Abstract
Introduction: In Japan, the incidence of colorectal cancer (CRC) is increasing. From 1987, Fukui Prefecture has been conducting a mass screening system aimed at reducing CRC related mortality. The purpose of this study was to analyze interval cancers in CRC mass-screening and to consider effective plans to decrease CRC mortality. Methods: We collated data from 168,259 individual screenings for CRC conducted between April 2004 and March 31 2009 with the Fukui Cancer Registry to measure sensitivity and specificity and to identify the CRC diagnosed outside cases of the screening program with a fecal occult blood test (2 days-method). Interval cancers are defined as false negative cases diagnosed outside the screening program within one year after the screening examination (EU guideline). Results: 46 interval cancers and 258 screening cases were detected, so sensitivity and specificity were 88.5% and 94.9% respectively. The mean age of interval cancer; 71.2 years-old is higher than that of screening cases; 68.5. Submucosal invasion cancers were 21.8% in interval cancers and 28.7% in screening cases, but stage IV cancer in interval cancers was statistically significantly higher than that of screening cases. There were no histological differences among interval cancers and screening cases. The 5-year relative survival rate for CRC was calculated as 95.1% of screening cases, compared to the significantly lower 88.7% of interval cancers cases. The hazard ratio of interval cancers is 2.98. Conclusions: CRC mortality is not significantly decreasing in Fukui Prefecture. The mass screening system seems to be effective for early diagnosis and treatment of CRC. We should continue to observe further trends in CRC mortality and improve public participation in mass screening examinations. Furthermore, we should endeavor to decrease the incidence of interval cancer. This data is useful for cancer control planning of local governments.
