Integrating migration into cancer geography: spatial clustering of five digestive cancer burden in China

China's digestive cancer landscape presents a dual challenge, the significant geographic disparity and the distorting effect of large-scale internal migration on burden estimation. The household-registered population (HRP)-based surveillance system does not fully capture the impact of large-scale internal migration, and county-level spatial evidence that accounts for migration remains limited. This study aimed to characterize the spatial distribution of the migration-adjusted burden of five digestive cancers in China, assess spatial autocorrelation, and identify county-level high-high and low-low clusters.

This spatial epidemiological study used previously developed migration-adjusted county-level incidence and mortality estimates for five digestive cancers in mainland China, derived using Bayesian INLA-SPDE modeling based on quality-controlled data from 487 cancer registries covering 28.6% of the national population. The spatial distribution was visualized using thematic mapping, and Global and Local Moran's I analyses were conducted to assess spatial autocorrelation and identify significant spatial clusters.

Spatial description revealed geographic patterns in cancer incidence and mortality, closely corresponded to clusters identified by spatial autocorrelation analysis. Global Moran's I analysis confirmed significant positive spatial autocorrelation in the migration-adjusted burden of all five cancers nationwide (p < 0.001). Distinct geographic patterns of HH clusters were evident across cancers: liver cancer in the southeastern coast, colorectal cancer in the eastern coast and northeast, gastric cancer in the east and northwest, esophageal cancer in central-eastern regions, and pancreatic cancer in the northeast and eastern coast. LL clusters were mainly in western, central-western, and southwestern China.

This study identified significant spatial clustering in the migration-adjusted burden of the five major digestive cancers in China. High-burden areas were mainly concentrated in eastern coastal, northeastern, and parts of central-eastern China, whereas lower-burden areas were more common in western and parts of southwestern China. These findings highlight the importance of incorporating population mobility into digestive cancer burden assessment and provide evidence to support region-specific cancer prevention, control prioritization, and more dynamic surveillance in China.