Flat adenomas

CT colonography for the detection of nonpolypoid adenomas: sensitivity assessed with restricted national CT colonography trial criteria

OBJECTIVE

The purpose of this study was to determine the prevalence of nonpolypoid adenomas and the sensitivity of CT colonography (CTC) in their detection by use of the restricted criteria of height-to-width ratio<50% and height elevation≤3 mm.

MATERIALS AND METHODS

In the National CT Colonography Trial (American College of Radiology Imaging Network protocol 6664), a cohort of 2531 participants without symptoms underwent CTC and screening colonoscopy. The CTC examinations were interpreted with both 2D and 3D techniques. Nonpolypoid adenomatous polyps identified with CTC or colonoscopy were retrospectively reviewed to determine which polyps met the restricted criteria. The prevalence of nonpolypoid adenomas and the prospective sensitivity of CTC were determined. Descriptive statistics were used to report the prevalence, size, and histologic features. The sensitivities (with 95% CIs) for nonpolypoid and polypoid lesions were compared by two-sided Z test for independent binomial proportions.

RESULTS

The retrospective review confirmed 21 nonpolypoid adenomas, yielding a prevalence of 0.83% (21 of 2531 participants). Eight (38.1%) were advanced adenomas, many (50% [4/8]) only because of large size (≥10 mm). The overall per polyp sensitivity of CTC (combined 2D and 3D interpretation) for detecting nonpolypoid adenomas≥5 mm (n=21) was 0.76; ≥6 mm (n=16), 0.75; and ≥10 mm (n=5), 0.80. These values were not statistically different from the sensitivity of detecting polypoid adenomas (p>0.37).

CONCLUSION

In this large screening population, nonpolypoid adenomas had a very low prevalence (<1%), and advanced pathologic features were uncommon in polyps<10 mm in diameter. Most nonpolypoid adenomas are technically visible at CTC. The prospective sensitivity is similar to that for polypoid adenomas when the interpretation combines both 2D and 3D review.

Flat adenomas

This article was presented at the conjoint CSSA and RACS (colorectal section) spring meeting Queensland, Australia, September 2004. The adenoma-carcinoma sequence describes a succession of events from polypoid adenoma to colorectal cancer. However, this model only accounts for up to two-thirds of colorectal cancers. There is growing evidence that flat adenomas are precursor lesions to a flat type of colorectal cancer and certain subtypes of these polyps are at greater risk of malignant transformation. If confirmed, the implications for screening, endoscopic recognition and management will become of increasing importance if we are to decrease the incidence of colorectal cancer.

Cyclooxygenase-2 overexpression is related to polypoid growth and K-ras gene mutation in T1 colorectal carcinomas

PURPOSE

Cyclooxygenase-2 is thought to play a role in the development of intestinal tumors and levels are elevated in approximately 80 to 90 percent of human colorectal carcinomas. To clarify the role that cyclooxygenase-2 plays in the development of colorectal carcinoma, we studied the relationship between cyclooxygenase-2 expression and tumor morphology and that between cyclooxygenase-2 expression and K-ras mutation.

METHODS

We classified 48 T1 colorectal carcinomas as polypoid or nonpolypoid and analyzed the clinicopathologic features. The expression of cyclooxygenase-2 was determined immunohistochemically, and nested polymerase chain reaction-restriction fragment length polymorphism detected a K-ras codon 12 mutation.

RESULTS

Cyclooxygenase-2 expression was higher in polypoid carcinomas than in nonpolypoid carcinomas (P < 0.001). The K-ras codon 12 mutation was associated with higher levels of cyclooxygenase-2 expression compared with carcinomas without this mutation (P = 0.028).

CONCLUSIONS

Polypoid growth and K-ras gene mutation are both associated with increased levels of cyclooxygenase-2 expression in T1 tumors.

NSAIDs and gastrointestinal cancer prevention

Numerous studies report the relationship between aspirin and other nonsteroidal anti-inflammatories (NSAIDs) and cancer incidence, in particular for colorectal cancer. This paper systematically reviews the evidence of the effect of aspirin and other NSAIDs on the primary prevention of colorectal and other gastrointestinal cancers in the general population. In 25 investigations of NSAIDs and colorectal cancer, 23 observational studies reported a relative risk reduction but estimates vary widely. Cohort studies generally indicate lesser reductions than case-control studies suggesting possible biases in the latter. Clear evidence of a dose relationship generally appears lacking but data do not indicate useful effects of aspirin in cardioprophylactic doses. Differences have otherwise not been detected between aspirin and other NSAIDs, nor between non-aspirin NSAIDs. There is some evidence that the risk of colorectal cancer reduces with increased duration of NSAID use. The lower incidence of oesophageal and gastric cancers results in smaller numbers of cases in the studies reporting these cancers, particularly in the cohort studies. The trend is for a risk reduction for oesophageal and gastric cancers in people taking NSAIDs, which is more likely to be statistically significant in the case-control studies. A very small number of observational studies have reported the relationship between NSAIDs and the incidence of pancreatic, gallbladder and liver cancers. These show no consistent relationship. In view of the inadequate information about optimal dose and duration of NSAIDs for colorectal cancer reduction, and the adverse effects of NSAIDs, we are not yet in a position to recommend NSAIDs for the primary prevention of colorectal cancer in the general population.

Barium enema and endoscopy for the detection of colorectal neoplasia: sensitivity, specificity, complications and its determinants

AIM

To analyse sensitivity, specificity and complication rate of endoscopy, and barium enema for the detection of colorectal neoplasia.

MATERIALS AND METHODS

A MEDLINE search was performed (1980-2000) directed at the endoscopic and radiologic literature on barium enema. Articles were selected based on the type of study, availability of sensitivity and specificity values in sizeable patient groups, and reports on complications. Sixty articles were included in the analysis.

RESULTS

Endoscopy proved to have superior sensitivity for polyps in patients at high-risk for colorectal neoplasia. The role of endoscopy and radiology in average-risk screening populations is not known. Sensitivity and specificity rates ranged widely, probably due to bias. For the detection of small polyps endoscopy has superior performance, whereas sensitivity is similar for endoscopy and barium enema for the detection of larger (>1 cm) polyps and tumours. Overall, endoscopy is associated with a higher complication rate.

CONCLUSION

Endoscopy is the preferred detection method in high-risk patients. The role of endoscopy and radiology in a screening setting requires evaluation. This review provides the test characteristics of endoscopy and radiology which are relevant for a cost-effectiveness analysis. Double-contrast barium enema may play an important role for screening purposes, owing to its good sensitivity for detecting larger (>1 cm) polyps and its lack of major complications. de Zwart, I. M.et al. (2001). Clinical Radiology56, 401-409.