Screening of colorectal cancer

Evaluation of a ‘DIY’ Test for the Detection of Colorectal Cancer

A new type of faecal occult blood test, EZ-Detect™, has been evaluated in 404 patients presenting with symptoms suggestive of colorectal disease. The test avoids handling of stools and gives a result which patients can read themselves - factors which may increase patient compliance. In comparison with the Haemoccult™ test, EZ-Detect has the same sensiti-vity for blood in laboratory conditions. In clinical use 98% of patients expressed a preference for EZ-Detect but it detected significantly fewer patients with cancer than did Haemoccult (P = < 0.05). In its present form, this type of test would be unsuitable for population screening for colorectal cancer even if improved compliance is achieved.

Views of a general population on mass screening for colorectal cancer: the Burgundy Study

BACKGROUND

The success of a screening program depends on a number of factors, including the validity of the test, its efficacy, its feasibility, and the rate of compliance. Thus, it is important to determine the factors influencing compliance to the screening test in order to obtain a high participation rate.

METHODS

A mass screening campaign for colorectal cancer using the Hemoccult test was conducted in Burgundy, France. One year later, a questionnaire was mailed to a random sample of the population to assess the views of the general public (870 persons who had not completed the Hemoccult test, 750 persons who had a negative test, and 100 persons who had a positive test). The compliance rate of this survey was 32.2% among persons who had not completed the screening test, 88.2% among persons with a negative result, and 98.0% among persons with a positive result.

RESULTS

The main reason for not participating was not wanting to know more about their health status (34.3%). Of the factors credited with encouraging persons to perform the test, the most important ones were the practitioner's explanations (55.7%) and the leaflet sent by mail (42.5%). The impact of the media campaign was weak. A small portion of the population (4.3%) said that they were very anxious while waiting for the results. Among persons with a positive screening test, only 1.2% regretted having taken it. Among those who took the test, 94.2% said they were ready to do it again; and among those who did not take it, 36.7% would accept it at a second screening.

CONCLUSIONS

The data suggest that overall the Hemoccult is well accepted, that the campaign did not upset the population, and that it is worthwhile at the second screening to include those who did not participate in the first screening test.

Cytologic detection of colorectal cancer after administration of oral lavage solution

Whether malignant cells can be detected in the bowel movements induced by oral gut lavage solution administration was studied in patients with known colonic adenocarcinomas. The induced bowel movements were collected in 27 patients, nine of whom had cancer proven by anatomic pathologic examination. The cells present were recovered with a simple technique and stained by the Papanicolaou method. Malignant cells were identified in the stained preparations in all nine patients with cancer (100% sensitivity), and there were few false positives (94.5% specificity). The authors concluded that if additional studies with greater numbers of subjects confirm the reliability of this technique, a test may be developed that would be useful for either early detection or screening.

Screening for colorectal carcinoma

Colorectal carcinoma will occur in some 147,000 Americans this year. This disease accounts for 15% of all cancers and 12% of all cancer deaths. Screening for colorectal carcinoma may allow the disease process to be found earlier and, in some situations such as when polyps are found and removed, may even prevent the disease. The two main modalities of screening are fecal occult blood tests and sigmoidoscopy. By general screening of asymptomatic patients as well as by selective screening of those at high risk, there is hope that the incidence and mortality of this cancer will diminish. Absolute confirmation of this benefit is still lacking, making the evaluation of the cost-effectiveness of this screening somewhat questionable. Current educational efforts are designed to increase compliance and to help solve some of these unanswered questions.

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.

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.

Initial mass screening for colorectal cancer with fecal occult blood test. A prospective randomized study at Funen in Denmark

A Danish study allocated at random 30,970 persons to screening with Hemoccult-II and 30,968 as controls in a population of 140,000 between 45 and 74 years old. Persons with known colorectal cancer, adenoma, and distant spread from all types of cancer were excluded. The test was completed in 20,672 persons from August 1985 to September 1986, and 215 (1%) were found to be positive. Colonoscopy in 203 and double-contrast barium enema in 6 detected 37 persons with cancer and 86 with adenomas. Dukes A cancer was detected in 19 in the screening group, in contrast to 2 among controls. Synchronous adenomas were found in 23 with a positive test and 10 controls. Interval cancer was found in nine persons within 1-11 months after a negative test. Eighteen persons got cancer before invitation and six defectors as well. In all, colorectal cancer was detected in 70 persons in the screening group and in 38 controls; the figures for adenomas alone were 103 and 38, respectively. The study is designed to detect a possible reduction in mortality from colorectal cancer of 25% within 5 years after three screenings with intervals of 2 years. The second screening will begin in September 1987. It remains to be shown whether a reduction may be obtained both in mortality and in incidence of colorectal cancer.