Global incidence patterns of early-onset gastrointestinal cancers and their ecological associations with behavioural risk factors

Background: Early-onset gastrointestinal cancers (EOGIC) are increasingly recognised as an urgent global health concern. We aimed to describe the global incidence patterns of EOGIC in 2022 and evaluate country-level ecological associations with behavioural risk factors. Methods: The incident cases and age-standardised incidence rates (ASIRs) of overall EOGIC, early-onset colorectal cancer (EOCRC), early-onset oesophageal cancer, early-onset gallbladder and biliary tract cancer, early-onset liver cancer (EOLC), early-onset pancreatic cancer (EOPC), and early-onset stomach cancer (EOSC) were extracted from the GLOBOCAN 2022 database. We used machine learning and generalised linear regression to screen and quantify the associations of behavioural risk factors and computed the model-based attributable fraction estimates. Results: In 2022, an estimated 465 584 new EOGIC cases occurred globally (9.49% of all-age gastrointestinal cancers), with an ASIR = 11.50 per 100 000 persons. Early-onset colorectal cancer was the highest in both incident cases (n = 186 840), and ASIR = 4.60 per 100 000, followed by EOLC and EOSC. High Human Development Index countries (n = 205 168 incident cases, ASIR = 13.20 per 100 000) showed highest incidence of EOGIC. The highest number of EOGIC incident cases was in Eastern Asia (n = 147 677) and the highest ASIR occurred in Australia-New Zealand (ASIR = 18.70 per 100 000). In the ecological analyses, diet high in red meat and smoking showed the largest attributable fraction estimates for overall EOGIC incidence, at 12.78% and 8.17%, respectively. Smoking also showed comparatively larger estimates for EOCRC (11.29%) and EOPC (23.97%). High alcohol use was associated with nonzero attributable estimates for EOCRC (3.14%), early-onset oesophageal cancer (1.57%), EOLC (7.39%), EOPC (3.75%), and EOSC (6.88%), whereas diet high in sodium showed the largest estimate for EOSC (15.41%). Conclusions: Early-onset gastrointestinal cancer was a significant global health challenge, particularly for EOCRC and in high Human Development Index countries. These findings may help inform surveillance priorities and hypothesis generation for future etiologic research.