Colorectal cancer: the challenge of early detection

Colorectal cancer: knowledge and attitude of surgeons in New Zealand

In order to determine surgeons' knowledge of colorectal cancer (CRC) in New Zealand, a questionnaire was sent to all general surgeons on the New Zealand Medical register. One hundred and thirty-three responses were received and 123 were analysed. In general, respondents seemed to have a better detailed knowledge of CRC than Australian physicians and surgeons, although trends were similar and knowledge was patchy and in some areas poor. The value of rectal examination and sigmoidoscopy in relation to the detection of colorectal neoplasia was overestimated. Knowledge of faecal occult blood testing was such as to preclude useful evaluation of test results. The findings have serious implications for medical education.

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.

Cancer of the colon and rectum in high-risk patients

The experience with colorectal cancer at the Denver Veterans Administration Hospital was retrospectively reviewed to characterize the high-risk population with this disease and to determine what impact, if any, screening high-risk patients might have on overall survival rates. The high-risk patients comprised 12 per cent of the overall population with colorectal cancer and did not differ from the latter in terms of age of onset, distribution of tumors, type of symptoms at diagnosis, or survival with a given stage of disease. They did, however, have more stage A and B lesions and a better overall survival than did the general population with colorectal cancer, as a result of screening. The findings suggest that surveillance of high-risk groups is beneficial. Until ways are found to increase the number of patients eligible for inclusion in this group, however, these benefits are unlikely to lead to improved survival of the general population with colorectal cancer.

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.

Knowledge of colorectal cancer and attitude to occult blood testing among recent medical graduates in New South Wales

The extent to which new information on colorectal cancer (C.C.) is being transmitted to medical undergraduates was assessed in a repeated survey of new interns' knowledge of and attitudes on C.C. A probability sample of 214 graduates of the two Sydney medical schools was drawn as they commenced their internships in 1978. A comparable sample of 186 was drawn in 1980. Interns in each sub-sample completed a questionnaire of 54 pre-coded items of knowledge of C.C. epidemiology, early diagnosis, and followup, and on their attitudes towards C.C. On most topics knowledge was not well developed, and 1980 graduates were not significantly better informed than those of 1978. Almost three-quarters of 1980 interns intend using faecal occult blood testing.

Colorectal cancer and hemoccult

Hemoccult slides have been used in an attempt to determine their usefulness as a screening method for the detection of colorectal neoplasia. Two methods have been used. In the first, 300 unprepared patients had an immediate single-stool specimen tested with Hemoccult. Only nine patients were referred for investigation after this single test, and no case of colorectal neoplasia was discovered. In the second method over 2,500 three-stool test kits were distributed to the public, of which 1,160 (46%) have been returned and tested. Positive tests were obtained in 68 patients. Follow-up of 58 of these patients has led to the detection of three cases of carcinoma of the colon and nine cases of benign polyps greater than one centimetre in diameter. The cost of screening patients with a three-stool test has been calculated to be $2.50 per patient.

Screening of patients after surgery for colorectal carcinoma: value of faecal occult blood testing and flexible sigmoidoscopy

Sixty asymptomatic patients aged less than 65 years, who had survived for more than two years after resection for colorectal carcinoma were tested for faecal occult blood loss using Hemoccult-II (six slides). In 55 patients, a double-contrast barium-enema X-ray examination was also performed, and 41 patients underwent flexible sigmoidoscopy. In two cases a positive Hemoccult result was obtained and no colonic lesion was found in one of these patients. Six patients who gave a negative Hemoccult result were found to have adenomatous polyps. Faecal occult blood testing is unsatisfactory for detection of polyps. Flexible sigmoidoscopy is a rapid and safe examination and complements radiology in the screening of patients.