Extent of prevalence and size of flat neoplasms in a heterogeneous population undergoing routine colorectal cancer screening

Prevalence of advanced histological features and synchronous neoplasia in patients with flat adenomas

BACKGROUND AND AIMS

The prevalence of advanced histology in flat adenomas is uncertain. There are limited data on the prevalence of synchronous adenomas in patients with flat adenomas. The aims of this study were to determine whether the flat adenomas harbor advanced histology more than the polypoid adenomas and whether the presence of flat adenomas is an independent predictor of synchronous adenomas.

METHODS

A retrospective analysis of data from 3 prospective clinical trials conducted at 2 tertiary care referral centers that included patients undergoing screening or surveillance colonoscopy was performed. The location, size, and morphology of each polyp resected was documented and sent for histopathological examination in a unique specimen jar.

RESULTS

A total of 2931 polyps were removed in 1340 patients. Of the 1911 adenomas (65.2%), 293 (15.3%) were flat and 1618 (84.7%) were polypoid. The prevalence of advanced histology did not differ between flat and polypoid adenomas (1.4% vs 3.1%; P = .13). Multivariate analysis confirmed that the presence of at least 1 flat adenoma was a predictor of the presence of a large adenoma (P < .01; odds ratio [OR], 2.80; 95% CI, 1.86-4.22), advanced adenoma (P < .01; OR, 2.70; 95% CI, 1.80-4.06), and 3 or more adenomas (P < .01; OR, 2.44; 95% CI, 1.66-3.59).

CONCLUSION

Although the prevalence of advanced histology in flat adenomas is similar to that of polypoid adenomas, flat adenomas are associated with increased prevalence of synchronous large and advanced adenomas. Whether these results imply shorter surveillance intervals in patients with flat adenomas needs to be explored in future studies.

Nonpolypoid colorectal neoplasms: gender differences in prevalence and malignant potential

OBJECTIVE

Colonoscopy may fail to prevent colorectal cancer, especially in the proximal colon and in women. Nonpolypoid colorectal neoplasms may potentially explain some of these post-colonoscopy cancers. In the present study, we aimed to examine the prevalence and malignant potential of nonpolypoid colorectal neoplasms in a large population, with special attention to gender and location.

METHODS

We performed a cross-sectional study of all consecutive patients undergoing elective colonoscopy at a single academic medical center. The endoscopists were familiarized on the detection and treatment of nonpolypoid lesions. Advanced histology was defined by the presence of high-grade dysplasia or early cancer.

RESULTS

We included 2310 patients (53.9% women, mean age 58.4 years) with 2143 colorectal polyps. Prevalences of colorectal neoplasms and nonpolypoid colorectal neoplasms were lower in women than in men (20.9% vs. 33.7%, p < 0.001 and 3.0% vs. 5.5%, p = 0.002). In women, nonpolypoid colorectal neoplasms were significantly more likely to contain advanced histology than polypoid ones (OR 2.89, 95% CI 1.24-6.74, p = 0.01), while this was not the case in men (OR 0.91, 95% CI 0.40-2.06, p = 0.83). Proximal neoplasms with advanced histology were more likely to be nonpolypoid than distal ones (OR 4.68, 95% CI 1.54-14.2, p = 0.006).

CONCLUSION

Nonpolypoid mechanisms may play an important role in colorectal carcinogenesis, in both women and men. Although women have fewer colorectal neoplasms than men, they have nonpolypoid colorectal neoplasms, which frequently contain advanced histology.