Background and study aims: Colonoscopy has replaced barium enema as the primary method for direct diagnosis of colorectal cancer, but detection may fail, and the reasons for this are not completely understood.
Patients and methods: In order to analyze the accuracy of colonoscopy for detecting invasive colorectal cancer, 7365 colonoscopic examinations were matched with the most accurate local government population-based cancer registry in Japan.
Results: In 15 colonoscopic examinations, patients were not diagnosed as having invasive colorectal cancer, but disease of this type was detected within 3 years of the examinations (false-negative examinations). During the same period, 233 colonoscopies were identified as true-positive examinations. The false-negative rate for detecting invasive colorectal cancer with colonoscopy was 6% at 3 years. The false-negative rate was significantly higher in individuals between 60 and 69 years of age and in invasive cancers located to the right of the splenic flexure.
Conclusions: Colonoscopists should receive adequate training in achieving easy cecal intubation, detecting small or flat lesions, and carrying out adequate biopsies.