Clinical significance of small colorectal adenoma less than 10 mm: the KASID study

Polypectomy is the current modality of choice to prevent benign colorectal adenoma from progressing to an invasive cancer. However, in cases of small colorectal adenoma, it remains unclear as to whether polypectomy is actually an effective treatment modality. We evaluated the clinical significance of polypectomy in cases of small colorectal adenomas, measuring less than 10 mm.

All colonoscopies were performed at 11 Korean tertiary medical centers, between July 2003 and March 2004. A total of 5996 colorectal adenomas were detected and divided into 5 groups according to their size (Group 1; 1-5 mm, Group 2; 6-7 mm, Group 3; 8-9 mm, Group 4; 10-19 mm, Group 5; more than 20 mm). The term 'advanced adenoma' refers here to tubular adenomas with diameters of at least 10 mm, or to tubulovillous, villous, or high-grade dysplasia, irrespective of size. 'Cancer' here is defined as the invasion of malignant cells beyond the muscularis mucosa.

As the sizes of the adenomas increased, the prevalence of advanced adenoma was also observed to increase. In Groups 2 and 3, the prevalence of tubulovillous or villous adenoma were higher than was expected (5.2% and 6.6%, p < 0.001). Interestingly enough, in Group 2, the prevalence of cancer was at least as high as in Group 4 (0.7% vs. 0.5%, p < 0.001).

In cases of small colorectal adenomas, measuring between 6 and 9 mm, the prevalence of cancer was at least as high as that seen in the cases of colorectal adenomas measuring between 10 and 19 mm. Therefore, small colorectal adenomas measuring between 6 and 9 mm should not be ignored, in order to decrease the prevalence of colorectal cancer.