Colonoscopic follow-up of adenomas and colorectal cancer

Risk prediction models for colorectal cancer: a review

Risk prediction models are important to identify individuals at high risk of developing the disease who can then be offered individually tailored clinical management, targeted screening and interventions to reduce the burden of disease. They are also useful for research purposes when attempting to identify new risk factors for the disease. In this article, we review the risk prediction models that have been developed for colorectal cancer and appraise their applicability, strengths, and weaknesses. We also discuss the factors to be considered for future development and improvement of models for colorectal cancer risk prediction. We conclude that there is no model that sufficiently covers the known risk factors for colorectal cancer that is suitable for assessment of people from across the full range of risk and that a new comprehensive model is needed.

Significance of a normal surveillance colonoscopy in patients with a history of adenomatous polyps

PURPOSE

The aim of this study was to determine the appropriate surveillance for patients with a history of adenomatous polyps whose last colonoscopic examination was normal.

METHODS

This was a retrospective review of a database of 7,677 colonoscopies (1990 to 1996). In patients under colonoscopic surveillance, we reviewed cases of patients who had received three colonoscopies (an index (initial) colonoscopy positive for adenomas and 2 follow-up colonoscopies (interim and final)). The risk of adenomas and cancers at final follow-up colonoscopy was compared between patients having a normal interim colonoscopy and those with a positive interim colonoscopy. The risk at final colonoscopy was also stratified by time interval and the size and number of adenomas at the initial index colonoscopy.

RESULTS

Two hundred four patients undergoing surveillance for adenomas met inclusion criteria. At index colonoscopy the median polyp size was 1 cm and median frequency was three polyps. At all follow-up colonoscopies, we detected 493 adenomas and one cancer (median follow-up, 55 months). At 36 months patients with a normal interim colonoscopy (n = 91) had significantly fewer polyps than patients with a positive interim colonoscopy (n = 113; 15 vs. 40 percent; P = 0.0001). By 40 months, adenomas were detected in more than 40 percent of patients in both groups. The risk after a normal interim colonoscopy was not affected by time interval or number or size of polyps. Adenomas found subsequent to a normal interim colonoscopy were dispersed throughout the colon in 28 patients and isolated to the rectosigmoid in 6 patients.

CONCLUSIONS

In patients with a history of adenomas, a normal follow-up colonoscopy is associated with a statistically but not clinically significant reduction in the risk of subsequent colonic neoplasms. These patients require follow-up surveillance colonoscopy at a four-year to five-year interval.

The natural history of isolated rectosigmoid adenomatous polyps: is flexible sigmoidoscopy a safe alternative for surveillance?

PURPOSE

Colonoscopic surveillance is recommended for patients with adenomatous polyps. Significant cost savings would result from identification of subgroups of patients in whom less costly surveillance would suffice. This study was performed to determine the natural history of patients undergoing removal of isolated rectosigmoid adenomas and to establish whether flexible sigmoidoscopy might be adequate for follow-up.

METHODS

A retrospective review of a database of 7,677 colonoscopies, from 1990 to 1996, identified patients who had a minimal follow-up of two years after removal of adenomatous polyps isolated to the rectosigmoid. Polyps detected on surveillance colonoscopy were categorized as distal (< or =60 cm from anal verge), proximal (>60 cm from anal verge), and diffuse (proximal plus distal). The risk of polyp formation was determined by actuarial analysis using the Kaplan-Meier method.

RESULTS

Sixty-two patients undergoing surveillance for adenomas met inclusion criteria. At the index colonoscopy, 124 isolated rectosigmoid polyps were identified. The median polyp size was 1 cm and median frequency was one polyp. The median follow-up time for the entire cohort (N = 62) was 53 months. At follow-up surveillance colonoscopy, 105 additional adenomas were discovered and removed in 40 patients. No malignant polyps were detected. The pattern of polyps detected were proximal (n = 19), rectosigmoid (n = 16), and diffuse (n = 5).

CONCLUSIONS

The majority (65 percent) of patients with isolated rectosigmoid polyps have additional polyps on long-term surveillance, and 60 percent of patients will have these polyps located proximal to the reach of a sigmoidoscope. Therefore, flexible sigmoidoscopy is not a safe alternative for surveillance of patients with isolated rectosigmoid polyps.

What is the risk factor for metachronous colorectal carcinoma?

PURPOSE

The purpose of this study was to determine the risk factors for developing metachronous colorectal carcinoma and to determine an adequate postoperative colonoscopic surveillance.

METHODS

Two hundred eighty-four patients, examined by routine colonoscopy after resection for colorectal carcinoma, were reviewed. Clinical and pathologic factors were assessed by multiple logistic regression analysis.

RESULTS

One hundred eighty-three patients with synchronous adenoma or carcinoma at the initial operation had a significantly higher incidence of both metachronous adenoma and carcinoma than the 101 patients without a synchronous lesion. Other clinical factors including age, gender, tumor stage, tumor site, and tumor grade were not significant for an increased incidence of metachronous carcinoma. The presence of synchronous lesions proved to be the only risk factor (relative risk, 3.293; P = 0.0155) for developing metachronous carcinoma. Metachronous carcinoma was detected in 30 patients (10.6 percent) and completely removed from all patients. Mucosal carcinoma was found in 25 patients (8.8 percent) and invasive carcinoma in 5 patients (1.8 percent). All five invasive carcinomas were detected in asymptomatic patients having synchronous lesion. Four patients required a second operation for metachronous carcinoma more than 13 months following the first.

CONCLUSION

The risk factor for developing metachronous carcinoma is the presence of synchronous adenoma or carcinoma at the initial operation. To detect metachronous carcinoma at a curable stage, annual colonoscopic surveillance should be performed for high-risk patients.

Development of a Haemophilus two-dimensional protein database

Members of the Haemophilus genus are responsible for various human infections including respiratory infections and meningitis. The complete nucleotide sequence of the Rd strain of Haemophilus influenzae has been reported and represents a valuable resource to investigate gene expression within this bacterial group. We described previously the application of two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) to characterise the proteins of Haemophilus influenzae (Cash et al., Electrophoresis 1995, 16, 135-148). We have extended these data with comparative studies of the proteins from other members of the Haemophilus genus (specifically H. parainfluenzae, H. haemolyticus and H. parahaemolyticus) to identify homologous proteins and, by extension, the genes encoding them, among these bacteria. The proteins extracted from each of these bacterial isolates were compared by coelectrophoresis to the 2-D protein profile of the reference nontypable strain of H. influenzae (HI-64443) used as the basis for the 2-D protein database. A composite reference 2-D protein profile of HI-64443 was derived from three independent analyses of the soluble bacterial proteins. Between 21% and 37% of the HI-64443 proteins from the reference 2-D protein profile comigrated with proteins in the other isolates from the Haemophilus genus. This compared with 62% and 64% comigration when HI-64443 was compared with the Eagan and Rd strains of H. influenzae, respectively. The 2-D protein profile of the Rd strain of H. influenzae was compared to that of HI-64443 by coelectrophoresis; 64% of the proteins detected for the Rd strain comigrated with proteins found for HI-64443 when analysed in parallel. The capacity of 2-D PAGE to investigate global interactions of gene expression was applied to the analysis of superoxide dismutase (SOD) expression in H. influenzae strain Eagan. A "knock-out" mutant in the sodA gene which encodes [Mn]-SOD was characterised with respect to protein synthesis compared to the parental isolate. From these analyses, the primary product of sodA was provisionally identified as a protein with a molecular mass of 25500 Da and an estimated pI of 6.55. Quantitative changes in the expression of two other proteins in the SOD mutant were detected by comparison with the parental isolate. These data are discussed in relation to the development of a 2-D protein database for H. influenzae and related bacteria to investigate genome homologies and gene expression.