Age-period-cohort modeling of colorectal cancer incidence and mortality in Spain.

Spain registers a much lower rate of colorectal cancer incidence and mortality than do other European countries, yet the rises observed in the adjusted rates over recent decades led us to attempt to monitor the trends over time using Poisson log-linear models. Incidence data were furnished by the Zaragoza and Navarre population-based cancer registries, whereas mortality data corresponded to Spain as a whole. For trend evaluation purposes, we made use of invariant parameters from age-period-cohort models (net drift and curvature) and a restriction of the cohort-effect slope range. The results suggest the presence of a marked rise in incidence of colorectal cancer for both sexes and across all age groups in the provinces studied. The rise in mortality was less pronounced than the rise in incidence and seemed to coincide with a marked cohort effect present throughout the study period. Both in incidence and mortality, the increases were more pronounced among men. When studied jointly, incidence and mortality trends tend to be complementary, rendering an approach of this nature especially important in sites with better survival, such as the case in point.