Abstract
There have been a few evidence-based studies concerning the relationship between the length of the screening interval of two-day immunological fecal occult blood testing (IFOBT) and the risk of colorectal cancer (CRC). The aim of the present retrospective study was to assess the appropriate interval of two-day IFOBT for CRC screening. The study included subjects in whom the initial twoday IFOBT was negative and a second two-day IFOBT was subsequently performed. The detection rates for cancer among those who underwent screenings at various intervals between the initial and second screening were assessed. Among the 76, 337 subjects, 57 invasive cancer cases and 46 mucosal cancer cases were found. The odds ratio (OR) for mucosal or invasive cancer was significantly elevated among the subjects in whom the interval was over 4 years (OR: 2.13, 95% confidence interval: 1.19 to 3.81) in comparison with that of the subjects in whom the interval was 1 year. Because the prolongation of the interval between initial and the second two-day IFOBT to up to 3 years did not result in any change in cancer risk among persons who were at average risk for CRC, it is presumed that three years is an adequate interval for two-day IFOBT in mass screenings for CRC.