External validation of nomogram for the prediction of recurrence after curative resection in early gastric cancer

Background: Nomograms are statistics-based tools that provide the overall probability of a specific outcome. In our previous study, we developed a nomogram that predicts recurrence of early gastric cancer (EGC) after curative resection. We carried out this study to externally validate our EGC nomogram. Patients and methods: The EGC nomogram was established from a retrospective EGC database that included 2923 consecutive patients. This nomogram was independently externally validated for a cohort of 1058 consecutive patients. For the EGC nomogram validation, we assessed both discrimination and calibration. Results: Within the follow-up period (median 37 months), a total of 11 patients (1.1%) experienced recurrence. The concordance index (c-index) was 0.7 (P = 0.02) and the result of the overall C index was 0.82 [P = 0.006, 95% confidence interval (CI) 0.59-1.00]. The goodness of fit test showed that the EGC nomogram had significantly good fit for 1- and 2-year survival intervals (P = 0.998 and 0.879, respectively). The actual and predicted survival outcomes showed good agreement, suggesting that the survival predictions from the nomogram are well calibrated externally. Conclusions: A preexisting nomogram for predicting disease-free survival (DFS) of EGC after surgery was externally validated. The nomogram is useful for accurate and individual prediction of DFS, patient prognostication, counseling, and follow-up planning.