Japanese Journal of Clinical Oncology Advance Access published online on May 30, 2009
Japanese Journal of Clinical Oncology, doi:10.1093/jjco/hyp047
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© The Author (2009). Published by Oxford University Press. All rights reserved
Five-year Incidence of Advanced Neoplasia after Initial Colonoscopy in Japan: A Multicenter Retrospective Cohort Study
1 Endoscopy Division, National Cancer Center Hospital, Tokyo
2 Division of Digestive Endoscopy and Gastrointestinal Oncology, National Cancer Center Hospital East, Kashiwa
3 Digestive Disease Center, Showa University, Northern Yokohama Hospital, Yokohama
4 Hattori GI Endoscopy and Oncology Clinic, Kumamoto
5 Division of Digestive Endoscopy, Cancer Institute Ariake Hospital, Tokyo
6 Division of Digestive Endoscopy and Gastrointestinal Oncology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka
7 Department of Health Science, Shiga University of Medical Science, Shiga
8 Department of Molecular-Targeting Cancer Prevention and Epidemiology for Community Health and Medicine, Kyoto Prefectural University of Medicine, Kyoto
9 Clinical Laboratory Division, National Cancer Center Hospital, Tokyo
For reprints and all correspondence: Takahisa Matsuda, Endoscopy Division, National Cancer Center Hospital, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan. E-mail: tamatsud{at}ncc.go.jp
Received February 15, 2009; accepted April 15, 2009
Objective: The National Polyp Study is used as the basis of recommendations for colonoscopic surveillance after polypectomy, establishing an interval of 3 years after removal of newly diagnosed adenomas. The aim of this retrospective cohort study was to estimate the incidence of advanced neoplasia after initial colonoscopy and compare the differences among risk groups.
Methods: Patients over 40 years who were referred for initial colonoscopy at six institutes were selected. They were classified into four groups based on the initial colonoscopy: A, patients without any adenoma; B, with adenomas of <6 mm only; C, with adenomas of 
6 mm; D, with any intramucosal cancer. The index lesion (IL) at follow-up colonoscopy was defined as large adenoma 10 mm, intramucosal/invasive cancer.
Results: A total of 5309 patients were enrolled in this study. Overall, median follow-up period was 5.1 years. The numbers of eligible patients in the various subgroups were A, 2006; B, 1655; C, 1123; D, 525. A total of 379 ILs were newly diagnosed during follow-up colonoscopy. The cumulative incidence of ILs in each group was A, 2.6%; B, 6.7%; C, 13.4%; and D, 12.6%.
Conclusions: Patients with any adenomas >6 mm or intramucosal cancer at the initial colonoscopy have a higher risk of advanced neoplasia during follow-up colonoscopy.
Key Words: colonoscopy • polyp • colorectal cancer • screening • surveillance