Multi-institutional development and validation of a nomogram to predict recurrence after curative resection of gastric neuroendocrine/mixed adenoneuroendocrine carcinoma

Objective To establish a novel nomogram to predict individual 1, 3, and 5 years disease-free survival (DFS) of patients with gastric neuroendocrine carcinoma/mixed adenoneuroendocrine carcinoma [(MA)NEC]. Background Among patients undergoing radical resection of gastric (MA)NEC, there is still a high tendency for relapse. Methods A retrospective analysis of 777 patients with gastric (MA)NEC at 23 centers in China from 2004 to 2015 was performed. Based on the established nomogram, which included age, ASA, pT, pN and Ki67, the overall patients were divided into low-risk group (LRG) and high-risk group (HRG). Results The median follow-up time was 40 months (1–169 months). The C-index, AUC and time-ROC of the nomogram were significantly higher than that of the 8th edition AJCC and ENETS TNM staging systems. The 3-year DFS of patients in HRG generated by the nomogram was significantly lower than that in LRG (all patients: 35% vs 66.9%, p < 0.001), and there were still significant differences in stratified analysis of the TNM staging systems. The local recurrence rate (10.5% vs 2.6%) and distant recurrence rate (45.1% vs 22.6%) in HRG were significantly higher than those in LRG, especially in anastomotic recurrence (6.3% vs 2%), liver recurrence (20.7% vs 13.4%) and peritoneal metastasis (12.7% vs 2.6%). Conclusions Compared with AJCC and ENETS TNM staging systems, the established novel validated nomogram had a significantly better prediction ability for DFS and recurrence patterns in patients with gastric (MA)NEC. It can also compensate for the shortcomings of existing AJCC and ENETS TNM staging in predicting individual recurrence risk.