Prognostic evaluation of planned follow-up in patients with colorectal adenomas. An interim report

Surveillance colonoscopy using a transparent hood and image-enhanced endoscopy

Colonoscopists can miss adenomas during colonoscopy screening. A transparent hood attached to the tip of the colonoscope helps detection of colorectal adenomas, but as far as we are aware, there has been no trial indicating its statistically significant effectiveness. Total colonic dye spray might improve the adenoma detection rate but it is complicated and time-consuming for routine clinical usage. Moreover, the efficacy of narrow band imaging for detection of colorectal adenoma is controversial and is still under debate. Autofluorescence imaging (AFI) might be better able to detect flat lesions than white light imaging (WLI), but its ability is influenced easily by the area of the observation. Therefore, we have attached a transparent hood to the tip of an AFI colonoscope during colonoscopy screening in clinical usage. AFI can detect a flat lesion, which is difficult to detect using WLI. A transparent hood can help to detect lesions behind the folds by pushing the colonic fold. We expect that mounting a transparent hood would work complimentary to AFI. Further improvements, including a combination of AFI and a transparent hood, are needed and they would provide optimal surveillance intervals.

Reduction in low-density lipoprotein cholesterol levels during statin therapy is associated with a reduced incidence of advanced colon polyps

BACKGROUND

Elevated serum cholesterol levels may stimulate proliferation in adenomatous polyps (AP). Our aim was to determine how a reduction of low-density lipoprotein (LDL) cholesterol levels in patients taking statins influences the incidence of APs.

METHODS

We performed a retrospective study of patients taking statins who were found to have > or =1 APs on an index colonoscopy, and who also had a follow-up colonoscopy within 3 to 5 years. Patients were divided into 2 groups: (1) those with > or =30% reduction in LDL levels and (2) those with < 30% reduction in LDL levels during the interval between colonoscopies. Univariate and multivariate analysis were evaluated for their association with advanced APs.

RESULTS

We identified 231 patients. Univariate analysis showed that patients with > or =30% LDL reduction had fewer mean total numbers of APs (2.6 versus 3.3, P = 0.02), fewer advanced APs (14% versus 26%, P = 0.04), and smaller APs (5 mm versus 6.1 mm, P = 0.01) than those with <30% reduction in LDL. Multiple logistic regression analysis confirmed that > or =30% LDL reduction was associated with smaller APs (P < 0.01). Subjects with > or =30% LDL reduction also had a 53% reduced incidence of advanced APs (OR, 0.47; CI, 0.22-0.96; P < 0.05). These findings remained significant even when adjusted for nonsteroidal antiinflammatory drug use, age, family history of APs, and body mass index.

CONCLUSIONS

A reduction in LDL levels of > or=30% during a 3- to 5-year period of statin therapy was associated with a 53% reduction in the incidence of advanced APs, even after adjustment for other known polyp risk factors.

Influence of long-term colonoscopic surveillance on incidence of colorectal cancer and death from the disease in patients with precursors (adenomas)

Case-control studies and short term prospective studies have suggested that selected groups of patients with precursors of colorectal cancer may benefit from colonoscopic surveillance after initial removal of adenomas. The aim of the present study was to demonstrate such a possible benefit from long term (1-24 years) colonoscopic surveillance in a population of patients with all types of adenomas regardless of size and way of removal. Two thousand and forty-one patients with a first time diagnosis of colorectal adenoma were included in prospective surveillance between year 1978 and 2002. All adenomas were considered. Incidence of CRC and mortality from CRC was calculated, using age, sex, and calendar specific number of person years of follow-up for comparison with the standard Danish population. CRC was found in 27 patients, the expected number being 41 (RR 0.65, 95% CI 0.43-0.95). Three of the 27 patients died from CRC, the expected number being 25 (RR 0.12, 95% CI 0.03-0.36). A total of 6 289 colonoscopies resulted in severe complications in 20 patients and two died from complications. Long-term colonoscopic surveillance may reduce incidence of CRC as well as mortality in patients with sporadic adenomas. The benefit is reduced to a minor degree by complications from surveillance.

Obesity is associated with an increased prevalence of advanced adenomatous colon polyps in a male veteran population

Obesity has been associated with an increased risk for colonic adenomatous polyps (APs) and colorectal cancers, but the influence of obesity on the development of advanced APs is not clear. The purpose of this study is to determine the influence of obesity on the prevalence of advanced APs in a male veteran population. We performed a retrospective study of patients (n = 2,903) with histologically confirmed APs on an index colonoscopy. APs were evaluated for advanced features (size > or = 1 cm in diameter and/or a villous component and/or high grade dysplasia). Patients were categorized as: normal weight (BMI > 18.5 and < 25), overweight (BMI > or = 25 and < 30), and obese (BMI > or = 30). An association between clinical factors and advanced APs was sought by Kruskal-Wallis test and Pearson Chi-square. Multiple logistic regression analysis was used to determine independent predictors for advanced APs. We identified 2,903 male patients with APs (mean age 64 + 1.1(SE) years; 770 (27%) normal weight, 1,029 (35%) overweight, 1,104 (38%) obese. By univariate analysis, obese patients had a greater prevalence of advanced APs than the overweight and normal weight patients (28 vs. 23 vs. 24%, p = 0.025). Multiple logistic regression analysis confirmed the association of obesity and advanced APs (OR = 1.01, CI = 1-1.02, p = 0.04). For every one-unit increase in BMI above 30, there was a corresponding 1% increase in the frequency of finding advanced APs. Obesity in male veteran patients is associated with the finding of advanced APs on colonoscopy. We speculate that obesity may increase the risk for CRC by promoting the development of advanced APs.

First-degree relatives of patients with advanced colorectal adenomas have an increased prevalence of colorectal cancer

BACKGROUND & AIMS

The risk of colorectal cancer in relatives of patients with adenomatous colonic polyps is not well defined. This study assessed whether finding colonic neoplasia during screening colonoscopy was related to the family history of colorectal cancer among the participants' parents and siblings.

METHODS

Self-reported family history of colorectal cancer was recorded for all participants in a screening colonoscopy study. The size and location of all polyps were recorded before their removal and histologic examination. Participants were grouped according to the most advanced lesion detected.

RESULTS

Three thousand one hundred twenty-one patients underwent complete colonoscopic examination. Subjects with adenomas were more likely to have a family history of colorectal cancer than were subjects without polyps (odds ratio [OR], 1.36; 95% confidence interval [CI], 1.09-1.70). The finding of a small (<1 cm) tubular adenoma as the most advanced lesion was associated with only a modest increase in the OR of colorectal cancer in family members (OR, 1.26; 95% CI, 0.99-1.61), but the presence of an advanced adenoma was associated with a higher OR (OR, 1.62;5% CI, 1.16-2.26). Younger age of adenoma diagnosis was not related to a higher prevalence of a family history of colorectal cancer.

CONCLUSIONS

Relatives patients with advanced colorectal adenomas have an increased risk of colorectal cancer. Individuals with advanced colorectal adenomas should be counseled about the increased risk of colorectal cancer among their relatives.

A comparison of colonoscopy and double-contrast barium enema for surveillance after polypectomy. National Polyp Study Work Group

BACKGROUND

After patients have undergone colonoscopic polypectomy, it is uncertain whether colonoscopic examination or a barium enema is the better method of surveillance.

METHODS

As part of the National Polyp Study, we offered colonoscopic examination and double-contrast barium enema for surveillance to patients with newly diagnosed adenomatous polyps. Although barium enema was performed first, the endoscopist did not know the results.

RESULTS

A total of 973 patients underwent one or more colonoscopic examinations for surveillance. In the case of 580 of these patients, we performed 862 paired colonoscopic examinations and barium-enema examinations that met the requirements of the protocol. The findings on barium enema were positive in 222 (26 percent) of the paired examinations, including 139 of the 392 colonoscopic examinations in which one or more polyps were detected (rate of detection, 35 percent; 95 percent confidence interval, 31 to 40 percent). The proportion of examinations in which adenomatous polyps were detected by barium enema colonoscopy was significantly related to the size of the adenomas (P=0.009); the rate was 32 percent for colonoscopic examinations in which the largest adenomas detected were 0.5 cm or less, 53 percent for those in which the largest adenomas detected were 0.6 to 1.0 cm, and 48 percent for those in which the largest adenomas detected exceeded 1.0 cm. Among the 139 paired examinations with positive results on barium enema and negative results on colonoscopic examination in the same location, 19 additional polyps, 12 of which were adenomas, were detected on colonoscopic reexamination.

CONCLUSIONS

In patients who have undergone colonoscopic polypectomy, colonoscopic examination is a more effective method of surveillance than double-contrast barium enema.

Screening for colorectal cancer

Colorectal cancer is the third most commonly diagnosed cancer and the second leading cause of cancer deaths in the United States. Fortunately, both the incidence and mortality associated with the disease have declined during the past 2 decades. This is likely due, at least in part, to improved efforts at screening and more aggressive removal of adenomatous polyps. However, colorectal cancer screening is still generally underutilized. This article reviews the current status and future outlook for colorectal cancer screening, including a discussion of risk factors for the disease, its anatomic distribution, proposed mechanisms of development from adenomatous polyps, rationale for screening, and screening options. Published literature concerning the cost-effectiveness of colorectal cancer screening is also summarized. The article concludes with a discussion of the emerging consensus regarding the importance of and approaches to screening.

Adenoma size and number are predictive of adenoma recurrence: implications for surveillance colonoscopy

BACKGROUND

Three-year colonoscopic surveillance after initial polypectomy may not be required for all patients. Those with multiple baseline polyps and large adenomas, implicated as predictors of colon cancer, merit close observation. Conversely, patients with single small adenomas may be subjected to early endoscopic surveillance unnecessarily.

METHODS

From our Adenoma Registry we evaluated patient and adenoma characteristics in 697 patients. All had an adenoma recurrence within 3 years of a positive baseline colonoscopy. Potential risk factors studied were age, gender, number of adenomas, size of largest adenoma and histology. We defined a significant outcome as size of 1 cm or greater, tubulovillous or villous histology, high-grade dysplasia, carcinoma in situ, invasive cancer, or 4 or more adenomas.

RESULTS

Having 3 or more adenomas on initial colonoscopy with at least 1 measuring 1 cm or larger greatly increased the chance of a significant finding on the first surveillance colonoscopy. Conversely, patients with 1 or 2 adenomas all measuring less than 1 cm were at extremely low risk of an important outcome within 3 years.

CONCLUSIONS

Patients with 1 or 2 adenomas all measuring less than 1 cm are an identified low risk group and their first surveillance examination may be delayed beyond the standard 3 years.

A randomized surveillance study of patients with pedunculated and small sessile tubular and tubulovillous adenomas. The Funen Adenoma Follow-up Study

BACKGROUND

We wanted to assess the influence of various surveillance intervals on the risk of new neoplasia after removal of pedunculated and small sessile tubular and tubulovillous adenomas.

METHODS

After initial colonoscopic polypectomy patients were randomized to surveillance with either 2 years (group A) or 4 years (group B) between colorectal examinations.

RESULTS

The cumulated risk of a patient having new adenomas was 35.0% (28.7-41.4%) in group A and 35.5% (28.4-42.7%) in group B after 48 months. The risk increased to 44.9% (36.0-53.9%) and 60.1% (48.5-71.7%), respectively, after 96 months. The risk of significant neoplasia (carcinoma or adenoma with villous structure, severe dysplasia, or diameter > 10 mm) was 5.2% (2.3-8.1%) and 8.6% (3.8-13.3%) after 48 months and 8.6% (4.2-13.0%) and 17.4% (7.6-27.2%) after 96 months. More than one adenoma at first examination was associated with higher risk of new adenomas. Furthermore, we found a tendency for age above 60 years and male gender to be associated with higher risk of new adenomas. More than two adenomas at first examination was the only factor found to be associated with a higher risk of new significant neoplasia. One patient in group A and two patients in group B developed cancer, which is not significantly different from the number expected (3.43) in the average Danish population (RR = 0.9, 0.2-2.6).

CONCLUSION

After colonoscopy with removal of all polyps, colorectal examination at 4 years resulted in a similar risk of new adenomas compared with examinations at 2 and 4 years. However, new significant neoplasia tended to be more frequent when first surveillance was at 4 years. Extending the surveillance to 8 years also tended to increase the risk more in the group being examined every 4 years, but reduction of the number of surveillance examinations by more than 50% and a probable reduction of complications from surveillance examinations themselves may justify a recommendation for the longest interval.

Quantification of proliferative activity in colorectal adenomas by mitotic counts: relationship to degree of dysplasia and histological type

AIM

Proliferative activity of tumours reflects their malignant potential. In colorectal adenomas, a subjective impression of the number of mitoses is a criterion often used to assess the degree of dysplasia. Since these subjective impressions of mitotic activity may lack reproducibility, the aim of this study was to perform an objective analysis.

METHODS

Mitotic counts were conducted in tissue sections of 59 colorectal adenomas. Of these, 20 showed mild, 20 moderate, and 19 severe dysplasia, according to blind duplicate assessments by two pathologists. Forty three were classified as tubular adenomas and 16 as "villous" adenomas (tubulo-villous and villous). The number of mitoses, both per unit area of epithelium (area weighted mitotic counts, AWMC) and per colonic crypt (mitotic counts per colonic crypt MCCC), was scored in the most dysplastic area within the adenoma. Mitotic figures were counted using a light microscope (ocular x 10, objective x 40, NA 0.75), and the area of the glandular epithelium was measured using an interactive video overlay measurement system. Twenty glands per specimen were assessed. In the intra-observer reproducibility tests, the coefficients of error for the AWMC and MCCC were 4.5% and 7.4% respectively.

RESULTS

For the AWMC a significant difference was found between mild and moderate as well as between mild and severe dysplasia, but not between moderate and severe dysplasia. The results of the MCCC showed the same trend, but the differences did not reach a significant level. Furthermore, cases classified as mild dysplasia were found that showed numerous mitoses, while cases classified as severe dysplasia were found with only very few mitoses. No significant difference in AWMC was found between tubular and villous adenomas. Thus the different malignant potential of tubular and villous adenomas was not reflected by a difference in AWMC. A seemingly strong difference for MCCC between tubular and "villous" adenomas appeared to depend completely on the difference in crypt size between these two groups.

CONCLUSIONS

The area weighted mitotic count, rather than the mitotic count per colonic crypt, may be useful for assessing the proliferation rate in colorectal adenomas.

Incidence and recurrence rates of colorectal adenomas: a prospective study

BACKGROUND/AIMS

The frequency of colorectal adenomas, the precursor lesions for most cases of colorectal carcinoma, has been generally measured as prevalence rates of adenomas at autopsy or colonoscopy. The aim of this study was to estimate the incidence rate of adenomas and compare it with the adenoma recurrence rate.

METHODS

Data on colonoscopies performed in three New York City practices were collected prospectively. The cumulative rate of adenoma diagnosis on repeat colonoscopy was calculated for patients with no abnormalities on index colonoscopy ("incidence" rate) and for patients with adenomas on the index colonoscopy ("recurrence" rate).

RESULTS

The cumulative incidence rate of adenomas at 36 months was 16%, and the cumulative recurrence rate at 36 months was 42% (P < 0.004). The recurrence rate was higher in patients with multiple adenomas than in those with a single adenoma on index colonoscopy, although the increase was not statistically significant.

CONCLUSIONS

Although the recurrence rate has always been assumed to be elevated, this study is the first to compare the recurrence rate of adenomas with the incidence rate directly and to show that the recurrence rate is indeed elevated.

Growth of colorectal polyps: recovery and evaluation of unresected polyps of less than 10 mm, 1 year after detection

BACKGROUND AND METHODS

Colonoscopic 1-year control of polyps of less than 10 mm left in situ was carried out in 103 (89%) of 116 originally examined patients.

RESULTS

Analysis showed an 85% recovery: 91% and 81% for polyps of 5-9 mm and < 5 mm, respectively. The recovery was significantly related to size and localization, whereas the growth rate was inversely correlated to the originally measured diameter. A linear relationship was demonstrated between anus-to-polyp distances 1 year apart, with a normalized agreement index of 0.70. In only 1 of 189 polyps, an increase of diameter to > 10 mm was demonstrated. The 79 new polyps in 52 (50%) of the patients were significantly smaller, more often right-sided, and related to multiplicity of polyps at the initial examination but not to growth of recovered polyps or cleansing status.

CONCLUSION

An acceptable recovery and growth rate of polyps < 10 mm seems to justify the continuation of the study for the remaining 2 years.

Stereological assessment of architectural changes in dysplastic epithelium of colorectal adenomas

BACKGROUND

Against the background of developing quantitative prognostic indicators for the future risk of colorectal cancer in adenoma bearing-patients, the possibilities of stereological measuring techniques for providing objective measures of architectural changes in colorectal adenomas were examined.

MATERIAL AND METHODS

The haematoxylin-eosin stained tissue sections of 59 adenomas, of which 20 showed mild dysplasia, 20 moderate dysplasis, and 19 severe dysplasia, were assessed. Using a projection microscope equipped with a coherent test system that was specifically designed to analyze anisotropic tissue, the volume density of stroma, epithelium and lumen, the outer and the inner gland surface density, and the length density lumen were determined.

RESULTS

With respect to grading, significant differences in the means of the inner gland surface density and the length density lumen were found mainly between mild and severe dysplasia as well as between moderate and severe dysplasia. This was especially evident when considering the subgroup of tubular adenomas. Stepwise discriminant analysis resulted in an overall correct jackknifed classification of 81.3% when mild and moderate dysplasia cases were taken as one group, and were compared with the group of severe dysplasia cases. With respect to histological type, the volume density lumen and the outer surface density glands, were most favourable. These two features allowed for an 87.5% overall correct jackknifed classification of tubular adenomas, versus adenomas with villous components. The analysis time was roughly 30 minutes per polyp. Intra-observer reproducibility was satisfying, with CE-values < or = 5% for all variables. Inter-observer reproducibility tests were encouraging.

CONCLUSIONS

The application of stereological techniques can be worthwhile in assisting in the classification of colorectal adenomatous polyps. Such techniques could therefore be a useful tool to estimate the prognostic value of adenoma morphology with respect to the development of metachronous colorectal tumours.

The Funen Adenoma Follow-up Study. Incidence and death from colorectal carcinoma in an adenoma surveillance program

The results of a prospective randomized study of 1056 patients with colorectal adenomas are presented. After initial polypectomy from 1978 to 1992, patients were allocated at random to different follow-up intervals varying from 6 to 48 months, except 53 patients who were allocated to intervals of 6 months. The examinations were mainly done by colonoscopy. Ten patients developed colorectal carcinoma, a number similar to that expected (7.96), when compared with a sex- and age-matched normal Danish population. The expected number of carcinomas was also calculated from adenoma to carcinoma conversion rates estimated in other studies and compared with that observed. If all carcinomas develop in large (> or = 10 mm) adenomas or adenomas with severe dysplasia, the expected number of carcinomas would have been 62 and 110, respectively, indicating a significant reduction of carcinomas in the present study. One patient died of colorectal carcinoma, which is significantly lower than the number expected (7.58). Two patients died of complications from therapeutic and diagnostic colonoscopy--that is, 2 deaths in 3959 colonoscopies. In conclusion, the follow-up strategy has resulted in a mortality from colorectal carcinoma which is reduced when compared with the normal population, in spite of an apparently similar incidence of carcinoma. However, previous suggested adenoma-carcinoma conversion rates indicate that a major reduction of incidence actually has taken place.

Randomized comparison of surveillance intervals after colonoscopic removal of newly diagnosed adenomatous polyps. The National Polyp Study Workgroup

BACKGROUND

The identification and removal of adenomatous polyps and post-polypectomy surveillance are considered to be important for the control of colorectal cancer. In current practice, the intervals between colonoscopies after polypectomy are variable, often a year long, and not based on data from randomized clinical trials. We sought to determine whether follow-up colonoscopy at three years would detect important colonic lesions as well as follow-up colonoscopy at both one and three years.

METHODS

Patients were eligible if they had one or more adenomas, no previous polypectomy, and a complete colonoscopy and all their polyps had been removed. They were randomly assigned to have follow-up colonoscopy at one and three years or at three years only. The two study end points were the detection of any adenoma, and the detection of adenomas with advanced pathological features (defined as those > 1 cm in diameter and those with high-grade dysplasia or invasive cancer).

RESULTS

Of 2632 eligible patients, 1418 were randomly assigned to the two follow-up groups, 699 to the two-examination group and 719 to the one-examination group. The percentage of patients with adenomas in the group examined at one and three years was 41.7 percent, as compared with 32.0 percent in the group examined at three years (P = 0.006). The percentage of patients with adenomas with advanced pathological features was the same in both groups (3.3 percent).

CONCLUSIONS

Colonoscopy performed three years after colonoscopic removal of adenomatous polyps detects important colonic lesions as effectively as follow-up colonoscopy after both one and three years. An interval of at least three years is recommended before follow-up colonoscopy after both one and three years. An interval of at least three years is recommended before follow-up examination after colonoscopic removal of newly diagnosed adenomatous polyps. Adoption of this recommendation nationally should reduce the cost of post-polypectomy surveillance and screening.

The National Polyp Study. Design, methods, and characteristics of patients with newly diagnosed polyps. The National Polyp Study Workgroup

The National Polyp Study (NPS) is a multicenter prospective randomized trial designed to evaluate follow-up surveillance strategies in patients who have undergone polypectomy for the control of large bowel cancer. The study design was developed by a joint research committee from American Gastroenterological Association, the American Society for Gastrointestinal Endoscopy, and the American College of Gastroenterology. Subjects who met the eligibility criteria were randomized into two different treatment arms. Eligibility criteria included: removal of one or more adenomas; complete colonoscopy; no prior polypectomy, inflammatory bowel disease, or familial polyposis; and no history of colon cancer. The treatment arms consisted of a frequent follow-up (1 and 3 years after initial polypectomy) and a less frequent follow-up (3 years). Follow-up examinations included fecal occult blood tests, air-contrast barium enema, and colonoscopy. The latter was done on 9112 referred patients at the seven participating centers from November 1980 until February 1990 who had no history of polypectomy, colon cancer, familial polyposis, or inflammatory bowel disease. Of these patients, 4763 (52.3%) had no polyps; 549 (6.0%) had an invasive cancer; 776 (8.5%) had nonadenomatous polyps; 208 (2.3%) had incomplete examinations; 184 (2.0%) had other findings; and 2632 (28.9%) had one or more adenomas, of which 1418 (53.9%) were randomized to one of the two treatment arms. This article reports the background, rationale, objectives, methods, and organization of this study and includes patient characteristics on initial presentation. Future data provided by the NPS may help in the development of recommendations for surveillance guidelines for such patients. This study also provides a framework to address questions regarding the natural history of adenomas and their relationship with colorectal cancer.

Precursors of colorectal carcinoma. Biopsy and biologic markers

The term biologic marker (biomarker) of colorectal cancer refers in this article to an early preclinical phenotypic characteristic that relates to the risk for developing this cancer. Putative biologic markers in the normal colorectal mucosa of patients at risk include abnormal cell proliferation as determined by kinetic studies, ornithine decarboxylase activity, and polyamine synthesis. Alterations of mucin synthesis have been studied using both histochemical stains and lectin-binding techniques. Blood group and related carbohydrate antigens also have been evaluated as potential biomarkers in the normal mucosa. Biopsy small (less than 5 mm) polyps encountered at endoscopy has become a standard practice. Although a small polyp found to be an adenoma has a low likelihood of harboring high-grade dysplasia or invasive carcinoma, it represents an indicator of risk for colorectal neoplasia. Hyperplastic polyps, however, even though they have certain epidemiologic associations with colorectal neoplasia, are controversial as putative biomarkers of clinical relevance. Current research supports a concept of a field defect of the colorectal mucosa at risk for neoplasia, which may be identified by phenotypic abnormalities of the normal mucosa and the development of small adenomas.

Can Hemoccult-II replace colonoscopy in surveillance after radical surgery for colorectal cancer and after polypectomy?

Surveillance after colorectal carcinoma and adenoma includes colonoscopy, which is a demanding procedure for the patient, doctor, and society. Therefore, it was investigated whether a simple fecal occult blood test could replace colonoscopy. Hemoccult-II (H-II) was performed before 1,244 colonoscopies in patients with previous cancer and before 328 colonoscopies in an adenoma surveillance program. The H-II test was positive in 3 of 9 patients with local recurrence, in 2 of 13 with metachronous cancer, and in 31 of 186 with adenomas. The test was positive more often in patients with large and multiple adenomas, sigmoid adenomas, and adenomas with villous elements and moderate-to-severe dysplasia, but the sensitivity did not reach more than 25 to 40 percent. It was concluded that markers more sensitive than H-II are needed to detect metachronous cancers and new adenomas. In the meantime, colonoscopy has to be used with intervals of several years, but not for detection of local recurrent cancer, which in most cases may be found by simpler means.

Screening guidelines for colorectal cancer

A review is given of methods and results of screening for colorectal cancer in average-risk and high-risk groups. Possible methods are digital rectal exploration, endoscopic examination, barium enemas, faecal occult blood tests, tumour markers like carcinoembryonic antigen, Ca-19-9, and others, and gene markers. Final results of large randomized population studies with faecal occult blood tests are expected within the next few years, but it will probably be necessary to add flexible sigmoidoscopy to achieve a major reduction in mortality from colorectal cancer in average-risk persons. Recommendations for screening in high-risk groups are proposed, but strong support for these guidelines are still missing, an exception being first-degree relatives of individuals with familial adenomatous polyposis; the other high-risk groups include members of hereditary non-polyposis colorectal cancer families, relatives of patients with sporadic colorectal cancer, patients with colorectal adenomas, patients with previous colorectal cancer, and patients with inflammatory bowel disease.

Reliability of in situ measurements of colorectal polyps

A reliable and sensitive in situ method for measuring polyp size is fundamental for growth studies of colonic polyps. A measuring probe inserted through a colonoscope can give a visual assessment of polyp diameter, and from a picture of the polyp the area of the polyp on the picture can be calculated by computerized analysis. To test the reliability and sensitivity of these two in situ measurements, 43 colonic polyps (mean diameter, 8.5 mm; range, 4-20 mm) removed by snare diathermy resection were examined. The maximal diameter was measured, and two Polaroid pictures taken of each polyp. After polypectomy each polyp was subjected to extracorporeal reassessment of diameter and measurement of weight and volume. By computerized analysis of the pictures the following variables were estimated: 1) area of the polyp on the picture; 2) largest diameter; 3) maximum width 90 degrees on the largest diameter; 4) maximum distance from centre of gravity; and 5) minimum distance from centre of gravity. Results showed good correlation between diameter measured in situ and after removal (r = 0.93), diameter raised to the 3rd power and weight (r = 0.93), and also to volume (r = 0.77). Area analysis compared with weight was less good (r = 0.72). A very high correlation was demonstrated between weight and volume (r = 0.99). We conclude that the measurement of diameter in situ with a measuring probe is sensitive and somewhat more reliable than computerized analysis of size. The present 3-year follow-up and intervention study will show which of the two methods is preferable for evaluation of polyp growth.

The natural history of colorectal cancer. Opportunities for intervention

There is now a better understanding of the natural history of colorectal cancer, which has provided a basis for intervention to influence outcome. The possible interventions include earlier detection of colorectal cancer, removal of premalignant adenomas, demonstration of the mucosal field defect that precedes neoplasia to evaluate baseline risk and its change with dietary modification, and identification of inherited and dietary risk factors. Five controlled trials evaluating early detection of colorectal cancer with fecal occult blood testing have enrolled more than 309,000 patients. Early stage cancers with improved survival has been observed, but data on mortality reduction have not as yet been reported. Studies of patients with adenomas have demonstrated high synchronous and metachronous rates as a basis for complete colon evaluation initially and a surveillance follow-up program. Hyperproliferation and lack of normal differentiation have been observed as a field defect in the colon preceding neoplasia. Inherited factors have recently been shown to be important in a larger proportion of individuals destined to develop colorectal adenomas and cancer. These observations of the natural history of colorectal cancer have provided new opportunities for the application of radiologic and endoscopic techniques in diagnosis and surveillance; each examination has its merit. Further research is needed to answer many critical questions that have been raised regarding the impact of these interventions.

Adenomas and hyperplastic polyps in screening studies

A survey is given of colorectal polyps detected in a prospective randomized screening study with the fecal occult blood test. It is demonstrated that colonoscopy in persons with positive Hemoccult-II tests results in detection of and removal of a higher number of adenomas than among controls. The strategy may, therefore, possibly be followed by a reduction of the incidence of colorectal cancer. Screen-detected adenomas were most often in males and were larger than among controls; they were most often in the sigmoid colon, whereas the rectum was the most frequent location for adenomas in controls. Eight percent of persons with screen-detected adenomas had some symptoms, which could be referred to adenomas, in contrast to 50% among controls. Hyperplastic polyps served as markers for adenomas in persons with positive Hemoccult-II as well as in controls with adenomas detected by colonoscopy; however, most persons with adenomas had no hyperplastic polyps. Endoscopic polypectomy did not result in any severe complications, but surgical removal in 2 of 22 patients proved fatal. The results presented are compared with those of other prospective randomized trials. The optimistic view--that the incidence of cancer may be reduced by polypectomy in persons with positive Hemoccult-II tests--stresses the importance of securing optimal colonoscopy service.

The benefit of colonoscopy

In a prospective study involving 833 consecutive outpatient and open-access colonoscopies, attempts were made to characterize the benefit of colonoscopy in terms of both predicted and unpredicted findings and therapeutic procedures. The endoscopist therefore predicted the endoscopic findings before the endoscopy. The results were compared for the different indications for colonoscopy. The overall agreement between the predictions and the colonoscopic findings was 61%. Clinically significant abnormalities were found in about half the examinations. The most frequent abnormal findings were benign polyps (24%), inflammatory bowel disease (17%), and malignancy (5%). In about half the patients with a malignancy the indication for colonoscopy was rectal bleeding, and half of the malignancies were not predicted. The greatest benefit of colonoscopy was found in patients referred because of overt rectal bleeding or occult faecal blood, and abnormal barium enema or endoscopy findings. The importance of complete colonoscopy in connection with operation for colorectal carcinoma is emphasized.

Follow-up after polypectomy of colorectal adenomas. The importance of total colonoscopy

Five hundred eighty-two patients with colorectal adenomas or early cancers were polypectomized from 1974 to 1985. In 100 patients, total colonoscopy was performed more than twice after the initial polypectomies. These patients were divided into three groups: group A patients underwent total colonoscopy at 1-year intervals; group B patients underwent total colonoscopy at 2-year intervals, group C patients underwent total colonoscopy at 3-year or more than 3-year intervals. The frequency and location of newly developed adenomas were investigated. The detection rate for new adenomas was 13% in group A and 50% in group B; thus, there was a significant difference between group A and group B (P less than 0.01). The transverse colon is the only segment where the topological proportion of newly developed adenomas increased in comparison with that of index adenomas (P less than 0.05). The detection rate for new adenomas was significantly higher in patients who had carcinoma in situ at the time of initial polypectomy (P less than 0.05). Questionnaires about colonoscopy and colonic adenomas were therefore mailed to the patients who were lost to follow-up after the polypectomy.