The study participants were a subset of the subjects of the
‘‘Colorectal Polyp Registry at the National Cancer Center of Korea’’
study [19]. All participants who underwent cancer screening and
colonoscopy at the National Cancer Center, Korea, between April
2007 and December 2009 were invited to participate in the
Colorectal Polyp Registry. Among 26,600 eligible population,
16,300 were enrolled in the Colorectal Polyp Registry. Among
them, 13,335 participants received colonoscopy for screening
purposes, 7278 were provided detailed information on their family
histories of cancer in a questionnaire, and 3070 of them were 40–
49 years old. Participants with a past history of cancer (n = 134) or
colorectal polyp (n = 259) were excluded. A further 402 participants
with a pathological diagnosis of non-adenomatous polyp
(i.e., hyperplastic polyp, serrated polyp, or other types of polyp) or
missing pathological reports were also excluded from the analysis.
Ultimately, 629 patients with adenomatous polyps and 1646
polyp-free controls were included in the analysis (Fig. 1).