Age-specific patterns in colorectal cancer incidence and survival over time: a 17-year population-based cancer registry study from northeastern Italy

Background: Age-specific differences in colorectal cancer remain insufficiently characterized in studies integrating incidence and survival dynamics. Aims: We analyzed age-specific patterns of colorectal cancer incidence and survival over time using population-based registry data from northeastern Italy, including 16,752 colorectal adenocarcinomas (2005–2021). Methods: Analyses examined early-onset (<50 years), screening-eligible (50–69 years), and late-onset (≥70 years) disease. Incidence trends were assessed using Joinpoint regression. Five-year net survival and conditional net survival were estimated using the Pohar-Perme method. Results: Early-onset cancers (4.2%) more often presented with advanced stage and high-grade histology, with stable incidence over time. Among screening-eligible individuals, incidence initially increased and then declined after the 2008 implementation of organized screening, particularly for stage I disease (annual percent change: +13.8% then -7.8%), left-sided (+7.3% then -19.9%), and rectal cancers. Five-year net survival improved over time, mainly in stage II-III. Stage IV survival remained poor, with modest gains in younger patients (16–29%) and persistently poor outcomes in older ones (6–8%). Conditional 5-year net survival increased across all age groups and stages, especially in stage IV (7–16% at diagnosis; 64–74% at 5 years). Conclusion: These findings support timely diagnosis and appropriate care across age groups, continued screening among eligible individuals, and dynamic prognostic assessment.