A commentary on “Global, regional, and national burdens of colorectal cancer and inflammatory bowel disease, 1990–2021 and projections to 2050: a cross-sectional study”

Dear Editor, We read with great interest the article by Zhang et al[1], “Global, regional, and national burdens of colorectal cancer and inflammatory bowel disease, 1990–2021 and projections to 2050: a cross-sectional study,” published in the International Journal of Surgery. Using age-standardized rates, EAPC/AAPC trend analyses, and Bayesian age–period–cohort (BAPC) projections, the authors present an ambitious synthesis of colorectal cancer (CRC) and inflammatory bowel disease (IBD) trends across 204 countries. The integrated “inflammation–tumor” framework is both timely and policy-relevant.However, several methodological and interpretive issues merit clarification.This correspondence also adheres to the TITAN Guidelines 2025 for the declaration and use of artificial intelligence in scientific manuscripts[2]. First, the ecological linkage between IBD and CRC remains inferential rather than directly modeled. Although the Introduction notes that IBD may increase CRC risk[3], the available text does not report country-level correlation analyses, mediation modeling, lag-structure assessments, or sociodemographic index (SDI)-stratified ecological regressions quantifying associations between IBD burden indicators [e.g., age-standardized incidence rate (ASIR)/age-standardized prevalence rate) and CRC incidence or mortality. Because both conditions are independently modeled within the Global Burden of Disease (GBD) framework[4], clarification as to whether joint modeling, cross-correlation with temporal lags, or stratified ecological regression was performed would strengthen the central epidemiologic premise. The available text does not report such analyses; clarification would enhance interpretive precision. Second, greater transparency regarding the BAPC projections is warranted. The manuscript states that nested Laplace approximation was used to avoid MCMC convergence concerns; however, the available text does not report prior specifications, model-fit diagnostics, posterior predictive checks, or out-of-sample validation. Given that projections extend to 2050 and inform policy implications, reporting calibration performance or sensitivity analyses under alternative priors would improve the credibility and decision relevance of the forecasts. Third, causal interpretation of declining age-standardized mortality rates (ASMRs) alongside increasing case counts requires caution. The authors attribute reductions in ASMRs to improvements in screening and treatment in high-SDI regions. Yet the available text does not report stage distribution, screening coverage, treatment uptake, or case-fatality proxies nor does it present decomposition analyses separating demographic aging effects from incidence and survival changes. Without such analyses, attributing mortality declines directly to health system gains may exceed the evidentiary boundary of the presented data. From a clinical workflow perspective – particularly in proctologic practice – the rapid ASIR growth (EAPC 1.38) and marked prevalence expansion in middle-SDI regions have tangible implications for service capacity. Risk-stratified pathways – such as structured colonoscopic surveillance intervals for patients with IBD, complication-monitoring frameworks, and capacity-adjusted screening algorithms – depend on age distribution, disease duration, and competing mortality risks, which are not detailed in the available text. Clarification would enhance translational applicability. We commend the authors for synthesizing extensive GBD data. Addressing these methodological clarifications – particularly explicit modeling of the IBD-CRC association and fuller reporting of projection uncertainty – would strengthen the policy conclusions while ensuring that inference remains aligned with the evidentiary scope presented.