Abstract
We evaluated the necessity of undergoing close examination in colorectal cancer screening. The course of detection of infiltrating colorectal cancer within 2 years of screening was classified into:(1) detection in the initial screening,(2) false-negative occult blood-detection of cancer in annual or biennial screening,(3) false-negative results of close examination,(4) not undergoing close examination, and (5) interval cancer. The cumulative survival rate calculated by Kaplan-Meier's method and the death risk ratio obtained using Cox's proportional hazard model were evaluated. The cumulative 5-year survival rate in the group who had not yet undergone close examination was the lowest (39.3%) among the above 5 groups. The death risk ratio in this group was significantly high (3.83, p=0.018) compared with the group in whom cancer was detected in the initial screening. When the follow-up period after screening was 3 years, the death risk ratio in the group who had not yet undergone close examination was 3.91 compared with the group who underwent close examination (p=0.012). Thus, close examination should be recommended to all persons who have not yet undergone close examination. However, considering that 36% have not yet undergone close examination in this country, close examination should be strongly recommended at least in the high-risk group in terms of cancer detection (both positive occult blood twice and a high total occult blood value).
