Colorectal polyps. Clinical implications: screening and cancer prevention

[Standardized and structured histopathological evaluation of colorectal polyps: a practical checklist against the background of the new WHO classification]

Gastroenterologists removing colorectal polyps expect standardized and well-structured pathological reports, providing them with all relevant data for the further clinical management of the patient. Over the last year, a task force of clinicians and pathologists has developed a checklist to improve and harmonize endoscopic and pathological reporting of colorectal polyps. This checklist concentrates more on concrete recommendations from evidence-based guidelines and established international classifications for daily practice rather than detailed molecular pathological pathways of carcinogenesis. These recommendations are based on the current S3 guidelines for colorectal cancer (the chapter entitled "Management of colorectal polyps"), the histomorphological consensus manuscript of the GI working group of the German Society for Pathology, as well as the current WHO classification for tumors of the digestive system.

The origins of colorectal carcinoma: specific nomenclature for different pathways and precursor lesions

BACKGROUND

The widespread application of molecular methods in pathology has yielded steady advances in our understanding of the origins of colorectal carcinoma. Multiple pathways of carcinogenesis have been demonstrated on the molecular level and visualized on the histopathological level. The WHO has accordingly proposed a number of new designations and terms, particularly for precursor lesions, in order to establish a uniform standard for clinical diagnosis. These should be put into practice at once.

METHODS

In this article, we explain the concept of intraepithelial neoplasia, which replaces the older concept of dysplasia. Moreover, we use this concept in describing a new mechanism of carcinogenesis for colorectal carcinoma, on the basis of a selective review of the literature. We estimate the frequency of precursor lesions according to the new concept using data from our own patient collective. Finally, we discuss the clinical consequences, which have been addressed in the German S3 guideline for colorectal carcinoma.

RESULTS

The new type of precursor lesion, called "sessile serrated adenoma" (SSA), accounts for some 7% of all adenomas in our patient collective and is usually found in the right hemicolon. Traditional serrated adenomas (TSA) made up 1% to 3% of our cases and were found mainly in the left hemicolon and rectum.

CONCLUSION

Our observations on the frequency and location of serrated adenomas accord with the initial findings published in the international literature. In view of the risk that serrated lesions will progress more rapidly, it is recommended that they should be completely removed, with follow-up at a short interval thereafter (three years according to the German S3 guidelines).

Population based randomized study of uptake and yield of screening by flexible sigmoidoscopy compared with screening by faecal occult blood testing

OBJECTIVES

To compare the feasibility of mass screening by flexible sigmoidoscopy with screening by faecal occult blood testing (Haemoccult) and both tests combined.

DESIGN

Patients were randomised to screening by flexible sigmoidoscopy, faecal blood testing, or both tests. The flexible sigmoidoscopy examinations were performed by a general practitioner.

SETTING

General practice.

SUBJECTS

3744 patients aged 50-75 years.

MAIN OUTCOME MEASURES

Uptake, positive results, detection of neoplasia, complications, and recall for diagnostic colonoscopy.

RESULTS

Uptake was significantly higher in the flexible sigmoidoscopy group (46.6%) than in the faecal blood test group (31.6%; P<0.001) or than in the group having both tests (30.1%; P<0.001). Telephone reminders increased uptake of sigmoidoscopy to 61.8%. In total, 1116 sigmoidoscopy examinations were performed without major complication. Polyps were found in 19. 3% (95% confidence interval 17.0% to 21.6%) but only 6.8% (5.3% to 8. 3%) had adenomas and 2.4% (1.5% to 3.3%) "high risk" adenomas. Cancer was detected in four subjects. The faecal blood test yielded positive results in 0.8% (0.2% to 1.4%) but missed at least one cancer and 30 cases of adenoma which were found by sigmoidoscopy in the combined group. Use of histological criteria-shown elsewhere to correlate with future risk of colorectal cancer-to select "positive" patients could reduce recall for diagnostic colonoscopy from about 20% to less than 5%.

CONCLUSIONS

Some of the predicted obstacles to screening with flexible sigmoidoscopy are surmountable. Clear evidence relating to efficacy will be obtained only from a randomised controlled trial.

Recent and past physical activity and prevalence of colorectal adenomas

Epidemiological evidence has generally supported a protective association of physical activity with large-bowel adenomas, but whether the protective effects are restricted to recent or past activity is uncertain. We determined whether recent and past recreational or total daily activity was associated with prevalence of colorectal adenomas among male and female members of a prepaid health plan in Los Angeles who underwent sigmoidoscopy (n = 488 matched pairs). Participants, aged 50-74 years, completed a 126-item semiquantitative food frequency questionnaire and were also interviewed regarding non-dietary risk factors in 1991-93. In the univariate analysis, all measures of recent recreational physical activity were associated with reduced prevalence of polyps. After adjustment for body mass index, smoking status, daily servings of fruit and vegetables, use of non-steroidal anti-inflammatory agents and intakes of calories, saturated fat and alcohol, the associations were weakened. For subjects engaging in high-intensity activities compared with subjects not engaging in vigorous activities, the multivariate odds ratio (OR) for recent recreational activity was 0.7 [95% confidence interval (CI) 0.4-1.1, trend P = 0.08]. Past recreational activity and past or recent total daily activity were not associated with prevalence of adenomas. These results support a modest association of recent recreational physical activity with prevalence of colorectal adenomas.

Screening for colorectal cancer: what are the costs?

We examined a screening program for colorectal cancer in South Australia in terms of its overall direct costs to society and costs to participants. The best estimate of the cost per cancer detected was $18,924 (Australian dollars). Potential improvements in health outcome through screening are discussed in light of these costs.

Immunochemical versus guaiac occult blood stool tests: results of a community-based screening program

This study was designed to investigate two guaiac-based and one immunochemical faecal occult blood test in a community screening program. A total of 39,000 test kits consisting of Hemoccult II, Hemoccult Sensa and HemeSelect were distributed and of these 8933 (23%) were returned for testing. Follow-up contact with 1165 individuals who tested positive on at least one of the nine test slides was successful in 1076 cases (92.4%). Physician verification in 631 individuals revealed 25 patients (4%) diagnosed with colorectal cancer and 145 (23%) with polyps, of which 120 (82.7%) were adenomatous. The percentage of smaller adenomatous polyps detected relative to the percentage of large polyps (> 1 cm) was: Hemoccult II 31% versus 60%, Hemoccult Sensa 73% versus 80% and HemeSelect 34% versus 57%, respectively. The proportion of adenomatous polyps greater than 2 cm detected by individual tests was even more striking with Hemoccult II positive for 83%, Hemoccult Sensa for 100% and HemeSelect for 75%. Of the 25 patients diagnosed with cancer, 17 (68%) were diagnosed with early-stage disease. A statistically significant trend (P < 0.001) was observed with positive predictive values ranging from 3.3% for individuals with only one positive test to one approaching 40% for individuals with 7 or more positive tests. In this study, the most sensitive predictor of colorectal cancer was found to be the combination of Hemoccult II/HemeSelect. While there was no increase in the positive predicted value for adenomatous polyps < or = 1 cm, there was a direct linear increase for adenomatous polyps > 1 cm.

Comparative evaluation of carcinoembryonic antigen, secretory component, and mucins in index and metachronous adenomas of the colorectum

Of 124 patients who underwent endoscopic polypectomy, 70 were colonoscopically reevaluated during a mean period of 10 years. On the basis of the clinical outcome, the patients were divided into three groups: group 1, 31 patients who had a colon still with no adenomas or cancer; group 2, 35 patients in whom one or more metachronous adenomatous polyps developed; and group 3, 4 patients in whom a carcinoma of the colon subsequently developed. In addition to the clinical and pathological features, the pattern of the immunohistologic staining for carcinoembryonic antigen and secretory component was studied. Moreover, the mucin histochemical staining intensity of neutral mucins, sulfomucins, and sialomucins was evaluated. The features of the 40 index adenomas obtained from patients in group 1 were compared with the features of the 51 index adenomas from patients in group 2. Furthermore, these characteristics of the index adenomas were compared with those in the 69 metachronous adenomas of the group 2 patients. It was found that male sex (P less than 0.005) and a history of colorectal neoplasia (P less than 0.02) are main factors for the development of new adenomas. The neutral mucins were less abundant in the group 2 index adenomas (r = -0.21; P less than 0.05). The expression of the other evaluated markers was not significantly different between both groups, although the group 2 index adenomas were significantly smaller (r = -0.22; P less than 0.05) and showed a trend toward a more pronounced cytoplasmic expression of carcinoembryonic antigen than the index adenomas from group 1 (22% vs. 12.5%). Moreover, it was found that in comparison with the index adenomas, metachronous adenomas were significantly smaller (r = -0.24; P less than 0.01) and more sessile (r = 0.20; P less than 0.002). Significant negative correlations, i.e., decrease, were also found in the expression of carcinoembryonic antigen (surface P less than 0.001; cytoplasmic P less than 0.05) and neutral mucins (P less than 0.005) between the index adenomas and the metachronous adenomas, whereas positive correlations were found for secretory component (P = 0.0001) and sulfomucins (P less than 0.05). These findings suggest that a limited production of neutral mucins in the goblet cells of a small index adenoma from a male patient with a history of colorectal neoplasia is indicative of an increased risk for the development of new colorectal adenomas. Furthermore, the clinical, mucin histochemical, and immunohistochemical findings of the metachronous adenomas show less malignancy-associated features than those of the index adenomas.

Prospective blinded trial of the colonoscopic miss-rate of large colorectal polyps

We prospectively studied the colonoscopic miss-rate of large colorectal polyps in a blinded trial featuring tandem colonoscopy. Sixty-three lesions greater than or equal to 1 cm in size were discovered and none were missed. Confidence intervals of 95% are a miss-rate of 0 to 4.6%. We conclude that less than 5% of large colorectal polyps are missed during the index colonoscopic examination in a well-prepared colon.

Physical activity, dietary habits and adenomatous polyps of the sigmoid colon: a study of self-defense officials in Japan

Physical activity and dietary habits were compared between 80 men with adenomatous polyps of the sigmoid colon and 1148 men with normal colonoscopy among male retiring self-defense officials. Physical activity as expressed in terms of time spent doing strenuous activities during leisure time was inversely related to the risk of adenomatous polyps. Controlling for rank, smoking, alcohol and body mass index (BMI), odds ratios for the categories of 0, 1-59, 60-119 and greater than or equal to 120 minutes per week were 1.0, 0.88, 0.70 and 0.44, respectively (trend p = 0.015). Among a limited range of foods and beverages, the consumption of rice, green tea and instant coffee tended to be associated with a decreased risk of adenomatous polyps. Although the associations observed with dietary habits still need to be substantiated, the findings on physical activity lend further evidence to the hypothesis that physical activity may be protective in the development of colon cancer.

Colon, rectum, and anus

Cancer of the colon is the second most common cancer. Adherence to principles of screening, diagnosis, and management have the potential to substantially improve survival.

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.

Pre-operative or postoperative colonic examination for synchronous lesions in colorectal cancer

A review of 130 consecutive large bowel examinations at which a cancer of the colon or rectum was diagnosed has been undertaken. Of 50 patients examined by colonoscopy, the whole colon was seen in only 21 (42 per cent) and almost half of these had a tumour in the caecum or ascending colon. In most cases, an incomplete examination was the result of narrowing of the lumen by the tumour preventing passage of the endoscope. Of 80 patients examined by double contrast barium enema, the entire length of the colon was visualized in 83 per cent but the quality of the examination was sufficient to confidently exclude synchronous neoplastic lesions in only 51 per cent. The incidence of synchronous cancer in this series was within the expected range, although two such cancers were not detected until laparotomy, but the incidence of synchronous adenomas was two-thirds of the expected number in colonoscopy patients and one-third in those examined by barium enema. It is concluded that, in patients with known colorectal cancer, preoperative investigation is unreliable for the detection of all synchronous neoplasia and that patients should have postoperative colonoscopy.