High Detection Rate Of Flat And Depressed Colonic Neoplasm In Elderly People

Background: Although depressed-type colon tumors mainly occur in Japan, such tumors have also been found in Europe and the United States. The incidence of this tumor is very low, but even a small tumor of this type is invasive and difficult to detect at an early stage. In this study, we conducted an immunochemical fecal occult blood test (IFOBT) on two samples in organized screening of an asymptomatic average-risk population, and performed total colonoscopy (TCS) as a detailed examination. The types of colon tumor were classified by age to investigate the incidence of depressed-type colon tumors in different age groups. Materials and Methods: The subjects were 10349 asymptomatic persons (males: 8081, females: 2268, mean age: 51 years old) who showed a positive result in an IFOBT of two samples in occupational screening performed for 4 years from June 1995 to June 1999, and subsequently underwent TCS. Results: Of 10349 subjects who underwent the initial TCS, 3903 were treated with an endoscope or surgically: these subjects comprised 3397 cases of adenoma, 422 cases of non-invasive carcinoma (carcinoma in situ) and 84 cases of invasive neoplasia. Detection rates in the IFOBT-positive subjects were 32.8% (3397/10349), 4.1% (422/10349) and 0.8% (84/10349), respectively. The detection rate for depressed-type colon tumors correlated with the increase of age: in subjects aged less than 60 years old and in those aged 60 or higher the detection rates were 7.1% (18/254) and 18.0% (18/99), respectively, with a significantly higher incidence of depressed-type colon tumors in the group aged 60 years old or higher (p < 0.02). Conclusions: In colonoscopy in persons aged 60 years old or higher, it is important to pay attention to the occurrence of flat and depressed colonic neoplasm.