The earlier detection of colorectal cancers: a preliminary report of the results of the Occult Blood Study

Improved screening for colorectal cancer by immunological detection of occult blood

A radial immunodiffusion technique for detecting faecal haemoglobin and the Hemoccult II kit used with and without rehydration of the faecal sample were compared in a screening programme for bowel cancer, in which 1328 subjects took part. A positive result was obtained in 170 (13%) subjects. Nineteen of the 153 subjects investigated were found to have colorectal carcinomas and 52 had polyps (40 with adenomas). Radial immunodiffusion and Hemoccult II with and without rehydration detected bleeding in, respectively, all 19, 15, and 11 subjects with colorectal carcinoma. Hemoccult II with and without rehydration detected only seven and six, respectively, of 11 Duke's stage A carcinomas, whereas all 11 were detected with the immunological test. Hemoccult II with and without rehydration and radial immunodiffusion detected bleeding from adenomas in, respectively, 22, 14, and 34 of the 40 subjects. False positive results occurred in 55 out of 1302 subjects by Hemoccult II with rehydration, in 28 out of 1304 by Hemoccult II without rehydration, and in 50 out of 1304 by the immunological technique; true positive results were defined as bleeding from carcinomas and adenomas. Immunological detection of occult blood in faecal samples seems to show more adenomas and carcinomas (particularly early lesions) than the Hemoccult II kit and has a rate of false positive results that is acceptably low.

Cost effectiveness of HemoQuant versus Hemoccult for colorectal cancer screening

Initial reports on HemoQuant, a new quantitative test for occult gastrointestinal bleeding, suggest it is more sensitive than Hemoccult. Increased detection of upper gastrointestinal tract bleeding and dietary hemoglobin may reduce HemoQuant's specificity in the screening setting. The authors performed a cost effectiveness analysis comparing Hemoccult and HemoQuant for colorectal cancer screening using assumptions based on probabilities and costs in the current literature, varying the specificity of HemoQuant. The analysis showed the marginal cost effectiveness of Hemoccult versus no test to be $43,000, and HemoQuant versus Hemoccult to be $296,000 if HemoQuant specificity is 0.95. The marginal cost effectiveness ratio increased to $601,000 if three HemoQuant tests were used. Survival benefit was small and highly dependent on Hemoccult sensitivity and mortality from colonoscopy if HemoQuant specificity was less than 0.9. The authors conclude that unless the high sensitivity reported for HemoQuant is accompanied by a specificity comparable to that of Hemoccult, HemoQuant may not be an acceptable alternative for colorectal cancer screening.

Colonoscopic detection of early colorectal cancers. Impact of a surgical endoscopy service

The Surgical Endoscopy Service has been aggressively evaluating gastrointestinal symptoms with colonoscopy and screening asymptomatic patients with flexible sigmoidoscopy in hopes of finding early curable colorectal cancers. The purpose of this study was to compare the stages of colorectal cancers resected during the 18-month period prior to (Pre-SES) and during the first 18 months (Post-SES) after the creation of the Surgical Endoscopy Service. In addition, the yield of lesions that would have been obtained by depending upon patient symptoms or occult blood testing were determined. A total of 361 colonoscopies were performed Pre-SES and 874 colonoscopies Post-SES; 26 patients underwent resection of colorectal cancers Pre-SES and 32 Post-SES. Whereas early colorectal cancers (Dukes' A and B1) were found in only three patients (12%) Pre-SES period, early cancers were found in 13 (41%) Post-SES. Doubling the number of colonoscopies produced a fourfold increase in the number of early lesions. Furthermore, disseminated cancers (D lesions) dropped from 19% Pre-SES to 3% Post-SES. Among the total 58 patients, 43% of the A lesions and 40% of the B1 lesions were asymptomatic. Even more alarming, 86% of the A lesions, 50% of the B1 lesions, 31% of the B2 lesions, and 14% of the C2 lesions were occult blood negative. Indeed, only the D lesions were uniformly occult blood positive. This study demonstrates that aggressive colonoscopy detects early colorectal cancers. Moreover, patient symptoms or occult blood testing will fail to indicate the majority of early colorectal cancers.

Endoscopy versus double-contrast barium enema in the evaluation of patients with symptoms suggestive of colorectal carcinoma

Two hundred seventy-six patients with positive findings on a stool guaiac test, hematochezia, a change in bowel habits, or a family history of colorectal carcinoma were referred to the colorectal clinic for further investigation. There were 105 men and 171 women. All patients underwent examination with the 65 cm flexible sigmoidoscope. Patients with no abnormalities on endoscopy underwent a double-contrast barium enema. If the barium enema revealed a polyp or other suspicious pathologic process, the patient was referred for colonoscopy. In 258 patients, findings of barium enema and flexible sigmoidoscopy were in agreement. The findings in 178 of these examinations were completely negative, and in the remaining 80 cases flexible endoscopy and barium enema revealed diverticulosis. In an additional 18 patients, negative findings on flexible sigmoidoscopy were followed by positive findings on barium enema. Thirteen of these 18 patients (72 percent) had negative findings on colonoscopies and therefore had false-positive findings on barium enema. In the remaining five patients (28 percent), an unsuspected colonic carcinoma or premalignant polyp was discovered on barium enema and documented by colonoscopy. Also, in four of these five patients, colonoscopy found additional polyps that were not seen on barium enema.

Perception errors with double-contrast enema after a positive guaiac test

Between 3 and 6 of 12 colorectal neoplasms larger than 1 cm in diameter were overlooked by each of 4 radiologists in 117 individuals investigated with double-contrast enema (DCE) after a positive guaiac test. Even when the individual results of 2, 3, or 4 experienced radiologists were combined, 2 small carcinomas were overlooked due to perception errors. One of these carcinomas was diagnosed by rectosigmoidoscopy, which is an important and necessary complement to DCE. Although small carcinomas may be missed even with this combination, meticulous exploitation of the 2 methods is absolutely necessary to minimize the risk of missing a colorectal neoplasm. A drawback when 2 or more radiologists read the radiographs is the increased number of false-positive findings.

Evaluation of an immunochemical test for faecal occult blood in screening for colorectal neoplasia in a high risk group

A group of 1615 asymptomatic individuals presumed to be at increased risk of colorectal neoplasia were selected as the study group. All were tested by an immunochemical test for faecal occult blood. In the second half of the study, individuals who were occult blood negative were offered colonoscopy. Ninety-nine individuals (6.1%) returned stools which were occult blood positive. Investigation by full colonoscopy was possible in 90 cases, revealing nine patients (10%) with invasive cancers, four patients (4.4%) with carcinomata in situ, and 36 patients (40%) with adenomata. Non-neoplastic pathology capable of producing occult blood positive stools was found in 31 individuals (34.4%). No pathology was found in 10 instances (11.1%). Of the 53 occult blood negative subjects who underwent colonoscopy, eight were found to have adenomata. Only one of these was larger than 5 mm in diameter (18 mm). No carcinomata were found. The site within the large bowel of the tumour did not appear to significantly affect the occult blood status of the faeces but the size of the tumours detected suggests that the presence of blood within the stool is more likely to be associated with larger lesions. The frequency of detection of both carcinomata and adenomata was greatest in individuals who had a past history of colorectal neoplasia. The individual cost of this immunochemical test is nominal. The high diagnostic yield and low false positive and negative rates suggest that case follow-up, surveillance, or screening utilizing this test is justified.

The pros and cons of fecal occult blood testing for colorectal neoplasms

Testing feces for occult blood is widely recommended as a means of detecting subclinical colorectal tumors. Guaiac tests such as Hemoccult are the most widely used, but chemical sensitivity is relatively low and the tests are affected by dietary peroxidases, the state of fecal hydration, and certain drugs. The newly devised HemoQuant and immunologic techniques appear more sensitive and specific, but they require further evaluation before widespread clinical usage can be recommended. Occult blood screening has both merits and weaknesses. Testing does uncover subclinical colorectal cancer, often at a relatively early stage, but whether this actually improves the prognosis remains to be proven. Benign neoplastic polyps are also detected, although it is debatable whether this is a valid rationale for screening. Test sensitivity for malignancy varies from good to moderate, but is poor for benign polyps. Specificity is usually around 97%-98%, yet the predictive value of a positive test for cancer is only about 10%; hence most test-positive individuals are needlessly subjected to invasive colonic investigations. Reported figures on public compliance with occult blood testing vary widely from excellent to poor. Published costs of screening are usually quite low, but these overlook important indirect and hidden expenses and are therefore misleading. On balance, the problems of occult blood testing currently appear to outweight the merits. This could change, however, with the newer testing techniques and with awaited mortality data from controlled clinical trials now underway.

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

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

Use of preventive care by the elderly

Use of five early disease detection tests was examined in relation to history of specific chronic disease and other health habits, as part of a cohort study including 11,888 residents of a retirement community in Southern California. Self-reported utilization rates by residents in the year preceding study entry were approximately 90, 30, 60, and 10% for blood pressure measurement, fecal occult blood test, Papanicolaou test, and mammography, respectively. Breast self-examination was practiced by 37% of the women on a regular basis. With the exception of the Pap test and blood pressure check, the majority of the study population did not use preventive procedures at the recommended frequencies. The most important determinants of use of screening tests in this elderly population were previous diagnosis of chronic disease, especially of the disease detected by the test itself, and having a regular physician. These two factors appeared to affect use independently.

Physician accuracy in diagnosing colorectal polyps

Since the medical management of persons with adenomatous colorectal polyps differs from that of those with hyperplastic polyps, accuracy of diagnosis is essential. Although many physicians have grown confident that their skills of visual diagnosis are adequate, few data exist to support this confidence. In order to examine the accuracy of physicians' judgments regarding colorectal polyp histology, the visual diagnosis of physicians experienced in endoscopy was compared with the histologic report. Eighty-one polyps were discovered by flexible sigmoidoscopy among 718 participants in a colon cancer screening program. Eighty percent of all polyps were detected accurately. The diagnostic sensitivity of detecting adenomas was 69 percent, while specificity (accurate diagnosis of hyperplastic polyps) was 86 percent, and there were an additional eight false negative and eight false positive diagnoses. Further analyses revealed that there are individual patterns of diagnostic mistakes made by physicians and that mistakes frequently are related to polyp size. These findings are particularly important in light of the expanding numbers of relatively inexperienced primary care providers performing flexible sigmoidoscopy whose diagnoses may be strongly dependent on polyp size.

Screening for colorectal cancer in a high-risk population. Results of a mathematical model

A mathematical model was used to estimate the cost-effectiveness of colorectal cancer screening strategies for people who are at high risk because of a first-degree relative with colorectal cancer. The model uses indirect evidence about such factors as cancer incidence, sensitivity and specificity of different tests, and treatment effectiveness. The analysis indicates that for screening people over 40 yr old an annual fecal occult blood test may reduce colorectal cancer mortality by about one-third, either colonoscopy or barium enema may reduce mortality by approximately 85%, a 3-5-yr frequency for endoscopies or barium enemas preserves 70%-90% of the effectiveness of an annual frequency, and beginning screening at age 50 reduces effectiveness by 5%-10%. Although both barium enemas and colonoscopies appear to be effective in reducing mortality, the lower cost of the barium enema makes it a more cost-effective strategy. All of these estimates depend on the baseline estimates of each of the factors incorporated in the model; the conclusions are most sensitive to assumptions about the natural history of adenomatous polyps, the bleeding of adenomas and presymptomatic cancers, and the sensitivity of the fecal occult blood test. Recommendations about colorectal cancer screening must also consider factors such as discomfort, inconvenience, and the availability of various technologies.

The macrophage migration inhibition (MIF) assay as a marker of colorectal cancer. Studies in patients with colorectal cancer, noncolonic neoplasms, and conditions predisposing to colorectal cancer

A specific macrophage migration inhibition assay, using patient lymphocytes incubated with a human colonic cancer extract, was studied in 92 patients with proven colorectal cancer and in 134 other individuals (20 normal controls, 80 patients with various nonmalignant gastrointestinal diseases, and 34 patients with extracolonic malignancies). A positive response was obtained in 78 of 92 colorectal cancer patients, but in none of the 20 normal controls. A positive response occurred in four of 34 patients with extracolonic malignancies and in approximately half of patients with colonic adenomas and in one third of patients with ulcerative colitis. The significance of positive results in these patients (with diseases considered premalignant) is unclear, and is being studied further. In patients with previous resection of colorectal cancers, positive responses were frequent during the first year following resection, and rare thereafter. The results suggest that this method may be useful as a clinical marker for colorectal cancer, and warrants further technical refinement and study of specific patient populations.

The workup of the asymptomatic patient with a positive fecal occult blood test

Twenty-two protocols for working up an asymptomatic patient who has a positive fecal occult blood test were evaluated using existing information on the prevalences of cancers, adenomas and other conditions in such patients; the natural history of colorectal cancer; the effectiveness of screening tests; risks; and costs. The authors estimate the impacts of the 22 workup strategies on outcomes such as the chance of finding an existing cancer or adenoma, risks (bleeding and perforation), and financial costs of different strategies involving rigid sigmoidoscopy, flexible sigmoidoscopy, barium enema, and colonoscopy. Two protocols were particularly effective. The first involves performing a barium enema study and following it with colonoscopy; if colonoscopy is negative, the barium enema study should be repeated. The second is to perform colonoscopy and if it is negative, follow it with a barium enema study.

Diagnostic accuracy of double-contrast enema and rectosigmoidoscopy in connection with faecal occult blood testing for the detection of rectosigmoid neoplasms

Four hundred and fifty-eight consecutive subjects with a positive faecal guaiac test when screened for early detection of colorectal neoplasms were investigated with double-contrast enemas and rectosigmoidoscopy (60 cm). The results of these two methods were compared. The radiologists and endoscopists were unaware of the result of each others' examination at the time of their own investigation. Altogether ten subjects with carcinoma in the rectosigmoid area were found. The radiologists and endoscopists each overlooked four of these ten carcinomas and only four of the carcinomas were diagnosed with both methods. Fifty-six of one hundred and seven adenomas were 1 cm or larger in diameter and located in the rectum or the sigmoid colon. Thirteen of the fifty-six adenomas were missed by double contrast enema and ten by endoscopy and only thirty-three adenomas were diagnosed with both methods. Neoplasms in the rectum and the sigmoid colon are sometimes difficult to diagnose with both radiology and endoscopy. Rectosigmoidoscopy (60 cm) should therefore be used as a complement to double contrast enemas if this method is chosen for investigation of a patient with rectal bleeding.

Evaluation of possibilities for mass screening for colorectal cancer with Hemoccult fecal blood test

Data from a health survey including the Hemoccult fecal blood test, together with official cause-specific death rates, were used to assess the magnitude of a controlled trial that would be required to prove a 25 percent reduction of the mortality from colorectal cancer associated with screening. All men in three age groups in the city of Malmö, Sweden, were invited, but 46 percent did not participate in, the Hemoccult screening. One carcinoma and 89 adenomas were detected in 56 of the 2422 who did. With the risk function used in our calculation and a compliance rate of 60 percent, a study population among 45- to 69-year-olds of 605,000 is required to prove an expected 25 percent reduction of the mortality with 90 percent power. Considering the size of such a trial, we question whether a controlled trial is feasible. With known risk functions for death from all causes and death from colorectal cancer, the study population was calculated using variable statistical power, participation rate, and risk reduction. Statistical methods and computer programs are given. In addition, alternative study models to assess the benefits associated with screening are discussed.

How important is rectal bleeding in the diagnosis of bowel cancer and polyps?

Overt bleeding from the anus is a common symptom of colorectal cancer but most frequently arises from a benign anal source. The aim of this study was to determine how successfully general practitioners and gastroenterologists could differentiate anal from colorectal sources of bleeding before full colonic investigation. 145 consecutive patients aged 40 years and over who had presented to a GP with rectal bleeding of less than 6 months' duration were referred to a specialist for total colonic investigation. The source of bleeding was diagnosed as colorectal cancer in 15 patients (7 stage A, 3 stage B) and polyps in 11. Of 63 patients in whom GPs predicted an anal source of bleeding only, 11 were ultimately found to be bleeding from a colonic or rectal source. The gastroenterologists (after rigid sigmoidoscopy) predicted an anal source of bleeding in 97, in 5 of whom the source was ultimately found to be colorectal. All patients aged over 40 who present with recent rectal bleeding should be referred for full colonic investigation.

Factors affecting compliance in colorectal cancer screening. Results of a study performed in Ballarat

Non-compliance in screening programmes for colorectal cancer is likely to be the most important factor limiting the impact of screening on mortality. This study aimed to determine risk factors and correlates of compliance that could be readily identified by general practitioners. A total of 581 eligible subjects aged 40 to 75 years completed a questionnaire that covered demographic factors, personal medical history, family history of colorectal cancer and smoking status. Faecal occult blood tests were then offered by the general practitioner and compliance correlated with responses. The over-all compliance was 44% and increased to 51% for those who accepted the self-testing kit at consultation. For men, compliance increased with increasing level of education and was significantly greater for non-smokers than for smokers. For women, compliance increased with increasing age, and was greater for those with either symptoms and/or a family history of colorectal cancer. A doctor group-practice factor appeared to influence acceptance versus refusal of the test kit from the doctor. A triage approach to screening in general practice may improve over-all compliance and the yield of tumours. With this strategy, patients at high risk (for example, those with a family history of colorectal cancer or in older age groups) are identified first. Particular attention should be given during consultation to those at high risk who have poor compliance profiles (for example male smokers with a family history of colorectal cancer). High-risk subjects with high compliance profiles would need less attention and low-risk individuals would need least attention.

[Early diagnosis of colorectal cancer: technical problems and acceptability]

There has been little change in the survival rate of colorectal cancer over the last 20 years. Earlier diagnosis probably offers the best hope for improving this survival. At the present time, the only practical method of population screening is by the detection of occult blood in the faeces. Almost all published screening trials are uncontrolled. Although cancer detected by occult blood screening tends to be at a relatively early stage, only controlled trials can answer the critical question of whether screening decreases mortality from bowel cancer. High risk patients (prior adenoma or colorectal cancer, extensive colitis of more than 10 years duration, family history of polyposis) should have colonoscopy at regular intervals.

[Methodological framework of the evaluation of systematic screening and treatment of preexistent lesions of the colon and the rectum]

Among the conditions which need to be filled when generalizing the mass screening of polyps in view of the secondary prevention of colorectal cancers, three are already present: 1) it is a frequent and serious cancer; 2) there is an affiliation between benign tumours and cancer; 3) an effective non-mutilating treatment of benign tumours is available. On the other hand, two additional conditions remain unfilled and yet lie within the domain of research by methodologically rigorous studies: the setting up of a screening test with a high cost-effectiveness relationship; the epidemiological demonstration of the decreasing incidence of colorectal cancers following screening and treatment of precancerous lesions.

The current status of early detection and screening for colorectal cancer

There are several approaches to the early detection of colorectal cancer that currently are in use in various segments of the health care system. Herein, the status of cancer control research regarding symptom and risk factor assessment, sigmoidoscopy and colonoscopy, double contrast barium enema, and fecal occult blood testing is reviewed. In addition to the different technologies of early cancer detection, there are different models of disease control intervention. These include the routine clinical activities of primary care providers as well as programmatic screening of mass populations. The currently available techniques for early colorectal cancer detection appear better suited for existing patient care settings than for programs outside the direct supervision and follow-up of the health professional.

Guaiac tests for detection of occult faecal blood loss in patients with endoscopically verified colonic polyps

To evaluate the sensitivity of guaiac tests for colonic polyps, two tests were made on occult blood in faeces--Hemoccult II and Fecatwin-S--from 625 and 549 patients, respectively, referred for colonoscopy. Polyps were found in 212 and 194 patients, and these had one or more tests positive in 41% (Hemoccult II) and 48% (Fecatwin-S). The incidence of positive tests was greater for polyps situated in the transverse, descending, and sigmoid colon; for polyps with a stalk, villous elements, and dysplasia; and especially for large polyps. Although size was the most important factor for the bleeding tendency, at least one third of patients with polyps over 10 mm in diameter had no positive guaiac reactions. In patients at high risk of developing polyps, therefore, these tests cannot replace, but may well be supplementary to, radiography with double-contrast technique and colonoscopy.

Cost benefits of hemoccult screening for colorectal carcinoma

Hemoccult screening for colorectal carcinoma was begun in 1979 at the Kaiser Permanente Medical Center, Oakland, California, as part of a program for periodic health examinations. A concomitant cost-benefit analysis was conducted to determine the long-term medical care costs and survival benefits of this procedure. Of 14,041 patients greater than or equal to 45 years of age mailed hemoccult slides, 10,255 (70.3%) returned them at the time of their examination. One hundred twelve (1.1%) were positive, and 12 colorectal carcinomas were detected. Additionally, 13 patients with one or more polyps greater than or equal to 1 cm and 45 patients with other gastrointestinal sources of blood were found. Of the screened cases of colorectal carcinoma, 50% were in Dukes' stage A compared with 25% found in this stage in our institution in 1974, when screening was not done. Five-year Dukes' stage-specific medical care costs and mortality rates were developed from the 1974 cases and were then applied to the screened cases of colorectal cancer. A savings in medical care costs of +14,685 and a projected increase of 22 years in life expectancy was found.

Immunochemical testing for faecal occult blood in patients with colorectal cancer

Eighty-six stool specimens collected from 36 patients with colorectal cancer were tested for occult blood by chemical and immunochemical methods. There was no dietary restriction. Positive results were obtained in 94% of patients by the immunochemical method when the presence of any positive immunochemical test was taken as a positive result. If greater than 1 mg of haemoglobin per gram of faeces was regarded as positive result, then 75% of patients would have been diagnosed as having occult blood in the stool by means of the immunochemical method. Positivity rates for Hemoccult II and rehydrated Hemoccult II were 53% and 81%, respectively.

The clinical value of Haemoccult and Fecatwin in the detection of colorectal neoplasia in hospital and general practice patients

Four hundred and fifty asymptomatic general practice patients and 330 hospital inpatients had their stools tested for occult blood with the Haemoccult and Fecatwin methods. In general practice, 9/64 (14%) of patients with a positive result had a colonic neoplasm (three carcinomas, one Dukes' Stage A, two Dukes' Stage C, six adenomas) and in hospital 12/142 patients (8%) were found to have colonic tumours, (nine carcinomas, two Dukes' Stage A, two Dukes' Stage B, five Dukes' Stage C and three adenomas). The overall detection rates for colonic neoplasia were 2% in general practice and 3.4% in hospital. In 2 years of follow-up, none of the general practice patients have presented with colonic symptoms. Two hospital patients with colonic carcinomas produced negative tests with both methods. Out of the total of 21 colonic neoplasms, nine were detected by Fecatwin alone, but this trend in favour of the more sensitive test did not reach the 5% level of statistical significance. In contrast, the number of false positive results were significantly greater with Fecatwin than Haemoccult. From our data it would appear that the Fecatwin method warrants assessment in a full controlled trial of its value as a population screening test for colonic cancer.

Fecal blood levels in health and disease. A study using HemoQuant

We tested HemoQuant, a quantitative assay of fecal blood based on the fluorescence of heme-derived porphyrin, in 106 healthy volunteers, 170 patients with gastrointestinal symptoms but with normal diagnostic studies, 44 patients with gastrointestinal cancer, 75 patients with benign polyps, and 374 patients with a variety of other benign gastrointestinal lesions, including ulcers and erosions. In 98 per cent of the healthy volunteers, fecal hemoglobin concentrations were less than 2 mg per gram of stool. Levels were similarly low in stools from patients with symptoms and normal studies and in patients with relatively minor benign lesions. Within these groups, levels were slightly higher in those who had ingested red meat or aspirin. The fecal hemoglobin concentration was higher in patients with gastrointestinal cancer than in any other group, and 97 per cent of those with colorectal cancer had levels above 2 mg per gram. The sensitivity of HemoQuant was significantly greater than that of the guaiac test Hemoccult, particularly when heme was degraded or stools were dry. Intestinal degradation of heme to porphyrin can be measured separately by HemoQuant, and was greater when bleeding was from proximal lesions rather than distal ones. We conclude that HemoQuant is a more sensitive measure of gastrointestinal bleeding than Hemoccult, and that its capacity to measure degraded heme may be useful in indicating the anatomic site of bleeding.

Occult blood screening for colorectal carcinoma: a critical review

The author reviews the literature on occult blood surveillance for colorectal carcinoma. The guaiac-based Hemoccult (SmithKline Diagnostics, Sunnyvale, Calif.) test is the most reliable and widely used. However, testing is complicated by several technical issues that can affect clinical results, and even successful screening programs will miss a high proportion of tumors. Public compliance is often poor, and a number of indirect and "hidden" costs make surveillance programs much more expensive than is usually claimed. Almost all published screening trials are uncontrolled. They generally detect about 3-20 colorectal malignancies for every 10,000 people enrolled, but only about 5%-10% of occult blood reactions are due to cancer. Though screen-detected tumors tend to be at a relatively early stage, this does not imply any benefit of surveillance because of lead time and length biases inherent in the screening process. Only controlled trials can answer the central question of whether screening decreases mortality from bowel cancer. Two such trials are underway, but mortality data are not yet available from either.

Relative sensitivity of the fecal occult blood test and flexible sigmoidoscopy in detecting polyps

A group of 1,002 male pattern and model makers, an occupational group at high risk for colorectal cancers, was screened for the presence of polyps and malignancies of the lower gastrointestinal tract. Flexible sigmoidoscopy and serial fecal occult blood testing were both performed on 988 of the participants, and 165 were found to have at least one colorectal polyp. Only 3% of all men with visualized polyps showed Hemoccult-positive stools. Only 2 (4%) of the 51 men with histologically proven adenomatous polyps were Hemoccult positive. Adenomatous polyps of 1 cm or greater in diameter are malignant 8% of the time. This study concludes that the fecal occult blood test sensitivity in detecting colorectal polyps is unacceptably low. It should be supplemented by more rigorous procedures, especially in populations at high risk for colorectal cancer.

Screening for colorectal cancer using the Hemoccult II stool guaiac slide test

Following a series of educational spots on colorectal cancer shown on a local television news program, stool guaiac slide kits (Hemoccult II; Smith Kline Diagnostics) were distributed in shopping malls in Erie County, New York during a 3-day period in February 1982. The tests kits were sold for $1.00 a piece. A total of 8711 persons purchased test kits and 3822 persons (44%) returned slides for testing. One or more slides were positive in 107 persons (2.8%). Ninety of the 107 positive screenees (84%) saw a physician for further evaluation after screening. Eighteen positive screenees had no evidence of pathology which could cause blood in their stool when evaluated by a physician, yielding an overall false-positive rate of less than 0.5%. Seven new cases of colorectal cancer were found through screening. Five of the seven cancers (71%) detected were localized disease (Dukes' Stage A, B1 or B2), and four cases had no symptoms of disease prior to diagnosis. The findings from this study suggest that screening for fecal occult blood using the stool guaiac slide test is effective in detecting some colorectal cancers at an early stage of disease, often before symptoms appear.

Patterns of pelvic recurrence following definitive resections of rectal cancer

Patterns of local and distant recurrences following resections for rectal cancer provide clinical perspective for multidisciplinary prevention and follow-up programs. From 1968 to 1976 at Memorial Hospital, 412 patients with potentially curable rectal cancer were treated by anterior (AR) or abdominoperineal (APR) resections. First sites of recurrences were categorized as pelvis, liver, distant viscera, and intraabdominal/retroperitoneal sites. Pelvic recurrences were further evaluated according to the location of the tumor, type of resection, and stage of disease. Among the 412 cases, 182 (44.2%) patients developed recurrence, of which 105 (57.6%) were pelvic. Pelvic recurrence was the predominating site either alone (55 of 103) or with concomitant extra-pelvic sites (50/79). In instances of single-site first recurrence, pelvic failure was recognized earliest at 19.1 months, which was significantly earlier than single-distant visceral sites at 34.9 months. Pelvic recurrence was selectively related to various categories of the Dukes and modified Dukes staging systems. Dukes stage significantly predicted pelvic recurrence rates for Dukes A verus B. Astler-Coller stages of B2 and C1 were associated with significantly lower rates of pelvic recurrence (29.7% and 22.1%, respectively) than C2 cancers. The incidence of pelvic recurrence was significantly increased for low and mid rectal cancers as compared with cancers at or above 12 cm. The type of resection utilized (APR versus AR) was associated with no difference in the rate of pelvic recurrence, except for the few patients in whom AR was performed for low rectal Dukes C cancers. Patients with pelvic recurrence had an ultimate disease-free survival of only 3.8% as compared with patients with no pelvic recurrence of whom 77% remained alive without disease or went on to die of other causes. The timing and predominance of pelvic failure in rectal cancer with its own treatment-related morbidity and overall dismal survival outcome justifies organized multidisciplinary efforts to prevent such failure and prospective trials of comprehensive follow-up programs to evaluate improved cure rates or palliation.

Screening for colorectal carcinoma

Since the introduction in the Federal Republic of Germany of free routine screening for colorectal carcinoma (digital examination of the rectum in 1971; test for occult blood in the faeces in 1977), the number of Dukes' stage A cases diagnosed at one hospital has increased by 30%. The average interval between onset of symptoms and diagnosis has shortened from 5 to 3.8 months, and the proportion of inoperable carcinomas has decreased by 10%.

Immunological detection of faecal occult blood in colorectal cancer

A new two-phase test kit for faecal occult blood combining a sensitive guaiac test (Fecatwin (S)ensitive) with an immunological test for human haemoglobin (FECA-EIA) was compared with three current guaiac tests (Fecatest, Fecatwin, Haemoccult) in 19 colorectal cancer patients and 11 controls on a restricted diet. A total of 43 48 h faecal samples (30 from cancer patients and 13 from controls) were collected for quantitative determination of faecal blood loss with the 51Cr method. Qualitative testing revealed that FECA-EIA was the most sensitive test, giving one (3%) false negative test result in the 30 tests on colorectal cancer patients and no false positives in the control subjects. It was also the only test that detected low-degree tumour bleeding. Fecatest and Fecatwin S were the most sensitive guaiac tests, giving 7 and 10% false negative test results, respectively, in the 30 colorectal cancer samples, whereas Haemoccult and Fecatwin gave 23% false negative test results. For screening purposes and in order to reduce costs it is suggested that only the positive test results of the very sensitive guaiac test (Fecatwin S) should be tested with the FECA-EIA test to eliminate false positive results. With this approach the diagnostic accuracy of the new two-phase test will be about twice as good as for the Haemoccult test.

Controlled trial of faecal occult blood testing in the detection of colorectal cancer

20 525 patients from general practitioners' lists were randomly allocated into test and control groups. The 10 253 test subjects were invited to perform haemoccult faecal occult blood testing over 3 days. 3613 (36 . 8%) of the 9807 who received their invitations completed the test. Compliance was improved by direct invitation from the general practitioner and by prior health education by letter or interview. 77 people (2 . 1%) had a positive test result, and 50% of these on investigation had neoplastic disease--12 had invasive carcinomas (9 Dukes' stage A, 2 stage B, 1 stage C) and 27 had 40 adenomas (12 over 2 cm, 2 of which contained areas of severe dysplasia). In the year following the screening test 1 carcinoma (stage C) has presented in the group which accepted the test, and 10 carcinomas (4 stage B, 4 stage C, 2 stage D) have presented in the control group. This respresents a 3 . 6 times greater detection rate per 1000 persons in the test group than in the control group. Only 8 adenomas have presented in the control and non-responding groups. Fibreoptic sigmoidoscopy identified the 10 carcinomas within its range and 39 of the 40 adenomas. Double-contrast barium enema identified only 9 of the 12 carcinomas and 24 (62%) of the 40 adenomas. All 3 carcinomas not identified by barium enema were polypoid Dukes' stage-A lesions.

How good is screening for colorectal cancer?

Colorectal cancer is potentially preventable. Use of fecal occult blood testing, flexible sigmoidoscopy, and a combination of air-contrast barium enema examination and colonoscopy has proved to be a safe, relatively inexpensive approach to detecting colon cancer in its early stages, decreasing morbidity and increasing survival. Future work in secondary prevention of colon cancer should be aimed at standardized trials of fecal occult blood agents, thus optimizing the yield of localized lesions and decreasing the cost so that mass screening becomes possible. Major efforts should be aimed at educating physicians and the public alike. Primary prevention will deserve greater emphasis when specific risk factors pathogenetic of colon cancer are discovered.

Colonoscopy: an essential monitoring technique after resection of colorectal cancer

A pilot study was undertaken to determine the usefulness of colonoscopy in the postoperative follow-up of patients with colorectal cancer. Of 56 patients, 9 (17 percent) had positive intraluminal examinations, including one recurrent cancer and three large polyps (greater than 1 cm) despite normal barium enema films. Twenty percent had negative colonoscopic findings which ruled out suspicious lesions on roentgenograms. More than one third had alterations in therapy as a result of colonoscopic examination. Colonoscopy is a useful and fruitful diagnostic aid in the follow-up of colon cancer. It should be used early in the postoperative period and added at rational intervals in long-term surveillance. It appears to complement other accepted methods of detecting recurrence.

Biases in the assessment of colorectal cancer screening programmes using hemoccult

Many reports of screening programmes using the 'Hemoccult' faecal occult blood test have been published recently. Falsely optimistic results in such short term or nonexperimental studies can be caused by three biases of method: the lead-time bias, the length bias, and the volunteer bias. Their mechanisms, and methods for counteracting their effects are described. Literature biases that occur in papers written on this subject by enthusiasts are also described. Many apparently valuable screening tests have failed in the practical setting, so caution in the use of occult blood screening is urged until long term follow-up results are obtained from a trial currently being conducted in Minnesota.

Colorectal cancer: knowledge and attitudes of doctors in Victoria

Successful introduction of screening for early colorectal cancer will depend, at least in part, on doctors' knowledge and attitudes. A 34-item questionnaire was sent to a random sample of one in five doctors in Victoria, with a final completion rate of 65%. The survey revealed gaps of knowledge, particularly about recognition of high-risk groups. Only 12% were aware of the degree of increased risk faced by first-degree relatives of patients with colorectal cancer and only 10% recognised the similar increase in risk for people with a history of resected colorectal cancer. While 73% of doctors order faecal occult blood tests, only 9% were aware that the more reliable quaiac method was used for their patients. Overall, 38% considered that faecal occult blood testing was a practical method for screening for colorectal cancer. Most of the doctors who accepted occult blood screening would follow up a positive test with digital rectal examination (80%) and barium enema (75%), but only 58% would want sigmoidoscopy performed and 34% colonoscopy. The diagnostic potential of digital rectal examination and sigmoidoscopy was over-estimated by half of the doctors surveyed. Recognition of subjects at high risk for colorectal cancer, and knowledge about the proper use, follow-up, and potential for screening of faecal occult blood tests need emphasis in medical educational programmes.

The costs and effects of screening for cancer among asbestos-exposed workers

Several million workers previously exposed to asbestos are at risk each year for developing asbestosis or cancer as a result of this exposure. We have reviewed the data on the general effectiveness of screening for the two most common cancers found in these workers (lung cancer and colo-rectal cancer) and have compared the relative benefits expected from screening workers for colon or lung cancer 10, 15, 20 or 25 yr after their initial exposure. Although lung cancer is common, there is little evidence at present that screening for this disease is effective in reducing mortality. Colon cancer is less common, there is more evidence that screening is effective, and the relatively high risk of dying from this disease in asbestos workers makes screening useful. The cost per additional year of life extended by screening is only a few hundreds of dollars, making colon cancer screening programs for asbestos workers considerably more cost-effective than most other screening programs. We conclude that occupational safety agencies should consider implementing screening programs for colon cancer in workers exposed to asbestos over 10 yr ago.