer in north-eastern New South Wales, 1987-1996

OBJECTIVE

To analyse results of Bowelscan, a community-based colorectal cancer screening program using Hemoccult II, and targeting people aged 40 years and over.

DESIGN

Survey of data from medical practitioners on follow-up of positive tests.

SETTING

North-eastern New South Wales (Rotary District 9650), 1987-1996.

SUBJECTS

3845 people with positive results for faecal occult blood.

OUTCOME MEASURES

Investigations performed; final diagnoses; number, site and Dukes' stage of colorectal carcinomas; number and histological diagnosis of colorectal polyps.

RESULTS

239,500 Hemoccult II kits were distributed between 1987 and 1996, with an estimated return rate of 80%-85%. Positive results for faecal occult blood were reported for 3845 tests (1.6% of those distributed), with 78% of these investigated by colonoscopy and/or barium enema. Investigation resulted in diagnosis of 260 colorectal carcinomas in 252 people (6.7%); 74 of these (29%) were in the caecum or ascending or transverse colon. Dukes' tumour stages were: A, 107 (41%); B, 86 (33%); C, 49 (19%); D, 16 (6%); and unknown, 2 (0.8%). (Corresponding figures from the NSW Central Cancer Registry were: A and B, 48%; C, 26%; D, 14% and unknown 12%) [corrected]. Colorectal polyps were found in a further 819 people (21.3%), and were adenomatous in 577 (79% of the 733 in whom histological diagnosis was available). Other gastrointestinal conditions were found in 1343 people (34.9%), while no cause was found for the positive result, despite adequate investigation, in 873 (22.7%).

CONCLUSION

Community-based screening with faecal occult blood testing detected colorectal carcinomas at earlier histological stages than colorectal carcinomas reported to the Cancer Registry and should reduce mortality from this disease. Treatment and follow-up of adenomatous polyps detected by such a program might minimise the incidence of colorectal carcinoma in this group.

Colorectal cancer screening by general practitioners: comparison with national guidelines

OBJECTIVE

To determine whether general practitioners (GPs) had received Australian guidelines on early detection, screening and surveillance for colorectal cancer or rectal bleeding, and whether their reported practice conformed with these guidelines.

DESIGN

Cross-sectional postal survey of self-reported practice.

PARTICIPANTS AND SETTING

213 GPs in practice in the southern metropolitan area of Perth, Western Australia, were randomly selected from the Fremantle Regional Division of General Practice database and surveyed in March 1997.

RESULTS

Replies were received from 155 (73%) of the GPs, and 110 reported receiving guidelines (from the Australian Gastroenterology Institute [AGI], 44; Gut Foundation of Australia [GFA], 40; others, 6; and not specified, 20). GPs who reported receiving guidelines were significantly more likely to screen for colorectal cancer (99/110; 90%) than those who reported not receiving guidelines (33/45; 73%) (P = 0.008). The commonest method to investigate people with identifiable risk factors for colorectal cancer was colonoscopy. Reported screening frequencies in asymptomatic patients with above-average risk (family history of colorectal cancer or past history of adenomatous polyps or colorectal cancer) were significantly higher than recommended by AGI and GFA guidelines (P < 0.05). Up to 24% of GPs investigated altered bowel habit or bleeding per rectum with faecal occult blood testing.

CONCLUSIONS

Most GPs report having received guidelines. Reported screening frequency was higher than recommended for most above-average-risk patients, which will result in excessive consumption of resources without benefits for cancer prevention.

Early colorectal cancer: recognition, classification and treatment

BACKGROUND

With the introduction of colorectal cancer screening and improvements in endoscopic technology, the recognition and management of early colorectal cancer assumes increasing importance.

METHODS

A literature review was undertaken using Medline (National Library of Medicine, Washington DC, USA) searches of the headings early colonic, colorectal and rectal cancer, carcinoma and adenocarcinoma up to and including 1997. All relevant references were examined.

RESULTS AND CONCLUSION

The diagnosis, classification and treatment options are described. Accurate diagnosis, preoperative and histopathological staging is crucial in the management of early colorectal cancer.

A study of laboratory based faecal occult blood testing in Melbourne, Australia. The Faecal Occult Blood Testing Study Group

Faecal occult blood tests (FOBT) are widely used in clinical practice and are under increasing scrutiny as a tool for colorectal cancer screening. However, there is little information regarding the quality of testing performed in pathology laboratories. Therefore, we asked 13 pathology laboratories in Melbourne, Australia, to test coded contrived faecal samples prepared from a composite stool specimen which had been spiked to various concentrations of haemoglobin. The samples were provided to the laboratories in two forms: (i) on/in the sample collection device appropriate for the faecal occult blood test they normally used; and (ii) as a moist faecal sample. Some variation in threshold analytical sensitivity between laboratories for the same FOBT was observed for Hemoccult SENSA, ColoRectal, Hematest, MonoHaem and Hemolex suggesting that, at least for those tests, technician training could be improved. Two tests, Hematest and an in-house FOBT did not perform as well as the other FOBT. When samples were sent in moist form, Hemoccult SENSA (P = 0.0002), ColoRectal (P = 0.02) and MonoHaem (P = 0.04) had significantly lower overall positivity rates; for Hemolex the decrease was not significant (P = 0.3). The lower positivity rate with moist samples is important, given that 11 of the 13 laboratories in the study stated that they receive at least some samples in moist form. Thus, technician training and laboratory procedure need to be reviewed to maximize the benefits of faecal occult blood testing in clinical practice, especially with its expanding role in colorectal cancer screening.

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.

Intention to screen for colorectal cancer among white male employees

BACKGROUND

This study identifies factors associated with employee intention to participate in a company-sponsored program of continuous screening for colorectal cancer. Automobile industry pattern and model makers who had been offered screening for over a decade were included in the study.

METHODS

Data were collected at the outset of a randomized trial of screening and nutrition interventions. A baseline survey was mailed to 4,490 white men without a history of colorectal cancer. This mailing generated complete responses from 2,693 (60%) individuals. Survey data obtained for these men, including measures of cognitive and psychological representations related to colorectal screening, social influence, and intention to screen, were supplemented by background information gathered from employment records of these men. Workplace screening services were documented via a survey of plant health care professionals.

RESULTS

Fifty-eight percent of respondents reported a high level of intention to screen. Multivariate analyses showed that intention to screen was positively associated with employee past participation in screening, belief in the salience and coherence of screening, belief in screening efficacy, perceived self-efficacy, belief that polyp removal prevents colorectal cancer, perceived personal susceptibility to colorectal cancer or polyps, receptivity to family member support for screening, and workplace scheduling of screening examinations.

CONCLUSIONS

Factors associated with intention to screen may contribute to participation in continuous screening programs. Research is needed to assess the impact of interventions that facilitate appointment scheduling, provide tailored education about screening, and encourage lay support.

Enteroscopy for the initial evaluation of iron deficiency

BACKGROUND

Occult gastrointestinal blood loss is generally investigated with colonoscopy and esophagogastroduodenoscopy in patients with iron-deficiency anemia. The aim of this study was to prospectively measure the additional diagnostic yield of examining the jejunum at the time of upper endoscopy in patients with iron-deficiency anemia.

METHODS

Asymptomatic patients with newly diagnosed iron-deficiency anemia who had no identifiable source of blood loss at colonoscopy underwent standard esophagogastroduodenoscopy with the Olympus SIF100L enteroscope followed by overtube-assisted enteroscopy. Upper tract and jejunal sources of blood loss were noted. Biopsy samples from the small bowel were taken when a bleeding lesion was not identified.

RESULTS

Thirty-one consecutive patients (13 men, mean age 71) with no gastrointestinal symptomatology were studied. Eleven patients (35%) had a bleeding source that required only esophagogastroduodenoscopy for identification; 8 patients (26%) had a source only in the jejunum; 2 patients (6%) (one with sprue) had a source in upper tract as well as jejunum. The enteroscopy was rated as causing minimal or mild discomfort in 25 of 31 patients (81%). Using Medicare reimbursement figures, a strategy of performing esophagogastroduodenoscopy first would have cost $656 per patient, whereas the strategy of performing esophagogastroduodenoscopy with enteroscopy as the initial test in all patients costs $467 per patient.

CONCLUSIONS

Performance of push enteroscopy along with esophagogastroduodenoscopy increases the diagnostic yield from 41% to 67% when evaluating the upper gastrointestinal tract of asymptomatic patients with iron-deficiency anemia and, because of a lower cost, should be the preferred initial diagnostic test.

Screening for colorectal cancer reduces emergency admissions

AIMS

Colorectal cancer is common and accounts for over 15,000 deaths annually in England and Wales. Up to 30% of these patients require emergency surgery. Screening for colorectal cancer can reduce the mortality of colorectal cancer. This study addresses the impact of a population-based screening study on emergency admissions with colorectal cancer.

METHOD

From 1981 a randomized trial of Faecal Occult Blood (FOB) screening has been undertaken in the Nottingham area, recruiting over 150,000 patients. The present study examined the records of patients enrolled in this study who presented as an emergency with colorectal cancer.

RESULTS

Colorectal cancer was identified in 1962 cases, of which 468 (23.9%) presented as emergencies. The overall compliance was 60% (proportion of individuals completing at least one test). There were significantly fewer emergencies in the Screen-detected group compared with the Control group (P = < 0.0001). This group also had a significantly reduced 30-day mortality and a lower stoma rate than the Control group. Conversely the Non-responders had a significantly greater proportion of emergency admissions and a significantly increased stoma rate compared with the Control group.

CONCLUSIONS

Screening for colorectal cancer using a faecal occult blood test can significantly reduce the number of emergency presentations with colorectal cancer. It is likely that the introduction of a national programme of screening for colorectal cancer would lead to increased compliance and that this would lead to a significant reduction in the emergency workload on the National Health Service from colorectal cancer.

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.

Cost analysis in a population based screening programme for colorectal cancer: comparison of immunochemical and guaiac faecal occult blood testing

OBJECTIVE

To compare the costs of colorectal cancer (CRC) screening by two faecal occult blood tests (FOBT)-namely, Hemoccult (guaiac based) and reversed passive haemagglutination (RPHA) tests. RPHA was interpreted according to two positivity thresholds (+ or +/-).

METHODS

Attenders performed both tests. Subjects with a positive FOBT test were invited to have a complete exploration of the colon. The total costs for every 10,000 screened subjects and costs for each unit of result (screened subject, or patient with adenoma/s or cancer detected) were calculated for both tests.

RESULTS

8353 subjects were enrolled. A total of 2109 repeated screening after two years. RPHA(+ and +/-) showed the highest and RPHA(+) the lowest positivity rate at first screening. The Hemoccult positivity rate was highest at repeat screening. Total costs of screening by RPHA(+ and +/-) were highest as this method had the highest recall rate. Screening by RPHA(+) was the least costly. Costs for each screened subject were highest for RPHA(+ and +/-) and lowest for RPHA(+). Costs for each cancer detected were lowest for RPHA(+) and highest for Hemoccult or RPHA(+ and +/-) in subjects aged > 49 or < 50, respectively. Costs for subjects with detected adenoma/s of > 9 mm were lowest for RPHA(+ and +/-) and highest for Hemoccult. At repeat screening total costs of RPHA(+ and +/-) were lower than at first screening, whereas for each subject with cancer or adenoma/s costs were increased.

CONCLUSIONS

Our data confirm that screening by RPHA is more cost effective than by Hemoccult.

Participation in faecal occult blood screening for colorectal cancer in a well defined French population: results of five screening rounds from 1988 to 1996

OBJECTIVE

To evaluate the influence on compliance of demographic variables and of the way of proposing a faecal occult blood test in a colorectal cancer mass screening programme.

SETTING

Well defined population in Burgundy (France).

METHODS

From 1988 to 1996 five screening rounds were conducted in people aged 45 to 74 on entering the study. The screening test was provided free of charge by primary care physicians over a four month period, then mailed to non-consultants, followed by a potential reminder letter. The whole population was invited to participate in each screening campaign.

RESULTS

During the five successive rounds, compliance was 52.8%, 54.0%, 57.3%, 58.3%, and 56.2%. It was higher in women than in men, in those initially aged 50 to 69 than in the extreme age groups, and in urban than in rural areas. Overall, 68.7% of the invited population completed at least one screening test and 37.2% completed the five rounds. Among those who participated once in a screening campaign, between 79.6% and 87.6% participated in the succeeding ones. Compliance was higher when the test was proposed by GPs (varying between 85.2% and 94.0% according to the screening campaign) than when it was sent by post (varying between 26.0% and 33.7%).

CONCLUSION

In France, a participation rate of over 50% can be achieved in colorectal cancer screening by means of a faecal occult blood test. To achieve this, primary care physicians have to play an active part in the programme and the test must be mailed to non-consultants.

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.

Colorectal cancer mass-screening: estimation of faecal occult blood test sensitivity, taking into account cancer mean sojourn time

Mass screening using the faecal occult blood test (FOBT) can reduce mortality from colorectal cancer. Reliable estimation of FOBT sensitivity is crucial in assessing the potential effectiveness of a mass-screening procedure. Available estimates could be inaccurate because they neglect the temporal aspect of screening. The aim of our study was to estimate the sensitivity of the FOBT in mass screening for colorectal cancer, taking into account the duration of the pre-clinical phase of the disease assessed by the mean sojourn time (MST), and to assess whether MST and FOBT sensitivity differ according to cancer subsite. We analysed data taken from the first round of the mass-screening programme of the department of Calvados (France), involving 164,364 subjects of whom 43.4% participated in FOB screening. MST and sensitivity were estimated using a simple empirical approach, a traditional maximum likelihood method and log-linear modelling using the Bayesian technique of Gibbs sampling. MST was estimated as between 4.5 and 5 years for all subsites combined. According to the Gibbs sampling method, MSTs were 3.5, 6.4 and 2.6 years for proximal colon, distal colon and rectal cancer, respectively. Our estimation methods give a low sensitivity for the FOBT (50%), results for different subsites being closer to each other, slightly higher for proximal cancer. Our results strongly suggest that tumour growth rates are very different according to subsite, slowest for distal cancer and speediest for rectal cancer. Consideration of FOBT sensitivity without MST appears unreliable. Our results by subsite suggest that combining FOBT and sigmoidoscopy could be a good strategy for colorectal cancer screening.

Measuring effectiveness of lung cancer screening: from consensus to controversy and back

BACKGROUND

While intense controversy exists regarding screening for breast, colorectal, and prostate cancer, a consensus exists regarding lung cancer screening. All organizations recommend against any efforts to detect early lung cancer because each of four randomized controlled trials (RCTs) has failed to demonstrate a significant reduction in lung cancer mortality as a result of screening.

SYNTHESIS

Disease-specific mortality is assumed to represent the best measure of screening effectiveness in RCTs, because it is not subject to confounding by lead time, length, or overdiagnosis biases. However, the effects of these biases are predictable, so accurate assessments of the degree of confounding by these biases can be made. Moreover, the ability of mortality to accurately reflect cancer death rates depends on the ability of randomization to create experimental and control populations that have an equal risk of dying of the disease under study, except insofar as early detection may reduce that risk. Because the majority of participants in screening trials never develop the disease under investigation, small absolute differences in disease risk between groups often persist despite randomization, and such differences translate into much larger proportional differences in the size of subgroups at risk for disease-specific mortality. This effect confounds the ability of disease-specific mortality to accurately measure screening effectiveness.

RESULTS

A total of 18 RCTs have been conducted to evaluate screening for breast, colorectal, and lung cancer. In the only two RCTs that reported a significant mortality reduction for screening mammography in breast cancer, and in the one RCT that reported a significant mortality reduction for fecal occult blood screening in colorectal cancer, population differences led mortality comparisons to overestimate the effectiveness of screening. In lung cancer, no significant mortality reductions have been reported (to my knowledge), but in the two RCTs most directly addressing the effectiveness of chest radiograph (CXR) screening, population differences led mortality comparisons to underestimate the ability of CXRs to reduce the risk of dying of lung cancer. Although mortality is believed to be the best measure of outcome, not a single example can be cited as definitive proof of efficacy for any screening strategy. Thus, screening cannot be recommended for any cancer on the basis of consistent reductions in mortality in RCTs.

ANALYSIS

Current policy, which calls for no early detection efforts for lung cancer, implicitly accepts the validity of two contradictory assertions. Conventional wisdom maintains that lung cancer is a highly virulent disease and that metastases are present at inception; accordingly, early detection is ineffective. However, RCTs suggest that lung cancer is an indolent disease and that radiographically detected lesions are clinically unimportant; accordingly, early detection is unnecessary. Such contradictions mandate some rethinking of the fundamental assumptions underlying screening evaluation.

CONCLUSIONS

Considerable evidence suggests that annual CXR screening could result in a dramatic reduction in lung cancer mortality in our society. However, proper interpretation of the data depends completely on how screening effectiveness is measured. Given the enormous public health importance of this issue, a consensus conference is recommended to determine whether lung cancer screening can save lives.

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.

Fecal occult blood screening in the Minnesota study: role of chance detection of lesions

BACKGROUND

In the Minnesota Colon Cancer Control Study, annual fecal occult blood testing reduced mortality from colorectal cancer by at least 33.4%. Some attribute a large part of this reduction to chance detection of cancers by colonoscopies; rehydration of guaiac test slides greatly increased positivity and consequently the number of colonoscopies performed. This study was conducted to determine how much of the reduction resulted from chance detection.

METHODS

We used a mathematical model developed by Lang and Ransohoff to estimate the proportion of the 33.4% mortality attainable by chance alone. Applying the model requires the specification of five parameters: duration of follow-up, rate of compliance with fecal occult blood testing, rate of compliance with colonoscopy, positivity rate, and efficacy of colonoscopy in reducing colorectal cancer mortality. We took values for four of the five parameters directly from the Minnesota study. For the fifth parameter, efficacy of colonoscopy, we selected a value of 60%, based on the conclusions of another study. Whereas the Lang-Ransohoff model selects persons for colonoscopy by chance alone, those with bleeding cancers would also be selected by sensitive fecal occult blood testing. We therefore adjusted the result of the Lang-Ransohoff model for this dual detectability.

RESULTS

We found that 16%-25% of the reduction in colorectal cancer deaths effected by fecal occult blood testing in the Minnesota study was due to chance detection; the remainder was due to sensitive detection.

CONCLUSION

Chance played a minor role in the detection of colorectal cancers by fecal occult blood testing in the Minnesota study.

Fecal occult blood screening in the Minnesota study: sensitivity of the screening test

BACKGROUND

In the Minnesota Colon Cancer Control Study, which used guaiac slides to annually screen stool samples for blood, mortality from colorectal cancer was reduced by 33.4%. The reported sensitivity of this test for colorectal cancer was about 90%. However, results from another study estimated the sensitivity to be 25%-33%; other investigators have reported intermediate values. Given these contradictions, we examined screening sensitivity for colorectal cancer in the Minnesota study by several direct and indirect methods.

METHODS

In this reanalysis of data from the Minnesota study, we distinguished between sensitivity for colorectal cancer of the screening test (composed of six slides) and of the screening program (a series of such tests). We estimated screen sensitivity by adjusting the crude estimate from the final tests in each screening phase for colorectal cancer incidence in 5 years of follow-up, by modeling guaiac slide results at each screen as a function of the presence of occult blood, and by incorporating sensitive detection into a modification of a mathematical model developed by Lang and Ransohoff. Program sensitivity was estimated from the fraction of screen-detected cancers among all cancers diagnosed in screened individuals.

RESULTS

The crude estimate of program sensitivity was 89.4%, whereas the modified Lang-Ransohoff model estimates screen sensitivities at 94.1%-96.2%, consistent with the estimates from the other methods. Indirect measures, such as the association between the number of positive slides among the six slides in each set and the positive predictivity for colorectal cancer, are consistent with these estimates.

CONCLUSIONS

The Minnesota study reduced mortality from colorectal cancer through use of a screening test with average screen and program sensitivities of about 90%.

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.