Colonoscopic screening of asymptomatic patients with a family history of colon cancer

Screening colonoscopy for colorectal cancer prevention: results from a German online registry on 269000 cases

BACKGROUND

The efficacy of screening colonoscopy in general use remains to be determined. Here we report data over a 39-month study period collected in a nationwide online registry.

STUDY

Data from consecutive screening colonoscopies performed on asymptomatic patients in the practices of 280 participating gastroenterologists (age 55-99 years) were collected in an online registry. The number and histology of colorectal polyps and carcinomas, complication rates of colonoscopy and polypectomy were registered. Advanced adenoma was defined as an adenoma of >or= 10 mm in diameter, villous or tubulovillous in histology, or presence of high-grade dysplasia.

RESULTS

A total of 269 144 colonoscopies (male 44%) were evaluated. Tubular, villous/tubulovillous adenomas and invasive cancers were found in 15.6, 3.7, and 0.8%, respectively. Advanced adenomas amounted to 7.1%. In 95% of polyps greater than 5mm and less than 30 mm immediate polypectomy was performed. In 399 of the 575 carcinomas with complete tumor node metastasis stages, which were detected during colonoscopy, early stages dominated (UICC stages I and II in 43 and 27%, respectively). Complication rate was low and no fatalities were observed: cardiopulmonary complication in 0.10% of the colonoscopies, bleeding in 0.8% of polypectomies most of which were managed endoscopically (surgery in 0.03% of polypectomies). Perforation occurred in 0.02% of the colonoscopies and 0.09% of polypectomies.

CONCLUSION

Colonic neoplasias are detected in about 20% of patients most of which are immediately removed by polypectomy at a low risk. Polypectomy of adenomas and low UICC stages in cancer patients during screening colonoscopy may be tools for fighting colorectal cancer mortality.

The BSG/ACPGBI guidelines for colonoscopic screening: what are we missing?

INTRODUCTION

Before publication of the British Society of Gastroenterology and Association of Coloproctology of Great Britain and Ireland guidelines in 2002, screening for people with a family history of colorectal cancer was sporadic and largely dependant on unvalidated local guidelines. Since 1990 we have been screening patients with both high and moderate risk family histories of colorectal cancer using local protocols which were more liberal than the new guidelines. In this study, we have analysed the pathology that would have been missed if we had been using the new guidelines in the period 1990-2002.

METHOD

A total of 399 consecutive patients with a positive family history of colorectal malignancy underwent screening endoscopy according to local guidelines. Demographic, endoscopic and pathologic data were prospectively collected. Patients were retrospectively divided into those who would have been screened under the new guidelines (group 1) and those who would not (group 2). The recorded pathology was graded as significant or insignificant and the findings compared between the two groups.

RESULTS

A total of 399 patients underwent 557 endoscopies of which 278 (50%) were indicated under the new guidelines (group 1) and 279 (50%) were not indicated (group 2). A significant pathology or carcinoma was found in 15.8% of group 1 endoscopies and 10.0% of group 2 endoscopies. This difference was significant.

CONCLUSION

If we had been using the new guidelines in the period 1990-2002, we would not have performed 279 (50%) of the 557 procedures, but would not have discovered significant pathology in 10% of the moderate risk endoscopies representing 39% of the significant pathology, which was actually present in this population.

Physiological concentrations of butyrate favorably modulate genes of oxidative and metabolic stress in primary human colon cells

Butyrate, a metabolite of gut flora-mediated fermentation of dietary fibre, was analysed for effects on expression of genes related to oxidative stress in primary human colon cells. An induction of detoxifying, antioxidative genes is expected to contribute to dietary chemoprevention. Cells were treated with butyrate (3.125-50 mM; 0.5-8 h), and kinetics of uptake and survival were measured. Gene expression was determined with a pathway-specific cDNA array after treating colon epithelium stripes with nontoxic doses of butyrate (10 mM, 12 h). Changes of hCOX-2, hSOD2 and hCAT expression were confirmed with real-time polymerase chain reaction (PCR) and by measuring catalase-enzyme activity. Primary colon cells consumed 1.5 and 0.5 mM butyrate after 4- and 12-h treatment, respectively. Cell viability was not changed by butyrate during 0.5-2-h treatment, whereas cell yields decreased after 1 h. Metabolic activity of remaining cells was either increased (4 h, 50 mM) or retained at 97% (8 h, 50 mM). Expression of hCAT was enhanced, whereas hCOX-2 and hSOD2 were lowered according to both array and real-time PCR analysis. An enhanced catalase-enzyme activity was detected after 2 h butyrate treatment. Healthy nontransformed colon cells well tolerated butyrate (50 mM, 2 h), and lower concentrations (10 mM, 12 h) modulated cyclooxygenase 2 (COX-2) and catalase genes. This points to a dual role of chemoprotection, since less COX-2 could reduce inflammatory processes, whereas more catalase improves detoxification of hydrogen peroxide (H(2)O(2)), a compound of oxidative stress. Changes of this type could reduce damaging effects by oxidants and protect cells from initiation.

Colorectal cancer screening: results of a 5-year program in asymptomatic subjects at increased risk

BACKGROUND AND AIMS

The province of Ferrara has one of the highest incidences of colorectal cancer (CRC) in Italy. In January 2000, we set up a colonoscopy screening program focussing on first-degree relatives of CRC patients. We now report the results 5 years after the beginning of the project. SCREENEES AND METHODS: In October 1999, we started a campaign stressing the usefulness of colonoscopy for the first-degree relatives of CRC patients. Subjects included in the screening program were aged between 45 and 75 years with at least one first-degree relative affected by CRC. They were invited to an interview where a physician suggested colonoscopy as a screening option.

RESULTS

In 5 years, 776 subjects were interviewed and 733 (94.4%) agreed to an endoscopic examination (M/F:375/401; mean age 55 years): 562 colonoscopies were performed. Adenomas and cancers were found in 122 (21.7%) and 12 (2.1%) subjects, respectively. Histological examination in 181 persons with lesions (32.8%) showed (most serious lesion quoted) 47 hyperplastic polyps (26% of all lesions), 2 serrated adenomas (1.1%), 68 tubular adenomas (48%), 24 tubulovillous adenomas (13.3%), 9 adenomas with high grade dysplasia (5%) and 12 adenocarcinomas (6.6%). The majority of the cancers were at an early stage (8 Dukes A and 3 Dukes B). Sedation was used in only 42 colonoscopies (7.5%).

CONCLUSIONS

A colonoscopy-based screening in this selected high-risk population is feasible. Even without sedation subjects readily agreed to the endoscopic procedure. We identified a significant number of advanced neoplasms and cancers at an early stage suggesting that this could be a useful tool in early identification of CRC.

Colonoscopy in asymptomatic individuals with a family history of colorectal cancer

BACKGROUND

This study was performed to evaluate the use of total colonoscopy as the optimal screening test in asymptomatic individuals with a family history of colorectal cancer (CRC).

METHODS

Colonoscopy was performed in 249 asymptomatic individuals who had one or two first-degree relatives (FDRs) with CRC; individuals with three or more FDRs with CRC were excluded.

RESULTS

Eighty-six colonic lesions were found in 51 individuals (51 of 249; 20.5%). Among these 51 subjects, 27 had neoplastic polyps (n = 38) and 29 had metaplastic polyps (n = 44). Although no invasive cancer was detected, in 14 individuals the lesions had a high malignancy potential because of their size and histopathology. We did not confirm a statistically significant difference in the incidence of neoplastic polyps according to the number of affected FDRs. Finally, the presence of metaplastic polyps was a very strong indication for the concomitant presence of metaplastic polyps (P <.0001).

CONCLUSIONS

Total colonoscopy is the optimal screening procedure for the examination of asymptomatic individuals with a family history of CRC.

Yield from colonoscopic screening in people with a strong family history of common colorectal cancer

BACKGROUND AND AIMS

People with a strong family history of common (so-called 'sporadic') colorectal cancer are generally advised to undergo colonoscopic screening, but the starting age for this is unclear. An audit was performed to study the age-related yield of screening colonoscopy in this risk group.

METHODS

A prospective audit of the outcome of screening colonoscopy was performed on a cohort of 232 people with a strong family history of common colorectal cancer. All were registrants in a familial bowel cancer service solely because of their family medical history. They had no bowel symptoms and no prior endoscopic investigation of the large bowel.

RESULTS

Neoplastic lesions were detected by using colonoscopy in 33 participants. In 27 participants, the major lesion was a small tubular adenoma, four had an advanced adenoma and two had cancer. More neoplastic (P= 0.02) and advanced neoplastic (P= 0.03) lesions were found in those patients aged > or = 50 years. Only one advanced adenoma was detected in a participant below the age of 50 years.

CONCLUSION

The yield from screening colonoscopy in young people (< 50 years) with a strong family history of common colorectal cancer is low, placing doubt on the need for colonoscopic screening before the age of 50 years.

Colonoscopic screening in first-degree relatives of patients with 'sporadic' colorectal cancer: a case-control study. The Association Nationale des Gastroentérologues des Hôpitaux and Registre Bourguignon des Cancers Digestifs (INSERM CRI 9505)

BACKGROUND & AIMS

A screening policy has not been well defined in first-degree relatives of patients with sporadic colorectal cancer. This study estimated the risk of colorectal adenoma in a cohort of individuals with only 1 affected first-degree relative.

METHODS

A total of 476 first-degree relatives (age, 40-74 years) of 195 patients with sporadic colorectal cancer were offered a colonoscopy. Each examined relative was matched with 2 controls for age, sex, symptoms, and center. The prevalence of colorectal adenomas was compared using a multiple logistic regression analysis.

RESULTS

In 185 relatives, odds ratios were 1.5 (95% confidence interval [CI], 1.0-2.4) for adenomas, 2.5 for large adenomas (95% CI, 1.1-5.4), 1.2 for small adenomas (95% CI, 0.7-1.9), and 2.6 (95% CI, 1.3-5.1) for high-risk adenomas (> or = 1 cm in size and/or with a villous component). The prevalence of high-risk adenomas in relatives was higher when the index patient was younger than 65 years, was male, and had distal rather than proximal cancer.

CONCLUSIONS

Subjects with only 1 affected first-degree relative are at increased risk for developing large adenomas.

Family history as a marker of risk for colorectal cancer: Austrian experience

A family history of colorectal cancer is a known risk factor for the disease. As a result of different study designs from different populations, the strength of this association varies in the literature. We intended to define the incidence and the risk predictors in first-degree relatives of patients with colorectal cancer in the Austrian population. A family history was obtained from first-degree relatives of 100 consecutive patients with sporadic colorectal cancer. Life-table methods were used to compare the observed and expected incidence of colorectal cancer and the influence of differences in risk for first-degree family members. The calculated lifetime risk for colorectal cancer in Austria is 1:16. Individuals with a positive family history had a 4.6-fold risk (p </= 0.0001), particularly in the case of a young index patient (p </= 0.011) or if two or more family members were affected (p </= 0. 001). In addition, the risk for gastric cancer in relatives was increased almost fourfold (p </= 0.0001). We have confirmed for Austria that a positive family history of colorectal cancer is a strong risk factor, and that this risk is comparable to that in other Western countries. We have shown that relatives are also at increased risk for gastric cancer.

Colorectal cancer screening

The decision whether to launch a screening program in asymptomatic patients of average risk for colorectal cancer and the selection of the appropriate protocol for screening are complex issues. There are still many unanswered questions. Many organizations such as the American Cancer Society, the World Health Organization Collaborating Center for the Prevention of Colorectal Cancer, and the U.S. National Cancer Institute advocate screening with annual Hemoccult tests and screening with flexible sigmoidoscopy every 3 to 5 years in patients more than 50 years of age. The U.S. Preventive Services Task Force, the Canadian Task Force on Periodic Health Examination, and the International Union Against Cancer have not recommended screening asymptomatic average-risk patients for colorectal cancer. One study showed a small but significant benefit (3 per 1000) of the rehydrated annual Hemoccult test in reducing mortality from colorectal cancer. To embark on a mass screening strategy as recommended, however, would require significant costs, increases in physician training, improved access to the requisite technology, and enhancements in patient and physician compliance. Furthermore, the high false-positive rates of the rehydrated Hemoccult tests would lead to many unnecessary tests, causing greater expense as well as patient discomfort and anxiety. It is, therefore, premature to recommend mass screening for colorectal cancer in asymptomatic individuals at this time. Further research is needed to identify risk factors (such as genetic markers) better and to develop and evaluate screening strategies targeted at those with high risk for colorectal cancer. In the meantime, efforts at primary prevention for the general population should be increased (through nutrition and exercise). Patients over the age of 50 who desire screening should be given information of the benefits and risks of screening and together with their physicians decide on a screening strategy that suits their needs and values.

The risk of adenomatous polyps in asymptomatic first-degree relatives of persons with colon cancer

BACKGROUND & AIMS

Increasing evidence indicates that inherited susceptibility is important in the pathogenesis of colorectal neoplasia. The aim of this study was to clarify whether having only one first-degree relative with colorectal cancer increases the risk of developing adenomatous polyps and whether total colonoscopy is an appropriate screening measure in these patients.

METHODS

The frequency of such a history was evaluated in 397 asymptomatic patients who underwent total colonoscopy. Of these patients, 155 had colorectal polyps and the remaining 242 did not have polyps.

RESULTS

Among polyp cases, 27 of 155 (17.4%) had a positive history; among those without polyps, 12 of 242 (5.0%) had a positive history. Alternatively expressed, 27 of 39 patients (69%) with family history and 128 of 358 patients (36%) without family history had adenomas. The estimated risk for polyps associated with family history was 1.9. Among polyp cases, 14 of 27 patients (51.9%) with family history and 32 of 128 patients (25.0%) without family history had only proximal polyps (chi 2 test; P = 0.006; odds ratio, 3.2), In the same groups, frequency of high-grade dysplasia was 8 of 27 patients (29.6%) and 16 of 128 patients (12.5%), respectively (chi 2 test; P = 0.04; odds ratio, 2.9).

CONCLUSIONS

Relative to subjects with no family history, asymptomatic patients with one first-degree relative with colorectal cancer had nearly double the risk of developing adenomatous polyps, greater frequency of severely dysplastic lesions, and significantly higher frequency of proximal polyp location. This suggests that total colonoscopy screening is indicated in these subjects.

The role of colonoscopy in screening persons with family history of colorectal cancer

First-degree relatives of colorectal cancer patients are at increased risk for developing colorectal neoplasms. In order to assess the potentiality of colonoscopy screening in this high-risk population, 213 asymptomatic family members (age range 30-69 years, mean 42.8 years) of those patients with colorectal cancer received colonoscopic examination at Chang-Gung Memorial Hospital from April 1992 to May 1994. Twenty-eight persons with 42 lesions (polyps or cancer) were identified, including 28 adenomas, nine hyperplastic polyps and five adenocarcinomas. The positive detection rate was 9.9% for adenoma and 2.3% for cancer. Colorectal neoplasms afflicted males more frequently than females (16.7 vs 5.7%, P < 0.05) and occurred less frequently in those < 40 years of age (5.5 vs 17.2%, P < 0.05). Forty-two per cent of the detected neoplastic lesions were beyond the reach of 60 cm flexible sigmoidoscopy and 36% of adenomas were < 0.5 cm in size and would be missed if patients were screened by air contrast barium enema. Cost analysis revealed that the charges of both screening colonoscopy and screening flexible sigmoidoscopy/air contrast barium enema were approximate. Colonoscopy also has a high acceptability and safety. It appears appropriate to use colonoscopy, rather than flexible sigmoidoscopy or air contrast barium enema, as an initial screening procedure for persons with a family history of colorectal cancer, especially those > 40 years of age.

Variables associated with the risk of colorectal adenomas in asymptomatic patients with a family history of colorectal cancer

The results of screening individuals referred to the Family Cancer Clinic at St Mark's Hospital from 1986 are presented. Colonoscopy was performed in 644 asymptomatic individuals (from 436 families) with a family history of colorectal cancer. Sixty nine (15.8%) of the families fulfilled the Amsterdam criteria for the hereditary non-polyposis colorectal cancer syndromes (HNPCC). Seven cases of colorectal cancer were diagnosed at an average age of 49 years; six at Dukes's stage A and one at stage C, four in subjects from Amsterdam criteria families. One hundred and forty four (22.4%) subjects had one or more adenomas. The prevalence of adenomas in the subjects from Amsterdam criteria families was 34 of 127 (26.8%) compared with 110 of 517 (21.3%) in those from other families; the age and sex adjusted odds ratio (OR) was 1.76 (p = 0.02). Factors influencing the prevalence of adenomas in screened individuals were evaluated. Multivariate analysis showed that independent variables significantly related to the risk of adenomas were: age (p < 0.0001), sex (p = 0.0002), and the number of generations (> or = 2 v 1) of relatives affected by either colorectal cancer or adenomas (p = 0.0006). The latter variable was more highly predictive of the probability of finding an adenoma at colonoscopy than a family history of two generations with cancer only (p = 0.056). The OR of having colorectal adenomas increased with age, by about twofold for each decade, and was twice as high in men than women, and in subjects with two or more generations relative to those with one generation affected by colorectal cancer or adenomas. Six of seven patients with cancer and 46 of 144 (31.9%) with adenomas had lesions proximal to the splenic flexure only. The proportion of individuals with proximal adenomas only was 47.1% in Amsterdam criteria families and 27.3% in the others (p=0.03). These findings support the view that colonoscopy rather than sigmoidoscopy is the method of choice for screening high risk groups.

Suggested screening guidelines for familial colorectal cancer

Guidelines for screening for colorectal cancer in subjects with a positive family history of the disease, without the use of DNA based screening, are outlined. These suggestions are derived from (a) the experience of screening 644 subjects at an estimated lifetime risk of dying from colorectal cancer of 10% or more, in the St Mark's Family Cancer Clinic, over six years, and (b) a review of published studies, particularly incorporating the experience of the International Collaboration Group on Hereditary Non-polyposis Colorectal Cancer (HNPCC). Selection of subjects for surveillance depends upon the empirical evaluation of their risk of colorectal cancer, based upon family history details, with the exclusion of a diagnosis of familial adenomatous polyposis in the family. When DNA predictive tests for genes predisposing to HNPCC are available, surveillance can be directed at subjects with a germline mutation known to confer an increased genetic risk of colorectal cancer and discontinued in those at lower (or average) risk. In many subjects, however, DNA testing may still not be possible because of the failure to identify a predisposing mutation in an affected subject in their family. Any surveillance protocol can only be evaluated by long term follow up of those subjects in multiple centres.

Folate status and adenomatous colonic polyps. A colonoscopically controlled study

PURPOSE

The aim of our study was to assess any association of folate with development of colonic adenomas.

METHODS

Serum and red blood cell folate levels were measured in 62 colonoscopically and histologically evaluated patients with colon adenomas (Group A) and in 50 selected colonoscopically negative controls (Group B). Patients with colon polyps underwent colonoscopy for alterations of bowel habits or abdominal pain, and detected polyps were found coincidentally. Controls underwent colonoscopy for alterations of bowel habits or abdominal pain. There was no difference in hematocrit between the two groups.

RESULTS

The mean serum folate level in patients with colonic adenomas was 4.57 ng/ml +/- 2.8 standard deviations (SD), and the mean red blood cells folate levels were 536 ng/ml +/- 273.3 (SD). In controls the mean folate levels in serum and red blood cells were 5.09 ng/ml +/- 2.7 (SD) and 743.8 ng/ml +/- 297.1 (SD), respectively. The red blood cell folate level of colon adenoma patients was statistically lower than the respective level of controls at a highly significant level (P < 0.01).

CONCLUSIONS

We suggest that depressed red blood cell folate levels are associated with development of colonic adenomas.

Should relatives of patients with colorectal cancer be screened? A critical review of the literature

PURPOSE

The objective of our investigation was to attempt to address the controversial issue concerning index screening and surveillance of relatives of patients with colorectal cancer and to identify those areas of research that should be considered in future studies.

METHODS

Relevant literature was reviewed concerning the screening of asymptomatic first-degree relatives of patients with colorectal cancer not associated with the rare autosomal dominant inherited colorectal cancer syndromes.

RESULTS

The data reviewed suggest that there is an increased risk of colorectal neoplasia in this population and a significantly higher yield of adenomas and carcinomas when colonoscopy is used for index screening. However, significant variability in study design and screening protocols and inconsistencies in data presentation make clinical interpretation and data analysis confusing and difficult.

CONCLUSIONS

There is a critical need for standardization in future studies. Furthermore, as there are no studies that document decreased overall mortality from colorectal cancer in first-degree relatives as a result of screening, the decision as to whether to screen this population needs to be based on future prospective controlled trials.

Hereditary nonpolyposis colorectal carcinoma (HNPCC): clinical application of molecular diagnostic testing

An increased risk of colorectal cancer amongst close relatives of afflicted patients has been recognized for some time. Hereditary nonpolyposis colorectal cancer (HNPCC) represents an extreme example of this risk, in which single-gene inheritance predisposes relatives of affected family members. Approaches to surveillance and management of subjects at greater or lesser heritable risk have been evolving in the past two decades, but these efforts have suffered due to our inability to better characterize and quantify that risk. Recent discovery of susceptibility loci that are linked to disease in HNPCC has already begun to refine our understanding of the pathogenesis of the disease. At a clinical level, these advances now offer an improved ability to recognize carriers of the condition. Speculation is provided as to the probable utility of genetic testing in groups with varying strengths of colorectal cancer familiality. Notions of how positive and negative tests might be applied to surveillance and treatment are explored.

Screening strategies for colorectal cancer

The efficacy of screening for colorectal cancer has not been established. Policy-making organizations differ in recommendations for asymptomatic and high-risk groups because of the inadequacy of current evidence. A critical appraisal of the current evidence for screening for colorectal cancer and a discussion of the aims and pitfalls of screening programs are presented.

Evolution of hereditary non-polyposis colorectal cancer

The prevalence of colorectal adenoma in 23 affected patients with hereditary non-polyposis colorectal cancer (HNPCC) was compared with that in an age matched forensic autopsy population. The mean ages at diagnosis of colorectal cancer in men (13) and women (10) were 39 and 37 years respectively. In HNPCC patients who presented below the age of 50 years, at least one adenoma was found in 3 of 10 (30%) men and in 4 of 9 (44%) women. In the age matched autopsy specimens of large bowel, a solitary adenoma was found in 2/42 (5%) men (p = 0.015) and 1/21 (5%) women (p = 0.0075). Of the 11 adenomas from HNPCC patients, nine were greater than 1 cm and six showed a pure villous architecture. Contiguous adenocarcinoma was observed with six adenomas. Adenomas do not occur in large numbers in HNPCC, but develop at a young age, attain a large size, often show a villous configuration, and are more prone to malignant conversion than sporadic adenomas.

Screening for large bowel neoplasms in individuals with a family history of colorectal cancer

Logistical problems associated with population screening for colorectal cancer are identified and the possibility of targeting screening to those with a familial predisposition to the disease is discussed. Evidence for a substantial genetic effect on the overall incidence of colorectal cancer is reviewed. The screening detection rate of colorectal neoplasms in relatives of patients with colorectal cancer has been shown to be higher than that expected in a non-selected population; the evidence that polypectomy will reduce future colorectal cancer risk in such individuals is explored. Recent advances in the molecular genetics of colorectal cancer susceptibility are reviewed; it is possible that a genetic test might be developed in the future which could identify at least a proportion of those at risk. Excluding financial considerations, the risk-benefit ratio of colonoscopy in a screened population is intimately related to the remaining risk of colorectal cancer in those who undergo the examination. At present, patients undergoing colonoscopy to investigate a positive faecal occult blood (FOB) test as part of a population-based screening programme include individuals with a familial predisposition as well as those without. About 20 per cent of all cases of colorectal cancer are associated with an obvious genetic predisposition, and the risk of cancer in their relatives is high. Because false positives occur with Haemoccult, the residual risk to the population who are FOB positive but do not have a familial trait may be sufficiently low that the dangers of colonoscopy could outweigh the potential benefits. Scotland has a high incidence of colorectal cancer, and analysis of recent Scottish incidence data shows an actuarial lifetime risk of developing this disease of one in 23 for men and one in 33 for women. As a family history of the disease increases that risk by two to four times and the neoplasms arise throughout the colon in such a group, there may be a case for offering colonoscopy to all first-degree relatives of those under 50 years of age at diagnosis, if not of all index cases of colorectal cancer.

Colonoscopic screening for neoplasms in asymptomatic first-degree relatives of colon cancer patients. A controlled, prospective study

Individuals with a family history of colorectal cancer are believed to be at an increased risk of developing colorectal neoplasia. To estimate this risk and the potential yield of screening colonoscopy in this population, we recruited and prospectively colonoscoped 181 asymptomatic first-degree relatives (FDR) of colorectal cancer patients and 83 asymptomatic controls (without a family history of colorectal cancer). The mean ages for the FDR and control groups were 48.2 +/- 12.5 and 54.8 +/- 11.0, respectively. Adenomatous polyps were detected in 14.4 percent of FDRs and 8.4 percent of controls. Although 92 percent of our FDRs had only one FDR afflicted with colon cancer, those subjects with two or more afflicted FDRs had an even higher risk of developing colonic adenomas (23.8 percent) than those with only one afflicted FDR (13.1 percent). A greater proportion of adenomas was found to be beyond the reach of flexible sigmoidoscopy in the FDR group than in the controls (48 percent vs. 25 percent, respectively). Logistic regression analysis revealed that age, male sex, and FDR status were independent risk factors for the presence of colonic adenomatous polyps (RR = 2.32, 2.86, and 3.49, respectively; P less than 0.001). Those at greatest risk for harboring an asymptomatic colonic adenoma are male FDRs over the age of 50 (40 percent vs. 20 percent for age-matched male controls). Based on probability curves, males with one FDR afflicted with colon cancer appear to have an increased risk of developing a colonic adenoma beginning at 40 years of age. Our results document, for the first time, an increased prevalence of colonoscopically detectable adenomas in asymptomatic first-degree relatives of colon cancer patients, as compared with asymptomatic controls, and support the use of colonoscopy as a routine screening tool in this high-risk group.

Colonoscopy in patients with a family history of colorectal cancer

Since 1982 it has been the second author's policy to advise all patients who have presented with a positive family history of bowel cancer and who are over the age of 30 years to undergo colonoscopy. In the period to August 1990, 600 such patients had at least one colonoscopy. Colorectal polyps or cancer were detected in 270 patients (45 percent). The incidence was essentially the same for the 171 patients with only second-degree relatives affected (43 percent), for the 194 patients with more than one affected relative (45 percent), and for the 429 patients with an affected first-degree relative (46 percent). Only the 55 patients with more than one affected first-degree relative had a higher incidence (67 percent). The incidence in the 136 totally asymptomatic patients was 36 percent but was 48 percent in the 464 with symptoms. In 37 patients carcinoma was diagnosed. Even in the 30- to 39-year age group there was a 29 percent incidence of polyps or carcinoma. Colonoscopic screening of patients with a family history of bowel cancer compares favorably with mass screening for breast cancer. It is currently advised that all patients over 30 years of age with a family history of colorectal cancer undergo colonoscopy on presentation and, if clear, every four years thereafter unless two first-degree relatives are affected, when it should be every two years.

Frequency of familial colorectal cancer

Familial clustering of cancer is not uncommon. The frequency of familial colorectal cancer was estimated by taking family histories from 100 patients presenting with apparently sporadic colorectal cancer. Compared with controls, the relative risk of a positive family history for colorectal cancer was 4.6. Life-table methods were used to examine the observed to expected mortality from colorectal cancer. Overall there was a fourfold increase in mortality rate (P less than 0.0001), which was greatest in female relatives of patients with colonic cancer (P less than 0.001). Three families with dominant inheritance of colorectal cancer and one family with Lynch type II syndrome were identified. Nine per cent of patients had siblings who had developed colorectal cancer a median of 4 years before the diagnosis of the index patient (range 1-17 years). It is recommended that a careful family history should be obtained from all patients with colorectal cancer. Where a positive history is obtained a geneticist may determine empirical risks for the development of colorectal cancer and the appropriate method of surveillance may be selected.