Polyps with advanced neoplasia are smaller in the right than in the left colon: implications for colorectal cancer screening

Colonoscopy is consistently associated with reduced left-sided, but not right-sided, colorectal cancer (CRC) incidence and mortality. This might be because polyps with advanced pathology are smaller and more easily missed in the right vs left colon. We explored this postulate by evaluating the relationship among size, location, and histology of polyps from a large nationwide sample.

We conducted a cross-sectional study of 233,414 polyps from 142,686 patients (47% women; mean age, 60 years), which were reviewed by Miraca Life Sciences in 2009. We assessed polyp histology, location, and size of largest fragment submitted. We compared size distribution of right vs left polyps with high-grade dysplasia (HGD) or adenocarcinoma as well as any advanced neoplasia.

The average size of right-sided polyps was smaller than that of left-sided polyps with HGD or adenocarcinoma (8.2 vs 12.4 mm, respectively); the same was true for polyps with advanced neoplasia (7.6 vs 11.1 mm, respectively) (P < .001). Most right-sided polyps with HGD, adenocarcinoma, or any advanced neoplasia were ≤9 mm, whereas most left-sided polyps with these findings were >9 mm. Polyps with advanced pathology were 5-fold more likely to be <6 mm in the right vs left colon: odds ratio, 5.27; 95% confidence interval, 4.06-6.82 for HGD or adenocarcinoma; odds ratio, 4.89; 95% confidence interval, 4.34-5.51 for advanced neoplasia.

Polyps with features of HGD, adenocarcinoma, or advanced neoplasia were significantly smaller in the right vs left colon. Strategies to prevent right-sided CRC require more accurate detection of small, advanced polyps.