The National Polyp Study

Polyps: the pathologist's perspective

Adenomas of the colon and rectum are perhaps the most commonly encountered of human benign epithelial neoplasms. Evidence of their relationship to the development of colorectal carcinoma has mounted over the years. They represent a phase present for significant duration in many fated to develop colon cancer. Because of this, and because of the technical advances in endoscopy, a great deal of effort has been expended on identifying and removing these lesions. Subsequent care of the patient is heavily dependent on the pathologic analysis of these lesions. they must be properly classified; the presence of cancer must be carefully sought. If present, the character and location of the cancer arising in the polyp must be carefully described. Communication between clinician and pathologist if of paramount importance. Attention must be paid to the precise meaning of such terms as dysplasia, carcinoma, and invasion. The pathologist's report needs to detail parameters important in determining prognosis and further therapy.

Adenoma-carcinoma sequence: a reappraisal with immunohistochemical expression of ferritin

To examine the biological significance of ferritin (FRN) expression, a retrospective immunohistochemical study was performed in normal colonic mucosae (n = 8), adenomas (n = 88), and colorectal carcinomas (n = 104). FRN was present in some epithelia in the crypt base of normal colonic mucosae. Significant cytoplasmic staining for FRN was revealed in 26 (29.5%) cases of adenoma and 54 cases (51.9%) of adenocarcinoma. The cancer cells had a higher proportion of FRN expression than those of adenomas or non-neoplastic mucosae (P < 0.001). Expression of FRN showed a positive association with the degree of dysplasia (P = 0.039) and the distal location of adenoma (P = 0.013). FRN expression tended to be associated with the tumor size (P = 0.083), but no substantial difference was observed among the histologic types of adenoma (P = 0.754). The results suggest that cytoplasmic FRN expression is associated with cellular proliferation. The proliferative index shows a significant difference through the adenoma-carcinoma sequence. Further investigation is necessary to clarify the clinical implication of FRN expression in tumor cells and normal-appearing mucosae.

Colonic investigations in the elderly: colonoscopy or barium enema?

Colonoscopy (CS) is currently considered the best diagnostic procedure for colonic imaging. The objectives of this multicentric study were to assess whether CS or simple contrast barium enema (SCBE) has the best effectiveness and tolerance in the elderly (over 80 years old). Except in cases of emergency, 67 elderly patients from 3 centers were randomized among three diagnostic strategies: CS, SCBE or barium enema+rectosigmoidoscopy (BERS). CSs were generally carried out after polyethylene-glycol (PEG) cleansing, and barium enemas after enema cleansing. The diagnostic effectiveness of the three strategies was not significantly different: a colonic abnormality was found in CS, SCBE, BERS groups in 65, 56 and 71% of the cases, respectively. No other investigation was needed in 61 to 76% of cases, and, on the basis of the exploration, final therapy was modified in less than 22% of cases. Overall cleansing quality was significantly better with barium enema (84.1%) than with CS (57.0%; p < 0.05). This was explained by a poor tolerance to PEG intake, which led to 28.2% of adverse effects, compared with 7.1% after enema preparation (p < 0.05). This resulted in a significantly higher failure rate of complete colonic exploration with CS (48%) than with barium enema (9%; p < 0.001). In conclusion, the effectiveness of the three diagnostic strategies is similar in the elderly. However, due to a better acceptance of the enema preparation, and to a better success rate of complete exploration, SCBE should be preferred to investigate colonic symptoms when the above preparations are used.

Detection of p21ras mutations in colorectal adenomas and carcinomas by enzyme-linked immunosorbent assay

BACKGROUND

Point mutations of the ras protooncogene, primarily within codons 12 and 13, are commonly identified in colorectal carcinomas and large adenomas. Despite data suggesting that ras genotyping may have clinical significance with respect to colorectal cancer screening and prognosis, more widespread use has been limited because of the lack of a suitable assay system. The principal objective of this study was to assess the feasibility and validity of a qualitative enzyme-linked immunosorbent assay (ELISA) for detecting the four most common ras mutations in human colorectal tumors at the protein (p21ras) level.

METHODS

Tissue homogenates (11-121 micrograms) from endoscopically or surgically resected colorectal adenomas, carcinomas, and normal mucosae were evaluated by a commercially available ELISA (Oncogene Science, Inc. Cambridge, MA) for mutant p21ras containing arginine position 12 (arg12), valine position 12 (val12), aspartate position 12 (asp12), and aspartate position 13 (asp13) amino acid substitutions. Portions of the same tissue from an initial series of 27 specimens also were subjected to mutant-enriched polymerase chain reaction (PCR) and/or PCR amplification with subsequent DNA sequence analysis to validate the ELISA data.

RESULTS

Forty-seven adenomas, 9 carcinomas, and 14 normal mucosae were assayed. Mutations were identified in 16 (34%) of the adenomas (7-asp12, 7-val12, 2-asp13), 3 (33%) of the carcinomas (1-asp12, 1-arg12, 1-asp13), and none of the normal mucosae by ELISA: Polymerase Chain Reaction and DNA sequencing analyses demonstrated identical results for 21 of the 23 (91%) and 14 of 16 (88%) homogenates tested, respectively. The ELISA demonstrated an overall sensitivity of 80-86%, specificity of 90-92%, positive predictive value of 86-100%, and negative predictive value of 86-91%.

CONCLUSIONS

The ELISA is a feasible and valid approach for identifying p21ras mutations in human colorectal adenomas and carcinomas.

Follow-up after polypectomy: consensus?

Patients who have had a colorectal adenoma resected have an increased risk of subsequent cancer and may benefit from follow-up surveillance. Surveillance strategies should be tailored to the assessed risk of each individual patient. A number of long-term follow-up studies indicate that the risk of metachronous neoplasia is higher if on index colonoscopy there were multiple (> or = 2) adenomas, or if any adenoma was large (> or = 1 cm), contained villous tissue or severe dysplasia, or if the patient had a family history of colorectal neoplasia. Data from the U.S. National Polyp Study indicate that polyp resection and follow-up surveillance greatly reduces the incidence of metachronous cancer, and that the first follow-up colonoscopy does not need to be performed for 3 years. Current data have been incorporated into a comprehensive consensus practice guideline.

Interference with the adenoma-carcinoma sequence

Epidemiological, pathological, and genetic studies indicate that most colorectal cancers arise in benign neoplastic polyps (adenomas). The likelihood of malignant change increases with adenoma size and volume of villous tissue. Adenomas are monoclonal products of a single stem cell mutation. Acquired genetic mutations and chromosomal deletions that occur late in the polyp-cancer sequence have been well described, although the initiating events leading to micro-adenoma formation are still unknown. Both inherited and environmental factors are implicated. Although the evidence in support of the adenoma-carcinoma sequence is indirect, it is compelling. Chemoprevention trials have not yet identified effective methods of primary prevention. Colonoscopic resection of adenomas (secondary prevention) plus post-polypectomy surveillance markedly decreases the incidence of colorectal cancer.

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.

Elevated c-yes tyrosine kinase activity in premalignant lesions of the colon

BACKGROUND/AIMS

The cellular oncogene c-yes and its viral homologue v-yes (the transforming gene of Yamaguchi 73 and Esh avian sarcoma viruses) encode 62-kilodalton, cytoplasmic, membrane-associated, protein-tyrosine kinases. For the related Src kinase, a close correlation exists between elevated kinase activity and cell transformation. Previously, we observed elevated Yes activity in many human colon carcinomas. Colonic neoplasia provides an opportunity to study tumor progression because most carcinomas arise from adenomas, which in turn arise from normal epithelia. The malignant potential of adenomas varies with size, histology, and degree of dysplasia. Large adenomas (> or = 2 cm) with villous architecture and severe dysplasia are most likely to develop carcinoma.

METHODS

To determine whether Yes is activated in premalignant lesions of the colon, we measured its in vitro protein-tyrosine kinase activity in 21 colonic adenomas from 17 patients.

RESULTS

Activity of Yes in adenomas at greatest risk for cancer was significantly greater (12- or 14-fold as measured by enolase or autophosphorylation, respectively) than activity in adjacent normal mucosa. Moreover, villous structure, large size (> or = 2 cm), or severe dysplasia correlated with elevated Yes activity.

CONCLUSIONS

The activity of Yes is elevated in adenomas that are at greatest risk for developing cancer.

Obesity and adenomatous polyps of the sigmoid colon

The relation between obesity and adenomatous polyps of the sigmoid colon was investigated in male self-defense officials who received a retirement health examination at three hospitals of the Self-Defense Forces in Japan between January 1991 and December 1992. Body mass index (BMI) and waist-hip circumference ratio (WHR) were used as indices of obesity. A total of 228 adenoma cases and 1484 controls with normal sigmoidoscopy were identified in 2228 men: cases having small adenomas (< 5 mm in diameter) and those with large adenomas (5 mm or greater) numbered 115 and 102, respectively. Smoking, alcohol use, physical activity, rank, and hospital were controlled for by multiple logistic regression analysis. BMI and WHR were classified into four levels using the 30th, 60th, and 90th percentiles of each distribution in the control as cut-off points. There was a significant two-fold elevation in the overall adenoma risk among men at the highest BMI level (> or = 26.95) compared with those at the lowest level (< 22.48), but the risk did not linearly increase: a similar increase was also noted for large adenomas. While WHR was only weakly related to the overall adenoma risk, the risk of large adenomas progressively increased with increasing levels of WHR; odds ratio (OR) 2.9 (95% confidence interval (CI) 1.4-5.9) for the highest (> or = 0.958) versus lowest (< 0.878) levels. BMI was not materially associated with adenoma risk after additional adjustment for WHR, but a positive association between WHR and large adenomas was independent of BMI: OR 3.4 (95% CI 1.5-7.6) for the highest versus lowest levels. These findings suggest that obesity is associated with an increased risk of colon adenomas, probably with adenoma growth.

Cancer of the colon and rectum in Ghana: a 5-year prospective study

A prospective study of 134 patients who presented to a teaching hospital in Ghana for the first time with colorectal cancer between January 1987 and December 1991 is reported. The mean number of new patients per year was nearly three times that of a decade ago. The disease afflicts both sexes equally and the age of highest incidence is in the seventh and eighth decades. Some 65 patients had colonic cancer and 69 rectal lesions. Most patients presented with advanced disease and only four of 109 in whom disease was staged (3.7 per cent) had Dukes A tumours. Right-sided cancer of the colon was more common than that of the left. The importance of rectal examination is emphasized by the finding that 78 per cent of rectal tumours were within reach of the examining finger. 'Curative' resection was possible in 60 per cent of patients with colonic cancer but in only 36 per cent of those with rectal tumours. The postoperative mortality rate of patients who underwent laparotomy was 13.6 per cent and in those who had resection 5.5 per cent. Long-term follow-up was poor. These results emphasize the need for accurate data collection on colorectal carcinoma, public education on the importance of early diagnosis and follow-up after treatment. These findings also call for a study of the epidemiology and aetiology of colorectal cancer in Ghana.

Screening for colorectal cancer by nurse endoscopists

BACKGROUND

Case-control studies have demonstrated that screening by sigmoidoscopy is effective in reducing mortality from colorectal cancer. If nurses performed screening examinations, more patients could be screened and, at current income levels, at a lower cost.

METHODS

Two registered nurses and two licensed practical nurses learned to perform examinations with the flexible fiberoptic sigmoidoscope in order to screen patients for colorectal tumors. They performed 1881 independent examinations of outpatients more than 45 years of age. During the same period, 730 examinations were performed by two gastroenterologists in similar patients.

RESULTS

The mean depth of insertion of the sigmoidoscope was slightly but significantly greater in the patients examined by the physicians than in those examined by the nurses (48 vs. 46 cm in men, P = 0.003; 41 vs. 38 cm in women, P = 0.002). Adenomas were found in 14 percent of the men and 8 percent of the women examined (P = 0.001). Nine cancers were found in men and four in women. There were no significant differences between the nurses and the physicians in the proportion of examinations that were positive for adenomas or cancer. No complications occurred during the initial examinations or during 894 follow-up sigmoidoscopic procedures. Among the patients whose initial examination results were normal, more of those examined by nurses returned for follow-up sigmoidoscopy after 12 months or more (45 percent, vs. 30 percent of those examined by physicians; P = 0.001).

CONCLUSIONS

Nurses can carry out screening by flexible sigmoidoscopy as accurately and safely as experienced gastroenterologists.

Prevention of colorectal cancer by colonoscopic polypectomy. The National Polyp Study Workgroup

BACKGROUND

The current practice of removing adenomatous polyps of the colon and rectum is based on the belief that this will prevent colorectal cancer. To address the hypothesis that colonoscopic polypectomy reduces the incidence of colorectal cancer, we analyzed the results of the National Polyp Study with reference to other published results.

METHODS

The study cohort consisted of 1418 patients who had a complete colonoscopy during which one or more adenomas of the colon or rectum were removed. The patients subsequently underwent periodic colonoscopy during an average follow-up of 5.9 years, and the incidence of colorectal cancer was ascertained. The incidence rate of colorectal cancer was compared with that in three reference groups, including two cohorts in which colonic polyps were not removed and one general-population registry, after adjustment for sex, age, and polyp size.

RESULTS

Ninety-seven percent of the patients were followed clinically for a total of 8401 person-years, and 80 percent returned for one or more of their scheduled colonoscopies. Five asymptomatic early-stage colorectal cancers (malignant polyps) were detected by colonoscopy (three at three years, one at six years, and one at seven years). No symptomatic cancers were detected. The numbers of colorectal cancers expected on the basis of the rates in the three reference groups were 48.3, 43.4, and 20.7, for reductions in the incidence of colorectal cancer of 90, 88, and 76 percent, respectively (P < 0.001).

CONCLUSIONS

Colonoscopic polypectomy resulted in a lower-than-expected incidence of colorectal cancer. These results support the view that colorectal adenomas progress to adenocarcinomas, as well as the current practice of searching for and removing adenomatous polyps to prevent colorectal cancer.

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.

Serum lipids and left-sided adenomas of the large bowel: an extended study of self-defense officials in Japan

In the on-going study of men retiring from the Self-Defense Forces in Japan, we previously reported that serum total cholesterol was not related to colorectal adenomas but that men with low levels of serum high-density lipoprotein (HDL) cholesterol had an elevated adenoma risk. We examined whether the previous observation was reproducible in a different set of data accrued subsequently in the study. Serum total cholesterol, HDL-cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides were compared between 138 cases of colorectal adenomas at the depth of 60 cm or less from the anus and 909 controls with normal sigmoidoscopy in the period from October 1988 to December 1990. There was virtually no relation between adenoma risk and any of the serum lipids studied with or without adjustment for smoking, alcohol use, and body mass index. In the analysis combining the earlier and present data, however, men with large adenomas (> or = 10 mm, n = 25) tended to have lower levels of total cholesterol and LDL-cholesterol compared with controls (n = 1,612); adjusted mean differences were -0.21 mmol/l (P = 0.24) and -0.26 mmol/l (P = 0.13), respectively. These findings are inconclusive, but hypocholesterolemia may be associated with the growth of colorectal adenoma.

The Funen Adenoma Follow-Up Study. Characteristics of patients and initial adenomas in relation to severe dysplasia

Between 1978 and 1992 a total of 1689 colorectal adenomas were removed in 1042 patients with no history of previous colorectal neoplasms. One hundred and eighteen patients had at least one adenoma with severe dysplasia. A 'clean colon' was ensured by total colonoscopy in 97% of the patients. A multiple logistic model was used to assess the independent risk factors associated with severe dysplasia. The size of largest adenoma and the extent of villous component were identified as independent patient risk factors associated with high risk of severe dysplasia. The results indicated that the risk of severe dysplasia is high in patients with large and/or villous adenomas and the risk is even higher when the adenomas are found in the sigmoid colon or rectum.

Patient characteristics and pathology in colorectal adenomas removed by colonoscopic polypectomy

Between September 1981 and August 1987 420 patients with 565 adenomas underwent colonoscopic polypectomy to produce a 'clean colon'. Data from these patients were analysed to identify associations between patient characteristics (age and sex), polyp characteristics (site, size, shape, multiplicity and villous content) and the degree of dysplasia in the index adenoma. In univariate analysis, severe dysplasia in the index adenoma was significantly but weakly associated with size (> or = 10 mm), peduncular shape and villous architecture. Logistic regression confirmed an independent effect only from villous architecture. These findings suggest that it is unlikely that strong predictors of a patient developing a metachronous adenoma or colorectal cancer can be identified on the basis of an index adenoma found at initial colonoscopy. These patients will continue to be followed to investigate this question.

Protein tyrosine kinase in colorectal adenoma

To determine whether protein tyrosine kinase (PTK) could be utilized as a biological indicator of colonic tumorigenesis, we examined the PTK activity in the cytosolic and particulate fractions of homogenates from 25 adenomas (polyps) and from adjacent normal mucosa. The particulate fraction PTK activity in the colorectal adenomas was significantly higher than in the normal mucosa. The adenomas were then analyzed according to size, histological type (tubular and tubulovillous), and degree of dysplasia (mild, moderate and severe). The average particulate fraction PTK activity ratio (adenoma/normal mucosa) of tubulovillous adenomas or adenomas with moderate to severe dysplasia was significantly elevated in comparison with that of tubular adenomas or adenomas with mild dysplasia. The particulate PTK activity ratio increased significantly with increasing adenoma size, while the cytosolic ratio did not. The cytosolic PTK activity ratio in tubulovillous adenomas or adenomas with severe dysplasia decreased significantly with increasing size. These findings suggest that colonic carcinogenesis might be associated with alterations in the cellular level of PTK activity and that the PTK activity ratio (adenoma/normal mucosa) in the particulate and/or cytosolic fractions may possibly correlate with the risk of malignant transformation.

Relationship of diet to small and large adenomas of the sigmoid colon

The relation of dietary factors to the risk of adenomas of the sigmoid colon was examined in men receiving a retirement health examination at the Self-Defense Forces Fukuoka Hospital between October 1986 and 1990. A total of 187 adenoma cases and 1557 controls with normal colonoscopy were identified in the series. Cases were further classified into small-adenoma (< 5 mm, n = 78) and large-adenoma (> or = 5 mm, n = 67) groups. The consumptions of selected foods and beverages were ascertained before colonoscopy by means of a self-administered questionnaire. After adjustment for smoking, alcohol use, rank and body mass index, low rice consumption and high meat intake were independently associated with an increased risk of large adenomas. The risk of small adenomas was not related to either rice consumption or meat intake. Adjusted odds ratios of large adenomas for the low, intermediate and high consumption levels of rice were estimated to be 1.0 (referent), 0.83 and 0.43, respectively (trend P = 0.08), and the corresponding figures for meat consumption were 1.0 (referent), 1.58 and 2.38, respectively (trend P = 0.02). The findings suggest that low rice consumption and high meat intake may promote the growth of colon adenomas, thereby increasing the risk of colon cancer.

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.

Cellular distribution of a colonic adenoma-associated antigen as defined by monoclonal antibody Adnab-9

Adenomatous colonic polyps constitute a precursor for colorectal cancer. Antibodies to these precancerous lesions might identify specific early tumor antigens. Adnab-9 is a murine monoclonal antibody raised against membranes of colonic adenomas. Adnab-9 binding in colonic washings (effluent) correlates with the presence of colorectal cancer. Immunohistochemical staining with Adnab-9 shows cytoplasmic reactivity in scattered cells in 4 of 31 adenomatous tissue sections, 0 of 14 sections of colorectal cancer cells, and 1 of 8 normal-appearing colonic mucosa specimens examined. Adnab-9 recognized a dominant M(r) 87,000 protein species in tissue extracts in the membrane-bound fraction of effluent by Western blotting. Adnab-9 binding by enzyme-linked immunosorbent assay in adenomatous extracts is higher than cancer or normal tissue, is membrane-bound, and is absent from established colorectal cancer cell lines. This distribution and nature of immunostaining suggest that Adnab-9 recognizes a determinant associated with the membrane component of a subpopulation of adenoma cells which may have a role in early colorectal neoplasia.

Estimates of costs and effects of screening for colorectal cancer in the United States

BACKGROUND

In many ways, colorectal cancer might be an excellent candidate for mass screening because of the following: (1) it is the second leading cause of cancer mortality in the United States; (2) it develops slowly from a precursor lesion; and (3) methods of early detection are available. Barriers to screening include unproven efficacy of the procedure and high costs.

METHODS

Cost analyses are derived from two mathematic models that estimate screening costs and effects based on expert opinion and data from uncontrolled screening studies.

RESULTS

One screening option that follows the guidelines of the American Cancer Society and the National Cancer Institute (annual testing for occult fecal blood and sigmoidoscopy every 5 years) could result in a 40% decrease in colon cancer mortality for American adults between the ages of 50 and 75 years if they comply with screening. This model, developed by David Eddy, projects an average of 44 days of extra life per person screened, at a net cost of $57 per day of life gained. Using assumptions much less favorable to screening, the Office of Technology Assessment modeled this same screening strategy for those aged 65 years and older. This model predicted a similar benefit of extra life per person at a cost of $118 per day of life gained. This doubling of the predicted cost was caused by the inclusion of subsequent colonoscopic surveillance costs for those found to have polyps. Direct costs of screening annually for fecal occult blood and every 5 years by sigmoidoscopy would cost an average of approximately $48 per person per year for screening and follow-up testing of all positive results. Fecal occult blood testing alone, although less effective, costs only $20 per person per year, including follow-up testing of all positive findings.

CONCLUSIONS

The results from randomized trials of fecal occult blood screening will be known in the next 5 years, but trials of screening with sigmoidoscopy will not be complete for 10-15 years. Because mass screening programs will be difficult to fund without better data on their efficacy, colorectal cancer screening will continue to be a matter of individual decision making in the clinical setting for years to come. Clearer presentations of costs and benefits that can be understood by both patients and physicians are needed.

Analysis of epithelial and lymphoid phenotypic markers in relation to growth pattern of colorectal adenomas

The relationship of villous to tubular adenomas is poorly understood and often difficult to characterize morphologically. A villous growth pattern in colorectal adenomas has been associated with a higher frequency of high-grade dysplasia. We compared phenotypic markers using immunoperoxidase techniques in paired samples of villous (75% to 100% villous) and pure tubular adenomas matched for size and degree of dysplasia, which were selected by review of 1,000 polyps from our files. The following monoclonal antibodies were used: CAM 5.2 and AE1/AE3 to cytokeratins; B18, D14, B7.1, and B7.8 to four distinct carcinoembryonic antigen epitopes; Leu-M1 and LN3 to HLA-DR antigen; LN2 to invariant chain class II major histocompatibility complex; LN1 and MB2 to B-cell markers; UCHL1 and MT1 to T-cell markers; Leu-7 to natural killer cells; Mac 387 to macrophages; S-100 to Langerhans-type cells; and a polyclonal antibody to secretory component. LN3 reactivity correlated with villous morphology and secretory component correlated with tubular morphology. Combined HLA-DR and secretory component expression discriminated between tubular and villous growth patterns in 12 of 15 pairs of adenomas (P less than .001). LN2 was expressed more frequently than LN3, but did not correlate with growth pattern. Neuroendocrine cells (Leu-7) were more frequent in tubular adenomas. Carcinoembryonic antigen epitopes did not relate to growth pattern. We did not confirm previously reported differences in cytokeratin expression. We concluded that among the markers tested, HLA-DR expression, which may have an immunologic basis, is most characteristic of colorectal adenomas that exhibit a villous growth pattern.

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.

High protein, saturated fat and cholesterol diet, and low levels of serum lipids in colorectal cancer

In a case-control study probing the role of diet on the occurrence of colorectal cancer and undertaken in Athens, Greece, sera were collected from 100 cases and 100 controls, and serum total cholesterol, high-density-lipoprotein (HDL) cholesterol and triglycerides were determined. The biochemical results were analyzed in conjunction with nutrient intakes and a dietary score that summarizes in a linear way the dietary contrast between high-risk (high protein, saturated fat and dietary cholesterol; low vegetable) and low-risk (low protein, saturated fat and cholesterol; high vegetable) patterns. Cases with colorectal cancer had significantly (p less than 0.001) and substantially lower values of serum total cholesterol and particularly HDL cholesterol, but these associations did not reflect dietary practices, since protein intake and, to a lesser (and nonsignificant) extent, saturated fat and dietary cholesterol intake were higher among cases than among controls. In absolute terms, the dietary effect (as summarized in the linear dietary score) is more evident among persons with low serum total cholesterol and HDL cholesterol than among those with high levels of these serum lipids. These results indicate that a diet beneficial with respect to the risk of coronary heart disease is also likely to reduce the risk of colorectal cancer, even though low levels of serum total cholesterol and particularly HDL cholesterol represent important independent correlates of clinically overt colorectal cancer.

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.

DNA ploidy of colorectal cancer and synchronous polyps in polyposis coli

Sixteen patients with polyposis coli and cancer were studied retrospectively to determine the incidence of DNA ploidy abnormalities in the tumors and synchronous polyps. Six patients (37 percent) had nondiploid tumors. Nondiploid tumors were more likely to be advanced and had a significantly worse prognosis (17 percent vs. 76 percent 5-year survival; P less than 0.01). Only 4 of 20 polyps studied were nondiploid. There was no association between tumor and polyp ploidy. All nondiploid polyps were found in patients with synchronous diploid cancers. Patients with nondiploid polyps were more likely to be older and have more advanced tumors than those with diploid polyps. DNA ploidy abnormalities seem to occur with the same frequency in polyposis coli as in the nonpolyposis population, and tumor ploidy correlates with prognosis.

Ethnic differences in the anatomical location of colorectal adenomatous polyps

The ratio of right- to left-sided colonic cancer is increasing, but data on the distribution of its usual precursor lesion, the colorectal adenoma, are contradictory. Therefore, we investigated the prevalence of right- and left-sided colorectal adenomatous polyps from January 1, 1970, to September 30, 1989, using the study design of "epidemiologic necropsy" and the autopsy files of The Johns Hopkins Hospital. Compared with the decade of the 1970's, the 1980's showed a slight decrease in the overall prevalence of right-sided adenomas (6.4 per 1,000, 95% confidence limits 4.7-8.8 vs. 5.1 per 1,000, 95% CL 3.6-6.5), but a marked decrease occurred in left-sided adenomas (11.8 per 1,000, 95% CL 9.3-14.3 vs. 6.7 per 1,000, 95% CL 4.8-8.6). As a result, the ratio of right-sided to left-sided adenomas increased from 0.55 in the 1970's to 0.77 in the 1980's. This increased ratio occurred in both sexes, although prevalences were lower in females, and in whites. Unexpectedly, blacks had a ratio of right-sided to left-sided adenomas greater than unity in both the 1970's and 1980's (1.19 vs. 1.79) due to a relatively high prevalence of right-sided adenomas (5.8 per 1,000, 95% CL 3.6-8.0 in 1970's; 5.8 per 1,000, 95% CL 3.3-8.3 in 1980's), but low prevalences of left-sided adenomas (4.9 per 1,000, 95% CL 3.0-6.8 in 1970's; 3.2 per 1,000, 95% CL 1.2-5.2 in 1980's). The overall adenoma prevalence in blacks was lower than in whites. We conclude that the right-sided predominance of colorectal adenomas in blacks suggests ethnic differences in the pathogenesis of colorectal adenomas. This observation may have important implications for secondary prevention of colorectal cancer.

Univariate and multivariate analyses of the relationship between adenocarcinoma and solitary and multiple adenomas in colorectal adenoma patients

In 584 consecutive patients with no previous history of cancer or polypectomy, 769 adenomas were excised endoscopically and classified retrospectively according to the following parameters: macroscopic growth pattern, size, histological type, grade of dysplasia, anatomical site, presence of adenocarcinoma (ADK), number of adenomas and sex and age of the patient. A multivariate logistic analysis confirmed that size and histological type are the 2 most important predictors of ADK, both in solitary and in multiple adenomas. Adenomas located in the sigmoid portion and in the rectum have an increased probability of ADK, independent of size and histology. Multiple polyps, when compared to solitary polyps, were more frequent in males (p less than 0.01) and were more often larger than 2 cm. Significant similarities in histology, morphology and degree of dysplasia were observed among multiple adenomas from the same patient.

Flexible sigmoidoscopy may be ineffective for secondary prevention of colorectal cancer in asymptomatic, average-risk men

Asymptomatic men (N = 114) 50 years of age or older had screening for colorectal neoplasia with flexible sigmoidoscopy followed by colonoscopy regardless of the sigmoidoscopic result. Our study objective was to determine the prevalence of patients having isolated adenomatous polyps in a proximal colonic segment in the absence of a distal index neoplasm within reach of the sigmoidoscope. Through the combined use of sigmoidoscopy and colonoscopy, adenomatous polyps were detected in 47 of 114 individuals (41%). A total of 88 adenomas was found. Seventeen patients had isolated neoplasms in proximal colonic segments in the absence of distal adenomas. These patients represented 15% of screened subjects (17 of 114) and 20% of individuals who lacked adenomas on sigmoidoscopy (17 of 84). The majority of proximal neoplasms were small (less than 1.0 cm), tubular adenomas. Flexible sigmoidoscopy may be ineffective for screening asymptomatic men for neoplasia. However, it remains to be determined if a 20% miss rate (for those with a normal sigmoidoscopic examination) is significant and whether small proximal adenomas are worth finding.

Follow-up after polypectomy

Progress in understanding the biology, natural history, and relationship to colorectal cancer has provided the basis for a rational approach to patients with adenomas. Pathological assessment of polyps is essential for initial management; only adenomas require search for synchronous neoplasia. A finding of a 30%-50% synchronous rate has been observed. After clearing of the colon of all adenomas, follow-up examination will reveal a 30%-50% rate of metachronous adenomas, but usually with unimportant pathology. Patients with no special concerns at initial polypectomy can have surveillance at intervals of approximately 3 years, while those with an incompletely cleared colon, numerous polyps, or large sessile or malignant adenomas need individualized surveillance. Working guidelines can be provided at this time pending observations in ongoing trials. It is expected but not yet proven that control of colonic adenomas will reduce the incidence and mortality from colorectal cancer. Further research into the biology of adenomas and cancer will undoubtedly provide a clear understanding of susceptibility for colorectal adenomas and more selective control strategies.

Treatment of chronic liver disease with ursodeoxycholic acid

Evidence is accumulating that ursodeoxycholic acid (UDCA), an agent widely employed for gallstone dissolution, exerts therapeutic effects in chronic liver disease. UDCA is thought to act mainly by reducing the detergent properties of bile, making it less toxic for the liver cells. Confirming the results of preliminary observations double-blind, placebo-controlled trials have shown that UDCA significantly decreased serum concentrations of liver enzymes such as alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and gamma-glutamyl transferase in primary biliary cirrhosis and other cholestatic conditions, as well as in chronic active hepatitis. A substantial improvement in liver histology has also been detected in UDCA-treated patients with primary biliary cirrhosis. The effect of UDCA in chronic hepatitis is currently a matter of investigation.

Neoplasia-related changes of two copper (Cu)/zinc (Zn) proteins in the human colon

Cu/Zn-containing proteins have recently become of interest with regard to their relation with malignant disorders. Cu Zn-superoxide dismutase (Cu/Zn-SOD) was found increased in chemically induced tumors of the large bowel whereas metallothionein (MT), containing Zn and some Cu, was shown important for the response of tumors to chemotherapy. In the present study, we evaluated the Cu/Zn-SOD and MT content of normal human colonic mucosa and colorectal carcinomas, obtained from 20 resection specimens, and of 47 adenomatous polyps. The Cu/Zn-SOD content of polyps and carcinomas was significantly (p less than 0.01) elevated when compared to normal mucosa. In the adenomatous polyps the Cu/Zn-SOD content increased significantly with increasing grade of epithelial cell dysplasia, diameter, and presence of a villous component. In the carcinomas no relation was noticed between the Cu/Zn-SOD content and the Dukes' stage or the grade of differentiation. The MT content was significantly decreased in both adenomatous polyps and carcinomas when compared to that in normal mucosa. The MT content was not related to the grade of epithelial cell dysplasia of the polyps, and to the Dukes' stage or the differentiation of the carcinomas. In conclusion, neoplasia of the colorectum is accompanied by an increase in Cu/Zn-SOD and a decrease in MT. These findings support the association between changes in Cu/Zn proteins and malignancy.