External validation and comparison of five prediction models for lymph node metastasis after noncurative endoscopic submucosal dissection for early gastric cancer

Background Additional gastrectomy is recommended after noncurative endoscopic submucosal dissection (ESD) for early gastric cancer (EGC) despite the low incidence of lymph node metastasis (LNM). The eCura system, W-eCura score, and 11-point score reportedly predict LNM risk; however, their comparative performance remains unclear. We aimed to externally validate and directly compare five risk stratification approaches in patients with noncurative ESD. Methods We retrospectively evaluated 634 consecutive patients with EGC who underwent noncurative ESD at a single high-volume center. Five prediction models were evaluated: the eCura system (7-point score and three-risk classification), W-eCura score (7-point score and three-risk classification), and 11-point score. All pathological findings were re-evaluated by an outcome-blinded expert pathologist. Model performance was assessed by discrimination, calibration, and decision-curve analysis (DCA). Results LNM was identified in 26 (4.9%) patients. All models showed comparable discrimination (c-statistics, 0.71 to 0.72). However, calibration-in-the-large and calibration slope were poorer in the W-eCura score and 11-point score (− 1.43 to − 0.96 and 0.26 to 0.64) than in the eCura system (− 0.43 to − 0.40 and 0.83 to 0.84). Using DCA, the eCura system and W-eCura score consistently showed higher net benefits than did the 11-point score across clinically relevant threshold probabilities. Recalibration improved both calibration and net benefits across all models. Conclusions Despite similar discriminative performance, the eCura system demonstrated relatively favorable calibration and potential clinical utility in this Japanese cohort. Given their simplicity and structural similarity, three-risk classifications of the eCura system and W-eCura score, when appropriately calibrated, may support decision-making regarding additional gastrectomy.