Age-period-cohort effects in utilization of diagnostic procedures leading to incidental colorectal cancer detection.

BACKGROUND AND AIM Despite the overall decrease in colorectal cancer (CRC) incidence, a small but constant rise has been recently observed in people younger than 50 years across several countries. This phenomenon can be explained by environmental or lifestyle factors, but it may also be partially justified by an increasing tendency in younger cohorts to undertake diagnostic procedures that may lead to CRC incidental diagnosis. METHODS We performed an age-period-cohort analysis on 1 815 694 diagnostic procedures undertook by the population of the City of Milan, served by the Agency for Health Protection of Milan, between 1999 and 2018. We considered all instances of colonoscopy, rectoscopy, fecal occult blood test (FOBT) and ultrasonography. We stratified by gender, nationality and quintile of socioeconomic deprivation. RESULTS Incidence of utilization rose with age for all procedures but rectoscopy; there was a marked increase from 2005 to 2010 for FOBT and colonoscopy. A strong all-procedures cohort effect was observed, greater for FOBT and colonoscopy. A steady increase of diagnostic procedures utilization started in cohorts born in the late 1950s, with a relative effect rising from 0.91 [95% confidence interval (CI) 0.90-0.92] for the 1950 cohort to 5.03 (95% CI, 4.58-5.48) for the 1990 one. CONCLUSION We found a growing tendency in younger cohorts to undertake diagnostic procedures, explainable by inappropriate access to endoscopic procedures, that can lead to an incidental diagnosis of CRC. This finding may at least partially explain the observed rising incidence of early-onset CRC.