External validation of recurrence predicting nomogram for early gastric cancer after curative resection

Abstract

[한글]

[영문]Purpose : Nomograms are statistically based tools that provide the overall probability of a specific outcome. In our previous study, nomogram which predict recurrence of EGC after curative resection was developed on the basis of the Cox regression. We performed this study to externally validate our previous EGC nomogram. Methods: Our previous EGC nomogram was established from a retrospective EGC database that included 2923 consecutive patients at Severance Hospital, Yonsei University between January 1987 and April 2005. This nomogram was externally validated by an independent 930 patients cohort who were retrospectively included between May 2005 and April 2007. Nomogram external validation consisted of discrimination and calibration. Results: A total of 11 patients (1.1%) experienced recurrence, and 4 (36.4%) out of them recurred within 2 years after surgery. With the median 37 months of follow up, median time to recurrence was 26.4 months and the mean score estimated predicting recurrence by the nomogram was 203.7 (SD 32.7). The concordance index (c-index) was 0.7 (p=0.02) and the result of overall C index was 0.82 (p=0.006, 95% CI 0.59-1.00). The goodness of fit test showed that the EGC nomogram had significantly good fit at 1- and 2-year survival interval (p=0.998 and 0.879, respectively). The predictions derived from the EGC nomogram were then divided into three groups depending on their points: high risk (less than 170 points, n=102), intermediate risk (170-208 points, n=427), low risk (more than 208 points, n=401). A Kaplan-Meier DFS curve among these three subgroups showed a significant difference (p=0.001). Conclusion: Preexisting nomogram for predicting recurrence-free survival of EGC after surgery was externally validated. It is useful for accurate and individual prediction of disease-free survival, patient prognostication, counseling and follow-up planning.