Incidence and risk factors of colorectal cancer based on 56324 health checkups: A 7-year retrospective cohort study.

Abstract

Although mortality rates of colorectal cancer (CRC) have been increasing in Japan, its screening rates remain stagnant at 19.2% among Japanese population aged >40years in 2014. To evaluate the importance of CRC screening by fecal occult blood test (FOBT), this study estimated the incidence of FOBT-positivity and CRC by sex-age stratification and clarified the risk factors for CRC. Between 2007 and 2014, 56324 residents (21517 men and 34807 women) were enrolled in this study. The sex-age-stratified incidence rates of FOBT-positivity and CRC were estimated by records from health checkups and colonoscopy. Regarding CRC incidence rate in particular, positive predictive value was adopted to adjust bias of FOBT-positivity that did not undergo colonoscopy by person-year method. To investigate the risks of CRC onset, a nested case-control study with 1:10 person-matching on sex and age was performed. Incidence rates of FOBT-positivity and CRC are 4183/100000 person-year (100Kpy) and 141.3/100Kpy, respectively. In both cases, men has higher incidence rate than women (1.3 times for FOBT; 4977 vs 3718/100Kpy and 2.3 times for CRC; 217.0 vs 96.4/100Kpy). The records from health checkups were useful to estimate incidence rates of CRC with this procedure. The age-stratified incidence rate indicated the importance of CRC screening by FOBT, especially for men and those aged >50years. Additionally, it is strongly recommended to do further investigation if positive for initial FOBT screening especially for those who are >70years.