CT imaging features in prognostic risk stratification compared to clinical staging in resectable gastric cancer: a multicenter study

To evaluate the incremental prognostic value of visually assessable CT features beyond clinical stage (cStage) for disease-free survival (DFS) risk stratification in gastric cancer.

Patients undergoing curative gastrectomy were retrospectively included in development and external cohorts. Clinical and pathological stages were reconstructed according to the AJCC 8th edition and simplified to three tiers. Clinical Stage, CT Imaging, and Combined models were evaluated for discrimination, calibration, bootstrap-corrected performance, and external validation. Incremental prognostic value was assessed using changes in the C-index and time-dependent AUCs. A development-derived CT Imaging Score (CIS) cutoff was locked for exploratory risk refinement within preoperative cStage strata.

Among 886 patients (development, n = 698; external, n = 188), cStage-pStage concordance was 51.0% and 61.2%, respectively (linear-weighted κ = 0.387 and 0.513). In the development cohort, adding CIS to cStage increased the C-index from 0.648 to 0.805 (ΔC-index = 0.160, P = 0.002) and the 1-, 3-, and 5-year AUCs by 0.159, 0.184, and 0.193, respectively (all P = 0.001). The optimism-corrected C-index was 0.797 for the Combined model. External C-indices were 0.676, 0.694, and 0.695 for the Clinical Stage, CT Imaging, and Combined models, respectively. In the development cohort, CIS-high status was associated with worse DFS within cStage II (HR = 8.66, 95% CI: 5.59-13.42) and cStage III (HR = 5.78, 95% CI: 3.74-8.92), with associations retained after adjustment for postoperative pStage.

Integrating visually assessable CT imaging features with conventional cStage improved DFS prognostic discrimination in the development cohort, while the derived CIS further refined risk stratification within preoperative cStage groups.