A Modified ypTNM Staging System-Development and External Validation of a Nomogram Predicting the Overall Survival of Gastric Cancer Patients Received Neoadjuvant Chemotherapy

Abstract

Purpose: Neoadjuvant chemotherapy is now widely used in gastric cancer patients. However, the current 8th ypTNM staging system is developed based on patients with less extensive lymph node dissection and the predictive value is relatively limited. In this study, we aim to develop and validate a nomogram that predicts overall survival in gastric cancer patients received neoadjuvant chemotherapy.

Patients and methods: From January, 2007 to December, 2014, 471 patients receiving neoadjuvant chemotherapy at our center were enrolled in the study. Based on the Cox proportional hazard model, a nomogram was developed from them and then an external validation was conducted on a cohort of 239 patients from another cancer center.

Results: The overall survival (OS) rates of 1 year and 3 years were 90.0% and 64.1%, respectively. Body mass index category, tumor location, T stage and N stage were independent prognostic factors for the survival outcome. The C-index of the model was 0.74 in the development cohort and 0.69 in the validation cohort. Our nomogram also showed good calibration in both cohorts.

Conclusion: We developed and validated a nomogram to predict the 1- and 3-year OS of patients who received neoadjuvant chemotherapy and radical gastrectomy with D2 lymph node dissection. This nomogram predicts survival more accurately than the AJCC TNM staging system, which is the current golden standard.

Keywords: nomograms; perioperative chemotherapy; stomach neoplasms; survival.

Figure 1

Nomogram was developed from 4 clinicopathological parameters (T stage, N stage, BMI group and Tumor Location) to predict 1- and 3-year survival. The first step to calculate the survival probability is to assign points for each parameter by drawing a vertical line from that variable to the points scale. The second step is to sum all the points and draw a vertical line from the total point to calculate the probability of survival.

Figure 2

Calibration curve of the nomogram for (A) 1-year OS in training cohort (B) 3-year OS in training cohort (C) 1-year OS in validation (D) 3-year OS in validation cohort. The x-axes represent the survival estimated by the nomogram, the y-axes are survival calculated by the Kaplan–Meier method.