Volume 165 Issue 2

Flexible sigmoidoscopy screening for colorectal cancer in average-risk subjects: a community-based pilot project John K Olynyk, Sina Aquilia, David R Fletcher and Jim A Dickinson ©MJA1996; 165: 74-76. This article has been cited in Sladden MJ, Ward JE. Australian general practitioners' views and use of colorectal cancer screening tests. MJA 1999; 170: 110-113 Readers may print a single copy for personal use. No further reproduction or distribution of the articles in whole or in part should proceed without the permission of the publisher. For copyright permission, contact the Australasian Medical Publishing Company Abstract - Introduction - Methods - Subjects - Data management - Acceptability survey - Results - Subject recruitment - Screening results - Reasons for non-compliance with screening - Discussion - Acknowledgements - References - Author's Details - Register to be notified of new articles by email - - To top of article - ©MJA; 1996 Abstract Objective: To test a pilot screening program for colorectal cancer. Design: Subjects, chosen at random and recruited by mail, were examined by flexible sigmoidoscopy. Participants and setting: Normal-risk, asymptomatic men and women aged 55-59 years recruited from the community, July to December, 1995. Main outcome measures: Number of polyps detected and cancers diagnosed, and compliance with screening. Results: Letters of invitation were sent to 3500 subjects; of these, 2881 were eligible for inclusion in the study and 342 (12%) consented to participate. A further 3.5% of non-compliant subjects attended the screening program after a telephone survey assessing reasons for non-attendance. Common reasons for non-attendance were a lack of interest (30%) or a lack of time, mainly due to work commitments (28%). A third of subjects had polyps and 46% of these were adenomas. Three subjects were found to have adenocarcinoma: in two the cancer was confined to a polyp and treated with polypectomy, and one subject underwent anterior resection (overall prevalence of cancer, 0.9%). The median depth of insertion achieved with flexible sigmoidoscopy was 55 cm (range, 25-100 cm). Median pain level (on a scale of 0 = no pain to 10 = worst pain imaginable) was 2 (range, 0-8.5), and 99% of the subjects would have the test again if required. Conclusions: Flexible sigmoidoscopy was well tolerated and had an acceptable detection rate of adenomatous polyps and early cancer. Subject compliance emerged as a major issue which requires further evaluation to maximise participation in future programs. MJA 1996; 165: 74-76 Introduction C olorectal cancer is the commonest cancer affecting both sexes and isnow the second-commonest cause of cancer-related death in both men and women. 1 Several studies have shown that screening asymptomatic populations may reduce mortality from colon cancer by up to 30%, 2-4 and recently the World Health Organization recommended screening of asymptomatic subjects beginning at age 50. 5 However, in Australia there are no uniformly agreed methods for screening asymptomatic subjects for colorectal cancer. 6 Factors such as screening efficacy, cost, subject compliance and strategies employed to evaluate positive results all influence the choice of screening test. Faecal occult blood testing for colo rectal cancer is relatively cheap, but is limited by a high rate of false positive results and poor sensitivity. 7-9 A recent report also suggests that up to half the mortality reduction observed with faecal occult blood screening may be due to chance selection for colonoscopy. 10 Flexible sigmoidoscopy has been proposed as an alternative screening test. It is more expensive but would prevent more cancer deaths than faecal occult blood testing alone. 8,11 Apart from determining the best screening methods, rates of compliance with screening programs range widely (8%-80%). 8,12 These issues, together with implications for health service resource allocation, have prompted recommendations for pilot programs to determine the efficacy of screening and compliance rates before more generalised screening is introduced. 6,8,13 The Western Australian Department of Health provided funds for such a pilot project at Fremantle Hospital. Thus, we were able to conduct a pilot community-based flexible sigmoid oscopy screening program, between July and December 1995, for colorectal cancer in normal-risk asymptomatic individuals, and in this setting determine (i) yield of screening, and (ii) subject compliance with screening and factors which influence compliance. Methods A flexible sigmoidoscopy facility dedicated to colorectal cancer screening was established at Fremantle Hospital. All procedures were performed on an outpatient basis after informed written consent. No sedation was used. After administration of a phosphate enema, procedures were performed either by a qualified gastroenterologist, or a general practitioner who was undergoing supervised training in flexible sigmoidoscopy. An Olympus TI100 colonoscope (Olympus Optical, Japan) was used, allowing insertion up to 100 cm. Biopsies were taken from polyps seen during the procedure. Subjects with biopsy-proven adenomas were advised to have a follow-up colonoscopy. A computer-generated report was issued to all subjects after the procedure, with instructions to return to their general practitioner for ongoing care. The study was approved by the Ethics Committee of Fremantle Hospital. Subjects We recruited male and female subjects aged 55 to 59 years of age using a computerised database derived from the Western Australian Electoral Commission. Letters were sent to 3500 randomly selected subjects inviting their participation. Exclusion criteria (apart from age less than 55 or greater than 59 years) were: symptoms of recent alteration in bowel habit, constipation, diarrhoea, or passage of blood with bowel motions; previous history of colonic polyps or colorectal cancer; and family history of colorectal cancer. A telephone survey of 200 subjects who did not respond to the initial letter showed that the reason for non-attendance in 14% of these subjects was that they met the exclusion criteria. Data management All data were recorded on a customised database from which reports were generated. We recorded basic demographic data, presence or absence of exclusion criteria, operator information, date of procedure, adequacy of bowel preparation, insertion depth, polyp data (number, size, pedunculated or sessile, biopsy report and date), and follow-up advice. Acceptability survey After the procedure, 77 consecutive subjects filled in a brief questionnaire, which included a standard 10-cm linear analogue pain scale. They marked a 10-cm line (labelled "0 = no pain" and "10 = worst pain imaginable") at a point which corresponded to their level of pain. Results Subject recruitment One hundred and fifty letters were returned, indicating that the subject was no longer resident at the mailing address. As 14% of non-attending subjects were found by the telephone survey to meet exclusion criteria, we estimate there were 2881 eligible subjects. Of those, 342 (12%) consented to participate in the study. There were 200 men and 142 women participants; 95% were born in Australia. Screening results Findings at flexible sigmoidoscopy are summarised in Box 1. The median depth of insertion achieved was 55 cm (range, 25-100 cm; 70% of subjects had at least 50 cm of bowel examined by flexible sigmoidoscopy. Thirty-five subjects (10%) were incompletely prepared with one enema and required a repeat bowel preparation before the procedure. Thirty-five per cent of subjects had polyps -- 46% of these polyps were adenomas, the remainder being hyperplastic or metaplastic polyps. The median adenoma size was 4 mm (range, 1-60 mm). Nineteen of the adenomatous polyps (5.6%) were at least 1 cm in size. One subject with a 6-cm sessile villous adenoma underwent anterior resection. Three subjects were found to have adenocarcinoma -- in two the cancer was confined to a polyp and treated with polypectomy, while the third required anterior resection for a cancer detected at follow-up colonoscopy. The overall prevalence of cancer in this group of subjects was 0.9%. The median pain score attributed to the procedure was 2 (range, 0-8.5). Seventy-six (99%) of these subjects would have the test again if required. Most subjects found the procedure interesting (they were able to watch on a video screen) and worthwhile. Reasons for non-compliance with screening The commonest reasons given for non-compliance were a lack of interest (30%) or a lack of time, mainly due to work commitments (28%) (Box 2). Interestingly, 16% of subjects who did not attend stated that they had either discussed the issue of bowel cancer screening to their satisfaction with their local general practitioner or had been screened for bowel cancer. Seventeen (8%) of the 200 subjects who did not attend as a result of the initial mail-out indicated that they would like to participate as a direct result of the telephone interview and were offered appointments; seven (3.5%) of these subjects have since attended for screening. Discussion The cancers detected by flexible sigmoidoscopy in our study were early cancers, but our three cases represent a detection rate of 8.8 cancers per 1000 asymptomatic subjects aged 55-59. Western Australian data for this age group predict an annual incidence of about 1 per 1000. 1 Our yield of polyps at least 1 cm in size (5.6%) is consistent with the previously reported prevalence of polyps in persons aged 55-59 14 and in asymptomatic Australian men of mean age 66 (3.8%). 15 However, the depth of insertion and number of polyps found in our study are both greater than those reported in several recent studies of flexible sigmoidoscopy: their average depth of insertion ranged from 30 to 50 cm 16-19 and polyp yield ranged from 1% to 4%. 18,19 There is little doubt that population response to screening will be a major determinant of the utility of flexible sigmoidoscopy as a screening tool for colo rectal cancer. The reasons given for non-compliance are similar to those reported for non-attendance in faecal occult blood screening programs. 20 Although the initial response in the pilot program was 12%, the survey of non-compliant subjects demonstrated a significant opportunity for improvement. An additional 3.5% of subjects could immediately be given an appointment at the time of the telephone survey of non-compliant subjects, bringing the compliance rate to 15.5%. Of the remaining reasons determined for non-compliance, most could be addressed by better education of subjects, and rescheduling of screening times to suit the work practices of potential candidates. It remains to be seen how much this would actually improve screening rates. Sixteen per cent of non-compliant subjects reported that they had either been screened for colorectal cancer or had discussed the issue to their satisfaction with their local general practitioner. This may reflect the growing public and general practitioner awareness of colon cancer screening; this has recently been reported from South Australia. 21 There is no doubt that the highest possible compliance should be aimed for, but in a society where currently only 41% of subjects with rectal bleeding seek medical attention 22 it would seem that much education needs to occur to facilitate this process. We have reported the first Australian pilot study of flexible sigmoidoscopy screening of asymptomatic subjects aged 55-59 years in which a high yield of adenomatous polyps and early cancers was found. The procedure was well tolerated. Subject compliance emerged as a major issue which requires further evaluation in order to maximise participation in future programs. This study strongly supports a more broad-scale evaluation of flexible sigmoidoscopy screening of asymptomatic subjects for colorectal cancer and polyps. Acknowledgements We wish to thank Dr Digby Cullen, Mr Graham Cullingford and the Gastroenterology Departments of Fremantle Hospital, Sir Charles Gairdner Hospital and Royal Perth Hospital; Dr Andrew Penman, formerly Chief Health Officer of the Health Department of Western Australia, and the Fremantle Division of General Practice, for their support of this study. References Dobson SK, Penman AG, and 82 others. Clinical health goals and targets for Western Australia, Vol. 2. First report of the Western Australian Task Force on State Health Goals and Targets. Perth: Health Department of Western Australia, July 1994. Mandel JS, Bond JH, Church TH, et al. Reducing mortality from colorectal cancer by screening for faecal occult blood. N Engl J Med 1993; 328: 1365-1371. Selby JV, Friedman GD, Quesenberry CP Jr, et al. A case-control study of screening sigmoidoscopy and mortality from colorectal cancer. N Engl J Med 1992; 326: 653-657 . Newcomb PA, Norfleet RG, Storer BE, et al. Screening sigmoidoscopy and colorectal cancer mortality. J Natl Cancer Inst 1992; 84: 1572-1575. Winawer SJ, St John DJ, Bond JH, et al. Prevention of colorectal cancer: guidelines based on new data. Bull World Health Organ 1995; 73: 7-10. Goulston K, St John J, Bokey L, et al. Guidelines for early detection, screening and surveillance for colo rectal cancer. 2nd edition. Sydney: Australian Gastroenterology Institute and Gastroenterological Society of Australia, 1994. Austoker J. Screening for colorectal cancer. BMJ 1994; 309: 382-386. Lieberman D. Screening/early detection model for colorectal cancer. Cancer 1994; 74: 2023-2027. Solomon MJ, McLeod RS and Canadian task force on periodic health examination. Can Med Assoc J 1994; 150: 1961-1970. Lang CA, Ransohoff DF. Faecal occult blood screening for colorectal cancer: is mortality reduced by chance selection for screening colonoscopy? JAMA 1994; 271: 1011-1013. Lieberman DA. Cost-effectiveness model for colon cancer screening. Gastroenterology 1995; 109: 1781-1790. Blalock SJ, De-Vellis BM, Sandler RS. Participation in faecal occult blood screening: a critical review. Prev Med 1987; 16: 9-18. St John J. Screening for colorectal cancer: "On your marks. . ." Med J Aust 1994; 160: 596-597. Arminski TC, McLean DW. Incidence and distribution of adenomatous polyps of the colon and rectum based on 1000 autopsy examinations. Dis Col Rectum 1964; 7: 249-261. Chapuis PH, Goulston KJ, Dent OF, Tait AD. Predictive value of rectal bleeding in screening for rectal and sigmoid polyps. BMJ 1985; 290: 1546-1548. Krevsky B, Fisher RS. Yield of rescreening for colonic polyps using flexible sigmoidoscopy. Am J Gastroenterol 1994; 89: 1165-1168. Maule WF. Screening for colorectal cancer by nurse endoscopists. N Engl J Med 1994; 330: 183-187. Renneker M, Saner H. Low-cost flexible sigmoid oscopy screening: a community demonstration and education project. J Cancer Educ 1995; 10: 25-30. Sakamoto MS, Hara JH, Schlumpberger JM. Screening flexible sigmoidoscopy in a low-risk, highly screened population. J Fam Pract 1994; 38: 245-248. Lindholm E, Berglund B, Haglind E, et al. Factors associated with participation in screening for colorectal cancer with faecal occult blood testing. Scand J Gastroenterol 1995; 30: 171-176. Weller D, Hiller J, Beilby J, et al. Screening for colorectal cancer: knowledge, attitudes and practices o f South Australian GPs. Med J Aust 1994; 160: 620-624. Crossland A, Jones R. Rectal bleeding: prevalence and consultation behaviour. BMJ 1995; 311: 486-488. (Received 6 Feb, accepted 22 Apr 1996) For editorial comment, see Solomon, page 68; see also Macrae, page 102. Authors' details University Department of Medicine and Department of Gastroenterology, Fremantle Hospital, Fremantle, WA. John K Olynyk , FRACP, MD, Senior Lecturer and Head of Department of Gastroenterology. Sina Aquilia , BA(Psych), Research Assistant. University Department of Surgery and Department of Gastroenterology, Fremantle Hospital, Fremantle, WA. David R Fletcher , FRACS, MD, Professor of Surgery, Head of Department of Surgery. University Department of General Practice, Fremantle Hospital, Fremantle, WA. Jim A Dickinson , FRACGP, PhD, Professor of General Practice. Reprints: Dr J Olynyk, University Department of Medicine, Fremantle Hospital, PO Box 480, Fremantle, WA 6160. E-mail: jolynyk AT uniwa.uwa.edu.au < URL: http://www.mja.com.au/> © 1996 Medical Journal of Australia.

John K Olynyk · Sina Aquilia · David R Fletcher · Jim A Dickinson

Screening for colorectal cancer, 1996 Finlay A Macrae Readers may print a single copy for personal use. No further reproduction or distribution of the articles in whole or in part should proceed without the permission of the publisher. For copyright permission, contact the Australasian Medical Publishing Company Screening average-risk people aged 55 to 70 years for colorectal cancer is now a public health priority in Australia. Pilot studies of faecal occult blood testing are required to find ways of achieving optimal compliance and cost efficiency in the Australian health care setting. Flexible sigmoidoscopy probably should be used as complementary screening but further trials are needed. High-risk groups (family history of colorectal cancer, or previous ulcerative colitis, adenomas or cancer) should already be in surveillance programs. (MJA 1996; 165: 102-105) Introduction - Average risk screening - Above average risk - Conclusion - References - Author's Details - Table 1 - Table 2 - Table 3 Introduction A convergence of events has placed colorectal cancer in the forefront of Australian public health policy formulation. Strategies to control the other major cancers (of the lung, breast and cervix) are now well developed, making it logical that colorectal cancer, as the commonest internal malignancy in Australia, 1 should now receive more attention. At the same time, techniques to detect colorectal cancer at an early (curable) stage have been refined, and large, long-term randomised studies to prove that these techniques can reduce mortality from colorectal cancer are nearing completion. 2-6 Our confidence in determining the outcome of these trials has increased with the development of rigorous methods to assess benefit. 7 Finally, the leading role that colorectal cell and molecular biology has taken in the science of carcinogenesis 8 means that delivery of molecular biological diagnostic services for cancer should already be a clinical service, at least for familial adenomatous polyposis and some other familial colo rectal cancers. Given the state of our knowledge, what should be done now about colorectal screening? Average risk screening Faecal occult blood testing The best chance of cure in colorectal cancer is surgical treatment when the disease is localised to the bowel wall (Australian Clinicopathological Staging System A [ACPS A]) or at least does not involve lymph nodes if it has penetrated through the muscle wall (ACPS B). This means the best chance of diagnosis is before symptoms develop. The most logical method of diagnosis is population screening to identify people with early-stage or premalignant (adenomatous polyps) tumours, but it is very difficult to prove that this will reduce mortality rate. Such proof is required to attract scarce health dollars. Rigorous controlled trials are needed to counter possible biases (e.g., lead-time bias: screening allowing an earlier diagnosis but not altering date of death or the tumour's natural history; and length bias: screening selecting biologically favourable tumours, such as slow-growing ones) and the requirement to analyse on an intention-to-treat basis 9 means recruiting over 100 000 people to adequately test the screening hypothesis. Three large randomised controlled trials of faecal occult blood testing are in progress 4-6 and several have been completed (Table 1). 2,3 The most important completed trial is the Minnesota trial, involving 46 551 subjects studied over 13 years and randomly allocated to annual, biennial or no Hemoccult testing (SmithKline Diagnostics Inc, San Jose, Calif, USA). 2 The trial demonstrated a statistically significant 33% relative reduction in mortality from colorectal cancer in subjects having annual testing. This result has withstood close scrutiny by critics, including those who believed that most of the benefit was attributable to chance because of the low specificity of the rehydrated Hemoccult test used, leading to over 30% of the screened population having a colonoscopy. 10 If the benefit was merely serendipitous, then the chance of a single positive occult blood test versus multiple tests (six were done with each screen) should not be linearly related (which it was), and the odds ratio for tumours in individuals testing positive versus negative to the presence of faecal occult blood would not have reached such high levels, far outstripping almost all other known risk factors. Thus, the Minnesota study shows that faecal occult blood testing does select patients with significant colorectal tumours. The three incomplete European randomised controlled trials are also on track to show a mortality reduction. 4-6 Supporting data come from case-control studies of faecal occult blood testing (Table 2). 11-13 The screening histories of people dying from colorectal cancer (cases) are compared with those of control subjects without apparent disease. A deficit of screening in the cases implies protection to the controls by screening. However, rigorous standards need to be applied to case-control studies to counter the subtle biases, which may account for the generally more favourable levels of protection found when compared with the results of randomised controlled trials. 7 Cohort studies of screening for colo-rectal cancer are curiously missing from the literature. Large cohort studies of diet and other possible risk factors for colo-rectal cancer have been published, 14,15 but none have recorded incidence of prior screening in those in the prospective cohort developing cancer versus those not developing cancer. Screening information is not reported in these studies, which seems a valuable opportunity lost. Many of the biases confounding case-control studies would be overcome in a cohort study of screening. New immunochemical tests have already demonstrated improved sensitivity and specificity, which will enhance the cost effectiveness and efficacy of screening programs. 16 Despite a statistically significant mortality benefit, the absolute number of lives saved per 1000 persons screened for faecal occult blood is small (about three). 2 This, of course, is a corollary of well patient screening (most of the people being screened are both free of disease and have negative results). We need to conduct studies to define cost-efficient procedures for screening, using tests with low false positive rates, and targeting particular communities. Sigmoidoscopy Sigmoidoscopy is likely to be an important adjunct for detection of distal colorectal cancer, as faecal occult blood testing has low sensitivity for rectosigmoid cancers. 17 Case-control studies of sigmoidoscopy screening show protection to the control groups (Table 2), 18,19 but it is difficult to identify the reason for the mortality benefit in terms of polyps removed or successful surgery for cancers detected at an early stage. Well accepted randomised controlled trials have not been done. Flexible sigmoidoscopy should detect 50%-70% of colorectal cancers, so its impact in screened populations is likely to be high. Indications from case-control studies are that protection lasts for 10 years, which augurs well for cost-benefit considerations. 18 Large randomised controlled trials of flexible sigmoidoscopy screening are commencing in Europe. 20 Colonoscopy Even once-off colonoscopy is comparable in cost with breast cancer screening. However, as with flexible sigmoidoscopy, colonoscopy screening does not have enough clinical research proof to be sure of its benefit, although this is probably just a matter of time. 21 Compliance in Australian populations at average risk is unknown. From clinical science to clinical service In summary, faecal occult blood testing is the screening method with the stongest data for deployment. But, should we wait for the results of the additional European controlled trials of screening, or act now on the evidence from the Minnesota trial and other published information? Despite its low sensitivity (about 50% for asymptomatic cancers), 4,21 repetitive screening programs have shown a reduction in mortality from colorectal cancer. Testing is cheap and simple and reasonably well accepted in Australian populations. 22 Provided specificity is high (and thus false positive results low), follow-up colonoscopy is both feasible and cost-manageable. 23 Although the scientific basis for implementing faecal occult blood screening for those aged 50-75 years of age is compelling, the best way to do this in Australia is uncertain. Should it be through dedicated centres providing testing and evaluation, as with breast screening in Australia? Should it be through general practice? through a central electoral-roll-resourced organisation? through hospitals? or through State cancer foundations/councils? These logistical questions need to be answered by pilot trials. 24 Mechanisms to evaluate the results on a population basis must be built into whichever system is introduced. Germany has funded faecal occult blood mass screening for over a decade but has a poorly developed evaluation infrastructure, thus denying the world an important opportunity for assessment. Sigmoidoscopy needs further study before introduction, but sufficient evidence is available to offer sigmoidoscopy to average-risk people in the age group 50 to 75 years who are already in the health care system (case finding). Technical skills and facilities for flexible sigmoidoscopy are limited and their availability must be increased. Issues of cleaning and disinfection, environmental hazards of glutaraldehyde, technical and lesion-recognition training, manpower, support personnel, capital support for equipment for a "type C" (office-based) procedure, all complicate the widespread use of flexible sigmoidoscopy. However, the benefits of being able to examine 50%-70% of the tumour territory of the large bowel make the objective worthwhile. Above average risk Family history For individuals with a family history of colorectal cancer the appropriate recommendations are generally less controversial (Table 3). Many consistent studies demonstrate risks two- to sixfold higher in individuals with first degree relatives with colorectal cancer, the risk relating to the earliest age of onset in the family and the number of first degree relatives affected. 25,26 If there is only one affected first degree relative, age at onset of the cancer is important: if the relative was under 55 years, the risk is six times the average risk (the same as the risk for those with two first degree relatives with onset at any age); if a single affected relative has older-onset cancer, the increased risk to family members is marginal. 25 Thus, average-risk screening is recommended for those families with a single affected relative with older-age onset ( > > 55 years) of colorectal cancer (faecal occult blood testing and five-yearly flexible sigmoidoscopy), but colonoscopy every five years is recommended for those with a first degree relative with early-age onset. 24 If multiple family members are affected in a nuclear family, colonoscopy is recommended for first degree relatives of affected members, either five-yearly or three-yearly, depending on whether two or more relatives are affected. This advice is based on logical grounds of cost benefit: the higher the risk (and therefore prevalence) the greater the positive predictive value of screening, and thus cost-benefit. Protection may be enhanced by annual faecal occult blood testing between colonoscopies. The significance of a family member with an adenoma (as distinct from a cancer) is less clear in defining risks to individuals in the family. Epidemiological studies suggest that adenomas are equivalent to cancers, 27,28 but problems of detection bias make it difficult to use this information for surveillance advice. Nevertheless, a relative with a confirmed adenoma should not be ignored in assessing family history, and for risk assessment purposes it should be considered that these lesions may represent early cancer. Hereditary Non-Polyposis Colorectal Cancer syndrome is suspected when three or more first degree relatives have colorectal cancer (especially right-sided or multiple), with at least one affected family member < 50 years of age or when colo rectal cancer is associated with ovarian, endometrial, gastric, small-bowel, pancreatic, biliary, kidney or ureteric tumours. 29,30 Genotyping for these families is available in Australian research studies, but it may take over 12 months to define the family- specific mutation of the mismatch repair genes responsible. 31 Colonoscopy every two years for affected and at-risk family members is important, with faecal occult blood testing between colonoscopies. Familial adenomatous polyp-osis should also be suspected in families with early-age-onset colo-rectal cancer. Enquiry should be made about polyps or polyposis in affected members and confirmation of the diagnosis sought. Genotyping is available but is still technically difficult due to the large gene responsible ( APC gene); mutations at different sites in the gene are responsible for the condition in different families. 32 Once the mutation in a family is identified in genomic DNA, a family-specific DNA test is easily developed and available for predictive (100% accurate) testing in at-risk family members of any age. Expert genetic counselling is required. Issues of threats to insurance of all types, employment, survivor guilt, prognosis and family planning all need to be handled sensitively and informatively both before and after testing. Screening of APC- mutation carriers needs to proceed as before: annual or biennial flexible sigmoidoscopy screening from 15 to 55 years of age. Those without the mutation are recommended to have average risk screening. They are still at risk for common colorectal cancer. Previous adenomas or cancer: "polyp follow-up" Patients with previous adenomas or cancers face a similar risk for future cancer. 33-36 Although no randomised controlled trials have been reported, several large follow-up studies of patients with adenoma have compared outcomes with suitable control groups -- some with adenomas untreated, some with age-sex-matched population control groups, some with patients with polyps detected by barium enema (not removed) before colonoscopy was available -- and demonstrated a convincing reduction in mortality from regular follow-up. 34,35,37,38 The only exception is patients with small tubular adenoma(s) in the rectosigmoid region, where risk for subsequent cancer is no higher than average and surveillance is unlikely to be of particular value. 35 Intervals of surveillance are controversial but the United States National Polyp Study clearly demonstrated that annual follow-up conferred no benefit over three-yearly follow-up; 39 two- to five-yearly follow-up is recommended, depending on multiplicity, size of index adenoma and, possibly, family history -- all independent risk factors for subsequent neoplastic risk. Ulcerative colitis Ulcerative colitis poses a cancer risk after eight years for total disease and 12 years for left-sided disease. 40 The programs with best results advocate multiple biopsies (18 biopsies from eight colonic sites). Controlled trials have not been performed. 40 In summary, controlled trials of surveillance in these above average risk groups would confirm the recommendations but, on current knowledge, ethical considerations would not permit randomisation to no surveillance. Case-control and cohort studies in these above average risk groups providing information on benefit have not been published. Conclusion The prevalence of colorectal cancer in Australia, its surgical curability if detected at an early stage and recent controlled- trial evidence of mortality reduction by faecal occult blood screening now place colorectal cancer on the public health prevention agenda in Australia. The conservative and influential US Preventative Services Task Force has recently, for the first time, accepted the evidence for benefit as fair, and recommended screening for all persons aged 50 and over with faecal occult blood testing, or sigmoidoscopy, or both. 41 The Canadian Task Force on the Periodic Health Examination also accepts the evidence for mortality benefit, but raises concerns about costs driven by low sensitivity and specificity of the tests used in the Minnesota trial. 42 The optimal processes for implementing screening in a cost efficient manner using up-to-date screening tests require studies in pilot public health programs. Australia needs to move forward in this area, to help control its commonest internal cancer (that touches so many Australian families), and its second-largest cause of cancer mortality. References Coates M, McCredie M, Armstrong B. New South Wales Central Cancer Registry, Cancer in New South Wales, Annual reports 1973-1990. 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Author's details Department of Gastroenterology, Royal Melbourne Hospital, Melbourne, VIC. Finlay A Macrae, MD, FRACP, Physician and Gastroenterologist. Reprints: Dr Finlay A Macrae, Department of Gastroenterology, The Royal Melbourne Hospital, PO Royal Melbourne Hospital, VIC 3050. To top of article - ©MJA; 1996 < URL: http://www.mja.com.au/> © 1996 Medical Journal of Australia.

Finlay A Macrae