A subset of patients may develop colorectal cancer after a colonoscopy that was negative for carcinoma. These missed or de novo developed lesions were termed as interval cancers. Many studies regarding interval cancer have been conducted in Western countries, whereas very limited data are available in Asian populations. Therefore, the purpose of this study was to investigate prevalence, clinicopathologic features, and predictors of interval colorectal cancers in the Korean population.

Interval cancer was defined as a cancer that is diagnosed within 5 years of a negative colonoscopy result. Among the patients who were diagnosed colorectal cancers at Kangbuk Samsung Hospital from January 2007 to April 2012, clinicopathologic characteristics of interval cancers were compared with those of sporadic cancers.

Among the 785 patients, 482 responded to telephone calls. Of these, 30 (6.2%) developed interval cancers. Finally, 28 patients who had interval cancers were compared with 415 patients who had sporadic cancers. Interval cancer group was significantly younger and more frequent in the right side colon than sporadic cancer group. There was no differences in sex, tumor size, differentiation, and staging between two groups. In multivariate analysis, young age and right side colon cancer were independent factors associated with an interval cancer.

A significant proportion of Korean patients developed interval colorectal cancer, especially at the young age and in the proximal colon.